Significant Height Revisions


For the latest news on any significant height revision due to a survey conducted with the Trimble GeoXH 6000 consult the Home page under the post heading Mapping Mountains Trimble Surveys or click {here} for the detailed Trimble Survey Spreadsheet.

This part of the Mapping Mountains blog is dedicated to any significant height revision for hills that either appear in listings, or have been initiated from surveys, that I have been a part of.

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised for detailing these revisions.





Mapping Mountains – Significant Height Revisions – Yr Uchafion


Moel Bowydd (SH 712 470)

This is the thirty ninth post under the heading of Significant Height Revisions, with the Trimble survey that resulted in this height revision being conducted on the 8th April 2017.

The thirty ninth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted on hills adjoined to the Arenig group in the northern part of the south-west Sub-Region of North Wales (Region A, Sub-Region A3), with the town of Blaenau Ffestiniog to the south-west of the hill.

The walk that took in this hill’s summit was suggested by Aled Williams who had analysed this hill’s Uchaf qualification via LIDAR data, and the walk and survey were conducted on a beautiful sunny day with hardly a breath of breeze.

The hill can be accessed via public footpaths from its west, east and south, with Blaenau Ffestiniog being a good starting point for an ascent; an alternate and longer ascent can start from above Llan Ffestiniog using a track beside the course of the Afon Teigl.  However, the summit of this hill is not on designated open access land, therefore permission to visit should be sought, but as the summit is relatively close to a public footpath and with open access land to its immediate north, common sense should prevail and if wanting to visit the summit there is likely to be no objection to doing so.

The name of the hill is Moel Bowydd and its addition to the list of Yr Uchafion was announced on Mapping Mountains on the 03.04.17, with its addition due to LIDAR data analysed by Aled Williams.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

Aled’s analysis of LIDAR data gives the hill the following details:


Moel Bowydd

Summit Height:  500.6m

Summit Grid Reference:  SH 71276 47053

Bwlch Height:  c 485m

Bwlch Grid Reference:  SH 71586 47206

Drop:  c 16m


Prior to analysis of LIDAR data the hill was not classified as contouring on current Ordnance Survey maps implied it did not have the required height to qualify as an Uchaf.  Ordnance Survey maps give this hill an uppermost 490m ring contour and bwlch contouring between 480m – 490m.

The survey with the Trimble GeoXH 6000 produced a summit height of 500.5m (converted to OSGM15) and a bwlch height of 482.4m (converted to OSGM15) with the summit height coming within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, or a previous estimated summit height based on interpolation of contours.  Also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised in favour of the 1:50,000 for detailing these revisions.

The summit of this hill is easily distinguishable and is positioned at the south-western end of a grassy ridge overlooking the Maen-offeren and Llechwedd quarries.

Therefore this hill’s new summit height is 500.5m (converted to OSGM15) which is 0.1m lower than the result produced by LIDAR data and 10.5m higher than the 490m uppermost ring contour on current Ordnance Survey maps.


The full details for the hill are:

Cardinal Hill:  Manod Mawr

Summit Height (New Height):  500.5m (converted to OSGM15)

Name:  Moel Bowydd

OS 1:50,000 map:  115

Summit Grid Reference:  SH 71272 47051
         
Drop:  18.1m (converted to OSGM15)


The Trimble GeoXH 6000 gathering data at the summit of Moel Bowydd (SH 712 470) which when coupled with the analysis of LIDAR data resulted in this hill's significant height revision




Myrddyn Phillips and Aled Williams (May 2017)





Mapping Mountains – Significant Height Revisions – Y Trichant


Moel Llaethbwlch (SJ 113 167)

This is the thirty eighth post under the heading of Significant Height Revisions, with the Trimble survey that resulted in this height revision being conducted on the 6th April 2017.

The thirty eighth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the Y Berwyn range of hills in the south-east part of North Wales, between the town of Llanfyllyn to the north-east and the village of Meifod to the south-east on a fine sunny day.

The summit of the hill is not on open access land so permission to visit should be sought, with the nearest public footpaths contouring round the hill’s northern lower slopes and also its lower southern slopes.

The name of the hill is Moel Llaethbwlch and the listing it is now a part of is named Y Trichant and these are the 300m height band of hills within the Twmpau (thirty welsh metre prominences and upward).  Prior to the survey with the Trimble GeoXH 6000 the height of the hill was estimated as c 370m based on the small uppermost 370m ring contour on Ordnance Survey maps, and to my knowledge no spot height has ever appeared on an Ordnance Survey map for this hill.

The 372.1m (converted to OSGM15) height produced by the Trimble is not a dramatic increase from the previously estimated summit height of c 370m, but it does come within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, or a previous estimated summit height based on interpolation of contours.  Also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised in favour of the 1:50,000 for detailing these revisions.

The summit of this hill is easily distinguishable and consists of closely cropped grass at the top of a field used for grazing.  Although the immediate summit area is relatively flat it is encircled by what looks like the remains of a small hill fort, although I have found no evidence to support this.

Therefore this hill’s new summit height is 372.1m (converted to OSGM15) which is 2.1m higher than its previously estimated height of c 370m and also 2.1m higher than its 370m uppermost ring contour on Ordnance Survey maps.


The full details for the hill are:

Cardinal Hill:  Moel y Fronllwyd

Summit Height (New Height):  372.1m (converted to OSGM15)

Name:  Moel Llaethbwlch

OS 1:50,000 map:  125

Summit Grid Reference:  SJ 11335 16724
          
Drop:  43.3m (converted to OSGM15)


The Trimble GeoXH 6000 gathering data at the summit of Moel Llaethbwlch (SH 113 167)  which resulted in this hill's significant height revision



Myrddyn Phillips (May 2017)






Mapping Mountains – Significant Height Revisions – Y Trechol and Y Pedwarau

Clepyn Melyn (SN 961 464)

This is the thirty seventh post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on the 28th December 2016.

The thirty seventh major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the hills of Mynydd Epynt in the south-easterly part of Mid and West Wales (Region B, Sub-Region B-2) on a beautiful winter’s morning with blue sky, frost and just a breath of breeze.  Large swathes of Mynydd Epynt is out of bounds for much of the year as it forms part of the Sennybridge Artillery Range Firing Area, and the hill range is positioned between those of Mynydd Du, Fforest Fawr, Bannau Brycheiniog (Brecon Beacons) and Mynyddoedd Duon (Black Mountains) to its south and the wilds of the Elenydd to its north.

The hill is situated just above the high point of the B 4519 as it climbs from the small community of Garth to the north toward the village of Upper Chapel to the south-east, the hill should only be ascended when it is appropriate to do so due to the presence of the military, otherwise it would be an easy ascent on a track from a car parking area near to the top of the road to the north-east of the summit.

The name of the hill is Clepyn Melyn and this was derived from local enquiry (see Significant Name Changes) and the survey conducted with the Trimble GeoXH 6000 was preceded with analysis of LIDAR data.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

Aled’s analysis of LIDAR data gives the hill the following details:


Clepyn Melyn

Summit Height:  475.5m

Summit Grid Reference:  SN 96120 46434

Prior to the analysis of LIDAR data and surveying the hill with the Trimble GeoXH 6000, Clepyn Melyn was listed as having a 478m summit height based on the spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, this height seems to be a relatively recent addition as no spot height is shown on any Ordnance Survey map examined prior to and including the historical 1:25,000 map.

Clepyn Melyn was surveyed with the Trimble GeoXH 6000 giving the hill the following details:


Summit Height:  475.7m (475.681m converted to OSGM15)

Summit Grid Reference:  SN 96124 46428


This is not a dramatic height revision when compared to some revised heights, but it does come within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised for detailing these revisions.

The summit of the hill consists of red grass that when last visited had been fenced with stakes and a single wire that is easy to either clamber under or as I found; over.  The ground hereabouts is mainly hidden by the length of the reed grass but the high point is accepted as being beside a small concrete pillar and this is where the Trimble was set up.  Therefore this hill’s new summit height as surveyed by the Trimble GeoXH 6000 is 475.7m (converted to OSGM15) which is 2.3m lower than its previously listed height of 478m which appears on the Ordnance Survey enlarged mapping on the Geograph website and the 1:50,000 Landranger and 1:25,000 Explorer maps.


The full details for the hill are:

Cardinal Hill:  Clepyn Melyn

Summit Height (New Height):  475.7m (converted to OSGM15)

Name:  Clepyn Melyn

OS 1:50,000 map:  147

Summit Grid Reference:  SN 96124 46428
  
Drop:  c 198


The Trimble GeoXH 6000 gathering data at the summit of Clepyn Melyn (SN 961 464) which resulted in this hill's significant height revision




Myrddyn Phillips and Aled Williams (January 2017)
 Mapping Mountains – Significant Height Revisions – Yr Uchafion 


Craig Gwaun Taf (SO 005 207)

This is the thirty sixth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on the 25th October 2016.

The thirty sixth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the hills of the Bannau Brycheiniog in the northern part of south Wales on a becalmed misty morning.  The Bannau Brycheiniog are referred to in English as the Brecon Beacons and are positioned between the hills of Mynydd Epynt to their north and the hills of the south Wales valleys to their south.

The hill is situated between the high cwm that holds the infant Blaen Taf Fechan to its east and the busy A 470 road to its west and is positioned above the towns of Aberhonddu (Brecon) to its north north-east and Merthyr Tudful (Merthyr Tydfil) to its south south-east, and the hill can be easily accessed from the car park at Pont ar Daf to its south south-west with the path leading toward the bwlch just north of its summit; Bwlch Duwynt, being on the Beacons Way and one of the main paths leading to the summit of south Wales’ highest mountain; Pen y Fan.

The name of the hill is Craig Gwaun Taf and the survey conducted with the Trimble GeoXH 6000 was instigated due to communication with Joe Nuttall, who had analysed this hill’s summit and bwlch height with LIDAR data.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales, and Joe has been diligently checking a number of hills for qualification to his parents 2,000ft list.  These lists are based on a minimum qualifying drop value of 15m and Joe found that LIDAR data gave Craig Gwaun Taf a drop of 15.783m.

However, if Craig Gwaun Taf has a minimum of 15m of drop it would also be included in the listing of Welsh hills at or over 500m in height that have a minimum of 15m of drop.  This list has the working title of Yr Uchafion and is co-authored with Aled Williams, and was detailed on the Mapping Mountains site on the 4th November 2015.

Craig Gwaun Taf is given an 824m summit spot height on current Ordnance Survey maps that derives from the 2,704ft height on the series of old Six-Inch maps and has current bwlch contouring between 800m – 810m, with an 815m spot height on the area of the bwlch on the Ordnance Survey enlarged mapping on the Geograph website.  These figures give this hill an approximate c 13m of drop based on interpolation of bwlch contours, or only 9m of drop if based on the 815m spot height.  However, when Joe Nuttall analysed this hill with LIDAR data he found that it gave the summit as 825.885m and the bwlch as 810.102m, giving a drop value of 15.783m, sufficient for both Uchaf and Nuttall qualification.

The 826.4m height produced by the Trimble is an average of three summit data sets and is 2.4m higher than the current Ordnance Survey map height of 824m, and therefore comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised in favour of the 1:50,000 for detailing these revisions.

The summit of this hill is easily identifiable and consists of ground at the top of a grassy hummock a few metres east of the ridge path, and therefore this hill’s new summit height as surveyed by the Trimble GeoXH 6000 is 826.4m which is 2.4m higher than the current map height of 824m which appears on the Ordnance Survey 1:50,000 Landranger and the 1:25,000 Explorer maps.


The full details for the hill are:

Cardinal Hill:  Pen y Fan

Summit Height (New Height):  826.4m (converted to OSGM15)

Name:  Craig Gwaun Taf

OS 1:50,000 map:  160

Summit Grid Reference:  SO 00548 20720   

Drop:  16.1m 



The Trimble GeoXH 6000 gathering data at the summit of Craig Gwaun Taf (SO 005 207) which resulted in this hill's significant height revision


Myrddyn Phillips and Aled Williams (November 2016)






Mapping Mountains – Significant Height Revisions – Y Trechol, Yr Uchafion and 600m Twmpau 


Mynydd yr Hewyrch (SH 816 150)

This is the thirty fifth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on the 2oth October 2016 in good, clear conditions.

The thirty fifth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the hills of the Bryniau Dyfi in the south-western part of north Wales during the late afternoon in the company of Alan Dawson, who had suggested the walk and also surveyed the hill with his Leica RX1250.  The Bryniau Dyfi are referred to in English as the Dovey Hills and are positioned between the Aran to their north and Cadair Idris to their west.

The hill is situated between the Afon Cerist and the A 470 road to its north and the conifer plantation of the Dyfi Fforest (Dovey Forest) to its south and is positioned above the small community of Dinas Mawddwy to its east, and the hill can be easily accessed from a lane leading to a path that heads for the summit via the escarpment edge above Craig Maesglase, or via the north-eastern ridge that heads straight for the summit of its adjacent top; Maen Du.

The name of the hill is Mynydd yr Hewyrch and prior to the survey with the Trimble GeoXH 6000 the height of the hill was listed as 676m based on the summit spot height on the Harvey 1:40,000 Britain Mountain Map.  However, the summit of Mynydd yr Hewyrch only has a 670m uppermost contour on current Ordnance Survey maps with the adjacent summit of Maen Du at SH 822 151 being given a 674m spot height, because of this the summit of Maen Du was previously listed as that for the hill, and the higher summit of Mynydd yr Hewyrch is therefore a recent addition and first noted by Tim Jones who reported that he believed this summit to be higher in to John and Anne Nuttall in 1996.

Three points were surveyed for summit position by the Trimble GeoXH 6000 and the Leica RX1250, each position being close in height and to ground consisting of moorland peat hags rising above a shapely large pool which is positioned on the summit area.

The 678.3m height produced by the Trimble is 2.3m higher than the previously listed height of 676m, which was based on the Harvey British Mountain Map spot height, and 8.3m higher than the uppermost contour on current Ordnance Survey maps and therefore comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised in favour of the 1:50,000 for detailing these revisions.

The summit of this hill is relatively easily distinguishable and consists of ground at the top of a moorland peat hag, and therefore this hill’s new summit height as surveyed by the Trimble GeoXH 6000 is 678.3m which is 2.3m higher than its previously listed height of 676m which appears on the Harvey 1:40,000 British Mountain Map and 8.3m higher than the uppermost 670m contour ring on Ordnance Survey maps.


The full details for the hill are:

Cardinal Hill:  Mynydd yr Hewyrch

Summit Height (New Height):  678.3m

Name:  Mynydd yr Hewyrch

OS 1:50,000 map:  124, 125

Summit Grid Reference:  SH 81697 15003 
  
Drop:  317.8m 



The Trimble GeoXH 6000 gathering data at one of the three positions surveyed atop Mynydd yr Hewyrch which resulted in this hill's significant height revision



Myrddyn Phillips and Aled Williams (November 2016)






Mapping Mountains – Significant Height Revisions – Yr Uchafion and 500m Twmpau 

This is the thirty fourth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on the 23rd July 2016 in good, clear conditions.

The thirty fourth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the hills of the Cymoedd in south Wales on a warm and sunny afternoon.  The Cymoedd are an extensive group of hills and comprise the area of the south Wales valleys.

The hill is situated between Cwm Ogwr Fawr to its west and the Rhondda Fawr valley to its east and is positioned above the towns of Treorci (Treorchy) and Treherbert to its north and Nant-y-moel, Price Town and Ogmore Vale to its south-west, and the hill can be easily accessed from a track that leaves the A 4061 near to its high point and continues south-eastward to the north-western edge of a large conifer plantation, a path continues gaining the access point to a wide forest break which is relatively near the summit of the hill.

The name of the hill is Mynydd Ton and prior to the survey with the Trimble GeoXH 6000 the height of the hill was listed as 539m at SS 94796 93958 which is beside an ancient cairn.  This height was based on a 1,769.3ft surface height given on the Ordnance Survey Six-Inch map published in 1885.  The 539m height was a relatively new addition to this hill’s listed height as its summit position was originally listed as ground beside its map heighted 535m triangulation pillar situated at SS 94931 94058.

The highest ground at the base of and beside the ancient cairn was surveyed with the Trimble GeoXH 6000 as being 534.2m high.  This data set was good with Estimated Accuracies of 5-15cm: 99.41%, a Standard Deviation of 0.0m and a margin of uncertainty for the height placement of the Trimble of 0.1m.

On my previous visit to this hill in February 2003 I judged ground approximately one minute away from the trig pillar to be slightly higher, and as the flush bracket adjoined to the trig pillar is given a height of 535.335m in the OS Trig Database it means that ground at its base is approximately 535m high.  This figure is dependent upon the accuracy of the flush bracket height which is given as 3rd order.   Therefore the ground at the base of or near to the triangulation pillar is likely to be higher than that beside the ancient cairn; this is dependent upon the accuracy of the flush bracket height and the Trimble survey.

The 534.2m height produced by the Trimble is 4.8m lower than the previously listed height of 539m, which was based on the 1,769.3ft surface height on the 1885 Ordnance Survey Six-Inch map and therefore comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised in favour of the 1:50,000 for detailing these revisions.

The summit of this hill is easily distinguishable and consists of ground at or near to the triangulation pillar, and therefore this hill’s new summit height is based on the 535m map height adjoined to the trig pillar, as the 534.2m result produced by the Trimble GeoXH 6000 is 4.8m lower than the hill’s previously listed height of 539m which appears as a 1,769.3ft imperial height on the Ordnance Survey Six-Inch map.


The full details for the hill are:

Cardinal Hill:  Werfa

Summit Height (New Height):  535m

Name:  Mynydd Ton

OS 1:50,000 map:  170

Summit Grid Reference:  SS 94931 94058 
Drop:  92m



The Trimble GeoXH 6000 gathering data beside the ancient cairn at the old summit position of Mynydd Ton which resulted in this hill's significant height revision



Myrddyn Phillips and Aled Williams (August 2016)






Mapping Mountains – Significant Height Revisions – Y Pedwarau 


Moelfre (SH 717 744)

This is the thirty third post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on the 14th July 2016 in clear albeit late evening conditions in the company of Aled Williams.

The thirty third major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the northern Carneddau in north-west Wales.  This hill range comprises some of the highest mountains in the country but the evening walk concentrated on some of its 300m and 400m lower hills.

The hill is positioned above the towns of Penmaenmawr which is to its north and Llanfairfechan which is to its west and it can be easily accessed from a green track that continues from the end of a minor lane to the hill’s west, or from its north-west where public footpaths and bridleways lead close to its summit.

The name of the hill is Moelfre and prior to the survey with the Trimble GeoXH 6000 the height of the hill was listed as 435m.  This height appears on the Ordnance Survey 1:25,000 Explorer and 1:50,000 Landranger maps and the Ordnance Survey enlarged map on the Geograph website.  This 435m height seems to be a recent addition as the series of Ordnance Survey Six-Inch maps from 1888 - 1946 have a 1,422ft (433.4m) height, whilst the Ordnance Survey Seventh Series One-Inch map and the Historical 1:25,000 map has 1,423ft (433.7m).

Moelfre was surveyed with the Trimble GeoXH as being 433.0m (converted to OSGM15) high.  This is not a dramatic height revision when compared to some revised heights, but it does come within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised for detailing these revisions.

The summit of the hill is easily distinguishable and consists of an ancient cairn that is now an oval mound, with the centre of the mound being slightly hollowed, and therefore this hill’s new summit height as surveyed by the Trimble GeoXH 6000 is 433.0m (converted to OSGM15) which is 2.0m lower than its previously listed height of 435m which appears on the Ordnance Survey enlarged mapping on the Geograph website and the 1:25,000 Explorer and 1:50,000 Landranger maps.


The full details for the hill are:

Cardinal Hill:  Tal y Fan

Summit Height:  433.0m (converted to OSGM15)

Name:  Moelfre

OS 1:50,000 map:  115

Summit Grid Reference:  SH 71733 74418

Drop:  18.3m


The Trimble GeoXH 6000 gathering data at the summit of Moelfre (SH 717 744) which resulted in this hill's significant height revision



Myrddyn Phillips and Aled Williams (August 2016)






Mapping Mountains – Significant Height Revisions – Y Pedwarau 



Clip yr Orsedd (SH 711 747) 

This is the thirty second post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on the 14th July 2016 in clear conditions during the evening in the company of Aled Williams.

The thirty second major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the northern Carneddau in north-west Wales.  This hill range comprises some of the highest mountains in the country but the evening walk concentrated on some of its lower hills.

The hill is positioned above the towns of Llanfaifechan which is to its west and Penmaenmawr which is to its north north-east and it can be easily accessed from a green track that continues from the end of a minor lane to the hill’s west.  An alternative route is via part of the Wales Coast Path, with both routes just bi-passing the summit to its south.

The name of the hill is Clip yr Orsedd and prior to the survey with the Trimble GeoXH 6000 the height of the hill was listed as 429m.  This height appears on the Ordnance Survey 1:25,000 Explorer map and the Ordnance Survey enlarged map on the Geograph website.

It was surveyed with the Trimble GeoXH as being 426.6m high.  This is not a dramatic height revision when compared to some revised heights, but it does come within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised for detailing these revisions.

The summit of the hill is easily distinguishable and consists of an outcrop of rock close to the ground and therefore this hill’s new summit height as surveyed by the Trimble GeoXH 6000 is 426.6m (converted to OSGM15) which is 2.4m lower than its previously listed height of 429m which appears on the Ordnance Survey enlarged mapping on the Geograph website and the 1:25,000 Explorer map.


The full details for the hill are:

Cardinal Hill:  Carnedd Llywelyn

Summit Height:  426.6m (converted to OSGM15)

Name:  Clip yr Orsedd

OS 1:50,000 map:  115

Summit Grid Reference:  SH 71185 74743

Drop:  39.5m


The Trimble GeoXH 6000 gathering data at the summit of Clip yr Orsedd (SH 711 747) which resulted in this hill's significant height revision



Myrddyn Phillips and Aled Williams (August 2016)






Mapping Mountains – Significant Height Revisions – Y Trichant  



Penmaen Mawr (SH 704 752)

This is the thirty first post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on the 14th July 2016 in good, clear conditions in the early evening, with the hill subsequently analysed with LIDAR data by Aled Williams and it is the latter result that is being detailed in this Significant Height Revisions post.

The thirty first major height revision initialised by a survey with the Trimble GeoXH 6000 was conducted in the hills of the northern Carneddau in the company of Aled Williams who had suggested the walk and researched what needed surveying.

The hill is positioned above and to the immediate south of the busy A 55 as it heads westward between the towns of Penmaenmawr and Llanfairfechan, which are situated to the hill’s east and west respectively.

The summit is a part of the hill named Penmaen Mawr and the extended hill has been quarried with its old 1,550ft (472m) map heighted summit now a distant memory as the whole inner section of the summit has been blown apart leaving two remaining tops with this post concentrating on the lower easterly summit.

The lower easterly summit is impressive as it forms a sheer rock face from its south and has steep slopes descending northward to the A 55 below. 

The summit area for the whole of Penmaen Mawr now appears on Ordnance Survey maps as a blank area with ‘Quarries’ written over it, and therefore is devoid of any continuous contour rings, which is the norm for quarried areas on Ordnance Survey maps, with the highest contour line being 350m for the area where the lower easterly peak is.

Therefore this hill’s new summit height is 385.8m (LIDAR data) which is 35.8m higher than its uppermost contour line on current Ordnance Survey maps and its drop is sufficient for it to be classified as a Trichant and 300m Twmpau (thirty welsh metre prominences and upward) hill.


The full details for the hill are:

Cardinal Hill:  Tal y Fan

Summit Height:  385.8m (LIDAR data)

Name:  Penmaen Mawr

OS 1:50,000 map:  115

Summit Grid Reference:  SH 70441 75241

Drop:  31.3m (LIDAR data)



Aled with Penmaen Mawr (SH 704 752) in the background

Myrddyn Phillips (July 2016)




Mapping Mountains – Significant Height Revisions – Y Pedwarau 



Penmaen Mawr (SH 698 755)

This is the thirtieth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on the 14th July 2016 in good, clear conditions.

The thirtieth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the northern Carneddau in the company of Aled Williams who had suggested the walk.

The hill is positioned above and to the immediate south of the busy A 55 as it heads westward between the towns of Penmaenmawr and Llanfairfechan, which are situated to the hill’s east and west respectively.

The hill is named Penmaen Mawr and its summit area has been quarried.  Before the first quarry opened in 1830 and the subsequent resulting expansion of operations the hill was substantially higher, with a 1,550ft (472m) map height given it on the Ordnance Survey Popular and New Popular One-Inch maps, with this height also appearing on the Ordnance Survey Six-Inch map published in 1888.

The quarrying of this hill has created two summits with a gaping hole between, the westerly summit is higher than the easterly, although the latter is more impressive due to a shear rock face leading up to its high point.  Both tops were Trimbled with the following results:


Penmaen Mawr:  390.4m (converted to OSGM15) at SH 69865 75523

Pt. 385m, Penmaen Mawr:  384.9m (converted to OSGM15) at SH 70200 75727


Over recent years the summit area of this hill has appeared without any uppermost contours as is the norm for quarried ground on Ordnance Survey maps, with the highest contour being 370m which appears on the upper western part of the hill.

Therefore this hill’s new summit height is 390.4m (converted to OSGM15) which is 20.4m higher than its uppermost contour on current Ordnance Survey maps.


The full details for the hill are:

Cardinal Hill:  Carnedd Llywelyn

Summit Height:  390.4m (converted to OSGM15)

Name:  Penmaen Mawr

OS 1:50,000 map:  115

Summit Grid Reference:  SH 69865 75523

Drop:  26.9m


The Trimble GeoXH 6000 gathering data 0.39m above the summit of Penmaen Mawr (SH 698 755) which resulted in this hill's significant height revision



Myrddyn Phillips and Aled Williams (July 2016)






Mapping Mountains – Significant Height Revisions – Y Pellennig and 30m-99m Twmpau


Emsger (SM 651 226)

This is the twenty ninth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on the 14th May 2016 in good, bright conditions, perched beside a lighthouse on one of the most remote places in the whole of Wales.

The twenty ninth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted on an island off the western Pembrokeshire coast that forms a part of the Bishops and Clerks chain of islands.  These islands form compact groups of islets; all are rocky and are aligned northward to southward with North Bishop, Carreg Rhoson, Daufraich and Emsger being the main named island in each small group. 

The hill is positioned on the island known as Emsger, which is also commonly known as South Bishop.  This island is positioned an approximate 8km (5 miles) west of St David’s Head in Pembrokeshire, and unless being a competent and enthusiastic seal, it can only be approached by boat.

The island is predominantly rock and if not for a series of steps leading up toward its summit its ascent would no doubt prove more problematic.  The upper part of Emsger has a lighthouse on it; this was built in 1839, and was converted to operating by electric in 1959, and demanned and automated in 1983.

The upper part of the island now has the lighthouse and associated buildings and platforms built on it, and therefore what once constituted the natural summit of the island is either buried under the lighthouse / platforms or it was destroyed during construction of the lighthouse.

I visited with Adrian Rayner, Ayako, Rob Woodall, Jon Glew, Sheila Glew, Sarah Kerr and Bob Kerr, and a quick assessment of what is left of natural ground pinpointed the highest point to be situated just to the south-west of the main southerly corner of the lighthouse and its grounds.  This position was adjacent to steps leading down to the island’s helipad.

The only height available of current Ordnance Survey maps is a 37m spot height with the spot positioned on the south-east part of the grounds of the lighthouse.  This is on a part of the construction and is man-made; however natural ground exists close to this point but is significantly lower when compared to where Trimble data was gathered from.

Therefore this island’s new summit height is 33.8m which is 3.2m lower than its previously listed height of 37m which appears as a spot height on current Ordnance Survey maps.


The full details for the hill are:

Cardinal Island:  Bishops and Clerks

Summit Height:  33.8m

Name:  Emsger

OS 1:50,000 map:  157

Summit Grid Reference:  SM 65116 22619

Drop:  33.8m



The Trimble GeoXH 6000 gathering data 0.99m above the highest remaining natural ground at the summit of Emsger, otherwise known as South Bishop (SM 651 226) which resulted in this island's significant height revision


Myrddyn Phillips and Aled Williams (May 2016)





Mapping Mountains – Significant Height Revisions – Y Pedwarau



Craig y Garreg Lwyd (SH 730 427)  

This is the twenty eighth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on the 14th March 2016 in good, bright conditions, albeit with a chilling easterly breeze blowing.

The twenty eighth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the compact group of hills between the Moelwynion to the west and the wilds of Y Migneint to the east, and which is situated in north-west Wales.

The hill is positioned above and to the north-west of Llyn Morwynion and can easily be accessed from a number of tracks that lead in from its south, south-west and south-east, with each track starting from the B 4391 road as it makes its way eastward from Llan Ffestiniog toward its connection with the A 4212.  The hill is positioned to the south-east of Blaenau Ffestioniog and to the east of Llan Ffestiniog.

The hill is named Craig y Garreg Lwyd and appears on the Ordnance Survey enlarged map on the Geograph website with a 478m spot height at its summit.  As the 473.4m (converted to OSGM15) Trimble result was significantly lower than this spot height I checked all available Six-Inch maps on the National Library of Scotland website, the Historical Ordnance Survey maps available on the Sabre Maps website and the Ordnance Survey Vector mapping and could find no evidence of a previous imperial height or another current metric height for this hill.  Therefore, it seems that the 478m spot height is the only height adjoined to the summit of this hill on publicly available maps.

Therefore this hill’s new summit height is 473.4m (converted to OSGM15) which is 4.6m lower than its previously listed height of 478m which appears on the Ordnance Survey enlarged mapping on the Geograph website.


The full details for the hill are:

Cardinal Hill:  Graig Goch

Summit Height:  473.4m (converted to OSGM15)

Name:  Craig y Garreg Lwyd

OS 1:50,000 map:  124

Summit Grid Reference:  SH 73044 42742

Drop:  29.9m


Gathering data 0.82m above the summit of Craig y Garreg Lwyd (SH 730 427) which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips and Aled Williams (March 2016)






Mapping Mountains – Significant Height Revisions – Y Pedwarau



Pt. 483.6m (SH 735 428)

This is the twenty seventh post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on 14th March 2016.

The twenty seventh major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the hills between the Moelwynion and the Migneint in north-west Wales, on a beautiful sunny, albeit chilly, early spring day.

The hill is situated above and to the north-west of Llyn Morwynion and can easily be accessed from a track leading to this lake from the B 4391 as it makes its way eastward from Llan Ffestiniog toward its connection with the A 4212.  The hill is positioned to the south-east of Blaenau Ffestioniog and to the east of Llan Ffestiniog.

The hill is not named on Ordnance Survey maps, although it appears next to the small mountain lake of Llyn y Drum, because of this its name currently follows the point (Pt.) notation; Pt. 483.6m.

When the Y Pedwarau was re-evaluated for Europeaklist publication this hill was listed with a summit height of 486m and its summit position given as the furthest north of four small 480m contour rings that appear on Ordnance Survey maps.  The high point of this contour ring is at SH 73542 42903 and the 486m height taken from a spot height on the Harvey 1:40,000 British Mountain Map to Eryri/Snowdonia.  The position of the listed summit of this hill was moved to SH 73541 42812 upon a visual inspection by Aled Williams.  This was later confirmed by a Trimble survey with the heights for these two points appearing below:


486m Harvey spot height at SH 73542 42903    Trimbled as 482.686m (converted to OSGM15)

480m OS ring contour at SH 73541 42812    Trimbled as 483.574m (converted to OSGM15)


Therefore this hill’s new summit height is 483.6m (converted to OSGM15) which is 2.4m lower than its previously listed height of 486m and 3.6m higher than the uppermost 480m ring contour that appears on current Ordnance Survey 1:25,000 maps.


The full details for the hill are:

Cardinal Hill:  Graig Goch

Summit Height:  483.6m (converted to OSGM15)

Name:  Pt. 483.6m

OS 1:50,000 map:  124

Summit Grid Reference:  SH 73541 42812

Drop:  34.4m


Gathering data from the summit of Pt. 483.6m which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips and Aled Williams (March 2016)





Mapping Mountains – Significant Height Revisions – Y Pedwarau



Cwm Cynydd Bank (SO 061 726)


This is the twenty sixth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on 18th February 2016.

The resulting significant height revision was conducted in the hills of the Pegwn Mawr range in mid Wales, during a walk taking in one 300m Twmpau and three Pedwarau, with some of these hills immersed in part of the conifer plantation that takes in land to the north of Abaty Cwm Hir (Abbey Cwmhir).

The hill is situated in this woodland, but can be accessed from open hillside and forest tracks to within a few metres of its summit which is positioned in mature conifer plantation and situated just to the north of a broad path.  The hill is situated to the north of the small community of Abaty Cwm Hir (Abbey Cwmhir) and to the south-east of the small community of Bwlch y Sarnau.

The name of the hill is Cwm Cynydd Bank and prior to the Trimble survey it was listed as a Pedwar with its summit height of 450m taken from the Ordnance Survey 1:50,000 map.  This height equates to the old imperial height of 1,477ft that is given on the Ordnance Survey 1:25,000 Historical Map which originates from the series of Ordnance Survey old Six-Inch maps.  This height appears near to or on the broad path that gives access to this hill’s summit and which traverses its broad north-east to south-west ridge.

When surveying this summit I waited a long time for the accuracy level of the Trimble to attain its 0.1m before data should be logged, during this time I assessed the lay of land around the summit and tried to keep warm.  I estimated the summit of the hill to be at least 3m higher than the path where the centralised imperial height appears on the old Six-Inch map. 

Therefore this hill’s new summit height is 454.9 (converted to OSGM15) which is 4.9m higher than its previously listed height of 450m and 14.9m higher than the uppermost 440m ring contour that appears on current Ordnance Survey 1:25,000 maps.



The full details for the hill are:


Cardinal Hill:  Brondre-fawr Hill

Summit Height:  454.9m (converted to OSGM15)

Name:  Cwm Cynydd Bank

OS 1:50,000 map:  136, 147

Summit Grid Reference:  SO 061 726

Drop:  83.9m (converted to OSGM15)


Gathering data from the summit of Cwm Cynydd Bank (SO 061 727)

For details on the survey of this hill please click {here}


Myrddyn Phillips and Aled Williams (February 2016)






Mapping Mountains – Significant Height Revisions – 100m Twmpau



Bryn Maelgwyn (SH 795 805)

This is the twenty fifth post under the heading of Significant Height Revisions, with the Trimble survey that resulted in this height revision being conducted on the 16th January 2016.

The twenty fifth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the north-western part of the Rhos range of hills that is connected to Gogarth (Great Orme), above the town of Llandudno.

The hill was surveyed in the company of Alex Cameron during a grey and damp day when we visited five P30 Twmpau hills over four separate small walks, with each summit being Trimbled.

The hill is listed in the 100m Twmpau (thirty welsh metre prominences and upward) list, and it has a 105m uppermost contour ring on the Ordnance Survey enlarged map on the Geograph website, which has contour intervals at 5m.  The hill has been listed with an estimated height of c 106m based on the dimensions of the uppermost contour in relation to the steepness of the surrounding ground.

The hill can be accessed from its south where a public footpath enters the Coed y Gell woodland.  However, to reach the summit one has to leave this footpath and the going thereafter becomes rougher with brambles and bracken creating a tangled web of undergrowth.  When I visited with Alex the underfoot conditions were never difficult and as the deciduous trees are growing relatively far apart from one another there are sufficient gaps in between to make good progress toward the summit.

The name of the hill is Bryn Maelgwyn and prior to the survey with the Trimble GeoXH 6000 the height of the hill was estimated as being c 106m based on 5m contour intervals on the Ordnance Survey enlarged map on the Geograph website, and to my knowledge no spot height has ever appeared on an Ordnance Survey map for this hill.

Therefore this hill’s new summit height is 102.1m (converted to OSGM15) which is 3.9m lower than its previously estimated height of c 106m and 2.9m lower than its uppermost ring contour on the Ordnance Survey enlarged map on the Geograph website.


The full details for the hill are:

Cardinal Hill:  Gogarth 

Summit Height (New Height):  102.1m (converted to OSGM15)

Name:  Bryn Maelgwyn

OS 1:50,000 map:  115

Summit Grid Reference:  SH 79580 80540 
         
Drop:  c 39


Gathering data from the summit of Bryn Maelgwyn which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (January 2016)






Mapping Mountains – Significant Height Revisions – 100m Twmpau


The Pimple (SJ 299 472)  

This is the twenty fourth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on the 2oth October 2015.

The twenty fourth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the eastern part of the Bryniau Clwyd range of hills, above the small community of Pentre Bychan which is adjacent to the larger community of Rhosllanerchrugog.

The hill is now listed in the Sub category of the 100m Twmpau (thirty welsh metre prominences and upward) list, as prior to the survey with the Trimble GeoXH 6000 it had not been listed in the Sub list adjoined to the original Welsh P30 lists published on Geoff Crowder’s v-g.me website.

The hill can be accessed from its west where a public footpath traverses the course of the valley where its bwlch is positioned.  However, permission should be sought for those wishing to visit as the summit is not on open access land.  When I visited I asked permission to do so and was kindly directed to the best ascent route.

The name of the hill is The Pimple; this is a locally known name and was found when I made enquiries during the survey for its bwlch position.  The hill remains unnamed on current Ordnance Survey maps and its locally known name relates directly to the past industrial heritage of the hill, as its summit is made of mining waste that is now stabilised and grassed over.  The uppermost part of the summit is relatively small in area and squat in shape, and resembles a pimple as it sits upon another elevated part of the hill.

Prior to the survey with the Trimble GeoXH 6000 this hill was not classified but its summit position was indicated to be at SJ 30075 47320, this is where a 154m spot height appears on current Ordnance Survey 1:25,000 maps, with a 23m difference in height compared to the current Ordnance Survey 1:50,000 spot height which is given as 131m.   This spot height is positioned in a field which had been ploughed and probably seeded when I visited.  However there is also high ground to the south-west of where the 154m spot height appears on the ground and each respective point was surveyed, with the following results:

                                                                                                                                 
South-western high point (The Pimple):  153.5m (converted to OSGM15) at SJ 29984 47262

North-eastern high point (154m spot height in field):  153.1m (converted to OSGM15) at SJ 30071 47279


The 153.5m (converted to OSGM15) summit height is not a dramatic height revision when compared to the 154m spot height, but the new summit position does not possess any ring contours on current Ordnance Survey maps and therefore meets the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised for detailing these revisions.

Although this hill’s new summit height of 153.5m (converted to OSGM15) is only 0.5m different from the spot height that appears on the 1:25,000 map, the hill’s summit position has now been established and this is 8.5m higher than the 145m contour ring shown on the 1:25,000 map at this point.


The full details for the hill are:

Cardinal Hill:  Moel y Gamelin

Summit Height (New Height):  153.5m (converted to OSGM15)

Name:  The Pimple

OS 1:50,000 map:  117

Summit Grid Reference:  SJ 29984 47262
          
Drop:  25.2m


Gathering data from the summit of The Pimple which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (October 2015)






Mapping Mountains – Significant Height Revisions – 100m Twmpau



Bersham Bank (SJ 311 481) 

This is the twenty third post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on the 13th October 2015.

The twenty third major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the easterly lower hills of the Bryniau Clwyd range, with the hill situated on the southern outskirts of Rhostyllen, which is a south-western suburb of Wrecsam (Wrexham).

The hill had no classification prior to the survey with the Trimble as although it is prominent and rises almost directly above the A 483; it possesses no contour rings on current Ordnance Survey maps, except for those at its bwlch.

There is a circuitous path on the southern and eastern middle section of the hill; this can be accessed from a road to its east that is adjacent to an industrial estate.  Beside the road is a perimeter fence seemingly barring entrance to a path on the lower slopes of the hill, however, one section of the six foot high fence has been toppled over giving access to the public, including local people, who I was told occasionally walk up the hill.

The name of the hill is Bersham Bank and its summit is positioned at SJ 311 481.  This is the preferred locally known name for the hill and was given me when I made enquiries after my ascent.  There is no name for the hill on current Ordnance Survey maps but ‘Colliery (disused)’ appears on the map where the hill is situated.  As the Ordnance Survey detail implies, this hill is the relic of coal waste which was deposited from the workings of the Bersham Colliery which closed its operations in December 1986.

Although this hill does not possess any ring contours on current mapping, there are two hills created from coal waste that are relatively near to Bersham Bank that do possess separate ring contours, these are situated at SJ 311 469 and SJ 300 473.  The bwlch contouring for Bersham Bank is between 100m – 105m, with the height of the bwlch estimated as being c 103m. 

Therefore this hill’s new summit height is 153.6m (converted to OSGM15), as no summit contours exist for this hill this is a dramatic 48.6m increase in height compared to its uppermost hill to hill bwlch contour of 105m.


The full details for the hill are:

Cardinal Hill:  Moel y Gamelin

Summit Height (New Height):  153.6m (converted to OSGM15)

Name:  Bersham Bank

OS 1:50,000 map:  117

Summit Grid Reference:  SJ 31159 48116
   
Drop:  c 51m


Gathering data from the summit of Bersham Bank which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (October 2015)






Mapping Mountains – Significant Height Revisions – Y Pedwarau


Cerrig y Gordref (SH 929 428)

This is the twenty second post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on the 2nd October 2015.

The twenty second major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the Arennig hills between Y Bala to the south and Cerrigydrudion to the north north-east.  The hill was surveyed in the company of Aled Williams who had suggested the walk.

The hill is listed in the Y Pedwarau (Europeaklist May 2013) as a 400m Sub-Pedwar with 28m of drop based on the 497m spot height that appears on Ordnance Survey maps at SH 93066 42836 and the 469m spot height at the bwlch that is positioned at SH 93210 42714.  However, the summit area of the hill also has a 495m spot height at SH 92974 42817 that appears on the Ordnance Survey enlarged mapping on the Geograph website.

The hill can be combined with its neighbours of Y Gesail and Garnedd Fawr but the best way to take the hill in is during an extended two car walk, giving the opportunity to visit many of the hills that are situated close to Foel Goch, which is the highest point in this compact group of hills.

The name of the hill is Cerrig y Gordref and prior to the survey with the Trimble GeoXH 6000 the height of the hill was listed as 497m.  The high point of the land where the 497m and the 495m spot heights appear on the ground were each surveyed with the Trimble GeoXH 6000 with the following results:


497m spot height:  490.8m (converted to OSGM15) at SH 93066 42834

495m spot height:  494.6m (converted to OSGM15) at SH 92971 42820


The actual height of the land where the 497m spot height is positioned is significantly lower than the current map suggests, and this is probably a typo on the part of the Ordnance Survey.  Although the actual height of the land where the 495m spot height is positioned is only 0.4m different to the map height, there is a significant height difference when compared to this hill’s previously listed summit height.

Therefore this hill’s new summit height is 494.6m (converted to OSGM15) which is 2.4m lower than its previously listed height of 497m which was based on the current Ordnance Survey spot height which is probably a typo as the land at this point is only 490.8m high.


The full details for the hill are:

Cardinal Hill:  Foel Goch

Summit Height (New Height):  494.6m (converted to OSGM15)

Name:  Cerrig y Gordref

OS 1:50,000 map:  125

Summit Grid Reference:  SH 92971 42820 
     
Drop:  26.0


Gathering data from the summit of Cerrig y Gordref which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips and Aled Williams (October 2015)





Mapping Mountains – Significant Height Revisions – 300m Twmpau


Cefn Llwydallt (SO 074 409)

This is the twenty first post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on the 29th September 2015.

The twenty first major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the south-eastern lands of Mynydd Epynt, above the small communities of Erwyd (Erwood) to the north-east, Capel Uchaf (Upper Chapel) to the west and Llaneglwys to the south-west.

The hill was surveyed in the afternoon toward the end of a ridge walk that took in a number of hills from Cefn Clawdd (SO 043 403) eastward.

The hill is listed as a 300m Twmpau (thirty welsh metre prominences and upward) and prior to the survey with the Trimble it was listed as being 378m high based on the old 1,240ft (378.0m) imperial height given the hill on the Ordnance Survey Six Inch map.

Access to the hill is easy as the summit is situated on open access land and there is a minor road to the north-west next to where the bwlch for the hill is positioned.  Alternate routes to the summit can use public footpaths from the north-east, east and south that head toward the open access land.  The high point of the hill is positioned amongst small gorse bushes and is easily found.

The name of the hill is Cefn Llwydallt and prior to the survey with the Trimble GeoXH 6000 the height of the hill was listed as 378m.  It was surveyed with the Trimble GeoXH as being 380.7m (converted to OSGM15) high.  This is not a dramatic height revision when compared to its old listed height, but it does come within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised for detailing these revisions.

Therefore this hill’s new summit height is 380.7m (converted to OSGM15) which is 2.7m higher than its previously listed height of 378m which was based on the old imperial Six Inch map height of 1,240ft.


The full details for the hill are:

Cardinal Hill:  Clepyn Melyn

Summit Height (New Height):  380.7m (converted to OSGM15)

Name:  Cefn Llwydallt

OS 1:50,000 map:  147, 160

Summit Grid Reference:  SO 07422 40950
  
Drop:  41.0m


Gathering data from the summit of Cefn Llwydallt which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (September 2015)





Mapping Mountains – Significant Height Revisions – Y Pellennig


Ynys Arw (SH 266 945) 

This is the twentieth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on the 13th September 2015.

The twentieth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted on one of the islands that make up Ynysoedd y Moelrhoniaid, these islands are positioned to the north-west of Ynys Mon, and the islands name is Ynys Arw.

Ynys Arw (SH 266 945) is the most south-westerly island of this archipelago and has two high points, with the more southerly of these being the highest.  This island is tidal and is connected to its higher neighbour at high tide, the higher island is where The Skerries Lighthouse is situated and is the highest point of the archipelago and is also listed as a Pellennig hill.

This hill’s survey was suggested by Rob Woodall and it was conducted in the late afternoon.  In all twelve of us visited Ynysoedd y Moelrhoniaid, we went over to the island by Rib using a company named RibRide who are based at the Holyhead Marina during the summer months, and the trip cost £35.00 per person.

The summit of Ynys Arw is easily accessed at low tide from the Lighthouse, although hands on rock are required to get down to the wet land between the higher island; Ynysoedd y Moelrhoniaid, and Ynys Arw.  This connecting land is cut off from the higher island at high tide.  The ascent from the connecting land is initially over wet rock and then grass which has a multitude of burrowed Tern nests excavated into it.

The island of Ynys Arw was not classified in any list prior to the survey with the Trimble as it is given an uppermost contour of only 10m on current Ordnance Survey maps.  It was surveyed with the Trimble GeoXH 6000 at being 15.2m (converted to OSGM15) high, and as the criteria for qualification to the Pellennig list is a hill whose summit is a minimum of 2.5 km from the nearest paved public road and which has a minimum drop of 15m, this hill easily qualifies on the distance criterion and now meets the necessary minimum drop criterion to become the latest entry to the Pellennig list.

The 15.2m (converted to OSGM15) height produced by the Trimble is not a dramatic height revision when compared to an estimated c 12m height for this island’s summit based on contour interpolation taken from its uppermost 10m map ring contour, but as the contours on the Ordnance Survey map are at 5m intervals it does come within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised for detailing these revisions.

Therefore this hill’s new summit height is 15.2m (converted to OSGM15) which is 3.2m higher than its previously estimated height and 5.2m higher than its uppermost ring contour on current Ordnance Survey maps.

The full details for the hill are:

Cardinal Island:  Ynysoedd y Moelrhoniaid

Summit Height (new height):  15.2m (converted to OSGM15)

Name:  Ynys Arw

OS 1:50,000 map:  114

Summit Grid Reference:  SH 26647 94598

Drop:  15.2m


Gathering data from the summit of Ynys Arw which resulted in this island's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips and Aled Williams (September 2015)






Mapping Mountains – Significant Height Revisions – 200m Twmpau


Winllan Hill (SJ 217 214)  

This is the nineteenth post under the heading of Significant Height Revisions, and the  Trimble survey that resulted in this height revision was conducted over two days; 28th / 29th August 2015.

The nineteenth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the lower easterly hills of Y Berwyn, above Llansanffraid-ym-Mechain which is situated beside where the Afon Cain flows in to the Afon Efyrnwy (River Vyrnwy).

The hill was surveyed in the late evening in the company of Mark Trengove after nourishing our appetite in the Bradford Arms in Llanymynech.

The hill is listed as a 200m Twmpau (thirty welsh metre prominences and upward) as prior to the survey with the Trimble it was listed as 216m high based on the spot height on the area of the summit on current Ordnance Survey maps, and an estimated drop value of c 48m, based on bwlch contour interpolation which gives the height of the bwlch as c 168m.

Access to the hill is good as public footpaths from the south, west, north and east head towards its summit and parking is easily found when approaching the hill from the west and north, this is also likely to be the case if approaching the hill from the east and south.  The high point of the hill is beside a fence and under a large overhanging tree, and is only a few metres from where a public footpath crosses the field that it is situated in.

The name of the hill is Winllan Hill and prior to the survey with the Trimble GeoXH 6000 the height of the hill was taken as 216m, after the spot height that appears on current Ordnance Survey maps, however there is significantly higher land to the north of where this spot height appears on the ground.

Therefore this hill’s new summit height is 220.3m (converted to OSGM15) which is 4.3m higher than its previously listed height of 216m which was based on the current Ordnance Survey spot height.


The full details for the hill are:

Cardinal Hill:  Rhialgwm

Summit Height (New Height):  220.3m (converted to OSGM15)

Name:  Winllan Hill

OS 1:50,000 map:  126

Summit Grid Reference:  SJ 21709 21460 
 
Drop:  c 52m


Gathering data from the summit of Winllan Hill which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (August 2015)






 Mapping Mountains – Significant Height Revisions – Y Pedwarau


Bryn Serth (SO 147 109)  

This is the eighteenth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on 12th August 2015.

The eighteenth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the hills of the Cymoedd in south Wales, during a walk in the company of Mark Trengove who had suggested the survey.

The hill is situated on the northern outskirts of Tredegar at the head of the Cwm Sirhywi (Sirhowey Valley) and it can be easily accessed from a car park beside the busy A4047 which is positioned south-east of the summit.  This car park also gives access to the Aneurin Bevan Memorial Stones; these consist of four monoliths and are set against the landscape of Ebbw Vale, Tredegar and Rhymney which form the constituencies which Aneurin Bevan represented during his years in Westminster.

The name of the hill is Bryn Serth and until the Trimble survey it was listed as a Pedwar with its summit height estimated as c 410m based on a small uppermost 410m ring contour that appears on current Ordnance Survey maps.  However, this point is not the high point of the hill as land approximately 100 metres further north was surveyed by the Trimble as being 2.0m higher than the position where the uppermost contour ring appears on the ground.

The two points surveyed with the Trimble GeoXH 6000 gave results that are significantly lower than current Ordnance Survey map data, these results are:


Northern summit:  403.927m (converted to OSGM15) at SO 14794 10908

Southern summit:  401.890m (converted to OSGM15) at SO 14782 10809


It is the southern summit where the small 410m ring contour appears on current Ordnance Survey maps.

Since processing the data sets from this survey Aled has scrutinised on-line mapping and found that the Ordnance Survey Six Inch map has a 1,327ft (404.47m) height on the area of the summit and a 1,242.5ft (378.71m) height on the area of the bwlch.  These Six Inch map values give Bryn Serth a drop of 25.76m which is comparable to the Trimble result.

Therefore using the Trimble result this hill’s new summit height is 403.9m (converted to OSGM15) which is 6.1m lower than its previously estimated height of c 410m and 6.1m lower than its uppermost ring contour on current Ordnance Survey maps.


The full details for the hill are:

Cardinal Hill:  Cefn Manmoel

Summit Height (New Height):  403.9m (converted to OSGM15)

Name:  Bryn Serth

OS 1:50,000 map:  161

Summit Grid Reference:  SO 147 109

Drop:  25.4m


Gathering data from the summit of Bryn Serth which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips and Aled Williams (August 2015)





Mapping Mountains – Significant Height Revisions – 100m Twmpau


Bryn Mawr (SJ 251 190)

This is the seventeenth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on 8th August 2015.

The seventeenth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the lower hills of the Carnedd Wen range, above the small community of Four Crosses which is situated beside the Afon Efyrnwy (River Vyrnwy) and part of the Montgomeryshire Canal.

The hill was surveyed in the company of Alex Cameron during a multi hill bagging day when the weather was set fine and we visited nine P30 Twmpau hills with seven of them being Trimbled.

The hill is listed as a 100m Twmpau (thirty welsh metre prominences and upward) and it has a 170m uppermost contour ring on current Ordnance Survey maps which have contour intervals at 5m.  The hill has been listed with an estimated height of c 174m based on the dimensions of the uppermost contour in relation to the steepness of the surrounding ground.

Access to the hill is good from west of its summit, as there is sufficient parking close to a gate that accesses a field to another gate which leads on to the hill.  However, the upper section is overgrown and the ancient earthen embankments of its hill fort are now immersed in long grass, nettles and brambles.  The summit is easily identified and the hill is recommended as there is a peaceful ambiance to it.

The name of the hill is Bryn Mawr and prior to the survey with the Trimble GeoXH 6000 the height of the hill was estimated as being c 174m based on 5m contour intervals on current Ordnance Survey maps, and to my knowledge no height has ever appeared on an Ordnance Survey map for this hill.

Therefore this hill’s new summit height is 178.1m (converted to OSGM15) which is 4.1m higher than its previously estimated height of c 174m and 8.1m higher than its uppermost ring contour on current Ordnance Survey maps.


The full details for the hill are:

Cardinal Hill:  Carnedd Wen

Summit Height (New Height):  178.1m (converted to OSGM15)

Name:  Bryn Mawr

OS 1:50,000 map:  126

Summit Grid Reference:  SJ 25117 19054 
 
Drop:  90m


Gathering data from the summit of Bryn Mawr which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (August 2015)






Mapping Mountains – Significant Height Revisions – 100m Twmpau


Y Gaer (SJ 204 155)  

This is the sixteenth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on 8th August 2015.

The sixteenth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the lower hills of the Carnedd Wen range, above the small community of Trefnanney which is situated beside the Afon Efyrnwy (River Vyrnwy) and the Dyffryn Meifod.

The hill was surveyed in the company of Alex Cameron during a multi hill bagging day when we had glorious weather and visited nine P30 Twmpau hills with seven of them being Trimbled.

The hill is listed as a 100m Twmpau (thirty welsh metre prominences and upward) and it has two uppermost 125m ring contours, these are bisected by the lane that follows this hill’s summit ridge in a south-west to north-east direction.  It is from the top of this narrow lane that easy access to the high point of the hill can be found.

The larger of the two uppermost contour rings is the one to the west and this is where the remains of the ancient earthen embankment that formed part of the old hill fort is indicated to be on current Ordnance Survey maps.  It is this ancient hill fort that gives the hill its name.

The name of the hill is Y Gaer and prior to the survey with the Trimble GeoXH 6000 the height of the hill was estimated as being c 129m based on the dimension of the uppermost westerly 125m contour ring against the steepness of ground as indicated by contours on this hill’s northern, western and southern slopes.

However, the summit of this hill now possesses a covered reservoir which is indicated as a small round circle on Ordnance Survey maps, and as the day when this hill was visited consisted of many walks the lay of land was quickly judged and the Trimble placed at a point that may have been on part of the ground that constitutes that of the covered reservoir.  If the hill is visited again the land will be re-assessed, but until then the height and position of the summit is being taken as that produced by the Trimble.  A second visit would also give chance to survey the highest point of the easterly contour, will have to see if the thought of a re-visit enthuses me this upcoming winter.

The 130.5m (converted to OSGM15) height produced by the Trimble is not a dramatic height revision when compared to this hill’s previously listed height of c 229m, but as the contours on the Ordnance Survey map are at 5m intervals it does come within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised for detailing these revisions.

Therefore this hill’s new summit height is 130.5m (converted to OSGM15) which is 1.5m higher than its previously estimated height and 5.5m higher than its uppermost ring contour on current Ordnance Survey maps.


The full details for the hill are:

Cardinal Hill:  Carnedd Wen

Summit Height (New Height):  130.5m (converted to OSGM15)

Name:  Y Gaer

OS 1:50,000 map:  126

Summit Grid Reference:  SJ 20413 15563 
 
Drop:  c 39m


Gathering data from the summit of Y Gaer which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (August 2015)





Mapping Mountains – Significant Height Revisions – Yr Uchafion and 600m Sub-Twmpau


Crib y Rhiw (SH 663 248)

This is the fifteenth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on 4th June 2015.

The fifteenth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the hills of the Rhinogydd in the west of North Wales on a warm and sunny day in the company of John Barnard and Graham Jackson, although they were not present during the accrual survey as John was inspecting the northerly top of this hill and Graham remained at the southerly connecting bwlch with our Leica GS15 that was gathering data to determine the drop value of Diffwys (SH 661 234).

The hill is relatively remote for Wales but it can be accessed during a traverse of the southern Rhinogydd ridge, either from Cwm Nantcol to the west or from the end of the paved road to the south which is above the small community of Bontddu.

The name of the hill is Crib y Rhiw and the height given the hill on current Ordnance Survey maps is c 670m, with the height resulting from the survey with the Trimble being 681.3m (converted to OSGM15).  This hill has a northerly top that has a 2,228ft (679.1m) height given it on the Ordnance Survey Six Inch Map, and its previously listed height in the 600m Twmpau list was c 680m based on the estimated height difference between this Six Inch Map height and its position on the northerly top and the high point of the hill which is positioned on the southerly top.

The 681.3m (converted to OSGM15) height produced by the Trimble is not a dramatic height revision when compared to this hill’s previously listed height of c 680m, but it does come within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised for detailing these revisions.

Therefore this hill’s new summit height is 681.3m (converted to OSGM15) which is 1.3m higher than its previously estimated height and 10.3m higher than its uppermost ring contour on current Ordnance Survey maps.



The full details for the hill are:

Cardinal Hill:  Y Llethr

Summit Height (New Height):  681.3m (converted to OSGM15)

Name:  Crib y Rhiw

OS 1:50,000 map:  124

Summit Grid Reference:  SH 66368 24868 
 
Drop:  c 28m


Gathering data from the summit of Crib y Rhiw which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips and Aled Williams (June 2014)





Mapping Mountains – Significant Height Revisions – Tumps


Caus Castle (SJ 337 077)

This is the fourteenth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on 21st April 2015.

The fourteenth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in part of the Shropshire hills that are adjoined to the Corndon range on a sunny and warm day in April in the company of Charlie Leventon, who had suggested the walk.

The hill is currently listed as a Tump and therefore the updating of this list with this result is the prerogative of the respective hill list author.  The hill is currently listed with a 223m summit height and a 181m col height, with these values giving the hill a drop of 42m.  This Tump summit height is based on the 223m spot height that appears at SJ 33772 07836 on the Ordnance Survey 1:25,000 map as well as the Ordnance Survey enlarged map on the Geograph website.  However, higher ground exists to the south-west from where this spot height appears on the ground.

Although the hill can be easily accessed from the south south-west, permission to do so should be sought as the summit is situated on private land.  When we visited Charlie had received permission for us to do so.

The name of the hill is Caus Castle and its summit height has been increased from its current Ordnance Survey map height, as prior to the survey with the Trimble GeoXH 6000 the hill was listed with a summit height of 223m based on the spot height that appears on current Ordnance Survey maps.  However, the result from the survey with the Trimble GeoXH 6000 gave the height of this hill’s summit as 233.6m (converted to OSGM15).

Therefore this hill’s new summit height is 233.6m (converted to OSGM15) which is 10.6m higher than its previously listed height which came from the 223m spot height on current Ordnance Survey maps.


The full details for the hill are:

Cardinal Hill:  Corndon

Summit Height (New Height):  233.6m (converted to OSGM15)

Name:  Caus Castle

OS 1:50,000 map:  126

Summit Grid Reference:  SJ 33713 07782
  
Drop:  53.2m


Gathering data from the prospective new summit position of Caus Castle which resulted in this hill's prospective significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (April 2015)





Mapping Mountains – Significant Height Revisions – The Fours


Minton Hill (SO 414 919)

This is the thirteenth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on 2nd January 2015.

The thirteenth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted on a clear and sunny winter’s day in the hills of the Long Mynd, which are situated in Shropsire.

The hill is listed as a Sub-Four with 22m of drop in the 1st edition of The Fours published by Europeaklist in December 2013.  This drop value was based on the 453m summit spot height and 431m col spot height that appear on current Ordnance Survey maps.  The summit spot height is given to an ancient tumulus which is just one of a number of Tumuli that appear on the summits of the surrounding hills.

The hill can be easily accessed on a good tack from the north-west from the high road that crosses the extended summit ridge of the Long Mynd.  Or a more satisfying walk to its summit can start from the south-east from the small community of Minton, from where the hill gets its name from.

The name of the hill is Minton Hill and its summit height has been increased from its current Ordnance Survey map height, as prior to the survey with the Trimble GeoXH 6000 the hill was listed with a summit height of 453m based on the spot height that appears on current Ordnance Survey maps.  However, the result from the survey with the Trimble GeoXH 6000 gave the height of this hill’s summit as 455.4m (converted to OSGM15).

Therefore this hill’s new summit height is 455.4m (converted to OSGM15) which is 2.4m higher than its previously listed height which came from the 453m spot height on current Ordnance Survey maps.


The full details for the hill are:

Cardinal Hill:  Stiperstones

Summit Height (New Height):  455.4m (converted to OSGM15)

Name:  Minton Hill

OS 1:50,000 map:  137

Summit Grid Reference:  SO 41456 91920 
 
Drop:  23.3m


Gathering data from the summit of Minton Hill which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips and Aled Williams (January 2015)





Mapping Mountains – Significant Height Revisions – Y Pedwarau


Mynydd Poeth (SH 953 513)

This is the twelfth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on 24th December 2014.

The twelfth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the Mynydd Hiraethog hills in north Wales on Christmas Eve, in the company of Mark Trengove who had suggested the walk.

The hill appeared in the listing of Y Pedwarau as a Sub-Pedwar with c 29m of drop and was reclassified to a Pedwar due to the survey with the Trimble.  The hill can be easily accessed from the B4501 which skirts its eastern fringes, and is situated just to the north of Cerrigydrudion and to the south of the Alwen Reservoir.

The name of the hill is Mynydd Poeth and its summit height has been increased from its current Ordnance Survey map height, as prior to the survey with the Trimble GeoXH 6000 the hill was listed with a summit height of 417m based on the spot height that appears on current Ordnance Survey maps.  However, higher ground exists to the north of where the 417m spot height appears on the ground.

Therefore this hill’s new summit height is 419.3m (converted to OSGM15) which is 2.3m higher than its previously listed height which came from the 417m spot height on current Ordnance Survey maps.

This hill is one of the rare few that can claim a Hill Reclassification, Summit Relocation and a Significant Height Revision all from the one survey.


The full details for the hill are:

Cardinal Hill:  Mwdwl Eithin

Summit Height (New Height):  419.3m (converted to OSGM15)

Name:  Mynydd Poeth

OS 1:50,000 map:  116

Summit Grid Reference:  SH 95375 51301
  
Drop:  31.7m


Gathering data from the summit of Mynydd Poeth which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips and Aled Williams (December 2014)





Mapping Mountains – Significant Height Revisions – 200m Twmpau


Pen y Berth (SJ 081 127)  

This is the eleventh post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on 19th October 2014.

The eleventh major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the lower Berwyn hills in the company of Mark Trengove on a colourful autumnal day in October.

The hill can be accessed from 1km east of the small community of Dolanog on a track that heads north-west and then east to sneak up to the summit from the opposing side of the hill.  The summit area of the hill is given two 280m uppermost ring contours aligned east and west of one another on Ordnance Survey maps, with each contour ring given a 282m spot height that appears on the Ordnance Survey enlarged map on the Geograph website.

The name of the hill is Pen y Berth and the following results were those obtained with the Trimble GeoXH 6000 for the two points surveyed:

Eastern 282m spot height:  283.7m (converted to OSGM15) at SJ 08322 12748

Western 282m spot height at SJ 08012 12780 not surveyed

Easterly high point of western 280m ring contour:  287.5m (converted to OSGM15) at SJ 08126 12730

The land at SJ 08126 12730 was visually judged to be higher than the land at SJ 08012 12780, therefore this latter position was not surveyed.  The height given the hill on current Ordnance Survey maps is 282m, with the height resulting from the survey with the Trimble being 287.5m.

Therefore this hill’s new summit height is 5.5m higher than its previously listed height which came from the 282m spot height on the Ordnance Survey enlarged map on the Geograph website.


The full details for the hill are:

Cardinal Hill:  Carreg y Big

Summit Height (New Height):  287.5m (converted to OSGM15)

Name:  Pen y Berth

OS 1:50,000 map:  125

Summit Grid Reference:  SJ 08126 12730
  
Drop:  134.2m


Pen y Berth (SJ 081 127) - a hill that's had its height significantly revised

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (October 2014)





Mapping Mountains – Significant Height Revisions – Yr Uchafion and 700m Sub-Twmpau


Llechog (SH 606 567) 

This is the tenth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on 9th September 2014.

The tenth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the hills of the Yr Wyddfa range in the heartland of Eryri on a beautiful sunny September day.

The hill can be accessed from the Llanberis Path which is one of the six main paths up Yr Wyddfa.  This path roughly follows the course of the railway line as it ascends the mountain from Llanberis, and the hill stands on a ridge that is seldom visited by the multitude of walkers who head toward the summit of Wales’ highest mountain.

The name of the hill is Llechog.  The height given the hill on current Ordnance Survey maps is 718m, with the height resulting from the survey with the Trimble being 720.0m (converted to OSGM15).  This is not a dramatic height revision but it does come within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised for detailing these revisions.

Therefore this hill’s new summit height is 2.0m higher than its previously listed height which came from the 718m spot height on current Ordnance Survey maps.


The full details for the hill are:

Cardinal Hill:  Yr Wyddfa

Summit Height (New Height):  720.0m (converted to OSGM15)

Name:  Llechog

OS 1:50,000 map:  115

Summit Grid Reference:  SH 60613 56751 
 
Drop:  28.0m


Gathering data from the summit of Llechog which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips and Aled Williams (September 2014)





Mapping Mountains – Significant Height Revisions – Y Pedwarau


Bryn Melyn (SO 109 184)

This is the ninth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on 22nd July 2014.

The ninth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the hills of the Bannau Brycheiniog (Brecon Beacons) in south Wales, in the company of Mark Trengove who had suggested the walk.

The hill appears in the listing of Y Pedwarau and can be easily accessed from the end of a minor road above the waters of the Talybont Reservoir which is situated in Glyn Collwn.  The hill can also be accessed from its opposing valley of Dyffryn Crawnon which gives a slightly more rewarding and lengthy walk.

The name of the hill is Bryn Melyn and its summit height has been increased from its current Ordnance Survey map height, as prior to the survey with the Trimble GeoXH 6000 the hill was listed with a summit height of c 446m based on it having an uppermost contour ring of 440m on current Ordnance Survey maps.  Its new summit height is 450.5m (converted to OSGM15) which is 4.6m higher than its previously estimated height and 10.5m higher than its uppermost ring contour on current Ordnance Survey maps.


The full details for the hill are:

Cardinal Hill:  Pen y Fan

Summit Height (New Height):  450.5m (converted to OSGM15)

Name:  Bryn Melyn

OS 1:50,000 map:  161

Summit Grid Reference:  SO 10941 18432
  
Drop:  38.6m


Gathering data from the summit of Bryn Melyn which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips and Aled Williams (July 2014)





Mapping Mountains – Significant Height Revisions – Yr Uchafion and 500m Sub-Twmpau


Twyn Walter (SN 828 175)

This is the eighth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on 10th July 2014.

The eighth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the hills of Y Mynydd Du in south Wales, in the company of Mark Trengove on a lovely summer’s day when we visited the remotest point of mainland Wales as well as the remotest hill of mainland Wales.

The hill whose height has been significantly revised was reclassified from a 500m Twmpau to a Sub-Twmpau after this survey and it can be accessed from Glyntawe on a good path and track that ascends above the Dan-yr-Ogof Showcaves.  Heading west beyond the hill is some of the remotest land in the whole of Wales with the southern land of Y Mynydd Du comprising hills with limestone outcrops and a great wilderness of open grassland, it is highly recommended to visit.

The name of the hill is Twyn Walter and its summit height has been dramatically decreased from its current Ordnance Survey map height of 509m, with the survey conducted with the Trimble GeoXH 6000 giving the height of the hill as 502.1m (converted to OSGM15).  As the height of this hill’s bwlch is estimated as c 478m the hill used to be listed as a 500m Twmpau with c 31m of drop based on the 509m Ordnance Survey summit spot height, as this hill’s summit height has been significantly decreased to the point that it loses its P30 status Twyn Walter is no longer classified as a Twmpau hill and is now listed in the 500m Sub-Twmpau.

Therefore this hill’s new summit height is 6.9m lower than its previously listed height which came from the 509m spot height on current Ordnance Survey 1:25,000 maps and the Ordnance Survey enlarged map on the Geograph website.


The full details for the hill are:

Cardinal Hill:  Fan Brycheiniog

Summit Height (New Height):  502.1m (converted to OSGM15)

Name:  Twyn Walter

OS 1:50,000 map:  160

Summit Grid Reference:  SN 82837 17506 
 
Drop:  c 24m


Gathering data from the summit of Twyn Walter which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips and Aled Williams (July 2014)





Mapping Mountains – Significant Height Revisions – Y Pedwarau


Craig y Ganllwyd (SH 707 258)

This is the seventh post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on 3rd May 2014.

The seventh major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the hills of the Rhinogydd, which are situated in the west of North Wales between Abermaw (Barmouth) in the south and Trawsfynydd in the north.

The hill was reclassified as a Pedwar after this survey and can be accessed from the small community of Ganllwyd to its south-east.  However, even though forest paths and tracks head toward the hill much of the land outside of these is rough and wild.  This should not put you off though, as when this hill is combined with its neighbours of Craig Aberserw and Craig y Ganllwyd they make one of the better outings in the eastern part of the Rhinogydd.

The name of the hill is Craig y Ganllwyd and its summit height has been dramatically increased from its current Ordnance Survey 1:25,000 map height, the detail on the 1:25,000 map does not have a spot height and its uppermost contour ring is 410m.  Whilst Harvey Maps has a 423m spot height for this hill, which Aled and I relied on when we listed this hill as a Sub-Pedwar.  To confuse matters even more the Ordnance Survey 1:50,000 map has an uppermost 430m contour ring and the 1:2,500 base map has an imperial height of 1,411ft (430m).

Although the new summit height of 430.9m is similar to the Ordnance Survey 1:50,000 and 1:2,500 map detail, the 1:25,000 map is being prioritised for this page heading where the summit height is not consistent between the different scales of mapping that the Ordnance Survey produce.  Therefore this hill’s new summit height is 7.9m higher than its previously listed height which came from the 423m Harvey Maps spot height, and it is a dramatic 20.9m higher than the uppermost 410m ring contour on current Ordnance Survey 1:25,000 maps.


The full details for the hill are:

Cardinal Hill:  Y Llethr

Summit Height (New Height):  430.9m (converted to OSGM15)

Name:  Craig y Ganllwyd

OS 1:50,000 map:  124

Summit Grid Reference:  SH 70775 25853
  
Drop:  33.4m


Gathering data from the summit of Craig y Ganllwyd which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips and Aled Williams (May 2014)





Mapping Mountains – Significant Height Revisions – Y Pedwarau


Craig y Derlwyn (SH 702 259) 

This is the sixth post under the heading of Significant Height Revisions, and the Trimble survey that resulted in this height revision was conducted on 3rd May 2014.

The sixth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the hills of the Rhinogydd, which are situated in the west of North Wales between Abermaw (Barmouth) in the south and Trawsfynydd in the north.

The hill is listed as a Sub-Pedwar and can be accessed from the small community of Ganllwyd to its south-east.  However, even though forest paths and tracks head toward the hill much of the land outside of these is rough and wild.  Don’t let this put you off though, as when this hill is combined with its neighbours of Craig Aberserw and Craig y Ganllwyd they make one of the better outings in the eastern part of the Rhinogydd.

The name of the hill is Craig y Derlwyn and its summit height has been increased from its current Ordnance Survey map height, as prior to the survey with the Trimble GeoXH 6000 the hill was listed with a summit height of c 428m based on it having a relatively large uppermost contour ring of 420m on current Ordnance Survey maps.  Its new summit height is 430.8m which is 2.8m higher than its previously estimated height and 10.8m higher than its uppermost ring contour on current Ordnance Survey maps.


The full details for the hill are:

Cardinal Hill:  Y Llethr

Summit Height (New Height):  430.8m (converted to OSGM15)

Name:  Craig y Derlwyn

OS 1:50,000 map:  124

Summit Grid Reference:  SH 70245 25934 
 
Drop:  25.3m


Gathering data at the summit of Craig y Derlwyn

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips and Aled Williams (May 2014)





Mapping Mountains – Significant Height Revisions – 100m Twmpau


Bryn y Beili (SJ 235 643)

This is the fifth post under the heading of Significant Height Revisions and the Trimble survey that resulted in this height revision was conducted on 8th April 2014.

The fifth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the Bryniau Clwyd range of hills in the centre of Yr Wyddgrug (Mold) which is situated in north-east Wales, the survey was conducted in the company of Mark Trengove over two days, three weeks apart, and it was Mark who proposed that this hill was a candidate for becoming a new P30, his inclination proved correct.  With the first survey concentrating on the bwlch resulting in an unfortunate incident when the Trimble wrestled with a car and was run over, the second survey concentrated on the summit.

The hill is listed in the height band of 100m Twmpau hills and can be accessed from the top of the High Street in Yr Wyddgrug (Mold).  Although the hill is prominent within the town it is almost hidden from view as it rises behind the former Pendref Chapel and is surrounded by a high wall, trees and shrubs.

The name of the hill is Bryn y Beili (Bailey Hill in English).  Its summit height has been increased from its current Ordnance Survey map height, as prior to the survey with the Trimble GeoXH 6000 the hill was not listed as it only had an uppermost ring contour of 130m on current Ordnance Survey maps, with a 135m spot height appearing on lower ground in the centre of a bowling rink on the Ordnance Survey enlarged map on the Geograph website.  Its new summit height is 143.0m which is 8.0m higher than the 135m spot height.


The full details for the hill are:

Cardinal Hill:  Moel y Gamelin

Summit Height (New Height):  143.0m (converted to OSGM15)

Name:  Bryn y Beili

OS 1:50,000 map:  117

Summit Grid Reference:  SJ 23544 64367
  
Drop:  31.5m


Bryn y Beili, a new P30 and a hill whose height has been significantly revised

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (April 2014)





Mapping Mountains – Significant Height Revisions – 300m Twmpau


Coed y Gaer (SO 004 843)

This is the fourth post under the heading of Significant Height Revisions and the Trimble survey that resulted in this height revision was conducted on 9th February 2014.

The fourth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the Pegwn Mawr range of hills to the east of Llanidloes in the company Mark Trengove on a particularly wet and cold day.

The hill is listed as a Hump as well as in the height band of 300m Twmpau hills and can be accessed from a minor lane to the south; it overlooks the A470 and the Afon Hafren (River Severn) to its north-west.

The name of the hill is Coed y Gaer.  The height given the hill on current Ordnance Survey maps is 362m, with the height resulting from the survey with the Trimble being 359.9m.  This is not a dramatic height revision but it does come within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term ‘significant height revision’ applies to any listed hill whose Ordnance Survey summit spot height has a 2m or more discrepancy when compared to the surveyed Trimble height, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 map is being prioritised for detailing these revisions.


The full details for the hill are:

Cardinal Hill:  Pegwn Mawr

Summit Height (New Height):  359.9m (converted to OSGM15)

Name:  Coed y Gaer

OS 1:50,000 map:  136

Summit Grid Reference:  SO 00488 84392
  
Drop:  121.7m

  
Gathering data with the Trimble GeoXH 6000 from the summit of Coed y Gaer

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (February 2014)





Mapping Mountains – Significant Height Revisions – 30m-99m Sub-Twmpau


Pt. 36.9m, Ynys Hir (SH 566 398)

This is the third post under the heading of Significant Height Revisions and the the Trimble survey that resulted in this height revision was conducted on 1st February 2014.

The third major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the lowlands outside of Porthmadog in north-west Wales in the company of Aled Williams who had suggested the walk, as he considered at least one of the hills he proposed for us to visit would become a new P30 – he was right!  The new P30 is Ynys Hir (SH 56695 39393) which is adjacent to the hill this blog post relates to; Pt. 36.9m, Ynys Hir (SH 56649 39840).

The hill is listed in the 30m-99m height band of Sub-Twmpau hills and is situated to the north of Porthmadog in the area known as Traeth Mawr, the area of the hill is easily accessed from a lay-by on the A487 to the south.  But its ascent can be problematical due to the undergrowth.

The name of the hill is Pt. 36.9m, Ynys Hir with its adjacent and higher hill taking on the full name without the point (Pt.) notation.  The hill should not be confused with its higher Cardinal Hill of Hir Ynys.  Its summit height has been dramatically increased from its current Ordnance Survey map height, as prior to the survey with the Trimble GeoXH 6000 the hill was not listed as it only had an uppermost ring contour of 20m on current Ordnance Survey maps, with an estimated summit height of c 24m.  Its new summit height is 36.9m, which is 12.9m higher than its previously estimated height and 16.9m higher than the 20m uppermost ring contour on the current Ordnance Survey map.

Although the new summit height of 36.9m is dramatically different to current Ordnance Survey map detail, the Historical 1:25,000 map has an uppermost ring contour of 100ft for this hill which is correct when compared to the surveyed height from the Trimble GeoXH 6000. 


The full details for the hill are:

Cardinal Hill:  Hir Ynys

Summit Height (New Height):  36.9m (converted to OSGM15)

Name:  Pt. 36.9m, Ynys Hir

OS 1:50,000 map:  124

Summit Grid Reference:  SH 56649 39840
  
Drop:  25.8m


Setting up the Trimble at the summit of Pt. 36.9m, Ynys Hir.  Photo: Aled Williams

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (February 2014)





Mapping Mountains – Significant Height Revisions – 30m-99m Twmpau


Ynys Hir (SH 566 396)

This is the second post under the heading of Significant Height Revisions and the Trimble survey that resulted in this height revision was conducted on 1st February 2014.

The second major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the lowlands outside of Porthmadog in north-west Wales in the company of Aled Williams who had suggested the walk, as he considered at least one of the hills he proposed for us to visit would become a new P30 – he was right!

The hill is listed in the 30m-99m height band of Twmpau hills and is situated to the north of Porthmadog in the area known as Traeth Mawr, the hill is easily accessed from a lay-by on the A487 to the south-west.  The term ‘easily accessed’ is only applicable to where the road is situated in relation to the hill as it can be a wee battle to reach its top.

The name of the hill is Ynys Hir which should not be confused with its higher Cardinal Hill of Hir Ynys.  Its summit height has been dramatically increased from its current Ordnance Survey map height, as prior to the survey with the Trimble GeoXH 6000 the hill was not listed as it only had an uppermost ring contour of 20m on current Ordnance Survey maps, with an estimated summit height of c 23m.  Its new summit height is 37.3m, which is 14.3m higher than its previously estimated height and 17.3m higher than the 20m uppermost ring contour on the current Ordnance Survey map.

Although the new summit height of 37.3m is dramatically different to current Ordnance Survey map detail, the Historical 1:25,000 map has an uppermost ring contour of 100ft for this hill  which is correct when compared to the surveyed height from the Trimble GeoXH 6000.  


The full details for the hill are:

Cardinal Hill:  Hir Ynys

Summit Height (New Height):  37.3m (converted to OSGM15)

Name:  Ynys Hir

OS 1:50,000 map:  124

Summit Grid Reference:  SH 56695 39693 
 
Drop:  c 35m


Beyond the trees, vertical cliffs and undergrowth is the summit of Ynys Hir, a new P30 which has a significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (February 2014) 





Mapping Mountains – Significant Height Revisions – 300m Twmpau


Old Radnor Hill (SO 251 587)

This is the first post under the heading of Significant Height Revisions and the Trimble survey that resulted in this height revision was conducted on 11th January 2014.

The first major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the southern part of Fforest Glud, otherwise known as the Radnor Forest, in the heartland of mid Wales on a fine and bright winter’s day.

The hill is listed in the 300m height band of Twmpau hills and is situated south-east of Maesyfed (New Radnor), with the nearest major road to the hill being the A44 which skirts the hill on its northern and eastern side, and by doing so this road significantly alters this hill’s drop as the natural bwlch no longer exists as it was once situated inside what is now an old Chapel, with the A44 cutting to the east of the hill now the position of its critical bwlch.

The name of the hill is Old Radnor Hill; its summit height has been dramatically decreased over time due to it being quarried.  However, prior to the survey with the Trimble GeoXH 6000 its listed height was c 317m based on the uppermost contour on current Ordnance Survey enlarged mapping on the Geograph website showing part of a 315m contour ring.

Its new summit height is 312.6m, which is 4.6m lower than its previously estimated listed height and 2.4m lower than the 315m uppermost ring contour on the enlarged Geograph map.


The full details for the hill are:

Cardinal Hill:  Gwaun Ceste

Summit Height (New Height):  312.6m (converted to OSGM15)

Name:  Old Radnor Hill

OS 1:50,000 map:  148

Summit Grid Reference:  SO 25135 58770 
 
Drop:  97.1m


The quarried remains of Old Radnor Hill

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (January 2014)




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