Wednesday, 29 March 2017

Mapping Mountains – Hill Reclassifications – 200m Twmpau


Mynydd y Drum (SN 807 097)

There has been a reclassification to the listing of Twmpau (thirty welsh metre prominences and upward) hills due to analysis of LIDAR data by Kevin McGovern and also independently by Aled Williams.  The hill has been reclassified from a 200m Twmpau to a 200m Sub-Twmpau, with the criteria for the former being all hills in Wales at or above 200m and below 300m in height that have a minimum drop of 30m, and the criteria for the sub category being all hills in Wales at or above 200m and below 300m in height with 20m or more and below 30m of drop.

The hill had been listed with an estimated drop of c 53m based on an estimated bwlch height of c 244m and the 297m summit height positioned at SN 807 098 derived from the spot height that appears on the Ordnance Survey 1:25,000 Explorer map numbers 12 and 165, whilst the Ordnance Survey 1:50,000 Landranger map number 160 gives a 298m summit spot height at the same position.  This latter spot height is derived from the 978.1ft (298.1ft) height on the Ordnance Survey old Six-Inch map.

When this hill was originally listed in the Welsh P30 lists on the v-g.me website it had an accompanying note which stated ‘3 points of 300m on 1985 map may probably no longer exist (quarrying)’.  The hand written Master List stated ‘Due to opencast workings the three points of 300c at GR 830 112 on 1985 1:50,000 map probably no longer exist’.  These three points are in the vicinity of where a 984ft (299.9m) height appears on the Ordnance Survey old Six Inch map and in all likelihood signified where the summit of this hill was once positioned.  Since this time the opencast workings which take in the northern and eastern part of the larger hill known as Mynydd y Drum have destroyed the old 984ft (299.9m) summit, but in its place are two separate hills comprising the spoil from the mine workings, with this Hill Reclassifications post concentrating on the remaining ‘natural’ and now lower of these three summits. 

Prior to analysis of LIDAR data Mynydd y Drum was listed with one summit, but due to opencast mining a further two summits have been created which are artificial and comprise the remains of waste spoil, the hill which this Hill Reclassifications post details is the remaining ‘natural’ summit, which is now lower in height compared to the two artificial summits, this has resulted in new bylchau heights and positions and also drop values for these three hills, all of these will be detailed in this and the two previous Hill Reclassifications posts, and as these three hills are all a part of the larger hill named Mynydd y Drum, each hill is being listed by this name.

The hill is adjoined to the Fforest Fawr group with its Cardinal Hill being Fan Gyhirych (SN 880 191) and is placed in the Region of South Wales (Region C, Sub-Region C2), and is positioned between the small town of Ystradgynlais to the north-west and the village of Blaendulais (Seven Sisters) to the south-east.

The upper part of the hill is situated within open access land and can be easily accessed from a number of public footpaths that emanate from Cwm Tawe (Swansea Valley) to the north-west and from Cwm Dulais (Dulais valley) from the south-east.

The name of the hill is Mynydd y Drum and its reclassification to a 200m Sub-Twmpau is due to the analysis of LIDAR data by Kevin McGovern and also independently by Aled Williams.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

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


Mynydd y Drum

Summit Height:  296.1m (converted to OSGM15)

Summit Grid Reference:  SN 80720 09754

Bwlch Height:  271.8m (converted to OSGM15)

Bwlch Grid Reference:  SN 81526 10520

Drop:  24.3m


Therefore, the 296.1m LIDAR data produced for the summit position at SN 80720 09754 and the 271.8m LIDAR data produced for the bwlch position at SN 81526 10520 is sufficient for this hill to be reclassified from a 200m Twmpau to a 200m Sub-Twmpau with 24.3m of drop.

This now revises the total in the 200m Twmpau and the list will be updated accordingly.


The full details for the hill are:

Cardinal Hill:  Fan Gyhirych

Summit Height:  296.1m (LIDAR data, converted to OSGM15)

Name:  Mynydd y Drum

OS 1:50,000 map:  160

Summit Grid Reference:  SN 80720 09754 
  
Drop:  24.3m (LIDAR data, converted to OSGM15)


My thanks to Mark Jackson for bringing the details of this hill to my attention, and to Kevin McGovern and Aled Williams for their analysis of LIDAR data.



Myrddyn Phillips (March 2017)

Tuesday, 28 March 2017

Mapping Mountains – Hill Reclassifications – 300m Twmpau


Mynydd y Drum (SN 828 114)

There has been a reclassification to the listing of Twmpau (thirty welsh metre prominences and upward) hills due to analysis of LIDAR data by Kevin McGovern and also independently by Aled Williams.  The 300m Twmpau height band takes in all hills in Wales at or above 300m and below 400m in height that have a minimum drop of 30m.

Prior to analysis of LIDAR data Mynydd y Drum was listed with one summit, but due to opencast mining a further two summits have been created which are artificial and comprise the remains of waste spoil, the summit which this Hill Reclassifications post details is the lower of these two artificial hills, this has resulted in new bylchau heights and positions and also drop values for these three hills, all of these will be detailed in this and the previous and next Hill Reclassifications posts, and as the three hills are all a part of the larger hill named Mynydd y Drum, each hill is being listed by this name.

The hill is adjoined to the Fforest Fawr group with its Cardinal Hill being Fan Gyhirych (SN 880 191) and is placed in the Region of South Wales (Region C, Sub-Region C2), and it is positioned between the small communities of Abercraf (Abercrave) to the north-west and Coelbren towards the east.

The summit of the hill is situated within the Nant Helen Opencast Coal Mine so permission to visit the high point should be sought, however it has open access land to its east and a little farther away to its south, and two public footpaths are marked on Ordnance Survey maps that head extremely close to the summit of this hill.

The name of the hill is Mynydd y Drum and its reclassification to a 300m Twmpau is due to the analysis of LIDAR data by Kevin McGovern and also independently by Aled Williams.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

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


Mynydd y Drum

Summit Height:  311.8m (converted to OSGM15)

Summit Grid Reference:  SN 82850 11432

Bwlch Height:  277.6m (converted to OSGM15)

Bwlch Grid Reference:  SN 82186 11128

Drop:  34.2m


Therefore, the 311.8m LIDAR data produced for the summit position at SN 82850 11432 and the 277.6m LIDAR data produced for the bwlch position at SN 82186 11128 is sufficient for this hill to be classified as a 300m Twmpau with 34.2m of drop.

This now revises the total in the 300m Twmpau and the list will be updated accordingly.


The full details for the hill are:

Cardinal Hill:  Fan Gyhirych

Summit Height:  311.8m (LIDAR data, converted to OSGM15)

Name:  Mynydd y Drum

OS 1:50,000 map:  160

Summit Grid Reference:  SN 82850 11432
   
Drop:  34.2m (LIDAR data, converted to OSGM15)


My thanks to Mark Jackson for bringing the details of this hill to my attention and to Kevin McGovern and Aled Williams for their analysis of LIDAR data.



Myrddyn Phillips (March 2017)

Monday, 27 March 2017

Mapping Mountains – Hill Reclassifications – 300m Twmpau


Mynydd y Drum (SN 820 108)

There has been a reclassification to the listing of Twmpau (thirty welsh metre prominences and upward) hills due to analysis of LIDAR data by Kevin McGovern and also independently by Aled Williams.  With the high point of the hill previously listed in the 200m height band when the Welsh P30 hills below 500m in height were published on Geoff Crowder’s v-g.me website.

The hill had been listed with a 297m summit height positioned at SN 807 098 based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map numbers 12 and 165, whilst the Ordnance Survey 1:50,000 Landranger map number 160 gives a 298m summit spot height at the same position.  This latter spot height is derived from the 978.1ft (298.1ft) height on the Ordnance Survey old Six-Inch map.

When this hill was originally listed in the Welsh P30 lists on the v-g.me website it had an accompanying note which stated ‘3 points of 300m on 1985 map may probably no longer exist (quarrying)’.  The hand written Master Lists stated ‘Due to opencast workings the three points of 300c at GR 830 112 on 1985 1:50,000 map probably no longer exist’.  These three points are in the vicinity of where a 984ft (299.9m) height appears on the Ordnance Survey old Six Inch map and in all likelihood signified where the summit of this hill was once positioned.  Since this time the opencast workings which take in the northern and eastern part of the larger hill known as Mynydd y Drum have destroyed the old 984ft (299.9m) summit, but in its place are two summits comprising the spoil from the mine workings, with this Hill Reclassifications post concentrating on the higher of these two artificial summits, whilst the 297m 1:25,000 map / 298m 1:50,000 map summit still remains. 
  
Prior to analysis of LIDAR data Mynydd y Drum was listed with one summit, the opencast mine has now created a further two summits which are artificial and comprise the remains of waste spoil, the summit which this Hill Reclassifications post details is now higher than the previously listed summit, resulting in new bylchau heights and positions and also drop values for these three hills, all of these will be detailed in this and two further Hill Reclassifications posts, and as the three hills are all a part of the larger hill named Mynydd y Drum, each hill is being listed by this name.

The hill is adjoined to the Fforest Fawr group with its Cardinal Hill being Fan Gyhirych (SN 880 191) and is placed in the Region of South Wales (Region C, Sub-Region C2), and it is positioned between the small communities of Abercraf (Abercrave) to the north and Coelbren towards the east.

The summit of the hill is situated within the Nant Helen Opencast Coal Mine so permission to visit the high point should be sought, however it has open access land to its south-west and a public footpath marked on Ordnance Survey maps that heads in a north- south direction and at its closest point is just to the west of the summit of this hill.

The name of the hill is Mynydd y Drum and its reclassification to a 300m Twmpau is due to the analysis of LIDAR data by Kevin McGovern and also independently by Aled Williams.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

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


Mynydd y Drum

Summit Height:  338.2m (converted to OSGM15)

Summit Grid Reference:  SN 82014 10832

Bwlch Height:  244.8m (converted to OSGM15)

Bwlch Grid Reference:  SN 84566 11384

Drop:  93.4m


Therefore, the 338.2m LIDAR data produced for the summit position at SN 82014 10832 and the 244.8m LIDAR data produced for the bwlch position at SN 84566 11384 is sufficient for this hill to be classified as a 300m Twmpau with 93.4m of drop and for it to be listed with a higher summit than the 297m 1:25,000 map heighted summit at SN 807 098.

This now revises the total in the 300m Twmpau which will be updated accordingly.


The full details for the hill are:

Cardinal Hill:  Fan Gyhirych

Summit Height:  338.2m (LIDAR data, converted to OSGM15)

Name:  Mynydd y Drum

OS 1:50,000 map:  160

Summit Grid Reference:  SN 82014 10832 
  
Drop:  93.4m (LIDAR data, converted to OSGM15)


My thanks to Mark Jackson for bringing the details of this hill to my attention and to Kevin McGovern and Aled Williams for their analysis of LIDAR data.



Myrddyn Phillips (March 2017)

Sunday, 26 March 2017

Mapping Mountains – Trimble Surveys – Beacon Hill


09.03.17  Cefn Nedd (SO 185 965)

Cefn Nedd (SO 185 965)

Cefn Nedd forms a neat triangle of land enclosed by minor roads above and to the south-east of the Afon Hafren (River Severn).  The name of Cefn Nedd is more strictly applicable to the uppermost enclosed field where the summit of the hill is situated, with the name deriving from the Tithe map, whilst the name usually given this hill in listings; Goron Ddu, is confirmed from local enquiry to be applicable to the lower slopes of the hill that overlook the Afon Hafren, this is where the name appears on the current Ordnance Survey 1:50,000 Landranger map.

As I parked my car on the side of the road next to the field enclosing the area of the bwlch, a farm vehicle approached, I flagged it down and talked with a local farmer for ten minutes or so, he confirmed where the name of Goron Ddu applied to, and had no objection to me taking a series of data sets in the fields next to the minor road close to the outskirts of Llandyssil.

The first data set I took was close to where the 119m spot height appears on Ordnance Survey maps, to do so I placed the Trimble on the roof of my car and measured a 1.46m offset to the road.  Over the next 90 minutes I took a further five data sets from the area of the bwlch, with the majority of these on the broad valley to valley traverse.  During this process the land remained quiet with just an occasion passing car and a distant farm vehicle chugging up a country lane breaking the silence.

The first data set at the bwlch

The third data set at the bwlch with the village of Llandyssil in the background

The fourth data set at the bwlch

The sixth data set at the bwlch

Packing the Trimble away I walked back toward the car happy in the knowledge that I judged most if not all eventualities for the position of this hill’s critical bwlch had been surveyed. 

As the weather was proving glorious with thick blue skies above and warmth cascading the land, I dispensed with my fleece.  It was a day to savour with the heralding of spring and new growth showing green in hedgerows.

I drove up the lane toward the summit of Cefn Nedd and parked beside the entrance to Coed y Wig.  An old green lane heads toward the hill from here and I followed it to two gates which give access to the upper field.

I passed this beautifully sculptured tree on the ascent of Cefn Nedd

The summit of Cefn Nedd consists of closely cropped grass close to the slopes of a wooded copse, the views northward down the Severn Valley toward Cefn Digoll and the Breiddin are expansive with both floating above the plain below.

Gathering data at the summit of Cefn Nedd

The Trimble set-up position at the summit of Cefn Nedd

After five minutes of summit data were gathered I headed back to the two gates and the old green track, a farm vehicle was approaching the green lane from the field opposite and not wanting to miss an opportunity for place-name research I waved and headed toward it.  I chatted with its occupant; Alan Harding for quite some time, he also confirmed the land where Goron Ddu is situated and gave me a number of names for local hills.

Alan Harding

After thanking Alan for his time it was only a short walk back to my car, on my way down toward it my mind wandered as the greened fields shone in front, a delicate patchwork of curves smoothed with years of grazing and interspersed with bordered and stunted trees giving slight variety to the land.  It had been a good few hours in the sunshine and enthused me to get out again the next day with the Trimble.

A greened patchwork
     

Survey Result:


Cefn Nedd (significant name change)

Summit Height:  207.2m (converted to OSGM15)

Summit Grid Reference:  SO 18524 96503

Bwlch Height:  118.1m (converted to OSGM15)

Bwlch Grid Reference:  SO 19564 95699

Drop:  89.1m (non Sub-Hump status confirmed)

Dominance:  23.26% 

 




Saturday, 25 March 2017

Mapping Mountains – Hill Reclassifications – Yr Uchafion


Fowler’s Arm Chair (SO 041 794)

There has been a reclassification to the listing of Yr Uchafion instigated from analysis of LIDAR data by Aled Williams.  Yr Uchafion is the draft title for a list of the Welsh 500m P15s that takes in all hills in Wales at or above 500m that have a minimum drop of 15m, the list is a joint compilation with Aled Williams, and details relating to this list were published on the Mapping Mountains site in November 2015.

Accompanying the main Yr Uchafion list are three sub lists; 500m Sub-Uchaf, 490m Sub-Uchaf and the Double Sub-Uchaf categories, with the reclassification of this hill affecting the Double Sub-Uchaf hills, with the criteria for inclusion to this sub category being Welsh hills at or above 490m and below 500m in height that have 14m or more and below 15m of drop.

Prior to analysis of LIDAR data by Aled the hill was listed with c 14m of drop based on an estimated summit height of c 491m and the 477m bwlch spot height that appears on the Ordnance Survey enlarged mapping hosted on the Geograph website.

The hill is situated in the Pegwn Mawr group with its Cardinal Hill being Brondre Fawr Hill (SO 041 783) and is placed in the Region of Mid and West Wales (Region B, Sub-Region B1), and is positioned between the small communities of Bwlch y Sarnau towards the south and Llanbadarn Fynydd towards the east south-east.

The hill can be accessed on public footpaths from a number of directions; however its summit is not on open access land, so if wanting to visit its high point permission to do so should be sought.

The name of the hill is Fowler’s Arm Chair and it is the first Double Sub-Uchaf to lose its status since the Yr Uchafion list was announced in November 2015, this is due to the analysis of LIDAR data by Aled.  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:


Fowler’s Arm Chair

Summit Height:  489.5m

Summit Grid Reference:  SO 04122 79426

Bwlch Height:  476.4m

Bwlch Grid Reference:  SO 04192 79062

Drop:  13.1m


Therefore, the 489.5m LIDAR data produced for the summit position at SO 04122 79426 and the 476.4m LIDAR data produced for the bwlch position at SO 04192 79062 gives this hill 13.1m of drop which along with its summit height is insufficient for it to retain its status as a Double Sub-Uchaf.

This now revises the listing of Yr Uchafion which will be updated accordingly and the hill is now deleted from the ranks of Double Sub-Uchaf, with this reclassification appearing in the appropriate Change Register.


The full details for the hill are:

Cardinal Hill:  Brondre Fawr Hill

Summit Height:  489.5m (LIDAR data)

Name:  Fowler’s Arm Chair

OS 1:50,000 map:  136, 147

Summit Grid Reference:  SO 04122 79426   

Drop:  13.1m (LIDAR data)


The reclassifications to the Double Sub-Uchaf category in Yr Uchafion / The Welsh 500m P15s reported on Mapping Mountains are ills of wales as follows:



DOUBLE SUB-UCHAF ADDITIONS




DOUBLE SUB-UCHAF DELETIONS

Fowler’s Arm Chair (SO 041 794) Double Sub-Uchaf deleted with 489.5m summit height and 13.1m drop




Myrddyn Phillips and Aled Williams (March 2017)

Friday, 24 March 2017

Mapping Mountains – Hill Reclassifications – Y Pedwarau


Cwmcynydd Bank (SO 053 724)

There has been a reclassification to the listing of Y Pedwarau with a 400m Sub-Pedwar being reclassified to Pedwar status due to analysis of LIDAR data by Aled Williams.  The 400m Sub-Pedwarau is one of five categories of sub hills that accompany the main Y Pedwarau list, with the criteria for 400m Sub-Pedwar status being all Welsh hills at or above 400m and below 500m in height with 20m or more and below 30m of drop, with the criteria for Pedwar status being all Welsh hills at or above 400m and below 500m in height with a minimum 30m of drop.

The hill is situated in the Pegwn Mawr group with its Cardinal Hill being Brondre Fawr Hill (SO 041 783) and is placed in the Region of Mid and West Wales (Region B, Sub-Region B1), and is positioned between the small communities of Bwlch y Sarnau to the north-west and Abaty Cwm Hir (Abbey Cwmhir) to the south.

The summit of the hill is situated in conifer plantation but the hill can be accessed via forestry tracks from a number of directions as these encircle the upper part of the hill.  The forestry track towards the north-east and also the south-west of the summit gives access to a forest ride that passes within a few metres and to the east of the high point of the hill.

The name of the hill is Cwmcynydd Bank (previously listed in Y Pedwarau as Pt. 444m, Cwmcynydd Bank) and prior to the analysis of LIDAR data and its subsequent listing as a Pedwar the hill had been listed as a 400m Sub-Pedwar with c 27m of drop based on the 444m spot height that appears at SO 05234 72506 on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 417m at SO 05783 72592.

As Aled was analysing other hills in the vicinity against LIDAR data, he did likewise with Cwmcynydd BankLIDAR (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:


Cwmcynydd Bank

Summit Height:  451.4m

Summit Grid Reference:  SO 05342 72437

Bwlch Height:  370.9m

Bwlch Grid Reference:  SO 04664 74187

Drop:  80.5m


The reason for the dramatic increase in drop from this hill’s previously listed c 27m to the 80.5m figure given above is that the summit height for this hill usurps that of the hill positioned at SO 06116 72668 (grid reference ascertained from Trimble), and therefore the positions of the bylchau are swapped, because of this the LIDAR data for what is now considered as the lower hill is also given, and this appears below.

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


Cwmcynydd Bank

Summit Height: 448.2m

Summit Grid Reference:  SO 06122 72660

Bwlch Height:  416.4m  

Bwlch Grid Reference:  SO 05788 72576

Drop:  31.8m


The hill now considered the lower of the two Cwmcynydd Bank summits was previously surveyed with the Trimble GeoXH 6000, but with a standard deviation of 0.4m the data set was considered unreliable and therefore the LIDAR data is being taken for the height of this hill, with the ten figure grid reference ascertained by the Trimble being used for its summit position.  The critical bwlch for the higher of these two hills was also surveyed using the Trimble and the comparison of data sets is given below:


Trimble:  370.934m (converted to OSGM15) at SO 04667 74183

LIDAR:  370.9m at SO 04664 74187 


Therefore, the 451.4m LIDAR data produced for the summit position at SO 05342 72437 is higher than the 448.2m LIDAR data produced for the Trimble summit position at SO 06116 72668, therefore the bwlch position for each hill is swapped, and with the 370.9m LIDAR and Trimble bwlch data produced for the Trimble bwlch position at SO 04667 74183 being sufficient for this hill to be reclassified to a Pedwar with 80.5m of drop.

The full details for the two hills are:


Cardinal Hill:  Brondre Fawr Hill  

Summit Height:  451.4m (LIDAR data)  

Name:  Cwmcynydd Bank  

OS 1:50,000 map:  136, 147  

Summit Grid Reference:  SO 05342 72437  

Drop:  80.5m (LIDAR summit data and Trimble and LIDAR bwlch data)  




Cardinal Hill:  Brondre Fawr Hill 

Summit Height:  448.2m (LIDAR data)

Name:  Cwmcynydd Bank

OS 1:50,000 map:  136, 147  

Summit Grid Reference:  SO 06116 72668 (Trimble data)

Drop:  31.8m (LIDAR data)


This now brings the overall total for Y Pedwarau to 445 hills with eight additions, and ten reclassifications to 400m Sub-Pedwar status since publication of the list by Europeaklist in May 2013.  The hill will be taken out of the 400m Sub-Pedwar list and added to the Pedwar list in forthcoming publications.  The list of Pedwar hills is available from the Haroldstreet website (January 2014) with all subsequent changes available via the Mapping Mountains site, with the list also having commenced publication on Mapping Mountains on the 30.01.17.

The list of additions and reclassifications from the Pedwar list since the 1st edition of Y Pedwarau was published by Europeaklist are as follows:



PEDWAR ADDITIONS









Cwmcynydd Bank (LIDAR data) (SO 053 724) 400m Sub-Pedwar reclassified to Pedwar with 80.5m drop





PEDWAR RECLASSIFICATIONS















Myrddyn Phillips and Aled Williams (March 2017)