Thursday, 29 June 2017

Mapping Mountains – Hill Reclassifications – 30-99m Twmpau


Ynys Gron (SH 596 392) – 30-99m Twmpau reclassified to 30-99m Sub-Twmpau


There has been a reclassification to the Twmpau (thirty welsh metre prominences and upward) list with a 30-99m Twmpau being reclassified to a 30-99m Sub-Twmpau due to surveying with the Trimble GeoXH 6000.  The details relating to this hill’s reclassification are retrospective as the survey with the Trimble took place on the 21th November 2014.

The criteria for 30-99m Twmpau status is all Welsh hills at or above 30m and below 100m in height with 30m minimum drop, whilst the criteria for 30-99m Sub-Twmpau status is all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop.

The hill had been listed in the original Welsh P30 lists when published on Geoff Crowder’s v-g.me website with a 96m summit height based on the Ordnance Survey 1:25,000 Outdoor Leisure spot height, with an accompanying note stating ‘98m on 1984 1:50,000 map.  Summit being reduced due to quarrying’.  When drop values were added to the P30 Master Lists this hill was given an estimated drop of c 50m.  The heights quoted appeared on maps of the day, although it was also known that the quarrying activities had already reduced the height of this hill.

The hill is situated in the Moelwynion group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Moelwyn Mawr (SH 658 448) and is situated between the towns of Porthmadog to the west and Penrhyndeudraeth to the east, and immediately above the busy A 487 road which is to its south.

The hill is not on open access land and the whole of its south-western section forms part of the Garth Quarry, which is operational, and because of this permission to visit should be sought.  However, the approach from the east is through woodland and would take a visitor direct to the remaining high point of the hill.

The name of the hill is Ynys Gron, which is a locally known name and it has been reclassified to a 30-99m Sub-Twmpau as the quarry has now obliterated the upper 30m of the hill and reduced it in height to 69.4m, and as its bwlch has been surveyed as 44.3m in height, it gives this hill only 25.1m of drop, which is insufficient for it to remain classified as a P30.


The full details for the hill are:


Cardinal Hill:  Moelwyn Mawr

Summit Height:  69.4m (converted to OSGM15)

Name:  Ynys Gron

OS 1:50,000 map:  124

Summit Grid Reference:  SH 59653 39268

Drop:  25.1m (converted to OSGM15)


The Trimble GeoXH 6000 gathering data at the remaining high point of Ynys Gron


Myrddyn Phillips (June 2017)


Wednesday, 28 June 2017

Mapping Mountains – Hill Reclassifications – 30-99m Twmpau


30-99m Twmpau – Hill Reclassifications

The 30-99m Twmpau (thirty welsh metre prominences and upward) are the Welsh hills at or above 30m and below 100m in height that have a minimum drop of 30m.  Accompanying the main P30 list are two sub lists entitled the 30-99m Sub-Twmpau with the qualification to this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, and the Double Sub-Twmpau with the qualification to this sub category being all Welsh hills at or above 20m and below 30m in height with 20m or more and below 30m of drop.

The list is authored by Myrddyn Phillips and the posts that have appeared on Mapping Mountains detailing the additions, reclassifications and deletions to the main P30 list and the sub lists appear below presented chronologically in receding order.








Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Cae Benglog (SH 316 380) – 30-99m Sub-Twmpau addition (23rd reclassification)

Summit Relocations post for Cae Benglog

Significant Name Changes post for Cae Benglog


There has been an addition to the 30-99m Twmpau due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

30-99m Twmpau - Welsh hills at and above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at and above 30m and below 100m in height with 20m and more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

This hill did not appear in the accompanying Hills to be surveyed sub list when the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website as it did not meet the criteria for this sub category; however this sub list has now been standardised including the addition of interpolated drop values and heights.

Prior to LIDAR analysis this hill was listed with an estimated c 19m of drop based on the 86m spot height positioned at SH 31361 38368 on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 67m based on bwlch contouring at 5m intervals and between 65m – 70m on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website.

Extract from the Ordnance Survey 1:25,000 Explorer map

The name of the bounded land where the summit of this hill is situated is Cae Benglog with these details derived from the Tithe map and the hill is adjoined to the Pen Llŷn group of hills, which is situated in the north-west part of North Wales (Region A, Sub-Region A1), and is positioned overlooking the A 497 road which is to its north-east and has the small community of Morfa Nefyn t0 its north-west and the town of Pwllheli towards the south-east.

If wanting to visit the hill permission to do so should be sought as it is not a part of designated open access land, with the nearest public footpath close to the summit to its east.

The addition of Cae Benglog to 30-99m Sub-Twmpau status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR analysis gives the hill the following details:


Cae Benglog

Summit Height:  86.8m

Summit Grid Reference:  SH 31635 38073

Bwlch Height:  65.9m

Bwlch Grid Reference:  SH 31523 38448

Drop:  20.9m


LIDAR image of Cae Benglog

Therefore, the 86.779m LIDAR analysis for the summit position at SH 31635 38073 and the 65.873m LIDAR analysis for the bwlch position at SH 31523 38448 gives this hill 20.906m of drop, which is sufficient for 30-99m Sub-Twmpau status.

A point to the north-west of this summit and which is given an 86m spot height on the Ordnance Survey 1:25,000 Explorer map was also examined via LIDAR, resulting in a 85.355m height positioned at SH 31355 38373.


The full details for the hill are:

Group:  Pen Llŷn

Name:  Cae Benglog

Summit Height:  86.8m (LIDAR)

Summit Grid Reference:  SH 31635 38073 (LIDAR)

OS 1:50,000 map:  123

Drop:  20.9m (LIDAR)


Myrddyn Phillips (April 2018)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Allt Fawr (SH 383 356) – 30-99m Sub-Twmpau addition (22nd reclassification)

Significant Height Revisions post for Allt Fawr

Summit Relocations post for Allt Fawr


There has been an addition to the 30-99m Twmpau due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

30-99m Twmpau - Welsh hills at and above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at and above 30m and below 100m in height with 20m and more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

This hill did not appear in the accompanying Hills to be surveyed sub list when the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website as it did not meet the criteria for this sub category; however this sub list has now been standardised and interpolated heights also included.

Prior to LIDAR analysis this hill was listed with an estimated c 18m of drop based on an estimated summit height of c 46m with the hill being given three uppermost 45m ring contours on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website and an estimated bwlch height of c 28m based on bwlch contouring at 5m intervals and between 25m – 30m on this same map.

Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website

The name of the hill is Allt Fawr and it is adjoined to the Pen Llŷn group of hills, which is situated in the north-west part of North Wales (Region A, Sub-Region A1), and is positioned with the A 499 and the A 497 roads to its west and east respectively and has the town of Pwllheli towards the south-west.

If wanting to visit the hill permission to do so should be sought as it is not a part of designated open access land and does not have any rights of way on it.

The addition of Allt Fawr to 30-99m Sub-Twmpau status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR analysis gives the hill the following details:


Allt Fawr

Summit Height:  48.9m

Summit Grid Reference:  SH 38347 35695

Bwlch Height:  25.8m

Bwlch Grid Reference:  SH 38411 35961

Drop:  23.1m


LIDAR image of Allt Fawr

Therefore, the 48.889 LIDAR analysis for the summit position at SH 38347 35695 and the 25.753m LIDAR analysis for the bwlch position at SH 38411 35961 gives this hill 23.136m of drop, which is sufficient for 30-99m Sub-Twmpau status.

Three other tops were also analysed by LIDAR on the hill of Allt Fawr, resulting in the following; 46.569m at SH 38145 35521, 44.962m at SH 38406 35898 and 44.944m at SH 38383 35833.


The full details for the hill are:

Group:  Pen Llŷn

Name:  Allt Fawr

Summit Height:  48.9m (LIDAR)

Summit Grid Reference:  SH 38347 35695 (LIDAR)

OS 1:50,000 map:  123

Drop:  23.1m (LIDAR)


Myrddyn Phillips (April 2018)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Carreg y Defaid (SH 341 325) – 30-99m Sub-Twmpau deletion (21st reclassification)


There has been a deletion to the 30-99m Twmpau due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

30-99m Twmpau - Welsh hills at and above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at and above 30m and below 100m in height with 20m and more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

This hill did not appear in the accompanying Hills to be surveyed sub list when the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website as it did not meet the criteria for this sub category; however this sub list has now been standardised and interpolated heights also included.

Prior to LIDAR analysis this hill was listed with an estimated c 20m of drop based on the 33m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 13m based on bwlch contouring at 5m intervals and between 10m – 15m on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website.

Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website

The name of the hill is Carreg y Defaid and it is adjoined to the Pen Llŷn group of hills, which is situated in the north-west part of North Wales (Region A, Sub-Region A1), and is positioned with the A 499 road to its west and between the village of Llanbedrog to the south-west and the town of Pwllheli towards the north-west.

If wanting to visit the hill permission to do so should be sought as it is not a part of designated open access land, for those wishing to do so the Wales Coast Path passes close to its summit and would give easiest access.

The deletion of Carreg y Defaid from 30-99m Sub-Twmpau status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR analysis gives the hill the following details:


Carreg y Defaid

Summit Height:  33.4m

Summit Grid Reference:  SH 34109 32555

Bwlch Height:  13.7m (natural bwlch)

Bwlch Grid Reference:  SH 33751 32623 (natural bwlch)

Drop:  19.7m


LIDAR image of Craig y Defaid

Therefore, the 33.389m LIDAR analysis for the summit position at SH 34109 32555 and the 13.693m LIDAR analysis for the bwlch position at SH 33751 32623 gives this hill 19.696m of drop, which is insufficient for 30-99m Sub-Twmpau status.

There is a 13.747m higher hill to hill traverse positioned at SH 33818 32605, but as this is to an elevated road which is considered man-made the remaining natural bwlch is being taken for the drop value of this hill.


The full details for the hill are:

Group:  Pen Llŷn

Name:  Carreg y Defaid

Summit Height:  33.4m (LIDAR)

Summit Grid Reference:  SH 34109 32555 (LIDAR)

OS 1:50,000 map:  123

Drop:  19.7m (LIDAR)


Myrddyn Phillips (April 2018)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Rhiw Tir (SH 601 451) – 30-99m Sub-Twmpau addition (20th reclassification)


There has been an addition to the listing of the 30-99m Twmpau (thirty welsh metre prominences and upward) due to analysis conducted by Aled Williams of data produced via LIDAR.  The 30-99m Twmpau is the title for the list of Welsh hills at and above 30m and below 100m in height that have a minimum 30m of drop.

Accompanying the main Twmpau list is a sub list entitled the Sub-Twmpau, with this hill being added to the 30-99m Sub-Twmpau category.  The criteria for 30-99m Sub-Twmpau status being all Welsh hills at and above 30m and below 100m in height with 20m or more and below 30m of drop.

Prior to analysis of data produced via LIDAR this hill was not listed in the Hills to be surveyed sub list that accompanied the Welsh P30 lists published on Geoff Crowder’s v-g.me website.  When these lists were re-evaluated after they were standardised and also drop values added, this hill was listed with c 19m of drop based on the 54m summit spot height that appears on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website and an estimated bwlch height of c 35m based on 10m contour intervals between 30m – 40m.

The name of the hill is Rhiw Tir and it is situated in the Moelwynion range of hills and is placed in the Region of North Wales (Region A, Sub-Region A1).  The hill is positioned with the Welsh Highland Railway and the A 498 road to its west and the A 4085 road to its north and east, and has the village of Beddgelert to its north north-west and the town of Porthmadog to its south south-west.

As the hill is not a part of designated open access land permission to visit should be sought, however the hill has a well-used path leading through the deciduous wood that takes in its summit indicating that people have visited this area for many years.

The addition of Rhiw Tir to 30-99m Sub-Twmpau status is due to analysis conducted by Aled Williams of data produced via LIDAR.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

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


Rhiw Tir

Summit Height:  54.4m

Summit Grid Reference:  SH 60112 45108

Bwlch Height:  31.3m

Bwlch Grid Reference:  SH 60060 44996

Drop:  23.1m


Therefore, the 54.4m data produced via LIDAR for the summit position at SH 60112 45108 and the 31.3m data produced via LIDAR for the bwlch position at SH 60060 44996 gives this hill 23.1m of drop, which is sufficient for its inclusion as a 30-99m Sub-Twmpau.


The full details for the hill are:

Group:  Moelwynion

Summit Height:  54.4m (data via LIDAR)

Name:  Rhiw Tir

OS 1:50,000 map:  115

Summit Grid Reference:  SH 60112 45108 
  
Drop:  23.1m (data via LIDAR)


My thanks to Aled Williams for sending the details of this hill to me

Myrddyn Phillips (February 2018)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pt. 47.8m (SH 604 438) – 30-99m Sub-Twmpau addition (19th reclassification)


There has been an addition to the listing of the 30-99m Twmpau (thirty welsh metre prominences and upward) due to analysis conducted by Aled Williams of data produced via LIDAR.  The 30-99m Twmpau is the title for the list of Welsh hills at and above 30m and below 100m in height that have a minimum 30m of drop.

Accompanying the main Twmpau list is a sub list entitled the Sub-Twmpau, with this hill being added to the 30-99m Sub-Twmpau category.  The criteria for 30-99m Sub-Twmpau status being all Welsh hills at and above 30m and below 100m in height with 20m or more and below 30m of drop.

Prior to analysis of data produced via LIDAR this hill was not listed in the Hills to be surveyed sub list that accompanied the Welsh P30 lists published on Geoff Crowder’s v-g.me website.  When these lists were re-evaluated after they were standardised and also drop values added, this hill was listed with c 20m of drop based on the 46m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 26m based on 10m contour intervals between 20m – 30m.

As I do not know a separate and independent name for this hill it is being listed by the point (Pt. 47.8m) notation, and it is situated in the Moelwynion range of hills and is placed in the Region of North Wales (Region A, Sub-Region A1).  The hill is positioned with the Welsh Highland Railway and the A 498 road to its west and the A 4085 road to its east, and has the village of Beddgelert to its north- north-west and the town of Porthmadog towards its south-west.

As the hill is not a part of designated open access land permission to visit should be sought, however the hill has a well-used path leading through the deciduous wood that takes in its summit indicating that people have visited this area for many years.

The addition of Pt. 47.8m to 30-99m Sub-Twmpau status is due to analysis conducted by Aled Williams of data produced via LIDAR.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

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


Pt. 47.8m

Summit Height:  47.8m

Summit Grid Reference:  SH 60404 43809

Bwlch Height:  24.0m

Bwlch Grid Reference:  SH 60344 43884

Drop:  23.8m


Therefore, the 47.8m data produced via LIDAR for the summit position at SH 60404 43809 and the 24.0m data produced via LIDAR for the bwlch position at SH 60344 43884 gives this hill 23.8m of drop, which is sufficient for its inclusion as a 30-99m Sub-Twmpau.


The full details for the hill are:

Group:  Moelwynion

Summit Height:  47.8m (data via LIDAR)

Name:  Pt. 47.8m

OS 1:50,000 map:  124

Summit Grid Reference:  SH 60404 43809 
  
Drop:  23.8m (data via LIDAR)


My thanks to Aled Williams for sending the details of this hill to me

Myrddyn Phillips (February 2018)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Bryn y Bont (SH 596 459) – Double Sub-Twmpau addition (18th reclassification)

Significant Height Revisions post for Bryn y Bont

Summit Relocations post for Bryn y Bont


There has been an addition to the listing of the Double Sub-Twmpau due to analysis conducted by Aled Williams of data produced via LIDAR.  With the title of Twmpau being an acronym for thirty welsh metre prominences and upward.

Accompanying each 100m height band within the main Twmpau list is a sub list entitled the Sub-Twmpau, with the Double Sub-Twmpau attached to the lower tier height band of Welsh hills.

The criteria for the lower tier of Twmpau hills are:

30-99m Twmpau – All Welsh hills at and above 30m and below 100m in height with 30m minimum drop.

30-99m Sub-Twmpau – All Welsh hills at and above 30m and below 100m in height with 20m or more and below 30m of drop.

Double Sub-Twmpau – All Welsh hills at and above 20m and below 30m in height with 20m or more and below 30m of drop.

Prior to analysis of data produced via LIDAR this hill was not listed in the Hills to be surveyed sub list that accompanied the Welsh P30 lists published on Geoff Crowder’s v-g.me website.  When these lists were re-evaluated after they were standardised and also drop values added, this hill was listed with c 16m of drop based on an estimated c 20m summit height which was based on this hill’s small uppermost 20m ring contour on Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps, and an estimated bwlch height of c 4m based on bwlch contouring at 10m intervals and between 0 – 10m, with the caveat that the 4m spot height positioned at SH 59756 45814 and shown on the Ordnance Survey 1:25,000 Explorer map is probably not at the position of the critical bwlch.

The name of the hill is Bryn y Bont and it is situated in the Moelwynion range of hills and is placed in the Region of North Wales (Region A, Sub-Region A1).  The hill is positioned with the A 4085 road to its north and its east and the A 498 road to its west, and has the Afon Glaslyn also to its immediate west, with the hamlet of Nantmor positioned to the east of the hill and the village of Beddgelert towards its north.

As the hill is not a part of designated open access land permission to visit should be sought, for those wishing to do so an ascent from the convenience of the road to its north or east is likely to be the easiest.

The addition of Bryn y Bont to Double Sub-Twmpau status is due to analysis conducted by Aled Williams of data produced via LIDAR.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

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


Bryn y Bont

Summit Height:  25.2m

Summit Grid Reference:  SH 59641 45973

Bwlch Height:  4.3m

Bwlch Grid Reference:  SH 59572 46137

Drop:  20.9m


Therefore, the 25.2m data produced via LIDAR for the summit position at SH 59641 45973 and the 4.3m data produced via LIDAR for the bwlch position at SH 59572 46137 gives this hill 20.9m of drop, which is sufficient for it to be classified as a Double Sub-Twmpau.


The full details for the hill are:

Group:  Moelwynion

Summit Height:  25.2m (data via LIDAR)

Name:  Bryn y Bont

OS 1:50,000 map:  115

Summit Grid Reference:  SH 59641 45973 
  
Drop:  20.9m (data via LIDAR)


My thanks to Aled Williams for sending the details of this hill to me

Myrddyn Phillips (February 2018)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Bryn y Gwynt (SH 599 449) – 30-99m Sub-Twmpau reclassified to 30-99m Twmpau (17th reclassification)

Significant Name Changes post for Bryn y Gwynt

Significant Height Revisions post for Bryn y Gwynt

Summit Relocations post for Bryn y Gwynt


There has been a reclassification to the listing of the 30-99m Twmpau (thirty welsh metre prominences and upward) due to analysis conducted by Aled Williams of data produced via LIDAR.  The 30-99m Twmpau is the title for the list of Welsh hills at and above 30m and below 100m in height that have a minimum 30m of drop.

Accompanying the main Twmpau list is a sub list entitled the Sub-Twmpau, with this hill being reclassified from the 30-99m Sub-Twmpau category.  The criteria for 30-99m Sub-Twmpau status being all Welsh hills at and above 30m and below 100m in height with 20m or more and below 30m of drop.

Prior to analysis of data produced via LIDAR this hill was listed in the Hills to be surveyed sub list that accompanied the Welsh P30 lists published on Geoff Crowder’s v-g.me website.  When these sub lists were standardised and also drop values added, this hill was listed with c 29m of drop based on the 56m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 27m based on contouring at 10m intervals and between 20m – 30m, with the caveat that the 27m spot height that appears on a road at SH 60168 45293 on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website is not positioned at the critical bwlch. 

The name of the hill is Bryn y Gwynt and it is situated in the Moelwynion range of hills and is placed in the Region of North Wales (Region A, Sub-Region A1).  The hill is positioned with the A 4085 road to its north-east and has the Welsh Highland Railway to its immediate west and overlooks the Afon Glaslyn also to its west, and has the village of Beddgelert to its north- north-west and the town of Porthmadog to its south south-west.

The hill is a part of Coed Hafod y Llyn, and as this name implies its summit is placed in woodland which is deciduous, and as the summit of the hill is not a part of designated open access land permission to visit should be sought, however paths are indicated on the map to the north, east and south of this hill’s summit and therefore gaining access to its lower slopes has probably been accepted for many years.

The reclassification of Bryn y Gwynt to 30-99m Twmpau status is due to analysis conducted by Aled Williams of data produced via LIDAR.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.  

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


Bryn y Gwynt

Summit Height:  58.2m

Summit Grid Reference:  SH 59949 44915

Bwlch Height:  28.0m

Bwlch Grid Reference:  SH 60222 45248

Drop:  30.2m


Therefore, the 58.2m data produced via LIDAR for the summit position at SH 59949 44915 and the 28.0m data produced via LIDAR for the bwlch position at SH 60222 45248 gives this hill 30.2m of drop, which is sufficient for its inclusion as a 30-99m Twmpau.


The full details for the hill are:

Group:  Moelwynion

Summit Height:  58.2m (data via LIDAR)

Name:  Bryn y Gwynt

OS 1:50,000 map:  124

Summit Grid Reference:  SH 59949 44915 
  
Drop:  30.2m (data via LIDAR)


My thanks to Aled Williams for sending the details of this hill to me

Myrddyn Phillips (January 2018)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Mynydd Carreg (SH 163 291) – 100m Twmpau reclassified to 30-99m Twmpau (16th reclassification)

Survey post for Mynydd Carreg


There has been a reclassification of a 100m Twmpau to a 30-99m Twmpau (thirty welsh metre prominences and upward) initiated by a survey with the Trimble GeoXH 6000.  The details relating to this hill’s reclassification are retrospective as the survey with the Trimble took place on the 28th December 2014.

The criteria for 100m Twmpau status is all Welsh hills at or above 100m and below 200m in height with 30m minimum drop, whilst the criteria for 30-99m Twmpau status is all Welsh hills at or above 30m and below 100m in height with 30m minimum drop.

When drop values were added to the original Welsh P30 lists that were published on Geoff Crowder’s v-g.me website, this hill was listed with an estimated c 95m summit height based on an uppermost 90m contour ring, and a bwlch height of c 54m, based on interpolation of bwlch contouring between 50m – 60m, with these values giving this hill c 41m of drop.  When the Ordnance Survey enlarged mapping hosted on the Geograph website became available online the whole of Wales was checked for new spot heights and as this hill was given a 100m summit spot height it was reclassified to the 100m P30 list, which was later renamed the 100m Twmpau.

Therefore, prior to the survey with the Trimble GeoXH 6000 this hill was listed with an estimated c 46m of drop based on its 100m summit spot height and an estimated c 53m bwlch height, based on interpolation of bwlch contouring between 50m – 55m.

The name of the hill is Mynydd Carreg and it is situated in the Pen Llŷn range of hills with its Cardinal Hill being Mynydd y Rhiw (SH 228 293and is placed in the North Wales Region (Region A, Sub-Region A1), and is positioned with the small community of Aberdaron to the south south-east of the hill.

As the summit of the hill is not a part of designated open access land permission to visit its high point should be sought.  However, as the summit is a local viewpoint with a car park at the foot of the hill it is likely that an ascent will have no objection.


The full details for the hill are:

Cardinal Hill:  Mynydd y Rhiw

Summit Height:  99.2m (converted to OSGM15)

Name:  Mynydd Carreg

OS 1:50,000 map:  123

Summit Grid Reference:  SH 16371 29168

Drop:  c 46m



The Trimble GeoXH 6000 gathering data at the summit of Mynydd Carreg


Myrddyn Phillips (September 2017)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Ynys Fadog (SH 564 398) – Double Sub-Twmpau addition (15th reclassification)

Survey post for Ynys Fadog


There has been an addition to the Twmpau (thirty welsh metre prominences and upward) list with this hill being included in the Double Sub-Twmpau that accompanies the 30-99m height band.  Accompanying all the 100m height band of hills within the Twmpau are sub lists with the one attached to this list being entitled the 30-99m Sub-Twmpau.  There is a second sub category that accompanies the 30-99m height band and which is entitled the Double Sub-Twmpau.

The criteria for 30-99m Twmpau status is all Welsh hills at or above 30m and below 100m in height with 30m minimum drop, the criteria for 30-99m Sub-Twmpau status is all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, whilst the criteria for Double Sub-Twmpau status is all Welsh hills at or above 20m and below 30m in height with 20m or more and below 30m of drop.

The details relating to this hill’s addition are retrospective as it was proposed as a possible new P30 by Aled Williams, and subsequently surveyed with the Trimble GeoXH 6000 on the 1st February 2014.

Prior to the survey with the Trimble this hill was unclassified, with the current Ordnance Survey 1:50,000 Landranger map, 1:25,000 Explorer map and the enlarged mapping hosted on the Geograph website all giving the hill an uppermost 20m ring contour, which implies that the hill does not have sufficient prominence for P30 status but may attain Double Sub-Twmpau status with 20m or more of drop.

The hill is in the Moel Hebog group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Pt. 734m (SH 525 502) and is situated between the communities of Porthmadog to its south and Tremadog to its north-west, with the A 487 road to its immediate south.  The hill can be visited from this road where a lay-by gives access through a gate into woodland that covers this and other adjacent small hills.

The name of the hill is Ynys Fadog and as its name implies it forms an island, which is attached to two higher hills both of which are known as Ynys Hir (SH 566 396 and SH 566 398) which are to the south-east and east respectively, with all three hills now being landlocked, it is included as a Double Sub-Twmpau as the survey with the Trimble GeoXH 6000 produced a summit height of 27.8m (converted to OSGM15) and with an estimated bwlch height of c 3m, it gives this hill c 25m of drop.


The full details for the hill are:


Cardinal Hill:  Pt. 734m (SH 525 502)

Summit Height:  27.8m (converted to OSGM15)

Name:  Ynys Fadog

OS 1:50,000 map:  124

Summit Grid Reference:  SH 56464 39823

Drop:  c 25m



The wooded summit of Ynys Fadog (SH 564 398)



Myrddyn Phillips (July 2017)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau


Pt. 36.9m, Ynys Hir (SH 566 398) – 30-99m Sub-Twmpau addition (14th reclassification)

Summit survey post for Pt. 36.9m, Ynys Hir

Bwlch survey post for Pt. 36.9m, Ynys Hir

Significant Height Revisions post for Pt. 36.9m, Ynys Hir


There has been an addition to the Twmpau (thirty welsh metre prominences and upward) list with this hill being included in the 30-99m height band.  Accompanying all the 100m height band of hills within the Twmpau are sub lists with the one attached to this list being entitled the 30-99m Sub-Twmpau.

The criteria for 30-99m Twmpau status is all Welsh hills at or above 30m and below 100m in height with 30m minimum drop, whilst the criteria for 30-99m Sub-Twmpau status is all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop.

The details relating to this hill’s addition are retrospective as it was proposed as a possible new P30 by Aled Williams, and subsequently surveyed with the Trimble GeoXH 6000 on the 1st February 2014.

Prior to the survey with the Trimble this hill was unclassified, with the current Ordnance Survey 1:50,000 Landranger map, 1:25,000 Explorer map and the enlarged mapping hosted on the Geograph website all giving the hill an uppermost 20m ring contour, which implies that the hill does not have sufficient prominence for P30 status but may attain Sub-Twmpau status with 20m or more of drop.

The hill is in the Moel Hebog group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Pt. 734m (SH 525 502) and is situated between the communities of Porthmadog to its south and Tremadog to its north north-west, with the A 487 road to its immediate south.  The hill can be visited from this road where a lay-by gives access through a gate into woodland that covers this and other adjacent small hills.

The name the hill is listed by is Pt. 36.9m, Ynys Hir and as its name implies it forms an island, which is attached to the higher hill known as Ynys Hir (SH 566 396) which is to the immediate south, with both hills now being landlocked, it is included as a 30-99m Sub-Twmpau as the survey with the Trimble GeoXH 6000 produced a summit height of 36.9m (converted to OSGM15) and a bwlch height of 11.1m (converted to OSGM15), with these values giving this hill 25.8m of drop.


The full details for the hill are:

Cardinal Hill:  Pt. 734m (SH 525 502)

Summit 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 (converted to OSGM15)


The Trimble GeoXH 6000 set-up position at the summit of Pt. 36.9m (SH 566 398).  Photo:  Aled Williams


For details on the summit survey and the bwlch survey that confirmed this hill’s 30-99m Sub-Twmpau status

Myrddyn Phillips (July 2017)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Ynys Hir (SH 566 396) – 30-99m Twmpau addition (13th reclassification)

Survey post for Ynys Hir

Significant Height Revisions post for Ynys Hir


There has been an addition to the Twmpau (thirty welsh metre prominences and upward) list with this hill being included in the 30-99m height band.  Accompanying all the 100m height band of hills within the Twmpau are sub lists with the one attached to this list being entitled the 30-99m Sub-Twmpau.

The criteria for 30-99m Twmpau status is all Welsh hills at or above 30m and below 100m in height with 30m minimum drop, whilst the criteria for 30-99m Sub-Twmpau status is all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop.

The details relating to this hill’s addition are retrospective as it was proposed as a possible new P30 by Aled Williams, and subsequently surveyed with the Trimble GeoXH 6000 on the 1st February 2014.

Prior to the survey with the Trimble this hill was unclassified as the Ordnance Survey 1:50,000 Landranger map, 1:25,000 Explorer map and the enlarged mapping hosted on the Geograph website all give the hill an uppermost 20m ring contour, implying that its height is not sufficient for P30 status.

The hill is in the Moel Hebog group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Pt. 734m (SH 525 502) and is situated between the communities of Porthmadog to its south and Tremadog to its north north-west, with the A 487 road to its immediate south.  The hill can be visited from this road where a lay-by gives access through a gate into woodland that covers this and other adjacent small hills.

The name of the hill is Ynys Hir and as its name implies it forms an island, which is now landlocked, it is included as a 30-99m Twmpau as the survey with the Trimble GeoXH 6000 produced a summit height of 37.3m (converted to OSGM15), and with an estimated bwlch height of c 3m it gives this hill c 34m of drop.


The full details for the hill are:

Cardinal Hill:  Pt. 734m (SH 525 502)

Summit Height:  37.3m (converted to OSGM15)

Name:  Ynys Hir

OS 1:50,000 map:  124

Summit Grid Reference:  SH 56695 39693

Drop:  c 34m


Beyond the cliffs and vegetation is the summit of Ynys Hir (SH 566 396) which has been confirmed as a 30-99m Twmpau


Myrddyn Phillips (July 2017)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Dinas Dinlle (SH 436 564) – 30-99m Twmpau addition (12th reclassification)

Survey post for Dinas Dinlle


There has been an addition to the Twmpau (thirty welsh metre prominences and upward) list with this hill being included in the 30-99m height band.  Accompanying all the 100m height band of hills within the Twmpau are sub lists with the one attached to this list being entitled the 30-99m Sub-Twmpau.

The details relating to this hill’s addition are retrospective as its P30 status is due to detail on the Ordnance Survey enlarged mapping hosted on the Geograph website and which was first spotted by Chris Watson, its status has subsequently been confirmed from a survey with the Trimble GeoXH 6000 which was conducted on the 26th December 2013.

The criteria for 30-99m Twmpau status is all Welsh hills at or above 30m and below 100m in height with 30m minimum drop, whilst the criteria for 30-99m Sub-Twmpau status is all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop.

Prior to Chris Watson raising the probability of this hill being a P30 and its subsequent survey it had remained unclassified, as the Ordnance Survey 1:50,000 Landranger map gives a 31m summit spot height and bwlch contouring between 0m – 10m, whilst the 1:25,000 Explorer map gives an uppermost 30m ring contour and the same bwlch contouring, this implied that the hill did not have the required 30m of drop to qualify for Twmpau status.

The hill is positioned in the Moel Hebog range and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Mynydd Mawr (SH 539 546) and is situated on the outskirts of the small community that takes its name from the hill; Dinas Dinlle, and is positioned with the sea to its immediate west which has eroded some of its western slopes over recent years.  If wanting to visit the hill it can be easily accessed from the car park adjacent to the sea front from where a path heads up its northern slopes.

The name of the hill is Dinas Dinlle and as its name implies the upper section of the hill comprises an ancient hill fort, it was included as a 30-99m Twmpau as the Ordnance Survey enlarged mapping hosted on the Geograph website has contours at 5m intervals giving the hill an uppermost contour of 35m and bwlch contouring between 0m – 5m, these values give the hill an estimated drop of c 31m – c 32m.  The summit of the hill has subsequently been surveyed with the Trimble GeoXH 6000 as being 34.7m (converted to OSGM15) high and with an estimated bwlch height of c 3m this gives the hill c 32m of drop. 


The full details for the hill are:

Cardinal Hill:  Mynydd Mawr

Summit Height:  34.7m (converted to OSGM15)

Name:  Dinas Dinlle

OS 1:50,000 map:  115, 123

Summit Grid Reference:  SH 43676 56438

Drop:  c 32m


Dinas Dinlle (SH 436 564) confirmed as a 30-99m Twmpau


Myrddyn Phillips (July 2017)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Bodlondeb Wood (SH 779 781) – 30-99m Twmpau addition (11th reclassification)


There has been an addition to the Twmpau (thirty welsh metre prominences and upward) list with this hill being included in the 30-99m Twmpau height band.  Accompanying all the 100m height band of hills within the Twmpau are sub lists with the one attached to this list being entitled the 30-99m Sub-Twmpau.  The details relating to this hill’s addition are retrospective as its inclusion as a P30 was reported on Mapping Mountains on the 17th December 2015.

The criteria for 30-99m Twmpau status is all Welsh hills at or above 30m and below 100m in height with 30m minimum drop, whilst the criteria for 30-99m Sub-Twmpau status is all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop.

Prior to this hill’s inclusion as a 30-99m Twmpau it had remained unclassified outside of its recent inclusion as a Tump, as Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps only gave the hill an uppermost 50m ring contour and bwlch contouring between 20m – 30m, with a drop of c 27m based on an estimated summit height of c 53m and an estimated bwlch height of c 26m.

The hill is positioned in the Carneddau group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Tal y Fan (SH 729 726) and is situated on the northern outskirts of Conwy with the Afon Conwy to its immediate north and east.

As the name of the hill suggests it is a part of a wood which is made up of deciduous trees and for those wanting to visit permission should be sought as it is not a part of designated open access land.  However, access is relatively easy with public parking available next to where the Offices are marked to the south of the summit on Ordnance Survey maps, and there are a number of paths marked on the map that head up to, or contour around the top of the hill.

The name of the hill is Bodlondeb Wood and it is included as a 30-99m Twmpau as the Ordnance Survey enlarged mapping hosted on the Geograph website has contours at 5m intervals giving the hill an uppermost contour of 55m and bwlch contouring between 20m – 25m.  Therefore the summit is estimated as being c 57m high and the bwlch estimated as being c 23m high, with these values giving this hill c 34m of drop. 


The full details for the hill are:

Cardinal Hill:  Tal y Fan

Summit Height:  c 57m

Name:  Bodlondeb Wood

OS 1:50,000 map:  115

Summit Grid Reference:  SH 77923 78114

Drop:  c 34m


Myrddyn Phillips (July 2017)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Ynys Gron (SH 596 392) – 30-99m Twmpau reclassified to 30-99m Sub-Twmpau (10th reclassification)

Survey post for Ynys Gron


There has been a reclassification to the Twmpau (thirty welsh metre prominences and upward) list with a 30-99m Twmpau being reclassified to a 30-99m Sub-Twmpau due to surveying with the Trimble GeoXH 6000.  The details relating to this hill’s reclassification are retrospective as the survey with the Trimble took place on the 21th November 2014.

The criteria for 30-99m Twmpau status is all Welsh hills at or above 30m and below 100m in height with 30m minimum drop, whilst the criteria for 30-99m Sub-Twmpau status is all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop.

The hill had been listed in the original Welsh P30 lists when published on Geoff Crowder’s v-g.me website with a 96m summit height based on the Ordnance Survey 1:25,000 Outdoor Leisure spot height, with an accompanying note stating ‘98m on 1984 1:50,000 map.  Summit being reduced due to quarrying’.  When drop values were added to the P30 Master Lists this hill was given an estimated drop of c 50m.  The heights quoted appeared on maps of the day, although it was also known that the quarrying activities had already reduced the height of this hill.

The hill is situated in the Moelwynion group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Moelwyn Mawr (SH 658 448) and is situated between the towns of Porthmadog to the west and Penrhyndeudraeth to the east, and immediately above the busy A 487 road which is to its south.

The hill is not on open access land and the whole of its south-western section forms part of the Garth Quarry, which is operational, and because of this permission to visit should be sought.  However, the approach from the east is through woodland and would take a visitor direct to the remaining high point of the hill.

The name of the hill is Ynys Gron, which is a locally known name and it has been reclassified to a 30-99m Sub-Twmpau as the quarry has now obliterated the upper 30m of the hill and reduced it in height to 69.4m, and as its bwlch has been surveyed as 44.3m in height, it gives this hill only 25.1m of drop, which is insufficient for it to remain classified as a P30.


The full details for the hill are:


Cardinal Hill:  Moelwyn Mawr

Summit Height:  69.4m (converted to OSGM15)

Name:  Ynys Gron

OS 1:50,000 map:  124

Summit Grid Reference:  SH 59653 39268

Drop:  25.1m (converted to OSGM15)


The Trimble GeoXH 6000 gathering data at the remaining high point of Ynys Gron


Myrddyn Phillips (June 2017)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pt. 23.8m (SM 706 236) - Double Sub-Twmpau addition (9th reclassification)

Survey post for Pt. 23.8m


There has been a confirmation of an addition to the listing of Twmpau (thirty welsh metre prominences and upward) hills due to a recent survey with the Trimble GeoXH 6000.  The hill is now listed in the Double Sub-Twmpau list adjoined to the 30–99m height band of Twmpau hills and is situated on the eastern part of Ynys Dewi, which is also commonly known as Ramsey, this is an island to the west of St David’s in south-west Wales.

The hill did not appear in the Sub-List which accompanied the original Welsh P30 listings on Geoff Crowder’s v-g.me website as the Sub-List only included hills whose map details showed that when surveyed they may stand a chance of qualification to the main P30 list, with the title of the Sub-List being ‘Hills to be surveyed.’  And as this hill only has an uppermost 20m ring contour it was judged that even when surveyed there was no chance of it reaching the dizzying heights of having a minimum of 30m of drop, and therefore it was not included in the Sub-List.  However, since first publication this Sub-List has been standardised and now includes all hills that have a minimum of 20m of drop and below 30m of drop.

The Trimble GeoXH 6000 survey that resulted in this hill’s confirmation as a Double Sub-Twmpau was conducted during the afternoon of 15th May 2016 in beautiful, sunny and still conditions.

As the hill is situated on an island the only way to approach is via boat and the only company with permission to land on Ynys Dewi is Thousand Island Adventures (tel: 01437-721721).  The hill can be easily accessed as it rises immediately above where the boat docks, however when I visited it I sought permission to do so as it is off the beaten track as far as visitors are concerned.

The hill does not possess either a map or local name and therefore the point (Pt. 23.8m) notation is being used.  It currently has an uppermost 20m ring contour encircling its summit on Ordnance Survey maps and is now joined to the remainder of Ynys Dewi by the walkway leading to the track above where the boat docks.  This walkway is elevated above the sea and is man-made, with the natural connection between this small hill and the bulk of the island being a small pebbled bit of land below the track, it is estimated that this natural land is c 2m high.

Therefore the survey with the Trimble GeoXH 6000 resulted in a 23.8m (converted to OSGM15) summit height and with an estimated bwlch height of c 2m, this hill has c 22m of drop and therefore qualifies as a Double Sub-Twmpau.


The full details for the hill are:

Cardinal Island:  Ynys Dewi

Summit Height:  23.8m (converted to OSGM15)

Name:  Pt. 23.8m

OS 1:50,000 map:  157

Summit Grid Reference:  SM 70677 23686

Drop:  c 22m



Pt. 23.8m (SM 706 236) now confirmed as a Double Sub-Twmpau


Myrddyn Phillips (May 2016)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Foel Fawr (SM 705 225) - 30-99m Sub-Twmpau reclassified to 30-99m Twmpau (8th reclassification)

Survey post for Foel Fawr


There has been a reclassification to the listing of Twmpau (thirty welsh metre prominences and upward) hills due to a recent survey with the Trimble GeoXH 6000.  The hill is listed in the 30m–99m height band of Twmpau hills and is situated on the southern part of Ynys Dewi (Ramsey), which is an island to the west of St David’s in south-west Wales.

The hill appeared in the original Welsh P30 listings on Geoff Crowder’s v-g.me website and was included in the Sub-List adjoined to the 30m-99m height band of hills, and was the only hill listed in this Sub-List under the grouping of the Pembrokeshire Islands.

The Trimble GeoXH 6000 survey that resulted in this hill’s reclassification was conducted on the 15th May 2016 in the mid-afternoon in beautiful, sunny and still conditions.

As the hill is situated on an island the only way to approach is via boat and the only company with permission to land on Ynys Dewi is Thousand Island Adventures (tel: 01437-721721).  The hill can be easily accessed from where the boat docks as a gravelled track leads up to The Farmhouse from where a good path heads toward the southern part of the island.

The name of the hill is Foel Fawr and it is given a 72m summit spot height on current Ordnance Survey maps, and has been listed with an estimated bwlch height of c 43m based on bwlch contouring between 40m – 45m, these values gave the hill c 29m of drop and therefore it remained listed as a Sub-Twmpau.

Two points were surveyed for summit position and also for bwlch position, these are given below:


Summit 1:  72.0m (71.954m, converted to OSGM15)) at SM 70542 22567

Summit 2:  71.8m (71.821m, converted to OSGM15) at SM 70539 22566

Bwlch 1:  41.8m (41.764m, converted to OSGM15)) at SM 70504 22667

Bwlch 2:  41.9m (41.899m, converted to OSGM15) at SM 70511 22665


The surveys for bwlch position were conducted on the valley to valley traverse and therefore the higher result is taken when calculating the drop value for the hill. 

Therefore the survey with the Trimble GeoXH 6000 resulted in a 72.0m (converted to OSGM15) summit height and a 41.9m (converted to OSGM15) bwlch height, with these values giving the hill 30.1m of drop.  As the minimum drop for qualification to the main Twmpau list is 30m this means that Foel Fawr is reclassified from a Sub-Twmpau to a Twmpau.


The full details for the hill are:

Cardinal Island:  Ynys Dewi

Summit Height:  72.0m (converted to OSGM15)

Name:  Foel Fawr

OS 1:50,000 map:  157

Summit Grid Reference:  SM 70542 22567

Drop:  30.1m (converted to OSGM15)


Foel Fawr (SM 705 225) now reclassified from a Sub-Twmpau to a Twmpau


Myrddyn Phillips (May 2016)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Ynys Fach (SM 822 327) - 30-99m Twmpau reclassified to 30-99m Sub-Twmpau (7th reclassification)

Survey post for Ynys Fach


There has been a reclassification to the listing of the Twmpau (thirty welsh metre prominences and upward) hills due to a recent survey with the Trimble GeoXH 6000.  The hill is listed in the 30m – 99m height band of Twmpau hills and is situated on the northern Pembrokeshire coast close to the small communities of Porthgain to its west and Trefin (Trevine) to its east.

The hill is better described as an island, and even more so as a tidal island, and is connected to the mainland of Wales by a pebbled beach that according to maps is cut off from the mainland at high water.  It can be approached by boat, but an ascent of the island is feasible, albeit steep and potentially dangerous, from the mainland.  This approach starts from directly opposite the island and necessitates finding a route down bi-passing the rock and cliffs that predominate this part of the coastline.  If attempting this route please be careful.

The island was surveyed on 14th May 2016 on a beautiful sunny evening in the company of Adrian Rayner, Ayako and Rob Woodall.  It was Rob’s suggestion to go and have a look at it, and he found the route down to the pebbled beach which constitutes this island’s connecting bwlch.

The name of the island is Ynys Fach and it first appeared in a hill list on Geoff Crowder’s v-g.me website as a part of the original listing of Welsh P30s taking in the 100m height bands below the height of 500m. 

Ynys Fach is given an uppermost contour ring of 30m on current Ordnance Survey maps with no adjoined spot height.  However, the Ordnance Survey Six Inch map revised in 1906 and published in 1908 gives a 99ft height for the island, this is when the composition of the name was presented as Ynys Fâch, as opposed to the current Ynys-fach.  The 99ft spot height was later given on the Ordnance Survey 1:25,000 Historical map, with 99ft being an approximate 30.2m in metric measurement.

Two points were surveyed for summit position and these are given below:


Summit 1:  30.8m (30.789m, converted to OSGM15) at SM 82209 32743

Summit 2:  30.7m (30.727m, converted to OSGM15) at SM 82217 32752


The data set for the bwlch was remarkably good when considering that the equipment was placed in what resembled an enclosed and walled canyon, with the result being 1.2m (1.225m, converted to OSGM15) at SM 82180 32693.  These values give Ynys Fach a drop of only 29.6m and therefore it is reclassified from a 30-99m Twmpau to a Sub-Twmpau.


The full details for the hill are:

Cardinal Hill:  Garn Fawr

Summit Height:  30.8m (converted to OSGM15)

Name:  Ynys Fach

OS 1:50,000 map:  157

Summit Grid Reference:  SM 822 327

Drop:  29.6m (converted to OSGM15)



Ynys Fach (SM 822 327) now reclassified from a Twmpau to a Sub-Twmpau



Myrddyn Phillips (May 2016)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Daufraich (SM 661 236) - Double Sub-Twmpau addition (6th reclassification)

Survey post for Daufraich


There has been an addition to the Sub category within the 30–99m Twmpau (thirty welsh metre prominences and upward) hill list instigated by a survey with the Trimble GeoXH 6000.   The hill is better described as an island and is situated to the west of St David’s in south-west Wales, and forms part of the chain of islands known as the Bishops and Clerks.

The Trimble GeoXH 6000 survey that resulted in this hill’s inclusion as a 30–99m Sub-Twmpau was conducted on the 14th May 2016 in the early afternoon on a fine day in good, dry and sunny conditions.  The trip to this and other islands was organised by Adrian Rayner and the survey took place in the company of Adrian, Rob Woodall, Bob Kerr and Jon Glew, with Sheila Glew, Akako and Sarah Kerr remaining on the RIB whilst we were on the island.

Not surprisingly the island can only be accessed by boat, and although landing is relatively easy the way to the summit involves a scramble, and although not difficult it is exposed, with the prospect of an undignified dunking in the sea a distinct probability if one foot hold proves a wee bit slippy.

The name of the island is Daufraich and it comprises two parts, with its easterly high point being given the map height of 20m, and its westerly high point being given two positions of 21m high on current Ordnance Survey maps.  We only had time to land on the westerly part of the island which proved visually higher than the easterly part.  I also only had time for one survey, and consensus of opinion was that the highest part of the island was where the south-eastern 21m spot height appears on the ground, with the ground where the north-western 21m spot height is positioned being assessed as slightly lower.

Daufraich was not included in the Sub-List which accompanied the original listing of 30m -99m hills that appeared on Geoff Crowders v-g.me website, as that Sub-List comprised ‘Hills to Survey’ and as this island was under 30m in height it was not included as the only hills that were, were those deemed to have chance of qualifying for the main P30 list after having been surveyed.  However, this Sub-List has now been standardised and includes all hills that are known to have at least 20m of drop and below 30m of drop.

The survey with the Trimble GeoXH 6000 resulted in a 21.7m (converted to OSGM15) summit height, which as an island is also this hill’s drop value, and therefore confirming its entry in to the 30–99m Sub-Twmpau ranks.


The full details for the hill are:

Cardinal Island:  Bishops and Clerks

Summit Height:  21.7m (converted to OSGM15)

Name:  Daufraich

OS 1:50,000 map:  157

Summit Grid Reference:  SM 66199 23673

Drop:  21.7m (converted to OSGM15)



Daufraich (SM 661 236) the new Double Sub-Twmpau



Myrddyn Phillips (May 2016)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Moel y Gadair (SH 521 391) 30-99m Twmpau reclassified to 30-99m Sub-Twmpau (5th reclassification)

Summit survey post for Moel y Gadair

Bwlch survey post for Moel y Gadair


There has been a reclassification to the listing of Twmpau (thirty welsh metre prominences and upward) hills due to a recent survey with the Trimble GeoXH 6000.  The hill is listed in the 30–99m height band of Twmpau hills and is situated to the south-west of the small community of Pentrefelin, which is situated between Porthmadog to the east and Cricieth to the south-west.

The hill has been reclassified from a P30 Twmpau to a Sub-Twmpau, and re-joins these ranks after being originally listed in the ‘Hills to Survey’ Sub-List that appeared on Geoff Crowder’s v-g.me website.  On subsequent reassessment the hill was promoted to full P30 status due to bwlch contour interpolation, with a drop value of c 30m based on a summit spot height of 67m and an estimated bwlch height of c 37m.

The hill is named Moel y Gadair and its summit was surveyed with the Trimble GeoXH 6000 on the 15th June 2015 giving a height of 66.7m (converted to OSGM15).  On that day I misinterpreted the bwlch contouring and therefore took a number of data sets from the incorrect place.  Having re-examined Ordnance Survey mapping and driven a Google Car on the A 497 which passes over this bwlch I was confident that I now knew where the critical bwlch was positioned.

The subsequent survey of this hill’s bwlch resulted in a height value of 38.1m (converted to OSGM15), giving the hill insufficient drop to retain its P30 Twmpau status.


The full details for the hill are:

Cardinal Hill:  Moel Hebog

Summit Height:  66.7m (converted to OSGM15)

Name:  Moel y Gadair

OS 1:50,000 map:  124

Summit Grid Reference:  SH 521 391

Drop:  28.5m (converted to OSGM15)


Moel y Gadair (SH 521 391) now reclassified from a P30 Twmpau to a Sub-Twmpau with 28.5m of drop

For details on the survey that reclassified this hill from P30 Twmpau to Sub-Twmpau status please click {here} for summit and {here} for the bwlch survey.


Myrddyn Phillips (February 2016)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Castell Cricieth (SH 500 377) - 30-99m Twmpau addition (4th reclassification)

Survey post for Castell Cricieth
  

There has been an addition to the listing of Twmpau (thirty welsh metre prominences and upward) hills due in part to a recent survey with the Trimble GeoXH 6000.  The hill is listed in the 30m-99m height band of Twmpau hills and is situated in the town of Cricieth.

Its P30 status was first discovered by Alex Cameron who rightly judged that with a 48m summit spot height which appears on the Ordnance Survey enlarged mapping hosted on the Geograph website, and with bwlch contouring between c 15m – c 20m, with an estimated bwlch height of c 18m, this hill should be listed as a P30 with c 30m of drop.

The hill is Castell Cricieth which as its name implies has a castle on top of it.

This hill is one of the rarities that have not appeared in previous Sub-Lists before its entrance as a fully-fledged P30.


The full details for the hill are:

Cardinal Hill:  Moel Hebog

Summit Height:  49.6m (converted to OSGM15)

Name:  Castell Cricieth

OS 1:50,000 map:  123

Summit Grid Reference:  SH 500 377

Drop:  30.3m (converted to OSGM15)


Castell Cricieth (SH 500 377) P30 status now confirmed by the Trimble GeoXH 6000

For details on the survey that confirmed this hill's status as a 30-99m Twmpau please click {here}


Myrddyn Phillips (June 2015)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Carreg yr Eryr (SH 526 378) - 30-99m Sub-Twmpau reclassified to 30-99m Twmpau (3rd reclassification)

Survey post for Carreg yr Eryr


There has been a new addition to the listing of Twmpau (thirty welsh metre prominences and upward) hills due to a recent survey with the Trimble GeoXH 6000.  The hill is listed in the 30m-99m height band of Twmpau hills and is situated on the outskirts of Morfa Bychan overlooking Black Rock Sands to its east and Castell Cricieth to its west.

The first time Carreg yr Eryr ever appeared in a hill list was in 2003 when the original Welsh P30 hills under 500m in height were published on Geoff Crowder’s v-g.me website.  It was then listed in the Sub-List which was named ‘Hills to Survey’.  The reason for this was that Carreg yr Eryr was not given a summit and bwlch spot height that gave it a minimum of 30m of drop on the then current Ordnance Survey map, because of this it was listed as a Sub.  When this list was first published on Geoff’s website it did not include a drop value for each hill, although the qualification for the main list and the Sub-List was based on drop.  These drop values were added at a later date.

When these drop values were added to the list I also decided to include hills in the Main P30 Twmpau list through interpolation of map contours, although some of these details were passed onto Geoff, the great majority were not.  When drop figures were added to the list I gave Carreg yr Eryr c 30m of drop and promoted it into the ranks of P30 hills.  This drop value was estimated from its 53m summit spot height and an estimated bwlch height of c 23m based on the 1:25,000 map bwlch contouring between c 20m – c 30m.  Since this hill was promoted into the P30 ranks the Ordnance Survey enlarged map on the Geograph website has been made available, and this map has contour intervals of 5m and gives the bwlch contouring between c 20m and c 25m, with an estimated bwlch height of c 23m, so the hill remained listed as a P30.  Even though the hill had been promoted in my list the details were never made public, so it was now time to have it Trimbled and to confirm its status via the Mapping Mountains blog.


The full details for the hill are:

Cardinal Hill:  Moel Hebog

Summit Height:  53.3m (converted to OSGM15)

Name:  Carreg yr Eryr

OS 1:50,000 map:  124

Summit Grid Reference:  SH 526 378

Drop:  30.9m (converted to OSGM15)


Carreg yr Eryr (SH 526 378) P30 status now confirmed by the Trimble GeoXH 6000

For details on the survey that confirmed this hill's 30m-99m Twmpau status please click {here}

Myrddyn Phillips (June 2015)






Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Ynys Tywyn (SH 571 385) - Double Sub-Twmpau addition (2nd reclassification)

Survey post for Ynys Tywyn
   

There has been an addition to the 30-99m Twmpau list with this hill entering the category of Double Sub-Twmpau.  The name of the hill is Ynys Tywyn (SH 571 385) and it is situated at the end of the Cob in Porthmadog in north-west Wales.  

Ynys Tywyn has a small uppermost 20m contour ring on Ordnance Survey maps, but no spot height, and a recent survey with the Trimble GeoXH 6000 confirms that the hill is over 20m but under 30m in height and as it is the high point of an island that is now connected to Porthmadog by the Cob, and therefore its height is also considered to be its drop, it has been included in the Double Sub-Twmpau category.  The summit is crowned by a large flat rock and gorse bushes and has fine views over the Afon Glaslyn to the higher mountains of Eryri.


The full details for the hill are:

Cardinal Hill:  Moel Hebog

Summit Height:  21.8m (converted to OSGM15)

Name:  Ynys Tywyn

OS 1:50,000 map:  124

Summit Grid Reference:  SH 571 385

Drop:  21.8m (converted to OSGM15)


Ynys Tywyn (SH 571 385) is now confirmed as a Double SubTwmpau

For details on the survey that promoted this hill to Double Sub-Twmpau status please click {here}


Myrddyn Phillips (January 2015)







Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Ynys Glog (SH 596 398) and Ynys Berfedd (SH 599 398) - 30-99m Twmpau additions (1st reclassification) 

Survey post for Ynys Glog

Survey post for Ynys Berfedd


There have been three new Welsh island P30 hills recently discovered.  These additions to the 30-99m Twmpau list were found by Aled Williams through map study and local knowledge of the area, with two of these hills accepted automatically to the listing of Twmpau hills and with the other hill entering the Twmpau list through surveying with the Trimble GeoXH 6000.

The two hills automatically accepted in to the 30-99m Twmpau list are Ynys Glog (SH 596 398) and Ynys Berfedd (SH 599 398).  Whilst the other hill is named Ynys Hir (SH 566 396) which was confirmed as a P30 through surveying with the Trimble GeoXH 6000.  

Aled considered the hill at SH 566 396 and its adjacent hill at SH 566 398 which is also known as Ynys Hir as suitable candidates for surveying with a high chance of promotion to the P30 ranks, and considered that the uppermost 20m ring contour given to both hills on the Ordnance Survey enlarged mapping hosted on the Geograph website was incorrect and a misrepresentation of their actual height.


A note from Aled:

Two New P30 Hills

Analysis of OS enlarged mapping on the Geograph website confirms two P30 hills that are absent from both the '30-99m Twmpau' list by Myrddyn Phillips (2004) and the 'Tumps' list by Mark Jackson (2009). I bring this information to the attention of the authors.


Name: Ynys Glog
Height: 40.6m (converted to OSGM15)
Drop: 32.7m (converted to OSGM15)
Grid Reference: SH 59647 39826



Name: Ynys Berfedd
Height: 42.9m (converted to OSGM15)
Drop: 36.1m (converted to OSGM15)
Grid Reference: SH 59943 39865



Aled Williams (03/02/2014).




The discovery of new P30’s is not a rarity, but what is unusual is that each of these hills was once an island that is now landlocked in the area known as Traeth Mawr, this is near to Aled’s home in Porthmadog.  Subsequently all of these hills have been surveyed using the Trimble GeoXH 6000 and their respective results are given above.



For more detail of the Trimble survey that promoted Ynys Hir to 30-99m Twmpau status click {here} 



A post by Aled on the land known as Traeth Mawr and its many small islands is due for publication in the Guest Contributor page on the Mapping Mountains blog in March. 


Aled Williams at the summit of Ynys Hir (SH 566 396)

Myrddyn Phillips (February 2014)