Mapping Mountains – Hill Reclassifications – 100m Twmpau

100m Twmpau – Hill Reclassifications

The 100m Twmpau (an acronym for thirty welsh metre prominences and upward) are the Welsh hills at or above 100m and below 20om in height that have a minimum drop of 30m.  Accompanying the main P30 list is a sub list entitled the 100m Sub-Twmpau with the qualification to this sub category being all Welsh hills at or above 100m and below 200m 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 list appear below presented chronologically in receding order.

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Bryn y Beudy (SH 507 404) – 100m Sub-Twmpau addition (70th reclassification)

Summit Relocations post for Bryn y Beudy

Significant Name Changes post for Bryn y Beudy

There has been confirmation of an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Bryn y Beudy (SH 507 404)

The criteria for the list that this addition applies to are:

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

100m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Bryn y Beudy and this was derived from the Tithe map, and it is adjoined to the Moel Hebog group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with minor roads to its north and south, the B4411 road to its south-west and the A487 road to its north-east, and has the town of Cricieth towards the south.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with 22m of drop, based on the 156m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 134m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the confirmation of the addition of this hill to 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 155.2m summit height and a 132.7m bwlch height, with these values giving this hill 22.5m of drop, which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Moel Hebog 

Name:  Bryn y Beudy 

OS 1:50,000 map:  124

Summit Height:  155.2m (LIDAR) 

Summit Grid Reference:  SH 50785 40428 & SH 50786 40429 (LIDAR) 

Bwlch Height:  132.7m (LIDAR) 

Bwlch Grid Reference:  SH 51229 40222 (LIDAR) 

Drop:  22.5m (LIDAR) 

 

Myrddyn Phillips (April 2024)

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Allt Pen y Lan (SN 707 323) – 100m Sub-Twmpau addition (69th reclassification)

There has been confirmation of an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Allt Pen y Lan (SN 707 323)

The criteria for the list that this addition applies to are:

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Allt Pen y Lan, and it is adjoined to the Mynydd Mallaen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with a minor road to its north-west, the A40 road to its south and the A482 road to its east, and has the village of Llanwrda towards the south-east.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 25m of drop, based on the 137m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 112m bwlch height, based on interpolation of 10m contouring between 110m – 120m. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the confirmation of the addition of this hill to 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 136.5m summit height and a 112.0m bwlch height, with these values giving this hill 24.5m of drop, which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Mallaen 

Name:  Allt Pen y Lan 

OS 1:50,000 map:  146, 160

Summit Height:  136.5m (LIDAR) 

Summit Grid Reference:  SN 70714 32376 & SN 70715 32374 & SN 70717 32374 (LIDAR) 

Bwlch Height:  112.0m (LIDAR) 

Bwlch Grid Reference:  SN 70316 32246 (LIDAR) 

Drop:  24.5m (LIDAR) 

 

Myrddyn Phillips (April 2024)

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Pt. 118.2m (SN 717 303) – 100m Sub-Twmpau addition (68th reclassification)

There has been confirmation of an addition to the list of the 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Pt. 118.2m (SN 717 303)

The criteria for the list that this addition applies to are:

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

100m Twmpau by Myrddyn Phillips

The hill is being listed by the point (Pt. 118.2m) notation as an appropriate name for it either through local enquiry and/or historic research has not been found by the author, and it is adjoined to the Mynydd Du group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and it is positioned with the A40 road to its north-west and a minor road to its immediate south-east, and has the village of Llangadog towards the south south-west.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 26m of drop, based on an estimated c 117m summit height and an estimated c 91m bwlch height, with both heights based on interpolation of 5m contouring that appeared on the OS Maps website.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the confirmation of the addition of this hill to 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 118.2m summit height and a 90.8m bwlch height, with these values giving this hill 27.4m of drop, which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Du 

Name:  Pt. 118.2m 

OS 1:50,000 map:  146, 160

Summit Height:  118.2m (LIDAR) 

Summit Grid Reference:  SN 71731 30341 & SN 71732 30342 (LIDAR) 

Bwlch Height:  90.8m (LIDAR) 

Bwlch Grid Reference:  SN 71320 29901 (LIDAR) 

Drop:  27.4m (LIDAR) 

 

Myrddyn Phillips (April 2024) 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Allt Pendugoedydd (SN 749 311) – 100m Sub-Twmpau addition (67th reclassification)

Significant Height Revisions post for Allt Pendugoedydd

Significant Name Changes post for Allt Pendugoedydd

There has been confirmation of an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Allt Pendugoedydd (SN 749 311)

The criteria for the list that this addition applies to are:

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

100m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Allt Pendugoedydd and this was confirmed by the Ordnance Survey series of Six-Inch maps, and it is adjoined to the Mynydd Du group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and it is positioned with the A4069 road to its north-west and minor roads to its west and east, and has the village of Llangadog towards the south-west.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 20m of drop, based on the 163m summit spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map and an estimated c 143m bwlch height, based on interpolation of 5m contouring between 140m – 145m that appeared on the OS Maps website.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the confirmation of the addition of this hill to 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 162.4m summit height and a 141.4m bwlch height, with these values giving this hill 21.0m of drop, which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Du 

Name:  Allt Pendugoedydd 

OS 1:50,000 map:  146, 160

Summit Height:  162.4m (LIDAR) 

Summit Grid Reference:  SN 74992 31127 (LIDAR) 

Bwlch Height:  141.4m (LIDAR) 

Bwlch Grid Reference:  SN 75086 31369 (LIDAR) 

Drop:  21.0m (LIDAR) 

 

Myrddyn Phillips (April 2024)

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Pt. 152.6m (SN 747 277) – 100m Sub-Twmpau addition (66th reclassification)

There has been confirmation of an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Pt. 152.6m (SN 747 277)

The criteria for the list that this addition applies to are:

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

100m Twmpau by Myrddyn Phillips

The hill is being listed by the point (Pt. 152.6m) notation as an appropriate name for it either through local enquiry and/or historic research has not been found by the author, and it is adjoined to the Mynydd Du group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and it is positioned encircled by minor roads, with the A4069 road farther to its west, and has the village of Llangadog towards the west.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with 21m of drop, based on the 153m summit spot height and the 132m bwlch spot height that appear on the contemporary Ordnance Survey 1:25,000 Explorer map. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the confirmation of the addition of this hill to 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 152.6m summit height and a 132.5m bwlch height, with these values giving this hill 20.1m of drop, which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Du 

Name:  Pt. 152.6m 

OS 1:50,000 map:  146, 160

Summit Height:  152.6m (LIDAR) 

Summit Grid Reference:  SN 74733 27758 (LIDAR) 

Bwlch Height:  132.5m (LIDAR) 

Bwlch Grid Reference:  SN 74874 27534 (LIDAR) 

Drop:  20.1m (LIDAR) 

 

Myrddyn Phillips (March 2024)

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Lan Fach (SN 630 267) – 100m Sub-Twmpau addition (65th reclassification)

Summit Relocations post for Lan Fach

Significant Name Changes post for Lan Fach

There has been confirmation of an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Lan Fach (SN 630 267)

The criteria for the list that this addition applies to are:100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

100m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Lan Fach and this was derived from the Tithe map, and it is adjoined to the Mynydd Mallaen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north, west, south and east, the A40 road farther to its south and the B4302 road farther to its east, and has the town of Llandeilo towards the south.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 20m of drop, based on an estimated c 181m summit height and an estimated c 161m bwlch height, with both heights based on interpolation of 10m contouring that appear on the contemporary Ordnance Survey 1:25,000 Explorer map. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the confirmation of the addition of this hill to 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 182.6m summit height and a 159.1m bwlch height, with these values giving this hill 23.4m of drop, which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Mallaen 

Name:  Lan Fach 

OS 1:50,000 map:  146

Summit Height:  182.6m (LIDAR) 

Summit Grid Reference:  SN 63091 26746 (LIDAR) 

Bwlch Height:  159.1m (LIDAR) 

Bwlch Grid Reference:  SN 62212 26133 (LIDAR) 

Drop:  23.4m (LIDAR) 

 

Myrddyn Phillips (March 2024)

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Coed Uchaf (SJ 232 683) – 100m Twmpau reclassified to 100m Sub-Twmpau (64th reclassification)

Significant Height Revisions post for Coed Uchaf

Summit Relocations post for Coed Uchaf

Significant Name Changes post for Coed Uchaf

There has been a reclassification to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail produced by Joe Nuttall in his surface analysis programme, with subsequent LIDAR analysis conducted by the DoBIH team and independently by Myrddyn Phillips. 

LIDAR image of Coed Uchaf (SJ 232 683)

The criteria for the list that this reclassification applies to are:

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Coed Uchaf, and it is adjoined to the Moel y Gamelin group of hills, which are situated in the north-eastern part of North Wales (Region A, Sub-Region A2), and it is positioned encircled by minor roads, with the A55 road farther to its north, the B5123 road farther to its west, the A541 road farther to its south and the A5119 road farther to its east, and has the town of Y Fflint (Flint) towards the north.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 category. 

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

Since the original publication of the Welsh P30 lists on Geoff Crowder’s v-g.me website there have been a number of maps made available online.  Some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website.  Whilst others were digitally updated such as the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map, whilst others are current and digitally updated such as the interactive mapping on the Magic Maps and WalkLakes websites.

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated against the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map.  This mapping had many spot heights not on other publicly available maps and for this hill it had a 162m summit spot height positioned at SJ 23209 68591 and with an estimated c 132m bwlch height based on interpolation of 5m contouring between 130m – 135m, these values gave this hill an estimated c 30m of drop and therefore it was reclassified to 100m Twmpau status.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the reclassification of this hill to 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 161.7m summit height and a 132.6m bwlch height, with these values giving this hill 29.1m of drop, which is insufficient for it to be classified as a 100m Twmpau. 

 

The full details for the hill are: 

Group:  Moel y Gamelin 

Name:  Coed Uchaf 

OS 1:50,000 map:  117

Summit Height:  161.7m (LIDAR) 

Summit Grid Reference:  SJ 23205 68344 (LIDAR) 

Bwlch Height:  132.6m (LIDAR) 

Bwlch Grid Reference:  SJ 23101 68383 (LIDAR) 

Drop:  29.1m (LIDAR) 

 

Myrddyn Phillips (January 2024)

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Pt. 102.2m (SM 886 395) – 100m Sub-Twmpau reclassified to 100m Twmpau (63rd reclassification)

Significant Name Changes post for Pt. 102.2m

There has been confirmation of a reclassification to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Pt. 102.2m (SM 886 395)

The criteria for the list that this reclassification applies to are:

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The hill is being listed by the point (Pt. 102.2m) notation as an appropriate name for it either through local enquiry and/or historic research has not been found by the author, and it is adjoined to the Garn Fawr group of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned with the coast to its north, west and south, and minor roads to its east and south-east, with the A487 road farther to its south-east, and has the town of Abergwaun (Fishguard) towards the east south-east.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 category.

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 30m of drop, based on the 103m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 73m bwlch height based on interpolation of 5m contouring between 70m – 75m. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the confirmation of the reclassification of this hill from 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 102.2m summit height and a 71.4m bwlch height, with these values giving this hill 30.8m of drop, which is sufficient for it to be classified as a 100m Twmpau. 

 

The full details for the hill are: 

Group:  Garn Fawr 

Name:  Pt. 102.2m 

OS 1:50,000 map:  157

Summit Height:  102.2m (LIDAR) 

Summit Grid Reference:  SM 88697 39503 (LIDAR) 

Bwlch Height:  71.4m (LIDAR) 

Bwlch Grid Reference:  SM 88963 39549 (LIDAR) 

Drop:  30.8m (LIDAR) 

 

Myrddyn Phillips (June 2023)

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Parc Tincer Uchaf (SN 026 261) – 100m Sub-Twmpau addition (62nd reclassification)

Significant Name Changes post for Parc Tincer Uchaf

There has been confirmation of an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Parc Tincer Uchaf (SN 026 261)

The criteria for the list that this addition applies to are:

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Parc Tincer Uchaf and this was derived from the Tithe map, and it is adjoined to the Mynydd Preseli group of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned with the B4329 road to its immediate west and a minor road to its south, and has the village of Maenclochog towards the east north-east.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 28m of drop, based on the 194m summit spot height adjoined to a triangulation pillar that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 166m bwlch height, based on interpolation of 5m contouring between 165m – 170m. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the confirmation of the addition of this hill to 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 194.4m summit height and a 164.5m bwlch height, with these values giving this hill 29.9m of drop, which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Preseli 

Name:  Parc Tincer Uchaf 

OS 1:50,000 map:  145, 157, 158

Summit Height:  194.4m (LIDAR) 

Summit Grid Reference:  SN 02657 26167 (LIDAR) 

Bwlch Height:  164.5m (LIDAR) 

Bwlch Grid Reference:  SN 02677 26867 (LIDAR) 

Drop:  29.9m (LIDAR) 

 

Myrddyn Phillips (April 2023)

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Pen y Foel (SN 000 381) – 100m Twmpau reclassified to 100m Sub-Twmpau (61st reclassification)

There has been a reclassification to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Pen y Foel (SN 000 381) 

The criteria for the list that this reclassification applies to are:

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Pen y Foel, and it is adjoined to the Mynydd Preseli group of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned with a minor road to its west, and the A487 road to its south-east, and has the town of Abergwaun (Fishguard) towards the west south-west.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the main P30 list, as the contemporary Ordnance Survey 1:25,000 Explorer map gives this hill an uppermost 110m contour and bwlch contouring between 75m – 80m, resulting in this hill having a minimum of 30m of drop.

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 31m of drop, based on an estimated c 110m summit spot height and an estimated c 79m bwlch height, with both heights based on interpolation of 5m contouring that appears on the Ordnance Survey 1:25,000 Explorer map. 

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

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had a 109m summit spot height which resulted in the drop value of this hill being amended to an estimated c 30m.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the reclassification of this hill to 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 108.5m summit height and an 80.1m bwlch height, with these values giving this hill 28.4m of drop, which is insufficient for it to be classified as a 100m Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Preseli 

Name:  Pen y Foel 

OS 1:50,000 map:  145, 157

Summit Height:  108.5m (LIDAR) 

Summit Grid Reference:  SN 00073 38103 (LIDAR) 

Bwlch Height:  80.1m (LIDAR) 

Bwlch Grid Reference:  SN 00179 37983 (LIDAR) 

Drop:  28.4m (LIDAR) 

 

Myrddyn Phillips (March 2023)

 

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Ffynnon Cyff (SN 187 505) – 100m Sub-Twmpau reclassified to 100m Twmpau (60th reclassification)

Significant Name Changes post for Ffynnon Cyff

There has been confirmation of a reclassification to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Ffynnon Cyff (SN 187 505)

The criteria for the list that this reclassification applies to are:

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Ffynnon Cyff and this was derived from the Tithe map, and it is adjoined to the Mynydd Bach group of hills, which are situated in the western part of South Wales (Region B, Sub-Region B1), and it is positioned with the coast to its north, minor roads to its west and south-east, and the B4548 road farther to its south-west and the A487 road farther to its south-east, and has the town of Aberteifi (Cardigan) towards the south.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 category.

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 30m of drop, based on the 151m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 121m bwlch height based on interpolation of 5m contouring between 120m – 125m. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the confirmation of the reclassification of this hill from 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 150.35m summit height and a 119.6m bwlch height, with these values giving this hill 30.8m of drop, which is sufficient for it to be classified as a 100m Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Bach 

Name:  Ffynnon Cyff 

OS 1:50,000 map:  145

Summit Height:  150.35m (LIDAR) 

Summit Grid Reference:  SN 18745 50585 (LIDAR) 

Bwlch Height:  119.6m (LIDAR) 

Bwlch Grid Reference:  SN 19222 50439 (LIDAR) 

Drop:  30.8m (LIDAR) 

 

Myrddyn Phillips (February 2023)

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Tan Pen y Graig Fawr (SN 584 702) – 100m Sub-Twmpau reclassified to 100m Twmpau (59th reclassification)

Significant Name Changes post for Tan Pen y Graig Fawr

There has been confirmation of a reclassification to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Tan Pen y Graig Fawr (SN 584 702)

The criteria for the list that this reclassification applies to are:

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Tan Pen y Graig Fawr and this was derived from the Tithe map, and it is adjoined to the Mynydd Bach group of hills, which are situated in the western part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north-west, immediate south and north-east, and the B4576 road farther to its east, and has the village of Llangwyryfon towards the east north-east.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 category.

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 28m of drop, based on an estimated c 174m summit height and an estimated c 146m bwlch height, with both heights based on interpolation of 10m contouring that appears on the Ordnance Survey 1:25,000 Explorer map. 

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

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had a 177m summit spot height and a 145m bwlch spot height, resulting in the drop value of this hill being amended to 32m.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the confirmation of the reclassification of this hill from 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 177.2m summit height and a 144.0m bwlch height, with these values giving this hill 33.3m of drop, which is sufficient for it to be classified as a 100m Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Bach 

Name:  Tan Pen y Graig Fawr 

OS 1:50,000 map:  135

Summit Height:  177.2m (LIDAR) 

Summit Grid Reference:  SN 58475 70282 (LIDAR) 

Bwlch Height:  144.0m (LIDAR) 

Bwlch Grid Reference:  SN 59667 70471 (LIDAR) 

Drop:  33.3m (LIDAR) 

 

Myrddyn Phillips (January 2023)

 

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Ffynnon Fair (SN 541 469) – 100m Sub-Twmpau reclassified to 100m Twmpau (58th reclassification)

Significant Name Changes post for Ffynnon Fair

There has been confirmation of a reclassification to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Ffynnon Fair (SN 541 469)

The criteria for the list that this reclassification applies to are:

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Ffynnon Fair and this was derived from the Tithe map, and it is adjoined to the Mynydd Bach group of hills, which are situated in the western part of South Wales (Region B, Sub-Region B1), and it is positioned with the A475 road to its north, the B4337 road to its west and the A485 road to its south, and has the town of Llanbedr Pont Steffan (Lampeter) towards the east north-east.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 category.

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 31m of drop, based on the 157m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 126m bwlch height based on interpolation of 10m contouring between 120m – 130m. 

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

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had bwlch contouring between 120m – 125m , with interpolation giving the height of the bwlch as an estimated c 123m, resulting in the drop value of this hill being amended to an estimated c 34m.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the confirmation of the reclassification of this hill from 100m Sub-Twmpau status is due to LIDAR analysis, , resulting in a 156.6m summit height and a 122.7m bwlch height, with these values giving this hill 34.0m of drop, which is sufficient for it to be classified as a 100m Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Bach 

Name:  Ffynnon Fair 

OS 1:50,000 map:  146

Summit Height:  156.6m (LIDAR) 

Summit Grid Reference:  SN 54187 46971 (LIDAR) 

Bwlch Height:  122.7m (LIDAR) 

Bwlch Grid Reference:  SN 53901 47269 (LIDAR) 

Drop:  34.0m (LIDAR) 

 

Myrddyn Phillips (January 2023)

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Cae Gafell (SN 431 282) – 100m Sub-Twmpau reclassified to 100m Twmpau (57th reclassification)

Significant Name Changes post for Cae Gafell

There has been confirmation of a reclassification to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Cae Gafell (SN 431 282)

The criteria for the list that this reclassification applies to are:

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Cae Gafell and this was derived from the Tithe map, and it is adjoined to the Mynydd Pencarreg group of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned with a minor road to its north and south, and the B4301 road and the A485 road to its east, has the town of Caerfyrddin (Carmarthen) towards the south.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 category.

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 30m of drop, based on the 173m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 143m bwlch height based on interpolation of 5m contouring between 140m – 145m. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the confirmation of the reclassification of this hill from 100m Sub-Twmpau status is due to LIDAR analysis, , resulting in a 173.4m summit height and a 143.1m bwlch height, with these values giving this hill 30.3m of drop, which is sufficient for it to be classified as a 100m Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Pencarreg 

Name:  Cae Gafell 

OS 1:50,000 map:  146

Summit Height:  173.4m (LIDAR) 

Summit Grid Reference:  SN 43157 28229 (LIDAR) 

Bwlch Height:  143.1m (LIDAR) 

Bwlch Grid Reference:  SN 42875 27715 (LIDAR) 

Drop:  30.3m (LIDAR) 

 

Myrddyn Phillips (July 2022)

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Bryn (SN 274 401) – 100m Sub-Twmpau reclassified to 100m Twmpau (56th reclassification)

Significant Name Changes post for Bryn

There has been a reclassification to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data. 

The criteria for the list that this reclassification applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Bryn and this was derived from the Tithe map, and it is adjoined to the Mynydd Pencarreg group of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north-east and south, the A484 road farther to its north-east and the B4332 road to its north-west, and has the town of Castellnewydd Emlyn (Newcastle Emlyn) towards the east.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 category.

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 30m of drop, based on the 178m summit spot height adjoined to a triangulation pillar that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 158m bwlch height based on interpolation of 10m contouring between 150m – 160m. 

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

Since the original publication of the Welsh P30 lists on Geoff Crowder’s v-g.me website there have been a number of maps made available online.  Some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website.  Whilst others were digitally updated such as the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map, whilst others are current and digitally updated such as the interactive mapping on the Magic Maps and WalkLakes websites.

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had a 148m spot height positioned on the area of the bwlch, and when coupled with the 178m summit spot height, these values gave this hill 30m of drop.

One of the mapping resources now available online is on the Magic Maps website which hosts an interactive map originated from Ordnance Survey data.  Until recently this mapping had many spot heights not on other publicly available maps and for this hill it also had the 148m spot height positioned on the area of the bwlch. 

Extract from the Magic Maps website

One of the resources recently available online is the mapping on the OS Maps website and the details for this hill were subsequently re-assessed against this mapping.  This is the replacement for OS Get-a-map and until recent times had contours at 5m intervals which were proving consistently more accurate compared to the 5m contours that sometimes appear on the Ordnance Survey 1:25,000 Explorer map and used to appear on the online Vector Map Local.  This mapping had bwlch contouring between 145m – 150m, with interpolation placing the height of the bwlch as an estimated c 148m, with this position favoured over that of the 148m spot height.

Therefore, the reclassification of this hill from 100m Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data, , resulting in a 178m summit height and an estimated c 148m bwlch height, with these values giving this hill an estimated c 30m of drop, which is sufficient for it to be classified as a 100m Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Pencarreg 

Name:  Bryn 

OS 1:50,000 map:  145

Summit Height:  178m (triangulation pillar) 

Summit Grid Reference:  SN 27426 40150 (triangulation pillar) 

Bwlch Height:  c 148m (interpolation) 

Bwlch Grid Reference:  SN 28020 40064 (interpolation) 

Drop:  c 30m (triangulation pillar summit and interpolated bwlch) 

 

Myrddyn Phillips (July 2022)

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Y Lan (SN 283 229) – 100m Twmpau reclassified to 100m Sub-Twmpau (55th reclassification)

Significant Name Changes post for Y Lan

There has been a reclassification to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Y Lan (SN 283 229)

The criteria for the list that this reclassification applies to are:

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Y Lan and this was derived from the Tithe map, and it is adjoined to the Mynydd Pencarreg group of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north, west and south and the B4299 road to its east, and has the small town of Sanclêr (St Clears) towards the south.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 category.

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with 30m of drop, based on the 188m summit spot height and the 158m bwlch spot height that appear on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the reclassification of this hill to 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 188.0m summit height and a 158.0m bwlch height, with these values giving this hill 29.97m of drop, which is insufficient for it to be classified as a 100m Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Pencarreg 

Name:  Y Lan 

OS 1:50,000 map:  145, 158

Summit Height:  188.0m (LIDAR) 

Summit Grid Reference:  SN 28371 22966 (LIDAR) 

Bwlch Height:  158.0m (LIDAR) 

Bwlch Grid Reference:  SN 28481 23410 & SN 28481 23413 (LIDAR) 

Drop:  29.97m (LIDAR) 

 

Myrddyn Phillips (July 2022)

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Bron y Gaer (SN 699 326) – 100m Sub-Twmpau reclassified to 100m Twmpau (54th reclassification)

Summit Relocations post for Bron y Gaer

Significant Name Changes post for Bron y Gaer

There has been confirmation of a reclassification to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Bron y Gaer (SN 699 326)

The criteria for the list that this reclassification applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Bron y Gaer and this was derived from the Tithe map, and it is adjoined to the Mynydd Mallaen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its west and south, the A40 road farther to its south and the A482 road to its east, and has the town of Llanymddyfri (Llandovery) towards the east north-east. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list that accompanied the main P30 list, as it was considered not to meet the criteria then used for the main P30 category. 

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 30m of drop, based on the 198m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 168m bwlch height based on interpolation of 10m contouring between 160m – 170m. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.  

Therefore, the confirmation of the reclassification of this hill from 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 199.7m summit height and a 166.5m bwlch height, with these values giving this hill 33.2m of drop, which is sufficient for it to be classified as a 100m Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Mallaen 

Name:  Bron y Gaer 

OS 1:50,000 map:  146, 160

Summit Height:  199.7m (LIDAR) 

Summit Grid Reference:  SN 69948 32662 & SN 69950 32662 (LIDAR) 

Bwlch Height:  166.5m (LIDAR) 

Bwlch Grid Reference:  SN 69362 32822 (LIDAR) 

Drop:  33.2m (LIDAR) 

 

Myrddyn Phillips (April 2022)

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Pant Gwyn (SN 615 793) – 100m Sub-Twmpau reclassified to 100m Twmpau (53rd reclassification)

Significant Name Changes post for Pant Gwyn

There has been confirmation of a reclassification to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Pant Gwyn (SN 615 793)

The criteria for the list that this reclassification applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Pant Gwyn and this was derived from the Tithe map, and it is adjoined to the Pen y Garn group of hills, which are situated in the north-western part of South Wales (Region B, Sub-Region B1), and it is positioned with the A4120 road to its north and the B4340 road to its south, and has the town of Aberystwyth towards the north-west. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list that accompanied the main P30 list, as it was considered not to meet the criteria then used for the main P30 category. 

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 31m of drop, based on the 158m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 127m bwlch height based on interpolation of 10m contouring between 120m – 130m.  With the drop value subsequently amended to an estimated c 32m following a further re-assessment of the details of this hill. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

Therefore, the confirmation of the reclassification of this hill from 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 158.1m summit height and a 123.6m bwlch height, with these values giving this hill 34.5m of drop, which is sufficient for it to be classified as a 100m Twmpau. 

 

The full details for the hill are: 

Group:  Pen y Garn 

Name:  Pant Gwyn 

OS 1:50,000 map:  135

Summit Height:  158.1m (LIDAR) 

Summit Grid Reference:  SN 61596 79302 (LIDAR) 

Bwlch Height:  123.6m (LIDAR) 

Bwlch Grid Reference:  SN 61317 79267 (LIDAR) 

Drop:  34.5m (LIDAR) 

 

Myrddyn Phillips (January 2022)

 

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Quarry Field (SJ 183 147) – 100m Sub-Twmpau addition (52nd reclassification)

Survey post for Quarry Field 

Significant Name Changes post for Quarry Field

 

There has been confirmation of an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips. 

Quarry Field (SJ 183 147)

The criteria for the list that this addition applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Quarry Field and this was derived from local enquiry, and it is adjoined to the Carnedd Wen group of hills which are situated in the south-eastern part of North Wales (Region A, Sub-Region A4), and it is positioned with the Afon Efyrnwy (River Vyrnwy) and the A495 road to its north-west, the A490 road to its east and minor roads to its north and south, and has the village of Meifod towards the west south-west. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 22m of drop, based on the 109m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 87m bwlch height, based on interpolation of 10m contouring between 80m – 90m. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR image of Quarry Field (SJ 183 147)

LIDAR analysis confirms this hill as having over 20m of drop, but as the summit of this hill has now been surveyed with the Trimble GeoXH 6000, it is this result that is being prioritised for listing purposes. 

The Trimble GeoXH 6000 gathering data at the summit of Quarry Field

Therefore, the confirmation of the addition of this hill to 100m Sub-Twmpau status is due to LIDAR analysis and a subsequent Trimble GeoXH 6000 survey, resulting in a 109.5m summit height and an 86.6m bwlch height, with these values giving this hill 22.9m of drop, which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Carnedd Wen 

Name:  Quarry Field 

OS 1:50,000 map:  125

Summit Height:  109.5m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SJ 18332 14741 (Trimble GeoXH 6000)

Bwlch Height:  86.6m (LIDAR)

Bwlch Grid Reference:  SJ 18549 14551 (LIDAR)

Drop:  22.9m (Trimble GeoXH 6000 summit and LIDAR bwlch) 

 

Myrddyn Phillips (September 2021)

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Cefn Cyfronydd (SJ 144 082) – 200m Twmpau reclassified to 100m Twmpau (51st reclassification)

Survey post for Cefn Cyfronydd

Summit Relocations post for Cefn Cyfronydd

Significant Name Changes post for Cefn Cyfronydd

There has been a reclassification to the list of 200m Twmpau and 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips. 

Cefn Cyfronydd (SJ 144 082) on the left

The criteria for the two listings that this reclassification applies to are: 

200m Twmpau – Welsh hills at or above 200m and below 300m in height that have 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 200m Twmpau by Myrddyn Phillips

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Cefn Cyfronydd and this was derived from local enquiry, and it is adjoined to the Carnedd Wen group of hills which are situated in the south-eastern part of North Wales (Region A, Sub-Region A4), and it is positioned with a minor road to its north, the B4389 road to its north-west, the A458 road to its south-west and the B4392 road to its east, and has the small town of Llanfair Caereinion towards the west south-west. 

When the original 200m height band of Welsh P30 hills was published on Geoff Crowder’s v-g.me website, this hill was included in the main P30 list and listed with an estimated c 200m summit height, based on interpolation of its uppermost 200m ring contour that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR image of Cefn Cyfronydd (SJ 144 082)

The result produced by LIDAR analysis gives this hill a 199.2m summit height, and as the summit has now been surveyed with the Trimble GeoXH 6000 it is this result that is being prioritised for listing purposes. 

The Trimble GeoXH 6000 gathering data at the summit of Cefn Cyfronydd

Therefore, the reclassification of this hill from 200m Twmpau status is due to LIDAR analysis and a subsequent Trimble GeoXH 6000 survey, resulting in 45.5m of drop, with a 199.1m summit height and a 150.6m bwlch height, with the summit height confirming its 100m Twmpau status. 

 

The full details for the hill are: 

Group:  Carnedd Wen 

Name:  Cefn Cyfronydd 

OS 1:50,000 map:  125

Summit Height:  199.1m (converted to OSGM15, Trimble GeoXH 6000)                                                          

Summit Grid Reference:  SJ 14459 08297 (Trimble GeoXH 6000) 

Bwlch Height:  150.6m (LIDAR) 

Bwlch Grid Reference:  SJ 14997 08587 (LIDAR) 

Drop:  48.5m (Trimble GeoXH 6000 summit and LIDAR bwlch) 

 

Myrddyn Phillips (July 2021)

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Bryn y Fedwen (SJ 115 125) – 100m Sub-Twmpau addition (50th reclassification)

Survey post for Bryn y Fedwen

Significant Name Changes post for Bryn y Fedwen

 

There has been confirmation of an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips. 

LIDAR image of Bryn y Fedwen (SJ 115 125) 

The criteria for the list that this addition applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Bryn y Fedwen and this was derived from the Tithe map, and it is adjoined to the Y Berwyn group of hills, which are situated in the south-eastern part of North Wales (Region A, Sub-Region A4), and it is positioned with minor roads to its north-east, north-west and south and the A495 road to its east, and has the village of Meifod towards the east north-east. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 20m of drop, based on the 157m summit spot height and an estimated c 137m bwlch height, with the latter based on interpolation of 10m contouring between 130m – 140m that appear on the Ordnance Survey 1:25,000 Explorer map. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR analysis confirms this hill as having over 20m of drop, but as this hill has now been surveyed with the Trimble GeoXH 6000 resulting in a 156.8m summit height, it is this result that is being prioritised for listing purposes. 

The Trimble GeoXH 6000 gathering data at the summit of Bryn y Fedwen

Therefore, the confirmation of the addition of this hill to 100m Sub-Twmpau status is due to LIDAR analysis and a subsequent Trimble GeoXH 6000 survey, resulting in a 156.8m summit height and a 134.9m bwlch height, with these values giving this hill 21.8m of drop, which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Y Berwyn 

Name:  Bryn y Fedwen 

OS 1:50,000 map:  125

Summit Height:  156.8m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SJ 11582 12548 (Trimble GeoXH 6000)

Bwlch Height:  134.9m (LIDAR)

Bwlch Grid Reference:  SJ 11523 12758 (LIDAR)

Drop:  21.8m (Trimble GeoXH 6000 summit and LIDAR bwlch) 

 

Myrddyn Phillips (July 2021)

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Cae Bonc (SJ 129 121) – 100m Sub-Twmpau deletion (49th reclassification)

Survey post for Cae Bonc

 

There has been a deletion to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips. 

Cae Bonc (SJ 129 121)

The criteria for the list that this deletion applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Cae Bonc and this was derived from the Tithe map, and it is adjoined to the Y Berwyn group of hills, which are situated in the south-eastern part of North Wales (Region A, Sub-Region A4), and it is positioned with minor roads to its north-east, north-west and south and the A495 road to its south-east, and has the village of Meifod towards the east north-east. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with 20m of drop, based on the 145m summit spot height and the 125m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR image of Cae Bonc (SJ 129 121)

LIDAR analysis gives this hill 20.3m of drop with a 145.2m summit height and a 124.9m bwlch height.  However, this hill has now been surveyed with the Trimble GeoXH 6000 resulting in a 144.8m summit height, and it is this result that is being prioritised for listing purposes. 

The Trimble GeoXH 6000 gathering data at the summit of Cae Bonc

Therefore, the deletion of this hill from 100m Sub-Twmpau status is due to LIDAR analysis and a subsequent Trimble GeoXH 6000 survey, resulting in a 144.8m summit height and a 124.9m bwlch height, with these values giving this hill 19.8m of drop, which is insufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Y Berwyn 

Name:  Cae Bonc 

OS 1:50,000 map:  125

Summit Height:  144.8m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SJ 12918 12172 (Trimble GeoXH 6000)

Bwlch Height:  124.9m (LIDAR)

Bwlch Grid Reference:  SJ 12993 12315 (LIDAR)

Drop:  19.8m (Trimble GeoXH 6000 summit and LIDAR bwlch) 

 

Myrddyn Phillips (July 2021)

 

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Lower Cil (SJ 185 016) – 100m Sub-Twmpau addition (48th reclassification)

Survey post for Lower Cil

Significant Name Changes post for Lower Cil

 

There has been confirmation of an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips. 

LIDAR image of Lower Cil (SJ 185 016)

The criteria for the list that this addition applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Lower Cil and this was derived from local enquiry, and it is adjoined to the Carnedd Wen group of hills which are situated in the south-eastern part of North Wales (Region A, Sub-Region A4), and it is positioned with the B4385 road to its west, a minor road to its south and the A483 road to its east, and has the village of Aberriw (Berriew) towards the south-south-east. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 21m of drop, based on the 158m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 137m bwlch height based on interpolation of 5m contouring between 135m – 140m. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR analysis confirms this hill has over 20m of drop and as the summit of the hill has now been surveyed with the Trimble GeoXH 6000 it is this result that is being prioritised for listing purposes. 

The Trimble GeoXH 6000 gathering data at the summit of Lower Cil

Therefore, the confirmation of the addition of this hill to 100m Sub-Twmpau status is due to LIDAR analysis and a subsequent Trimble GeoXH 6000 survey, resulting in a 159.3m summit height and a 137.8m bwlch height, with these values giving this hill 21.5m of drop, which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Carned Wen 

Name:  Lower Cil 

OS 1:50,000 map:  136

Summit Height:  159.3m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SJ 18556 01630 (Trimble GeoXH 6000)

Bwlch Height:  137.8m (LIDAR)

Bwlch Grid Reference:  SJ 18939 01777 (LIDAR)

Drop:  21.5m (Trimble GeoXH 6000 summit and LIDAR bwlch) 

 

Myrddyn Phillips (July 2021)

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Allt Dderw (SN 638 832) – 100m Sub-Twmpau reclassified to 100m Twmpau (47th reclassification)

There has been confirmation of a reclassification to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Allt Dderw (SN 638 832)

The criteria for the list that this reclassification applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Allt Dderw and it is adjoined to the Pumlumon group of hills, which are situated in the north-western part of Mid and West Wales (Region B, Sub-Region B2), and it is positioned with minor roads to its north, south and east, and the A4159 road to its west, and has the town of Aberystwyth towards the west south-west. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was included in the Hills to be surveyed sub list that accompanied the main P30 list, as it was considered not to meet the criteria then used for the main P30 category. 

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 30m of drop, based on the 142m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 112m bwlch height based on interpolation of 10m contouring between 110m – 120m. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR image of Allt Dderw (SN 638 832)

Therefore, the confirmation of the reclassification of this hill from 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 142.2m summit height and a 111.5m bwlch height, with these values giving this hill 30.7m of drop, which is sufficient for it to be classified as a 100m Twmpau. 

 

The full details for the hill are: 

Group:  Pumlumon 

Name:  Allt Dderw 

OS 1:50,000 map:  135

Summit Height:  142.2m (LIDAR) 

Summit Grid Reference:  SN 63838 83206 & SN 63838 83204 & SN 63840 83203 (LIDAR) 

Bwlch Height:  111.5m (LIDAR) 

Bwlch Grid Reference:  SN 64419 83203 & SN 64418 83202 & SN 64419 83198 (LIDAR) 

Drop:  30.7m (LIDAR) 

 

Myrddyn Phillips (June 2021)

 

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Plas Newydd (SH 614 807) – 30-99m Sub-Twmpau reclassified to 100m Sub-Twmpau (46th reclassification)

Significant Name Changes post for Plas Newydd

There has been a reclassification to the listings of 30-99m Twmpau and 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data and LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR bwlch image of Plas Newydd (SH 614 807)

The criteria for the two listings that this reclassification applies to are: 

30-99m Twmpau – Welsh hills at or above 30m and below 100m in height that have 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 or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 30-99m Twmpau by Myrddyn Phillips

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Plas Newydd and this was derived from the Tithe map, and it is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the coast to its north and a minor road to its south, and has the small community of Glan-yr-afon towards the west. 

When the original 30-99m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with 27m of drop based on the 99m summit spot height and the 72m bwlch spot height that appear on the Ordnance Survey 1:25,000 Explorer map.  Therefore, the hill was an addition to the 30-99m Sub-Twmpau list. 

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

Since the original publication of the P30 lists of Geoff Crowder’s v-g.me website there have been a number of Ordnance Survey maps made available online, some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website, whilst others are current and digitally updated such as the mapping on the WalkLakes website and the Magic Maps website. 

One of the mapping resources now available online is the WalkLakes website which hosts an interactive map originated from the Ordnance Survey Open Data programme.  This map has many spot heights not on other publicly available Ordnance Survey maps and for this hill a 100m spot height is given on the area of its summit and it is this height that is being favoured in preference to the 99m spot height that appears on the Ordnance Survey 1:25,000 Explorer map. 

Extract from the WalkLakes website

However, it was not until LIDAR became available that the bwlch details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

Therefore, the reclassification of this hill from 30-99m Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data and LIDAR bwlch analysis, resulting in a 100m summit height and a 71.7m bwlch height, with these values giving this hill 28m of drop, which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Plas Newydd 

OS 1:50,000 map:  114, 115

Summit Height:  100m (spot height) 

Summit Grid Reference:  SH 61430 80710 (spot height) 

Bwlch Height:  71.7m (LIDAR) 

Bwlch Grid Reference:  SH 60600 81404 (LIDAR) 

Drop:  28m (spot height summit and LIDAR bwlch) 

 

Myrddyn Phillips (May 2021)

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Morben Mawr (SN 712 990) – 100m Sub-Twmpau reclassified to 100m Twmpau (45th reclassification)

Significant Name Changes post for Morben Mawr

There has been confirmation of a reclassification to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Morben Mawr (SN 712 990)

The criteria for the list that this reclassification applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Morben Mawr and this was derived from the Tithe map, and it is adjoined to the Banc Llechwedd Mawr group of hills, which are situated in the north-western part of South Wales (Region B, Sub-Region B1), and it has the A487 road to its north and west, and a minor road to its immediate south-east, and has the town of Machynlleth towards the north north-east.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was included in the Hills to be surveyed sub list that accompanied the main P30 list, as it was considered not to meet the criteria then used for the main P30 category. 

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 25m of drop, based on an estimated c 102m summit height and an estimated c 177m bwlch height, both heights based on interpolation of 10m contouring that appear on the Ordnance Survey 1:25,000 Explorer map. 

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

The details for this hill we re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill a 104m spot height was given on the area of its summit and with a re-appraisal of its estimated bwlch height to c 74m, these values gave this hill an estimated c 30m of drop. 

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

Therefore, the confirmation of the reclassification of this hill from 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 104.6m summit height and a 73.1m bwlch height, with these values giving this hill 31.5m of drop, which is sufficient for it to be classified as a 100m Twmpau.

 

The full details for the hill are: 

Group:  Banc Llechwedd Mawr 

Name:  Morben Mawr 

OS 1:50,000 map:  135

Summit Height:  104.6m (LIDAR) 

Summit Grid Reference:  SN 71208 99001 (LIDAR) 

Bwlch Height:  73.1m (LIDAR) 

Bwlch Grid Reference:  SN 71490 98974 & SN 71489 98977 (LIDAR) 

Drop:  31.5m (LIDAR) 

 

Myrddyn Phillips (April 2021)

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Pen y Cefn (SH 571 796) – 100m Sub-Twmpau addition (44th reclassification)

Significant Name Changes post for Pen y Cefn

 

There has been an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data. 

The criteria for the list that this addition applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Pen y Cefn and this was derived from the Tithe map, and it is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the coast to its north-west, minor roads to its north, west, south and east, and has the village of Llanddona towards the south-east. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with 25m of drop, based on the 157m summit spot height and the 132m bwlch spot height that appear on the Ordnance Survey 1:25,000 Explorer map. 

Therefore, the addition of this hill to 100m Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data, resulting in a 157m summit height and a 132m bwlch height, with these values giving this hill 25m of drop which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Pen y Cefn 

OS 1:50,000 map:  114, 115

Summit Height:  157m (spot height) 

Summit Grid Reference:  SH 57163 79686 (spot height) 

Bwlch Height:  132m (spot height) 

Bwlch Grid Reference:  SH 58344 80453 (spot height) 

Drop:  25m (spot height summit and bwlch) 

 

Myrddyn Phillips (April 2021)

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Glan yr Afon (SH 558 793) – 100m Sub-Twmpau addition (43rd reclassification)

Significant Name Changes post for Glan yr Afon

 

There has been an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data. 

The criteria for the list that this addition applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Glan yr Afon and this was derived from the Tithe map, and it is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the coast to its north-west, minor roads to its west, south-east and north-east and the B5109 road to its south-west, and has the village of Llanddona towards the east. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 22m of drop, based on the 129m summit spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map and an estimated c 107m bwlch height based on interpolation of 5m contouring between 105m – 110m that appear on the Ordnance Survey 1:25,000 Explorer map. 

Therefore, the addition of this hill to 100m Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data, resulting in a 129m summit height and an estimated c 107m bwlch height, with these values giving this hill an estimated c 22m of drop which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Glan yr Afon 

OS 1:50,000 map:  114, 115

Summit Height:  129m (spot height) 

Summit Grid Reference:  SH 55815 79322 (spot height) 

Bwlch Height:  c 107m (interpolation) 

Bwlch Grid Reference:  SH 56143 78764 (interpolation) 

Drop:  c 22m (spot height summit and interpolated bwlch) 

 

Myrddyn Phillips (April 2021)

 

 

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Pen Ucheldref (SH 558 773) – 100m Sub-Twmpau addition (42nd reclassification)

Significant Name Changes post for Pen Uchedref

There has been an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data. 

The criteria for the list that this addition applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Pen Ucheldref and this was derived from the Tithe map, and it is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with a minor road to its immediate south-east and the B5109 road to its immediate south-west, and has the village of Llanddona towards the north-east. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with 21m of drop, based on the 133m summit spot height and the 112m bwlch spot height that appear on the Ordnance Survey 1:25,000 Explorer map. 

Therefore, the addition of this hill to 100m Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data, resulting in a 133m summit height and a 112m bwlch height, with these values giving this hill 21m of drop which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Pen Ucheldref 

OS 1:50,000 map:  114, 115

Summit Height:  133m (spot height) 

Summit Grid Reference:  SH 55805 77334 (spot height) 

Bwlch Height:  112m (spot height) 

Bwlch Grid Reference:  SH 57062 78438 (spot height) 

Drop:  21m (spot height summit and bwlch) 

 

Myrddyn Phillips (March 2021)

 

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Mynydd Llwydiarth (SH 545 791) – 100m Sub-Twmpau addition (41st reclassification)

 

There has been confirmation of an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Mynydd Llwydiarth (SH 545 791)

The criteria for the list that this addition applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Mynydd Llwydiarth, and it is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the coast to its north, minor roads to its west and east and the B5109 road to its south, and has the village of Llanddona towards the east. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 22m of drop, based on an estimated c 155m summit height and an estimated c 133m bwlch height, the latter based on interpolation of 5m contouring between 130m – 135m that appear on the Ordnance Survey 1:25,000 Explorer map. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

Therefore, the confirmation of the addition of this hill to 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 156.1m summit height and a 132.6m bwlch height, with these values giving this hill 23.5m of drop which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Mynydd Llwydiarth 

OS 1:50,000 map:  114, 115 

Summit Height:  156.1m (LIDAR) 

Summit Grid Reference:  SH 54519 79147 (LIDAR) 

Bwlch Height:  132.6m (LIDAR) 

Bwlch Grid Reference:  SH 54380 78960 (LIDAR) 

Drop:  23.5m (LIDAR) 

 

Myrddyn Phillips (March 2021)

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Bonc y Garreg (SH 486 804) – 100m Sub-Twmpau addition (40th reclassification)

Significant Name Changes post for Bonc y Garreg

 

There has been confirmation of an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Bonc y Garreg (SH 486 804)

The criteria for the list that this addition applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Bonc y Garreg and this was derived from the Tithe map, and it is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the B5110 road to its west and has a minor road to its south-east, and has the village of Benllech towards the north-east. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 27m of drop, based on the 114m summit spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage map and an estimated c 87m bwlch height based on interpolation of 5m contouring between 85m – 90m that appear on the Ordnance Survey 1:25,000 Explorer map. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

Therefore, the confirmation of the addition of this hill to 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 114.0m summit height and an 87.1m bwlch height, with these values giving this hill 26.9m of drop which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Bonc y Garreg 

OS 1:50,000 map:  114, 115 

Summit Height:  114.0m (LIDAR) 

Summit Grid Reference:  SH 48627 80418 (LIDAR) 

Bwlch Height:  87.1m (LIDAR) 

Bwlch Grid Reference:  SH 48221 80516 (LIDAR) 

Drop:  26.9m (LIDAR) 

 

Myrddyn Phillips (March 2021)

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Rhuddlan Fawr (SH 486 812) – 100m Sub-Twmpau addition (39th reclassification)

Significant Name Changes post for Rhuddlan Fawr

 

There has been an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data. 

The criteria for the list that this addition applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Rhuddlan Fawr and this was confirmed via the Tithe map, and it is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with a minor road to its north-east and the B511o road to its north-west, and has the village of Benllech towards the east north-east. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with 22m of drop, based on the 114m summit spot height adjoined to a triangulation pillar and the 92m bwlch spot height that appears on the Ordnance Survey 1:50,000 Landranger map at SH 48784 81428 and appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map at SH 48697 81460. 

Therefore, the addition of this hill to 100m Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data, resulting in a 114m summit height and a 92m bwlch height, with these values giving this hill 22m of drop which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Rhuddlan Fawr 

OS 1:50,000 map:  114, 115

Summit Height:  114m (triangulation pillar) 

Summit Grid Reference:  SH 48673 81249 (triangulation pillar) 

Bwlch Height:  92m (spot height) 

Bwlch Grid Reference:  SH 48784 81428 & SH 48697 81460 (spot height) 

Drop:  22m (triangulation pillar summit and spot height bwlch) 

 

Myrddyn Phillips (March 2021)

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Mynydd Mwyn (SH 409 823) – 100m Sub-Twmpau addition (38th reclassification)

Significant Name Changes post for Mynydd Mwyn

 

There has been an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data. 

The criteria for the list that this addition applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Mynydd Mwyn and this was derived from the Tithe map, and it is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the B5112 road to its north-west and has a minor road immediately to its east, and has the village of Llannerch-y-medd towards the north north-east. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 22m of drop, based on the 101m summit spot height and an estimated c 79m bwlch height based on interpolation of 5m contouring between 75m – 80m that appear on the Ordnance Survey 1:25,000 Explorer map. 

Therefore, the addition of this hill to 100m Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data, resulting in a 101m summit height and an estimated c 79m bwlch height, with these values giving this hill an estimated c 22m of drop which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Mynydd Mwyn 

OS 1:50,000 map:  114, 115

Summit Height:  101m (spot height) 

Summit Grid Reference:  SH 40983 82338 (spot height) 

Bwlch Height:  c 79m (interpolation) 

Bwlch Grid Reference:  SH 40939 83375 (interpolation) 

Drop:  c 22m (spot height summit and interpolated bwlch) 

 

Myrddyn Phillips (March 2021)

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Mynydd Cerrig y Bleiddiau (SH 445 902) – 100m Sub-Twmpau deletion (37th reclassification)

Significant Name Changes post for Mynydd Cerrig y Bleiddiau

 

There has been a deletion to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Mynydd Cerrig y Bleiddiau (SH 445 902)

The criteria for the list that this deletion applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Mynydd Cerrig y Bleiddiau and this was derived from the Tithe map, and it is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the B5111 road to its north-west and the A5025 road to its east, and has the village of Pen-y-sarn towards the east. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was included in the Hills to be surveyed sub list with a 131m summit height. 

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 24m of drop, based on the 131m summit spot height and an estimated c 107m bwlch height based on interpolation of 5m contouring that was thought to be between 105m – 110m that appear on the Ordnance Survey 1:25,000 Explorer map.  With the estimated drop value later re-evaluated and listed as c 23m.  However, due to past quarrying activity the contours on the area of this hill’s bwlch are not continuous; therefore there was conjecture to its drop value. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

Therefore, the deletion of this hill from 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 131.1m summit height and a 113.1m bwlch height, with these values giving this hill 18.0m of drop which is insufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Mynydd Cerrig y Bleiddiau 

OS 1:50,000 map:  114 

Summit Height:  131.1m (LIDAR) 

Summit Grid Reference:  SH 44539 90284 (LIDAR) 

Bwlch Height:  113.1m (LIDAR) 

Bwlch Grid Reference:  SH 44495 90291 (LIDAR) 

Drop:  18.0m (LIDAR) 

 

Myrddyn Phillips (March 2021)

 

 

Mapping Mountains - Hill Reclassifications - 100m Twmpau

Foel (SH 305 898) – 100m Sub-Twmpau addition (36th reclassification)

Significant Name Changes post for Foel

 

There has been an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data. 

The criteria for the list that this addition applies to are: 

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Foel and this was derived from the Tithe map, and it is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the coast to its west and has minor roads to its north, south and east, with the A5025 road farther to its south-east, and has the small community of Llanfair-yng-Nghornwy towards the east north-east. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 23m of drop, based on the 141m summit spot height and an estimated c 118m bwlch height based on interpolation of 5m contouring between 115m – 120m that appear on the Ordnance Survey 1:25,000 Explorer map. 

Therefore, the addition of this hill to 100m Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data, resulting in a 141m summit height and an estimated c 118m bwlch height, with these values giving this hill an estimated c 23m of drop which is sufficient for it to be classified as a 100m Sub-Twmpau.

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Foel 

OS 1:50,000 map:  114

Summit Height:  141m (spot height) 

Summit Grid Reference:  SH 30558 89859 (spot height) 

Bwlch Height:  c 118m (interpolation) 

Bwlch Grid Reference:  SH 31026 90339 (interpolation) 

Drop:  c 23m (spot height summit and interpolated bwlch) 

 

Myrddyn Phillips (March 2021)