Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

30-99m Twmpau – Hill Reclassifications

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

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

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Y Werthyr (SH 363 843) – 30-99m Sub-Twmpau addition (105th reclassification)

 

There has been an addition to the list of 30-99m 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. 

LIDAR image (part coverage) of Y Werthyr (SH 363 843)

The criteria for the list that this addition 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

The name the hill is listed by is Y Werthyr 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 is encircled by minor roads with the A5025 road farther to its west, and has the small community of Llandeusant towards the north-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 21m of drop, based on the 63m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 42m 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

Therefore, the addition of this hill to 30-99m Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data, resulting in a 63m summit height and a 42m bwlch height, with these values giving this hill 21m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Y Werthyr 

OS 1:50,000 map:  114

Summit Height:  63m (spot height) 

Summit Grid Reference:  SH 36311 84342 (spot height)               

Bwlch Height:  42m (spot height) 

Bwlch Grid Reference:  SH 36670 83487 (spot height) 

Drop:  21m (spot height summit and bwlch) 

 

Myrddyn Phillips (September 2021)

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Twyn y Parc (SH 368 649) – 30-99m Sub-Twmpau addition (104th reclassification)

 

There has been an addition to the list of 30-99m 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: 

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

The name the hill is listed by is Twyn y Parc 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 surrounding it on all sides except for its north-east, and has the A4080 road and the small village of Malltraeth towards the north-east. 

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 an estimated c 20m of drop, based on the 33m 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 13m bwlch height, based on interpolation of 5m contouring between 10m – 15m that appears on the Ordnance Survey 1:25,000 Explorer map. 

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

Therefore, the addition of this hill to 30-99m Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data, resulting in a 33m summit height and an estimated c 13m bwlch height, with these values giving this hill an estimated c 20m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Twyn y Parc 

OS 1:50,000 map:  114

Summit Height:  33m (spot height) 

Summit Grid Reference:  SH 36861 64945 (spot height)               

Bwlch Height:  c 13m (interpolation) 

Bwlch Grid Reference:  SH 36998 65143 (interpolation) 

Drop:  c 20m (spot height summit and interpolated bwlch) 

 

Myrddyn Phillips (September 2021)

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Ynys Dafydd (SH 646 134) – 30-99m Sub-Twmpau reclassified to 30-99m Twmpau (103rd reclassification)

Significant Height Revisions post for Ynys Dafydd

There has been a reclassification to the list of 30-99m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill initiated by Joe Nuttall who produced a summit analysis programme using LIDAR, and then by LIDAR analysis initially conducted by Jim Bloomer and subsequently by Myrddyn Phillips. 

LIDAR image of Ynys Dafydd (SH 646 134)

The criteria for the list 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

The name the hill is listed by is Ynys Dafydd, and it is adjoined to the Rhinogydd group of hills, which are situated in the western part of North Wales (Region A, Sub-Region A3), and it is positioned with the coast to its south-west, the Afon Dyfi (River Dovey) to its south and the A496 road to its north-west, and has the town of Abermaw (Barmouth) towards the west south-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 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 in 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-evaluated and it was listed with an estimated c 27m of drop based on an estimated c 42m summit height and an estimated c 15m bwlch height, with both values 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

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 from 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 52.8m summit height and a 17.1m bwlch height, with these values giving this hill 35.7m of drop, which is sufficient for it to be classified as a 30-99m Twmpau. 

 

The full details for the hill are: 

Group:  Rhinogydd 

Name:  Ynys Dafydd 

OS 1:50,000 map:  124

Summit Height:  52.8m (LIDAR) 

Summit Grid Reference:  SH 64636 17484 (LIDAR) 

Bwlch Height:  17.1m (LIDAR) 

Bwlch Grid Reference:  SH 64599 17744 (LIDAR) 

Drop:  35.7m (LIDAR) 

 

Myrddyn Phillips (September 2021)

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Allt Fawr (SH 346 685) – 30-99m Sub-Twmpau addition (102nd reclassification)

 

There has been confirmation of an addition to the list of 30-99m 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 Allt Fawr (SH 346 685)

The criteria for the list that this addition 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

The name the hill is listed by is Allt Fawr 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, a minor road to its immediate east and the A4080 road to its north-east, and has the village of Aberffraw towards the east north-east. 

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 an estimated c 24m of drop, based on the 42m summit spot height adjoined to a triangulation pillar and an estimated c 18m bwlch height, based on interpolation of 5m contouring between 15m – 20m that appears 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 30-99m Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data and LIDAR analysis, resulting in a 42m summit height and a 17.0m bwlch height, with these values giving this hill 25m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Allt Fawr 

OS 1:50,000 map:  114

Summit Height:  42m (triangulation pillar) 

Summit Grid Reference:  SH 34639 68534 (triangulation pillar)               

Bwlch Height:  17.0m (LIDAR) 

Bwlch Grid Reference:  SH 34974 69389 (LIDAR) 

Drop:  25m (triangulation pillar summit and LIDAR bwlch) 

 

Myrddyn Phillips (September 2021)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Bryn Ifan (SH 336 703) – 30-99m Sub-Twmpau addition (101st reclassification)

 

There has been an addition to the list of 30-99m 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 Ifan (SH 336 703)

The criteria for the list that this addition 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

The name the hill is listed by is Bryn Ifan 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 the A4080 road to its north-east, and has the village of Aberffraw towards the south-east. 

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 an estimated c 19m of drop, based on an estimated c 42m summit height and an estimated c 23m bwlch height, with both values 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

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 addition of this hill to 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 43.4m summit height and a 23.2m bwlch height, with these values giving this hill 20.2m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Bryn Ifan 

OS 1:50,000 map:  114

Summit Height:  43.4m (LIDAR) 

Summit Grid Reference:  SH 33612 70347 (LIDAR)               

Bwlch Height:  23.2m (LIDAR) 

Bwlch Grid Reference:  SH 35753 72013 (LIDAR) 

Drop:  20.2m (LIDAR) 

 

Myrddyn Phillips (August 2021)

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Whiteford Burrows (SS 448 964) – Double Sub-Twmpau addition (100th reclassification)

 

There has been an addition to the list of Double Sub-Twmpau adjoined to the 30-99m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips. 

LIDAR image of Whiteford Burrows (SS 448 964)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, this height band of hills has two accompanying sub lists, the first of which is 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, and the second sub category is entitled the Double Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 20m and below 30m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 30-99m Twmpau by Myrddyn Phillips

The name the hill is listed by is Whiteford Burrows and it is adjoined to the Gŵyr group of hills, which are situated in the western part of South Wales (Region C, Sub-Region C1), and it is positioned overlooking Whiteford Point and the coast, and has the small community of Llanmadog towards the south. 

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. 

Prior to LIDAR analysis this hill was not catalogued as the uppermost contour given it on the Ordnance Survey 1:25,000 Explorer map is 5m, whilst the Ordnance Survey 1:50,000 Landranger map has no contours. 

Extract from the Ordnance Survey 1:50,000 Landranger 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 addition of this hill to Double Sub-Twmpau status is due to LIDAR analysis, resulting in a 29.6m summit height and a 9.2m bwlch height, with these values giving this hill 20.4m of drop, which is sufficient for it to be classified as a Double Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Gŵyr

Name:  Whiteford Burrows

OS 1:50,000 map:  159

Summit Height:  29.6m (LIDAR)

Summit Grid Reference:  SS 44870 96422 (hand-held GPS)

Bwlch Height:  9.2m (LIDAR)

Bwlch Grid Reference:  SS 44631 95701 (LIDAR)   

Drop:  20.4m (LIDAR)

 

Myrddyn Phillips (August 2021)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Tan y Bryn (SH 321 733) – Double Sub-Twmpau addition (99th reclassification)

Significant Name Changes post for Tan y Bryn

 

There has been confirmation of an addition to the list of Double Sub-Twmpau adjoined to the 30-99m 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 y Bryn (SH 321 733)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, this height band of hills has two accompanying sub lists, the first of which is 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, and the second sub category is entitled the Double Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 20m and below 30m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 30-99m Twmpau by Myrddyn Phillips

The name the hill is listed by is Tan y Bryn 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 is positioned with the coast to its west and is encircled by the A4080 road, and has the village of Llanfaelog towards the east. 

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. 

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 20m of drop, based on the 24m 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 4m bwlch height based on interpolation of 5m contouring between 0m – 5m 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 Double Sub-Twmpau status is due to LIDAR analysis, resulting in a 25.1m summit height and a 3.8m bwlch height, with these values giving this hill 21.3m of drop, which is sufficient for it to be classified as a Double Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn

Name:  Tan y Bryn

OS 1:50,000 map:  114

Summit Height:  25.1m (LIDAR)

Summit Grid Reference:  SH 32145 73399 (LIDAR)

Bwlch Height:  3.8m (LIDAR)

Bwlch Grid Reference:  SH 32945 73411 (LIDAR) 

Drop:  21.3m (LIDAR)

 

Myrddyn Phillips (August 2021)

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pt. 37.2m (SH 313 789) – 30-99m Sub-Twmpau addition (98th reclassification)

There has been confirmation of an addition to the list of 30-99m 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 Pt. 37.2m (SH 313 789)

The criteria for the list that this addition 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

The hill is being listed by the point (Pt. 37.2m) 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 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, the B5109 road to its north-east, the A5025 road to its north-west and the A55 and A5 roads to its immediate south, and has the village of Caergeiliog towards the south-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 an estimated c 24m of drop, based on the 38m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 14m bwlch height based on interpolation of 5m contouring between 10m – 15m. 

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 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 37.2m summit height and a 13.4m bwlch height, with these values giving this hill 23.8m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Pt. 37.2m 

OS 1:50,000 map:  114

Summit Height:  37.2m (LIDAR) 

Summit Grid Reference:  SH 31399 78967 (LIDAR) 

Bwlch Height:  13.4m (LIDAR) 

Bwlch Grid Reference:  SH 31873 78918 & SH 31791 78933 (LIDAR) 

Drop:  23.8m (LIDAR) 

 

Myrddyn Phillips (August 2021)

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pt. 27.4m (SH 319 764) – Double Sub-Twmpau addition (97th reclassification)

 

There has been confirmation of an addition to the list of Double Sub-Twmpau adjoined to the 30-99m 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. 27.4m (SH 319 764)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, this height band of hills has two accompanying sub lists, the first of which is 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, and the second sub category is entitled the Double Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 20m and below 30m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 30-99m Twmpau by Myrddyn Phillips

The hill is being listed by the point (Pt. 27.4) 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 Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and is positioned with the coast to its west, minor roads to its north-west and south-east and the A55 and A5 roads to its north-east, and has the village of Llanfihangel-yn-Nhywyn towards the north. 

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. 

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 20m of drop, based on the 28m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 8m bwlch height based on interpolation of 5m contouring between 5m – 10m 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 Double Sub-Twmpau status is due to LIDAR analysis, resulting in a 27.4m summit height and a 5.0m bwlch height, with these values giving this hill 22.35m of drop, which is sufficient for it to be classified as a Double Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn

Name:  Pt. 27.4m

OS 1:50,000 map:  114

Summit Height:  27.4m (LIDAR)

Summit Grid Reference:  SH 31929 76427 (LIDAR)

Bwlch Height:  5.0m (LIDAR)

Bwlch Grid Reference:  SH 31835 76966 (LIDAR) 

Drop:  22.35m (LIDAR)

 

Myrddyn Phillips (August 2021)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Tŷ Newydd (SH 307 810) – 30-99m Sub-Twmpau addition (96th reclassification)

Significant Name Changes post for Tŷ Newydd

 

There has been confirmation of an addition to the list of 30-99m 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 Tŷ Newydd (SH 307 810)

The criteria for the list that this addition 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

The name the hill is listed by is Tŷ 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 west and the A5025 road to its south-east, and has the village of Y Fali (Valley) towards the south-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 an estimated c 27m of drop, based on the 35m 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 8m bwlch height based on interpolation of 5m contouring between 5m – 10m that appears 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 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 35.65m summit height and a 6.3m bwlch height, with these values giving this hill 29.3m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Tŷ Newydd 

OS 1:50,000 map:  114

Summit Height:  35.65m (LIDAR) 

Summit Grid Reference:  SH 30777 81080 (LIDAR) 

Bwlch Height:  6.3m (LIDAR) 

Bwlch Grid Reference:  SH 31999 81570 (LIDAR) 

Drop:  29.3m (LIDAR) 

 

Myrddyn Phillips (August 2021)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Arw Fawr (SH 314 816) – 30-99m Sub-Twmpau addition (95th reclassification)

Significant Name Changes post for Arw Fawr

There has been confirmation of an addition to the list of 30-99m 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 Arw Fawr (SH 314 816)

The criteria for the list that this addition 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

The name the hill is listed by is Arw Fawr 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 the A5025 road to its immediate east, and has the village of Llanfachreth towards the north. 

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 22m of drop, based on the 30m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 8m 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 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 30.9m summit height and a 7.8m bwlch height, with these values giving this hill 23.15m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Arw Fawr 

OS 1:50,000 map:  114

Summit Height:  30.9m (LIDAR) 

Summit Grid Reference:  SH 31485 81608 (LIDAR) 

Bwlch Height:  7.8m (LIDAR) 

Bwlch Grid Reference:  SH 31747 81483 (LIDAR) 

Drop:  23.15m (LIDAR) 

 

Myrddyn Phillips (August 2021)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Tyn Llan (SH 327 820) – 30-99m Sub-Twmpau addition (94th reclassification)

Significant Name Changes post for Tyn Llan

There has been confirmation of an addition to the list of 30-99m 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 Tyn Llan (SH 327 820)

The criteria for the list that this addition 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

The name the hill is listed by is Tyn Llan 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 and the A5025 road to its west, the B5109 road to its south and minor roads to its north and east, and has the village of Llanfachreth towards the west north-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 an estimated c 21m of drop, based on an estimated c 38m summit height and the 17m 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 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 38.5m summit height and an 8.6m bwlch height, with these values giving this hill 29.9m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Tyn Llan 

OS 1:50,000 map:  114

Summit Height:  38.5m (LIDAR) 

Summit Grid Reference:  SH 32709 82087 (LIDAR) 

Bwlch Height:  8.6m (LIDAR) 

Bwlch Grid Reference:  SH 33264 82316 (LIDAR) 

Drop:  29.9m (LIDAR) 

 

Myrddyn Phillips (August 2021)

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Maes Llwyn (SH 435 920) – 30-99m Sub-Twmpau deletion (93rd reclassification)

There has been a deletion to the list of 30-99m 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 Maes Llwyn (SH 435 920)

The criteria for the list that this deletion 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

The name the hill is listed by is Maes Llwyn 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 is encircled by minor roads with the B5111 road and the A5025 road farther to its north and also east, and has the town of Amlwch towards the north-east. 

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 25m of drop, based on the 77m summit spot height positioned on or near to a covered reservoir that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map and the 52m bwlch spot height that appears on the Ordnance Survey 1:50,000 Landranger 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 deletion of this hill from 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 74.0m height to a natural summit and a 54.9m bwlch height, with these values giving this hill 19.1m of drop, which is insufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Maes Llwyn 

OS 1:50,000 map:  114

Summit Height:  74.0m (LIDAR) 

Summit Grid Reference:  SH 43593 92022 (LIDAR) 

Bwlch Height:  54.9m (LIDAR) 

Bwlch Grid Reference:  SH 43658 91747 (LIDAR) 

Drop:  19.1m (LIDAR) 

 

Myrddyn Phillips (August 2021)

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pen y Graig Wen (SH 446 879) – 30-99m Sub-Twmpau addition (92nd reclassification)

Significant Height Revisions post for Pen y Graig Wen

Summit Relocations post for Pen y Graig Wen

Significant Name Changes post for Pen y Graig Wen

There has been confirmation of an addition to the list of 30-99m 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 Graig Wen (SH 446 879)

The criteria for the list that this addition 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

The name the hill is listed by is Pen y Graig Wen 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 east, minor roads to its north, south and east and the B5111 road to its west, and has the village of Rhos-y-bol towards the west north-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 an estimated c 24m of drop, based on an estimated c 92m summit height and an estimated c 68m 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

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 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 94.3m summit height and a 68.2m bwlch height, with these values giving this hill 26.1m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Pen y Graig Wen 

OS 1:50,000 map:  114

Summit Height:  94.3m (LIDAR) 

Summit Grid Reference:  SH 44637 87986 (LIDAR) 

Bwlch Height:  68.2m (LIDAR) 

Bwlch Grid Reference:  SH 45162 88579 (LIDAR) 

Drop:  26.1m (LIDAR) 

 

Myrddyn Phillips (July 2021)

 

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Llanol (SH 380 882) / Fferam Isaf (SH 384 881) – 30-99m Sub-Twmpau addition (91st reclassification)

Significant Name Changes post for Llanol (SH 380 882) / Fferam Isaf (SH 384 881)

There has been an addition of a twin summit to the list of 30-99m 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: 

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

The name the hill is listed by is Llanol / Fferam Isaf 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 encircled by minor roads with Llyn Alaw to its south-east, and has the village of Carreglefn towards the north. 

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 as a twin summit with 24m of drop, based on the 98m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map adjoined to the Llanol summit and the 98m 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 adjoined to the Fferam Isaf summit, and the 74m 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

Therefore, the addition of this hill to 30-99m Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data, resulting in a 98m twin summit height and a 74m bwlch height, with these values giving this hill 24m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Llanol / Fferam Isaf 

OS 1:50,000 map:  114

Summit Height:  98m (spot height) 

Summit Grid Reference:  SH 38057 88231 (Llanol spot height) & SH 38425 88175 (Fferam Isaf spot height) 

Bwlch Height:  74m (spot height) 

Bwlch Grid Reference:  SH 38310 88630 (spot height) 

Drop:  24m (spot height summit and bwlch) 

 

Myrddyn Phillips (July 2021)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Yr Ogof (SH 356 888) – 30-99m Sub-Twmpau addition (90th reclassification)

Significant Name Changes post for Yr Ogof

There has been an addition to the list of 30-99m 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: 

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

The name the hill is listed by is Yr Ogof 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, the A5025 road to its north-west and minor roads to its west, south and east, and has the village of Llanfechell towards the north north-east. 

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 an estimated c 24m of drop based on the 92m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 68m bwlch height, based on interpolation of 5m contouring between 65m – 70m. 

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

Therefore, the addition of this hill to 30-99m Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data, resulting in a 92m summit height and an estimated c 68m bwlch height, with these values giving this hill an estimated c 24m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Yr Ogof 

OS 1:50,000 map:  114

Summit Height:  92m (spot height) 

Summit Grid Reference:  SH 35650 8879 (spot height) 

Bwlch Height:  c 68m (interpolation) 

Bwlch Grid Reference:  SH 37450 88739 (interpolation) 

Drop:  c 24m (spot height summit and interpolated bwlch) 

 

Myrddyn Phillips (July 2021)

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pen Ucheldref (SH 349 882) – 30-99m Sub-Twmpau deletion (89th reclassification)

There has been a deletion to the list of 30-99m 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 image of Pen Ucheldref (SH 349 882)

The criteria for the list that this deletion 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

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 two minor roads beside its summit and the A5025 road to its north-west, and has the village of Llanrhuddlad also towards the north-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 an estimated c 23m of drop, based on an estimated c 90m summit height and an estimated c 67m bwlch height, with both heights based on interpolation of 5m contouring that appears on the Ordnance Survey 1:25,000 Explorer map, with the 85m upper summit contour mistaken for 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. 

Therefore, the deletion of this hill from 30-99m Sub-Twmpau status is due to a combination of detail on contemporary maps produced from Ordnance Survey data and LIDAR analysis, resulting in an 85.4m summit height and an estimated c 67m bwlch height, with these values giving this hill an estimated c 18m of drop, which is insufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Pen Ucheldref 

OS 1:50,000 map:  114

Summit Height:  85.4m (LIDAR) 

Summit Grid Reference:  SH 34917 88259 (LIDAR) 

Bwlch Height:  c 67m (interpolation) 

Bwlch Grid Reference:  SH 35183 88544 (interpolation) 

Drop:  c 18m (LIDAR summit and interpolated bwlch) 

 

Myrddyn Phillips (July 2021)

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Foel Fawr (SH 357 919) – 30-99m Sub-Twmpau addition (88th reclassification)

There has been confirmation of an addition to the list of 30-99m 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 Foel Fawr (SH 357 919)

The criteria for the list that this addition 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

The name the hill is listed by is Foel Fawr 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 north, south and east and the A5025 road to its west, and has the village of Cemaes towards the north-east. 

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. 

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-evaluated and it was listed with 23m of drop based on the 49m 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 which now appears on the interactive mapping available on the Magic Maps website, and the 26m bwlch spot height that appears on the Ordnance Survey 1:25,000 Explorer map. 

Extract from the Magic 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. 

LIDAR summit image of Foel Fawr

Therefore, the confirmation of the addition of this hill to 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 48.9m summit height and a 28.25m bwlch height, with these values giving this hill 20.6m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Foel Fawr 

OS 1:50,000 map:  114

Summit Height:  48.9m (LIDAR) 

Summit Grid Reference:  SH 35728 91981 (LIDAR) 

Bwlch Height:  28.25m (LIDAR) 

Bwlch Grid Reference:  SH 35963 91346 (LIDAR) 

Drop:  20.6m (LIDAR) 

 

Myrddyn Phillips (July 2021)

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Cromlech (SH 365 924) – 30-99m Sub-Twmpau deletion (87th reclassification)

There has been a deletion to the list of 30-99m 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 Cromlech (SH 365 924)

The criteria for the list that this deletion 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

The name the hill is listed by is Cromlech 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 and the A5025 road to its north, and minor roads to its south and east, and has the village of Cemaes towards the north north-east. 

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 an estimated c 21m of drop based on the 49m summit spot height and an estimated c 28m bwlch height, with the latter based on interpolation of 5m contouring between 25m – 30m that appears 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 deletion of this hill from 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 47.95m summit height and a 28.1m bwlch height, with these values giving this hill 19.8m of drop, which is insufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Cromlech 

OS 1:50,000 map:  114

Summit Height:  47.95m (LIDAR) 

Summit Grid Reference:  SH 36568 92457 (LIDAR) 

Bwlch Height:  28.1m (LIDAR) 

Bwlch Grid Reference:  SH 36561 91044 (LIDAR) 

Drop:  19.8m (LIDAR) 

 

Myrddyn Phillips (July 2021)

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Penymorwydd (SH 384 912) – 30-99m Sub-Twmpau addition (86th reclassification)

Significant Height Revisions post for Penymorwydd

There has been confirmation of an addition to the list of 30-99m 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 image of Penymorwydd (SH 384 912)

The criteria for the list that this addition 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

The name the hill is listed by is Penymorwydd 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 encircled by minor roads with the A5025 road farther to its north-west, and has the village of Cemaes towards the north-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 an estimated c 26m of drop based on the 69m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 43m bwlch height based on interpolation of 5m contouring between 40m – 45m. 

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 30-99m Sub-Twmpau status is due to a combination of detail on contemporary maps produced from Ordnance Survey data and LIDAR analysis, resulting in a 70.5m summit height and an estimated c 43m bwlch height, with these values giving this hill an estimated c 28m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Penymorwydd 

OS 1:50,000 map:  114

Summit Height:  70.5m (LIDAR) 

Summit Grid Reference:  SH 38471 91255 (LIDAR) 

Bwlch Height:  c 43m (interpolation) 

Bwlch Grid Reference:  SH 38636 90826 (interpolation) 

Drop:  c 28m (LIDAR summit and interpolated bwlch) 

 

Myrddyn Phillips (July 2021)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Cemaes Fawr (SH 379 928) – 30-99m Sub-Twmpau addition (85th reclassification)

Significant Name Changes post for Cemaes Fawr

There has been confirmation of an addition to the list of 30-99m 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 image of Cemaes Fawr (SH 379 928)

The criteria for the list that this addition 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

The name the hill is listed by is Cemaes Fawr 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, the A5025 road also to its north-west and minor roads to its west, south and immediate east, and has the village of Cemaes towards the north-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 an estimated c 22m of drop based on the 56m 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 34m bwlch height based on interpolation of 5m contouring between 30m – 35m. 

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 30-99m Sub-Twmpau status is due to a combination of detail on contemporary maps produced from Ordnance Survey data and LIDAR analysis, resulting in a 55.9m summit height and an estimated c 34m bwlch height, with these values giving this hill an estimated c 22m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Cemaes Fawr 

OS 1:50,000 map:  114

Summit Height:  55.9m (LIDAR) 

Summit Grid Reference:  SH 37927 92898 & SH 37925 92896 & SH 37927 92896 (LIDAR) 

Bwlch Height:  c 34m (interpolation) 

Bwlch Grid Reference:  SH 38185 93111 (interpolation) 

Drop:  c 22m (LIDAR summit and interpolated bwlch) 

 

Myrddyn Phillips (July 2021)

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Teilia (SH 381 941) – 30-99m Sub-Twmpau addition (84th reclassification)

Significant Name Changes post for Teilia

There has been an addition to the list of 30-99m 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 mapping on the Magic Maps website. 

The criteria for the list that this addition 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

The name the hill is listed by is Teilia 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 west, minor roads also to its north and west and the A5025 road to its south, and has the village of Cemaes towards the south-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 an estimated c 23m of drop based on an estimated c 51m summit height and an estimated c 28m bwlch height, with both heights based on interpolation of 5m contouring that appear on the Ordnance Survey 1:25,000 Explorer map. 

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

Since the original publication of the P30 lists on Geoff Crowder’s v-g.me website and the re-assessment of this hill’s details 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 Magic Maps website. 

One of the mapping resources now available online is the Magic Maps website which hosts an interactive map originated from Ordnance Survey data.  This mapping has many spot heights not on other publicly available Ordnance Survey maps and for this hill a 51m summit spot height is given on the area of its summit. 

Extract from the Magig Maps website

Therefore, the addition of this hill to 30-99m Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data, resulting in a 51m summit height and an estimated c 28m bwlch height, with these values giving this hill an estimated c 23m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Teilia 

OS 1:50,000 map:  114

Summit Height:  51m (spot height) 

Summit Grid Reference:  SH 38125 94148 (spot height) 

Bwlch Height:  c 28m (interpolation) 

Bwlch Grid Reference:  SH 38469 94108 (interpolation) 

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

 

Myrddyn Phillips (June 2021)

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Ysgellog & Minffordd (SH 409 912) – 30-99m Sub-Twmpau deletion (83rd reclassification)

There has been a deletion to the list of 30-99m 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 Ysgellog & Minffordd (SH 409 912)

The criteria for the list that this deletion 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

The name the hill is listed by is Ysgellog & Minffordd 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 encircled by minor roads with the A5025 road farther to the north and the B5111 road farther to the south-east, and has the town of Amlwch towards the east north-east. 

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 an estimated c 23m of drop based on an estimated c 65m summit height and the 42m 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 deletion of this hill from 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 60.2m summit height and a 41.7m bwlch height, with these values giving this hill 18.5m of drop, which is insufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Ysgellog & Minffordd 

OS 1:50,000 map:  114

Summit Height:  60.2m (LIDAR) 

Summit Grid Reference:  SH 40921 91218 & SH 40923 91218 & SH 40925 91220 (LIDAR) 

Bwlch Height:  41.7m (LIDAR) 

Bwlch Grid Reference:  SH 40915 91509 (LIDAR) 

Drop:  18.5m (LIDAR) 

 

Myrddyn Phillips (June 2021)

 

  

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Graianfryn (SH 325 839) – 30-99m Sub-Twmpau addition (82nd reclassification)

Significant Name Changes post for Graianfryn

There has been confirmation of an addition to the list of 30-99m 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 Graianfryn (SH 325 839)

The criteria for the list that this addition 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

The name the hill is listed by is Graianfryn 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 minor roads to its north, south and east and the A5025 road to its west, and has the village of Llanfachreth towards the south-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 23m of drop based on the 46m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 23m 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 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 45.4m summit height and a 22.2m bwlch height, with these values giving this hill 23.2m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Graianfryn 

OS 1:50,000 map:  114

Summit Height:  45.4m (LIDAR) 

Summit Grid Reference:  SH 32558 83967 (LIDAR) 

Bwlch Height:  22.2m (LIDAR) 

Bwlch Grid Reference:  SH 33278 84232 (LIDAR) 

Drop:  23.2m (LIDAR) 

 

Myrddyn Phillips (June 2021)

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Cae Penorsedd (SH 305 834) – 30-99m Sub-Twmpau addition (81st reclassification)

Significant Name Changes post for Cae Penorsedd

There has been confirmation of an addition to the list of 30-99m 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 Penorsedd (SH 305 834) 

The criteria for the list that this addition 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

The name the hill is listed by is Cae Penorsedd 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, minor roads to its north and west and the A5025 road to its south-east, and has the village of Llanfachreth towards the south-east. 

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 24m of drop based on the 33m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 9m 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 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 33.5m summit height and a 9.9m bwlch height, with these values giving this hill 23.65m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Cae Penorsedd 

OS 1:50,000 map:  114

Summit Height:  33.5m (LIDAR) 

Summit Grid Reference:  SH 30528 83481 (LIDAR) 

Bwlch Height:  9.9m (LIDAR) 

Bwlch Grid Reference:  SH 30834 83544 (LIDAR) 

Drop:  23.65m (LIDAR) 

 

Myrddyn Phillips (June 2021)

 

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Cae Mawr (SH 290 834) – Double Sub-Twmpau addition (80th reclassification)

Significant Name Changes post for Cae Mawr

 

There has been confirmation of an addition to the list of Double Sub-Twmpau adjoined to the 30-99m 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 Cae Mawr (SH 290 834)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, this height band of hills has two accompanying sub lists, the first of which is 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, and the second sub category is entitled the Double Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 20m and below 30m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 30-99m Twmpau by Myrddyn Phillips

The name the hill is listed by is Cae Mawr 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 is positioned with the coast to its west and has a minor road to its north and east, and has the village of Llanfachreth towards the east south-east. 

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. 

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 21m of drop, based on the 24m summit spot height and an estimated c 3m bwlch height, with the latter based on interpolation of 5m contouring between 0 – 5m 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 Double Sub-Twmpau status is due to LIDAR analysis, resulting in a 25.1m summit height and a 4.2m bwlch height, with these values giving this hill 20.9m of drop which is sufficient for it to be classified as a Double Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn

Name:  Cae Mawr

OS 1:50,000 map:  114

Summit Height:  25.1m (LIDAR)

Summit Grid Reference:  SH 29051 83437 (LIDAR)

Bwlch Height:  4.2m (LIDAR)

Bwlch Grid Reference:  SH 29254 83269 (LIDAR) 

Drop:  20.9m (LIDAR)

 

Myrddyn Phillips (June 2021)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pt. 30.8m (SH 296 848) – 30-99m Sub-Twmpau addition (79th reclassification)

There has been confirmation of an addition to the list of 30-99m 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 Pt. 30.8m (SH 296 848)

The criteria for the list that this addition 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

The hill is being listed by the point (Pt. 30.8m) 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 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 a series of minor roads to its north, south and east, and has the village of Llanfachreth towards the south-east. 

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 an estimated c 22m of drop, based on the 31m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 9m bwlch height based on interpolation of 5m contouring between 5m – 10m. 

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 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 30.8m summit height and an 8.7m bwlch height, with these values giving this hill 22.1m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Pt. 30.8m 

OS 1:50,000 map:  114

Summit Height:  30.8m (LIDAR) 

Summit Grid Reference:  SH 29675 84885 (LIDAR) 

Bwlch Height:  8.7m (LIDAR) 

Bwlch Grid Reference:  SH 29963 84611 (LIDAR) 

Drop:  22.1m (LIDAR) 

 

Myrddyn Phillips (June 2021)

 

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pt. 39.7m (SH 299 859) – 30-99m Sub-Twmpau addition (78th reclassification)

There has been confirmation of an addition to the list of 30-99m 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 summit image of Pt. 39.7m (SH 299 859)

The criteria for the list that this addition 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

The hill is being listed by the point (Pt. 39.7m) 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 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 series of minor roads to its north, south and east and the coast to its west, and has the village of Llanfaethlu towards the north-east. 

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. 

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-evaluated and it was listed with 21m of drop, based on the 39m summit and 18m bwlch spot heights 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 bwlch image of Pt. 39.7m (SH 299 859)

Therefore, the confirmation of the addition of this hill to 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 39.7m summit height and a 19.2m bwlch height, with these values giving this hill 20.5m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Pt. 39.7m 

OS 1:50,000 map:  114

Summit Height:  39.7m (LIDAR) 

Summit Grid Reference:  SH 29920 85948 (LIDAR) 

Bwlch Height:  19.2m (LIDAR) 

Bwlch Grid Reference:  SH 30092 86343 (LIDAR) 

Drop:  20.5m (LIDAR) 

 

Myrddyn Phillips (June 2021)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Tyn Llan (SH 320 933) – Double Sub-Twmpau addition (77th reclassification)

Significant Name Changes post for Tyn Llan

 

There has been an addition to the list of Double Sub-Twmpau adjoined to the 30-99m 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:

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, this height band of hills has two accompanying sub lists, the first of which is 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, and the second sub category is entitled the Double Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 20m and below 30m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 30-99m Twmpau by Myrddyn Phillips

The name the hill is listed by is Tyn Llan 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), as is positioned with the coast on all sides except for its south-east and has a minor road to its south-east and east, and has the village of Llanfair-yng-Nghornwy towards the south. 

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. 

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 27m of drop, based on the 29m summit spot height and an estimated c 2m bwlch height, with the latter based on interpolation of 5m contouring between 0 – 5m 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 have been re-evaluated and it is now listed with 25m of drop, based on the 29m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 4m bwlch spot height that appears on the interactive mapping on the Magic Maps website. 

Extract from the Magic Maps website

Therefore, the addition of this hill to Double Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data, resulting in a 29m summit height and a 4m bwlch height, with these values giving this hill 25m of drop which is sufficient for it to be classified as a Double Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn

Name:  Tyn Llan

OS 1:50,000 map:  114

Summit Height:  29m (spot height)

Summit Grid Reference:  SH 32084 93367 (spot height)

Bwlch Height:  4m (spot height)

Bwlch Grid Reference:  SH 32275 93087 (spot height) 

Drop:  25m (spot height summit and bwlch)

 

Myrddyn Phillips (June 2021)

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pen yr Orsedd (SH 325 924) – 30-99m Sub-Twmpau addition (76th reclassification)

Significant Name Changes post for Pen yr Orsedd 

There has been an addition to the list of 30-99m 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: 

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

The name the hill is listed by is Pen yr Orsedd 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 and north-east, and is encircled by minor roads with the A5025 road further to its south-east, and has the village of Cemaes towards the east. 

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 an estimated c 21m of drop based on the 44m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 23m bwlch height based on interpolation of 5m contouring between 20m – 25m. 

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

Therefore, the addition of this hill to 30-99m Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data, resulting in a 44m summit height and an estimated c 23m bwlch height, with these values giving this hill an estimated c 21m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Pen yr Orsedd 

OS 1:50,000 map:  114

Summit Height:  44m (spot height) 

Summit Grid Reference:  SH 32516 92447 (spot height) 

Bwlch Height:  c 23m (interpolation) 

Bwlch Grid Reference:  SH 32408 92169 (interpolation) 

Drop:  c 21m (spot height summit and interpolated bwlch) 

 

Myrddyn Phillips (June 2021)

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Cafnan (SH 347 929) – 30-99m Sub-Twmpau addition (75th reclassification)

Significant Name Changes post for Cafnan

There has been confirmation of an addition to the list of 30-99m 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 Cafnan (SH 347 929)

The criteria for the list that this addition 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

The name the hill is listed by is Cafnan 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, minor roads to its north and south-west and the A5025 road to its south-east, and has the village of Cemaes towards the east. 

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 23m of drop based on the 42m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 19m bwlch spot height positioned at SH 34895 93133 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 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 41.8m summit height and a 21.1m bwlch height, with these values giving this hill 20.7m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Cafnan 

OS 1:50,000 map:  114

Summit Height:  41.8m (LIDAR) 

Summit Grid Reference:  SH 34714 92915 (LIDAR) 

Bwlch Height:  21.1m (LIDAR) 

Bwlch Grid Reference:  SH 34936 92892 (LIDAR) 

Drop:  20.7m (LIDAR) 

 

Myrddyn Phillips (May 2021)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Mynydd y Wylfa (SH 356 944) – 30-99m Sub-Twmpau addition (74th reclassification)

There has been confirmation of an addition to the list of 30-99m 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 Mynydd y Wylfa (SH 356 944)

The criteria for the list that this addition 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

The name the hill is listed by is Mynydd y Wylfa 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 on all sides except for its south-west and the A5025 road to its south, and has the village of Cemaes towards the south-east. 

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 an estimated c 20m of drop based on the 38m summit spot height and an estimated c 18m bwlch height based on interpolation of 5m contouring, 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 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 39.7m summit height and a 17.5m bwlch height, with these values giving this hill 22.3m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Mynydd y Wylfa 

OS 1:50,000 map:  114

Summit Height:  39.7m (LIDAR) 

Summit Grid Reference:  SH 35676 94469 (LIDAR) 

Bwlch Height:  17.5m (LIDAR) 

Bwlch Grid Reference:  SH 35423 94228 (LIDAR) 

Drop:  22.3m (LIDAR) 

 

Myrddyn Phillips (May 2021)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Rhwng Dau Fynydd (SH 351 929) – 30-99m Sub-Twmpau addition (73rd reclassification)

Significant Name Changes post for Rhwng Dau Fynydd

There has been an addition to the list of 30-99m 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 Rhwng Dau Fynydd (SH 351 929)

The criteria for the list that this addition 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

The name the hill is listed by is Rhwung Dau Fynydd 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, a minor road to its immediate north and the A5025 road to its south south-east, and has the village of Tregele towards the south-east. 

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 an estimated c 18m of drop based on an estimated c 40m summit height and an estimated c 22m bwlch height, with both heights based on interpolation of 5m contouring 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 addition of this hill to 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 42.0m summit height and a 22.0m bwlch height, with these values giving this hill 20.0m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Rhwng Dau Fynydd 

OS 1:50,000 map:  114

Summit Height:  42.0m (LIDAR) 

Summit Grid Reference:  SH 35146 92985 (LIDAR) 

Bwlch Height:  22.0m (LIDAR) 

Bwlch Grid Reference:  SH 35426 92899 (LIDAR) 

Drop:  20.0m (LIDAR) 

 

Myrddyn Phillips (May 2021)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Plas Newydd (SH 614 807) – 30-99m Sub-Twmpau reclassified to 100m Sub-Twmpau (72nd reclassification)

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 - 30-99m Twmpau

Tyddyn Gwydryn Llain Fan (SH 495 681) – 30-99m Sub-Twmpau addition (71st reclassification)

Significant Height Revisions post for Tyddyn Gwydryn Llain Fan

Summit Relocations post for Tyddyn Gwydryn Llain Fan

Significant Name Changes post for Tyddyn Gwydryn Llain Fan

 

There has been confirmation of an addition to the list of 30-99m 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 Tyddyn Gwydryn Llain Fan (SH 495 681)

The criteria for the list that this addition 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

The name the hill is listed by is Tyddyn Gwydryn Llain Fan 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 its summit adjacent to the A4080 road, and has the village of Brynsiencyn towards the south-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 an estimated c 26m of drop based on the 59m spot height adjoined to a triangulation pillar positioned at SH 49980 68424 and the 59m spot height positioned at SH 50109 68526 and an estimated c 33m bwlch height based on interpolation of 5m contouring between 30m – 35m 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 bwlch image of Tyddyn Gwydryn Llain Fan

Therefore, the confirmation of the addition of this hill to 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 60.4m summit height and a 31.9m bwlch height, with these values giving this hill 28.5m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Tyddyn Gwydryn Llain Fan 

OS 1:50,000 map:  114, 115

Summit Height:  60.4m (LIDAR) 

Summit Grid Reference:  SH 49584 68102 (LIDAR) 

Bwlch Height:  31.9m (LIDAR) 

Bwlch Grid Reference:  SH 51324 71408 (LIDAR) 

Drop:  28.5m (LIDAR) 

 

Myrddyn Phillips (May 2021)