Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

 

30-99m Twmpau – Hill Reclassifications

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

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

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Cae Pen y Cefn (SH 532 377) – 30-99m Sub-Twmpau addition (120th reclassification)

Summit Relocations post for Cae Pen y Cefn

Significant Name Changes post for Cae Pen y Cefn

 

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 Pen y Cefn (SH 532 377)

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. 

30-99m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Cae Pen y Cefn and this was derived from the Tithe map, and it is adjoined to the Moel Hebog group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with a minor road to its north and south, and the A497 road farther to its north, and has the town of Porthmadog 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 20m of drop, based on the 58m summit spot height that appears on the contemporary Ordnance Survey 1:25000 Explorer map, and an estimated c 38m bwlch height, based on interpolation of 5m contouring between 35m – 40m. 

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 57.8m summit height and a 37.3m 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:  Moel Hebog 

Name:  Cae Pen y Cefn 

OS 1:50,000 map:  124

Summit Height:  57.8m (LIDAR) 

Summit Grid Reference:  SH 53267 37729 (LIDAR)               

Bwlch Height:  37.3m (LIDAR) 

Bwlch Grid Reference:  SH 53729 38357 (LIDAR) 

Drop:  20.5m (LIDAR) 

 

Myrddyn Phillips (May 2024)

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Coed y Chwarel (SH 539 394) – 30-99m Sub-Twmpau addition (119th 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 by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Coed y Chwarel (SH 539 394)

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. 

30-99m Twmpau by Myrddyn Phillips

The name the hill is listed by is Coed y Chwarel, and it is adjoined to the Moel Hebog group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A497 road to its north and a minor road to its east, and has the town of Porthmadog 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 25m of drop, based on the 59m summit spot height that appears on the contemporary Ordnance Survey 1:25000 Explorer 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 LIDAR analysis, resulting in a 58.4m summit height and a 34.8m bwlch height, with these values giving this hill 23.6m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Moel Hebog 

Name:  Coed y Chwarel 

OS 1:50,000 map:  124

Summit Height:  58.4m (LIDAR) 

Summit Grid Reference:  SH 53911 39499 (LIDAR)               

Bwlch Height:  34.8m (LIDAR) 

Bwlch Grid Reference:  SH 54045 39449 (LIDAR) 

Drop:  23.6m (LIDAR) 

 

Myrddyn Phillips (April 2024)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Carreg Waring (SH 537 390) – 30-99m Sub-Twmpau addition (118th reclassification)

Significant Name Changes post for Carreg Waring

 

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 by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Carreg Waring (SH 537 390)

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. 

30-99m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Carreg Waring, and this was derived by a combination of the Ordnance Survey series of Six-Inch maps and local enquiry, and it is adjoined to the Moel Hebog group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A497 road to its north and a minor road to its east, and has the town of Porthmadog 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 23m of drop, based on the 57m 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 LIDAR analysis, resulting in a 57.15m summit height and a 33.0m bwlch height, with these values giving this hill 24.1m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Moel Hebog 

Name:  Carreg Waring 

OS 1:50,000 map:  124

Summit Height:  57.15m (LIDAR) 

Summit Grid Reference:  SH 53734 39025 (LIDAR)               

Bwlch Height:  33.0m (LIDAR) 

Bwlch Grid Reference:  SH 53892 38892 (LIDAR) 

Drop:  24.1m (LIDAR) 

 

Myrddyn Phillips (April 2024)

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pen Brwsh (SM 880 396) – 30-99m Twmpau addition (117th 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 by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Pen Brwsh (SM 880 396)

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 Brwsh, and it is adjoined to the Garn Fawr group of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1).  As this is a tidal island it is surrounded by sea at high tide, and it is positioned with a minor road to its east and the A487 road farther to its south-east, and has the town of Abergwaun (Fishguard) 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.

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 42m of drop, based on an estimated c 42m summit height based on interpolation of its uppermost 40m ring contour 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 Twmpau status is due to LIDAR analysis, resulting in a 41.8m summit height and a 0.2m bwlch height, with these values giving this hill 41.6m of drop, which is sufficient for it to be classified as a 30-99m Twmpau. 

 

The full details for the hill are: 

Group:  Garn Fawr 

Name:  Pen Brwsh 

OS 1:50,000 map:  157

Summit Height:  41.8m (LIDAR) 

Summit Grid Reference:  SM 88067 39675 (LIDAR)               

Bwlch Height:  0.2m (LIDAR) 

Bwlch Grid Reference:  SM 88117 39673 (LIDAR) 

Drop:  41.6m (LIDAR) 

 

Myrddyn Phillips (June 2023)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Rhos Trebared (SN 173 475) – 30-99m Twmpau reclassified to 30-99m Sub-Twmpau (116th reclassification)

Significant Name Changes post for Rhos Trebared

 

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 derived by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Rhos Trebared (SN 173 475)

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 now listed by is Rhos Trebared and this was derived from local enquiry, and it is adjoined to the Mynydd Bach group of hills, which are situated in the western part of South Wales (Region B, Sub-Region B1), and it is positioned with the coast to its north-west, the B4548 road to its north-east and a minor road to its south, and has the town of Aberteifi (Cardigan) 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 included in the main P30 list.

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 30m of drop, based on the 69m summit spot height and the 39m bwlch spot height that appear on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

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

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

Therefore, the reclassification of this hill to 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 70.3m summit height and a 40.3m bwlch height, with these values giving this hill 29.9m of drop, which is insufficient for it to be classified as a 30-99m Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Bach 

Name:  Rhos Trebared 

OS 1:50,000 map:  145

Summit Height:  70.3m (LIDAR) 

Summit Grid Reference:  SN 17391 47521 (LIDAR)               

Bwlch Height:  40.3m (LIDAR) 

Bwlch Grid Reference:  SN 17728 47659 (LIDAR) 

Drop:  29.9m (LIDAR) 

 

Myrddyn Phillips (February 2023)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Allt Dan Tŷ Mawr (SN 520 228) – 30-99m Sub-Twmpau reclassified to 30-99m Twmpau (115th reclassification)

Significant Height Revisions post for Allt Dan Tŷ Mawr

  

There has been confirmation of 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 confirmed by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Allt Dan Tŷ Mawr (SN 520 228)

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 Allt Dan Tŷ Mawr and it is adjoined to the Mynydd Mallaen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north, west and south, and the A40 road to its south-west, and has the town of Llandeilo 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 included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 category.

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with an estimated c 29m of drop, based on an estimated c 67m summit height and the 38m bwlch spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

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

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

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had a 69m summit spot height positioned at SN 51824 22804, and when coupled with the 38m bwlch spot height these values gave this hill 31m of drop.

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

Therefore, the confirmation of the reclassification of this hill from 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 72.65m summit height and a 39.0m bwlch height, with these values giving this hill 33.7m of drop, which is sufficient for it to be classified as a 30-99m Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Mallaen 

Name:  Allt Dan Tŷ Mawr 

OS 1:50,000 map:  159

Summit Height:  72.65m (LIDAR) 

Summit Grid Reference:  SN 52004 22867 (LIDAR)               

Bwlch Height:  39.0m (LIDAR) 

Bwlch Grid Reference:  SN 52223 22857 (LIDAR) 

Drop:  33.7m (LIDAR) 

 

Myrddyn Phillips (May 2022)

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Pen Lan Fawr (SN 626 222) – 30-99m Sub-Twmpau reclassified to 30-99m Twmpau (114th reclassification)

Significant Height Revisions post for Pen Lan Fawr

 

There has been confirmation of 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 derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Pen Lan Fawr (SN 626 222)

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 Pen Lan Fawr and it is adjoined to the Mynydd Mallaen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with a minor road to its north, the Afon Tywi to its south and the A483 road to its east, and has the town of Llandeilo 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 included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the 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 29m of drop, based on the 95m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 66m bwlch height, based on interpolation of 10m contouring between 60m – 70m. 

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

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

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had a 65m bwlch spot height, and when coupled with the 95m summit spot height these values gave this hill 30m of drop.

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

Therefore, the confirmation of the reclassification of this hill from 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 98.3m summit height and a 64.9m bwlch height, with these values giving this hill 33.4m of drop, which is sufficient for it to be classified as a 30-99m Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Mallaen 

Name:  Pen Lan Fawr 

OS 1:50,000 map:  159

Summit Height:  98.3m (LIDAR) 

Summit Grid Reference:  SN 62626 22229 (LIDAR)               

Bwlch Height:  64.9m (LIDAR) 

Bwlch Grid Reference:  SN 61761 22561 (LIDAR) 

Drop:  33.4m (LIDAR) 

 

Myrddyn Phillips (April 2022)

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Moel y Gadair (SH 521 391) – 30-99m Sub-Twmpau reclassified to 30-99m Twmpau (113th reclassification)

Summit survey post for Moel y Gadair

Bwlch survey post for Moel y Gadair

 

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 derived from a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and LIDAR analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips. 

Moel y Gadair (SH 521 391)

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 Moel y Gadair and it is adjoined to the Moel Hebog group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the coast to its south and the A497 road to its north-west, and has the town of Cricieth 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, as it was considered not to meet the criteria then used for the main P30 category. 

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with an estimated c 31m of drop, based on the 67m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 36m bwlch height based on interpolation of 10m contouring between 30m – 40m.  The details for this hill were subsequently reassessed and its drop value amended to an estimated c 30m based on an estimated bwlch height of c 37m. 

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

This hill was then surveyed on the 15^th June 2015 using the Trimble GeoXH 6000, resulting in a 66.7m summit height and a 35.9m bwlch height, with these values seemingly confirming its P30 status. 

The Trimble GeoXH 6000 gathering data at the summit of Moel y Gadair

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

One of a series of surveys conducted at the bwlch on the 15th June 2015 

One of the resources recently available online is the mapping on the OS Maps website and the details for this hill were subsequently re-assessed against this mapping.  This is the replacement for OS Get-a-map and until recent times had contours at 5m intervals which were proving consistently more accurate compared to the 5m contours that sometimes appear on the Ordnance Survey 1:25,000 Explorer map and used to appear on the online Vector Map Local.  This mapping had bwlch contouring between 35m – 40m, with interpolation placing the height of the bwlch as an estimated c 37m, with the 5m contouring helping to indicate the position of the bwlch. 

With the aid of a ten figure grid reference for the bwlch position taken from the 5m contouring on the OS Maps website the bwlch of this hill was re-surveyed using the Trimble GeoXH 6000 on the 23^rd February 2016, resulting in the hill being reclassified to 30-99m Sub-Twmpau status. 

One of two surveys conducted at the bwlch on the 23rd February 2016

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. 

Initial LIDAR analysis indicated that the position of the bwlch was at SH 52007 39290, which is relatively close to where the Trimble GeoXH 6000 was placed on the survey conducted on the 23^rd February 2016.  LIDAR gives this position as 36.8m in height and when coupled with the 66.7m summit height, these values gave this hill 29.9m of drop. 

LIDAR bwlch image with the joining of the red contour positioned on the road at SH 52007 39290 

However, the 36.8m bwlch height ascertained from LIDAR is placed on an artificially raised road which is considered a relatively recent man-made construct and therefore not taken as a part of the height of the bwlch.  Further LIDAR analysis was required. 

The initial re-assessment of LIDAR was undertaken by Aled Williams and he concluded that this hill is a natural P30, with only the height of the artificially raised road excluding it from being listed as a 30-99m Twmpau.  His conclusion was that the height of the bwlch could be listed as an estimated and conservative c 36m or if using remaining natural ground; 35.8m positioned at SH 52020 39324.  Either value classifies this hill as a P30. 

LIDAR image of Moel y Gadair with the white contour placed 30m below the summit indicating this hill is a natural P30 with only the artificially raised road stopping the two respective white contours from being continuous

Having studied LIDAR, I concur with Aled’s conclusion that this hill is a natural P30, the bwlch height quoted is 35.8m positioned at SH 52013 39319.  This position is indicated as a joining on the hill to hill traverse excluding the artificially raised road and is approximately four metres from remaining natural ground. 

LIDAR image of Moel y Gadair (SH 521 391) showing the various height contours used to conclude this hill is a natural P30 and its bwlch height and position

Therefore, the reclassification of this hill from 30-99m Sub-Twmpau status and its re-instatement as a 30-99m Twmpau is due to a Trimble GeoXH 6000 summit survey and LIDAR bwlch analysis, resulting in a 66.7m summit height and a 35.8m bwlch height, with these values giving this hill 30.9m of drop, which is sufficient for it to be classified as a 30-99m Twmpau. 

 

The full details for the hill are: 

Group:  Moel Hebog 

Name:  Moel y Gadair 

OS 1:50,000 map:  124

Summit Height:  66.7m (converted to OSGM15, Trimble GeoXH 6000) 

Summit Grid Reference:  SH 52165 39135 (Trimble GeoXH 6000)               

Bwlch Height:  35.8m (LIDAR) 

Bwlch Grid Reference:  SH 52013 39319 (LIDAR) 

Drop:  30.9m (Trimble GeoXH 6000 summit and LIDAR bwlch) 

 

Myrddyn Phillips (March 2022)

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Cefn Coch (SH 610 396) – 30-99m Sub-Twmpau reclassified to 30-99m Twmpau (112th reclassification)

Survey post for Cefn Coch

Significant Height Revisions post for Cefn Coch

Significant Name Changes post for Cefn Coch

 

There has been confirmation of 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 derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Cefn Coch (SH 610 396)

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 now listed by is Cefn Coch and it is adjoined to the Moelwynion 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 A498 road and the B4410 road to its north-west, the A497 road and the A487 road to its south-west and the A4085 road to its east, and has the town of Penrhyndeudraeth 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 included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the P30 category.  This hill was listed with an 81m summit height, with an accompanying note stating; 86m on 1984 1:50,000 map. 

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

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 33m of drop, based on the 81m summit spot height and the 48m bwlch spot height that appear on the Ordnance Survey 1:25,000 Explorer map. 

The details for this hill were subsequently re-assessed as the bwlch contouring on the Ordnance Survey 1:25,000 Explorer map is between 50m – 60m, therefore according to map contouring the 48m spot height is below the position of the bwlch.  This reassessment resulted in the hill being listed with an estimated c 26m of drop, based on the 81m summit spot height and an estimated c 55m bwlch height. 

The details for this hill were later reassessed and the 86m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger map was favoured over that of the 81m spot height, and with the bwlch height amended to an estimated c 54m, these values gave this hill an estimated c 32m of drop. 

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 confirmation of the reclassification of this hill from 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in an 86.6m summit height and a 51.5m bwlch height, with these values giving this hill 35.1m of drop, which is sufficient for it to be classified as a 30-99m Twmpau. 

 

The full details for the hill are: 

Group:  Moelwynion 

Name:  Cefn Coch 

OS 1:50,000 map:  124

Summit Height:  86.6m (LIDAR) 

Summit Grid Reference:  SH 61030 39620 (LIDAR)               

Bwlch Height:  51.5m (LIDAR) 

Bwlch Grid Reference:  SH 61461 39763 (LIDAR) 

Drop:  35.1m (LIDAR) 

 

Myrddyn Phillips (December 2021)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Mynydd Pant y Gaseg (SH 414 944) – 30-99m Sub-Twmpau deletion (111th 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. 

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 Mynydd Pant y Gaseg 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 immediate north and the A5025 road to its south, and has the town of Amlwch 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 included in the Hills to be surveyed sub list, with an accompanying note stating; Height is also 80c.  1:50,000 and 1:25,000 maps differ. 

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

The contouring on the two publicly available Ordnance Survey maps of the time differed with the 1:50,000 Landranger giving an uppermost 80m contour and the 1:25,000 Explorer giving an uppermost 65m contour.  In the original hand-written list the height given is c 80, however when this list was published it was decided to use the 1:25,000 map height but at the same time retain the hill as a sub. 

Extract from the Ordnance Survey 1:50,000 Landranger map

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 15m of drop, based on an estimated c 67m summit height and an estimated c 52m bwlch height, with both heights based on interpolation of 5m contouring that appear on the Ordnance Survey 1:25,000 Explorer map. 

Since publication of the P30 lists on 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 old Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available maps and for this hill it had a 67m summit spot height and a 51m bwlch spot height, with these values giving this hill 16m of drop. 

Therefore, the deletion of this hill from 30-99m Sub-Twmpau status is due to detail on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map, resulting in a 67m summit height and a 51m bwlch height, with these values giving this hill 16m 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:  Mynydd Pant y Gaseg 

OS 1:50,000 map:  114

Summit Height:  67m (spot height) 

Summit Grid Reference:  SH 41410 94459 (spot height)               

Bwlch Height:  51m (spot height) 

Bwlch Grid Reference:  SH 41246 94369 (spot height) 

Drop:  16m (spot height summit and bwlch) 

 

Myrddyn Phillips (September 2021)

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Cerrig Engan (SH 403 733) – 30-99m Sub-Twmpau addition (110th 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 Cerrig Engan (SH 403 733)

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 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 Cerrig Engan, 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 A55 and A5 roads to its north, the B4422 road to its south-east and minor roads to its north-east and north-west, and has the town of Llangefni 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 20m of drop, based on the 72m 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 52m bwlch height based on interpolation of 5m contouring between 50m – 55m 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 71.8m summit height and a 51.8m 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:  Cerrig Engan 

OS 1:50,000 map:  114, 115

Summit Height:  71.8m (LIDAR) 

Summit Grid Reference:  SH 40381 73301 (LIDAR)               

Bwlch Height:  51.8m (LIDAR) 

Bwlch Grid Reference:  SH 40471 73329 (LIDAR) 

Drop:  20.0m (LIDAR) 

 

Myrddyn Phillips (September 2021)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Bwlch y Fen & Tyddyn Gwyn (SH 417 783) – 30-99m Sub-Twmpau addition (109th reclassification)

Summit Relocations post for Bwlch y Fen & Tyddyn Gwyn

Significant Name Changes post for Bwlch y Fen & Tyddyn Gwyn

  

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 Bwlch y Fen & Tyddyn Gwyn (SH 417 783)

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 Bwlch y Fen & Tyddyn Gwyn 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, west and east, and the B5109 road to its south, and has the village of Gwalchmai 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 21m of drop, based on the 89m 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

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 an 88.15m summit height and an estimated c 68m 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:  Bwlch y Fen & Tyddyn Gwyn 

OS 1:50,000 map:  114, 115

Summit Height:  88.15m (LIDAR) 

Summit Grid Reference:  SH 41738 78329 (LIDAR)               

Bwlch Height:  c 68m (interpolation) 

Bwlch Grid Reference:  SH 41140 80401 (interpolation) 

Drop:  c 20m (LIDAR summit and interpolated bwlch) 

 

Myrddyn Phillips (September 2021)

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Dinas Fach (SM 825 226) – 30-99m Twmpau addition (108th 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 obtained from the summit analysis programme that uses LIDAR produced by Joe Nuttall, and then by LIDAR analysis initially conducted by Jim Bloomer and subsequently by Myrddyn Phillips. 

LIDAR image of Dinas Fach (SM 825 226)

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 Dinas Fach, and it is adjoined to the Carn Llidi group of hills which are situated in the south-western part of Mid and West Wales (Region B, Sub-Region B4), and it is a tidal island with its connection to the mainland at low tide positioned to the north-east of its summit, and has the A487 road to its north and the village of Solfach (Solva) 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 main P30 list or the accompanying Hills to be surveyed sub list, as it was considered not to meet the criteria then used in either category. 

Extract from the Ordnance Survey 1:50,000 Landranger 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 remained unlisted, due to a single uppermost ring contour being shown on the Ordnance Survey 1:50,000 Landranger map and intermittent ring contours being shown on the 1:25,000 Explorer map. 

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

Just prior to analysing this hill via LIDAR its details were re-examined against online interactive mapping and it was listed with an estimated c 29m of drop, based on the 30m summit spot height that appears on the Magic Maps website and an estimated c 1m bwlch height, based on interpolation of 5m contouring between 0 – 5m 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. 

Therefore, the addition of this hill to 30-99m Twmpau status is due to LIDAR analysis, resulting in a 30.45m summit height and a 0.3m bwlch height, with these values giving this hill 30.15m of drop, which is sufficient for it to be classified as a 30-99m Twmpau. 

 

The full details for the hill are: 

Group:  Carn Llidi 

Name:  Dinas Fach 

OS 1:50,000 map:  157

Summit Height:  30.45m (LIDAR) 

Summit Grid Reference:  SM 82559 22659 (LIDAR) 

Bwlch Height:  0.3m (LIDAR) 

Bwlch Grid Reference:  SM 82605 22745 (LIDAR) 

Drop:  30.15m (LIDAR) 

 

Myrddyn Phillips (September 2021)

 

 

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Bodowen (SH 376 669) – 30-99m Sub-Twmpau addition (107th reclassification)

Significant Name Changes post for Bodowen

 

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 Bodowen (SH 376 669)

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 Bodowen 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 south-west, a minor road to its north and the A4080 road farther to its north, and has the village of Aberffraw 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 23m of drop, based on the 64m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 41m 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 detail on contemporary maps produced from Ordnance Survey data and LIDAR analysis, resulting in a 63.4m summit height and a 41m bwlch height, with these values giving this hill 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:  Bodowen 

OS 1:50,000 map:  114

Summit Height:  63.4m (LIDAR) 

Summit Grid Reference:  SH 37608 66991 (LIDAR)               

Bwlch Height:  41m (spot height) 

Bwlch Grid Reference:  SH 39614 69511 (spot height) 

Drop:  22m (LIDAR summit and spot height bwlch) 

 

Myrddyn Phillips (September 2021)

Mapping Mountains - Hill Reclassifications - 30-99m Twmpau

Din Dryfol (SH 396 724) – 30-99m Sub-Twmpau addition (106th 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 Din Dryfol (SH 396 724)

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 Din Dryfol 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 south-west, minor roads to its north-west and south-east, the A55 road to its north and the B4422 road to its south-east, and has the village of Bethel 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. 

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 66m summit height and an estimated c 43m 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 confirmation of the addition of this hill to 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 65.15m summit height and a 44.0m bwlch height, with these values giving this hill 21.1m 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:  Din Dryfol 

OS 1:50,000 map:  114

Summit Height:  65.15m (LIDAR) 

Summit Grid Reference:  SH 39603 72469 (LIDAR)               

Bwlch Height:  44.0m (LIDAR) 

Bwlch Grid Reference:  SH 39640 72534 (LIDAR) 

Drop:  21.1m (LIDAR) 

 

Myrddyn Phillips (September 2021)