Mapping Mountains – Summit Relocations – 100m Twmpau

Coed Penllyn (SH 786 696)

There has been a Summit Relocation to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Coed Penllyn (SH 786 696)

The criteria for the list that this summit relocation applies to are:

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

100m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Coed Penllyn, and this was derived from the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map, and it is adjoined to the Mynydd Hiraethog group of hills, which are situated in the northern part of North Wales (Region A, Sub-Region A2), and it is positioned with the A470 road to its west and a minor road to its east, and has the town of Llanrwst towards the south.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 list, and listed with a 193m summit height positioned at SH 786 697 with an accompanying note stating; Height from 1989 1:50000 map. 

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-assessed and it was listed as a twin top with an estimated c 25m of drop, based on the 193m spot height that appears on the 1:50,000 Landranger map and a twin 193m map heighted top positioned at SH 78713 69823 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 168m bwlch height, based on interpolation of 10m contouring between 160m – 170m. 

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

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

LIDAR summit image of Coed Penllyn (SH 786 696)

LIDAR analysis gives the highest ground on this hill as 198.0m positioned at SH 78630 69665, and compared to its previously listed twin summit position this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour either on Ordnance Survey maps or interactive mapping, to a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is considered a relatively recent man-made construct, or the listing of a new twin summit or de-twinning of a summit, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist.

Therefore, the height produced by LIDAR analysis to the summit of this hill is 198.0m and is positioned at SH 78630 69665, this position is close to the spot height that appears on the Ordnance Survey 1:50,000 Landranger map and approximately 158 metres south-westward from where the twin map heighted spot height appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

 

The full details for the hill are: 

Group:  Mynydd Hiraethog 

Name:  Coed Penllyn 

OS 1:50,000 map:  115

Summit Height:  198.0m (LIDAR) 

Summit Grid Reference (New Position):  SH 78630 69665 (LIDAR) 

Bwlch Height:  170.9m (LIDAR) 

Bwlch Grid Reference:  SH 78892 70134 (LIDAR) 

Drop:  27.1m (LIDAR)

Myrddyn Phillips (April 2026) 

Mapping Mountains – Summit Relocations – 100m Twmpau

Llety Llwydin (SN 672 923) 

There has been a Summit Relocation to a hill that is now listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Llety Llwydin (SN 672 923) 

The criteria for the list that this summit relocation applies to are:

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

100m Twmpau by Myrddyn Phillips

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

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 19m of drop, based on an estimated c 176m summit height positioned at SN 67433 92548 and an estimated c 157m bwlch height, with both heights based on interpolation of 10m contouring that appears on the Ordnance Survey 1:25,000 Explorer map. 

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

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 Llety Llwydin (SN 672 923)

LIDAR analysis gives the highest ground on this hill as 178.8m positioned at SN 67233 92384, and compared to its previously listed summit position this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour either on Ordnance Survey maps or interactive mapping, to a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is considered a relatively recent man-made construct, or the listing of a new twin summit or de-twinning of a summit, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist.

Therefore, the height produced by LIDAR analysis to the summit of this hill is 178.8m and is positioned at SN 67233 92384, this position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and is approximately 200 metres south-westward from where the previously listed summit is positioned. 

 

The full details for the hill are:

Group:  Banc Llechwedd Mawr 

Name:  Llety Llwydin 

OS 1:50,000 map:  135

Summit Height:  178.8m (LIDAR) 

Summit Grid Reference (New Position):  SN 67233 92384 (LIDAR) 

Bwlch Height:  155.5m (LIDAR) 

Bwlch Grid Reference:  SN 66961 92762 (LIDAR) 

Drop:  23.3m (LIDAR) 

 

Myrddyn Phillips (August 2025) 

Mapping Mountains – Summit Relocations – 100m Twmpau

Cae Cefn (SO 315 009) 

There has been a Summit Relocation to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Cae Cefn (SO 315 009)

The criteria for the list that this summit relocation applies to are:

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

100m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Cae Cefn and this was derived from the Tithe map, and it is adjoined to the Cefn yr Ystrad group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and it is positioned with minor roads to its west, south and east, and the A4042 road farther to its west, and has the town of Pont-y-pŵl (Pontypool) towards the west.

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

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with a 156m summit height, based on the spot height positioned on a road at SO 31429 00880 that appears on the Ordnance Survey 1:50,000 Landranger map. 

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. 

LIDAR summit image of Cae Cefn (SO 315 009)

LIDAR analysis gives the highest ground on this hill as 159.4m positioned at SO 31564 00957 and SO 31565 00959, and compared to its previously listed summit position this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour either on Ordnance Survey maps or interactive mapping, to a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is considered a relatively recent man-made construct, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist.

Therefore, the height produced by LIDAR analysis to the summit of this hill is 159.4m and is positioned at SO 31564 00957 and SO 31565 00959, this position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and is approximately 130 metres east north-eastward and positioned to a different feature from where the previously listed summit is positioned. 

 

The full details for the hill are: 

Group:  Cefn yr Ystrad 

Name:  Cae Cefn 

OS 1:50,000 map:  171

Summit Height:  159.4m (LIDAR) 

Summit Grid Reference (New Position):  SO 31564 00957 & SO 31565 00959 (LIDAR) 

Bwlch Height:  135.7m (LIDAR) 

Bwlch Grid Reference:  SO 31507 01161 (LIDAR) 

Drop:  23.7m (LIDAR) 

 

Myrddyn Phillips (March 2025)

 

 

 

 

  

Mapping Mountains – Summit Relocations – 100m Twmpau

 

Cae Ton Bach Ucha (ST 320 991) 

There has been a Summit Relocation to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Cae Ton Bach Ucha (ST 320 991)

The criteria for the list that this summit relocation applies to are:

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

100m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Cae Ton Bach Ucha, and this was derived from the Tithe map, and it is adjoined to the Cefn yr Ystrad group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and it is positioned with a minor road to its north and the A4042 road to its west, and has the town of Pont-y-pŵl (Pontypool) towards the north north-west.

When the original Welsh 100m P30 list was published on Geoff Crowder’s v-g.me website, this hill was listed with a 144m summit height, based on the spot height positioned on a road at ST 32028 99148 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

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 Cae Ton Bach Ucha (ST 320 991)

LIDAR analysis gives the highest ground on this hill as 144.6m positioned at ST 32053 99100, and compared to its originally listed summit position this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour either on Ordnance Survey maps or interactive mapping, to a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is considered a relatively recent man-made construct, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist.

Therefore, the height produced by LIDAR analysis to the summit of this hill is 144.6m and is positioned at ST 32053 99100, this is approximately 48 metres south-eastward and positioned to a different feature from where the originally listed summit is positioned. 

 

The full details for the hill are: 

Group:  Cefn yr Ystrad 

Name:  Cae Ton Bach Ucha 

OS 1:50,000 map:  171

Summit Height:  144.6m (LIDAR) 

Summit Grid Reference (New Position):  ST 32053 99100 (LIDAR) 

Bwlch Height:  106.0m (LIDAR) 

Bwlch Grid Reference:  ST 31267 99414 (LIDAR) 

Drop:  38.6m (LIDAR) 

 

Myrddyn Phillips (February 2025)

 

 

 

Mapping Mountains – Summit Relocations – 100m Twmpau

Pt. 143.7m (ST 330 982) 

There has been a Summit Relocation to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Pt. 143.7m (ST 330 982)

The criteria for the list that this summit relocation applies to are:

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

100m Twmpau by Myrddyn Phillips

The hill is now listed by the point (Pt. 143.7m) notation, and it is adjoined to the Cefn yr Ystrad group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and it is positioned with minor roads to its north and south-east, and the A4042 road to its west, and has the town of Pont-y-pŵl (Pontypool) towards the west north-west.

When the original Welsh 100m P30 list was published on Geoff Crowder’s v-g.me website, this hill was listed with a 142m summit height, based on the spot height positioned at ST 332 984 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. 

LIDAR summit image of Pt. 143.7m (ST 330 982)

LIDAR analysis gives the highest ground on this hill as 143.7m positioned at ST 33080 98268.  With LIDAR giving the originally listed summit as 143.3m positioned at ST 33256 98508, and this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour either on Ordnance Survey maps or interactive mapping, to a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is considered a relatively recent man-made construct, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist.

Therefore, the height produced by LIDAR analysis to the summit of this hill is 143.7m and is positioned at ST 33080 98268, this is approximately 240 metres south-westward and positioned in a different map contour from where the originally listed summit is positioned. 

 

The full details for the hill are: 

Group:  Cefn yr Ystrad 

Name:  Pt. 143.7m 

OS 1:50,000 map:  171

Summit Height:  143.7m (LIDAR) 

Summit Grid Reference (New Position):  ST 33080 98268 (LIDAR) 

Bwlch Height:  119.3m (LIDAR) 

Bwlch Grid Reference:  ST 33629 99205 (LIDAR) 

Drop:  24.4m (LIDAR) 

 

Myrddyn Phillips (February 2025)