Monday, 26 June 2017

Mapping Mountains – Hill Reclassifications – 200m Twmpau


200m Twmpau – Hill Reclassifications

The 200m Twmpau (thirty welsh metre prominences and upward) are the Welsh hills at or above 200m and below 30om in height that have a minimum drop of 30m.  Accompanying the main P30 list is a sub list entitled the 200m Sub-Twmpau with the qualification to this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop.

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









Mapping Mountains - Hill Reclassifications - 200m Twmpau

Foel (SH 632 045) – 200m Sub-Twmpau reclassified to 200m Twmpau (22nd reclassification)

Survey post for Foel

Significant Name Changes post for Foel


There has been a reclassification to the listing of 200m Twmpau due to LIDAR analysis conducted by Myrddyn Phillips and subsequently confirmed via a survey with the Trimble GeoXH 6000 which took place on the 14.05.18, with the criteria for this list being:

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

Prior to LIDAR analysis this hill was listed in the Hills to be surveyed sub list when the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website, and after this sub list was standardised with interpolated heights and drop values also included it was initially listed with an estimated c 31m of drop and later changed to 29m of drop, based on the 288m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 259m bwlch spot height that appears on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website.

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

The locally known name of the hill is Foel and it is adjoined to the Tarennydd range of hills which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and it overlooks the B 4405 road and the Afon Fathew to the south-east and the Afon Dysynni to the north-west, and has the small community of Dolgoch to its east and Bryn-crug to its south-west. 

Foel (SH 632 045)

As the summit of the hill is not a part of designated open access land permission to visit should be sought, for those wishing to do so a public footpath to the south and east of the summit can gain the eastern ridge of the hill or this can also be gained using a green track that makes its way up toward this ridge.

The reclassification of Foel to 200m Twmpau status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR image of Foel

The 1m DTM LIDAR analysis gives the hill the following details:


Name:  Foel

Summit Height:  288.2m

Summit Grid Reference:  SH 63297 04584

Bwlch Height:  257.7m

Bwlch Grid Reference:  SH 62972 04434

Drop:  30.5m


Therefore, the 288.2m LIDAR analysis for the summit position at SH 63297 04584 and the 257.7m LIDAR analysis for the bwlch position at SH 62972 04434 gives this hill 30.5m of drop, which is sufficient for it to be classified as a 200m Twmpau, with the details from the Trimble GeoXH 6000 survey being 288.3m (converted to OSGM15) summit at SH 63297 04583 and 257.7m (converted to OSGM15) bwlch at SH 62971 04432, giving this hill 30.6m of drop. 


The full details for the hill are:

Group:  Tarennydd

Name:  Foel

OS 1:50,000 map:  135

Summit Height:  288.3m (converted to OSGM15)

Summit Grid Reference:  SH 63297 04583

Bwlch Height:  257.7m (converted to OSGM15)

Bwlch Grid Reference:  SH 62971 04432

Drop:  30.6m


The Trimble GeoXH 6000 gathering data at the summit of Foel


Myrddyn Phillips (July 2018)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Pt. 232.1m (SH 675 157) – 200m Sub-Twmpau addition (21st reclassification)


There has been an addition to the 200m Twmpau list due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

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

Prior to LIDAR analysis this hill was listed with 18m of drop based on the 233m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 215m bwlch spot height that appears on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website.

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

As the name of this hill has not been confirmed by the author the hill is being listed by the point (Pt. 232.1m) notation and it is adjoined to the Cadair Idris group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and the hill is positioned with the A 493 road to its north-west and has the town of Dolgellau towards its east north-east.

The summit of the hill is a part of designated open access land with the most probable and convenient access to the hill via a public footpath approaching this land from a minor road towards the south-west of the summit.

The addition of this hill to 200m Sub-Twmpau status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The 1m DTM LIDAR analysis gives the hill the following details:


Name:  Pt. 232.1m

Summit Height:  232.1m

Summit Grid Reference:  SH 67577 15753

Bwlch Height:  210.0m

Bwlch Grid Reference:  SH 67357 15854

Drop:  22.1m

LIDAR image of Pt. 232.1m

Therefore, the 232.1m LIDAR analysis for the summit position at SH 67577 15753 and the 210.0m LIDAR analysis for the bwlch position at SH 67357 15854 gives this hill 22.1m of drop, which is sufficient for it to be classified as a 200m Sub-Twmpau.


The full details for the hill are:

Group:  Cadair Idris

Name:  Pt. 232.1m

OS 1:50,000 map:  124

Summit Height:  232.1m (LIDAR)

Summit Grid Reference:  SH 67577 15753 (LIDAR)

Bwlch Height:  210.0m (LIDAR)

Bwlch Grid Reference:  SH 67357 15854 (LIDAR)

Drop:  22.1m (LIDAR)


Myrddyn Phillips (June 2018)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Pt. 252.3m (SH 697 167) – 200m Sub-Twmpau addition (20th reclassification)


There has been an addition to the 200m Twmpau list due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

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

Prior to LIDAR analysis this hill was listed with c 19m of drop based on the 252m summit spot height that appears on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website and an estimated bwlch height of c 233m based on bwlch contouring between 230m – 240m.

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

As the name of the ffridd taking in this hill’s summit has not been confirmed the hill is being listed by the point (Pt. 252.3m) notation and it is adjoined to the Cadair Idris group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and the hill is positioned with the A 493 road to its north and has the town of Dolgellau towards its east north-east.

As the hill is a part of designated open access land the summit can be approached from a number of directions, with a bridleway to the south of the hill probably giving easiest access.

The addition of this hill to 200m Sub-Twmpau status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The 1m DTM LIDAR analysis gives the hill the following details:


Name:  Pt. 252.3m

Summit Height:  252.3m

Summit Grid Reference:  SH 69722 16736

Bwlch Height:  232.05m

Bwlch Grid Reference:  SH 69739 16620 & SH 69730 16624 & SH 69732 16628

Drop:  20.2m

LIDAR image of Pt. 252.3m

Therefore, the 252.3m LIDAR analysis for the summit position at SH 69722 16736 and the 232.05m LIDAR analysis for the bwlch position at SH 69739 16620 and SH 69730 16624 and SH 69732 16628 gives this hill 20.2m of drop, which confirms its addition to 200m Sub-Twmpau status.


The full details for the hill are:

Group:  Cadair Idris

Name:  Pt. 252.3m

OS 1:50,000 map:  124

Summit Height:  252.3m (LIDAR)

Summit Grid Reference:  SH 69722 16736 (LIDAR)

Bwlch Height:  232.05m (LIDAR)

Bwlch Grid Reference:  SH 69739 16620 & SH 69730 16624 & SH 69732 16628 (LIDAR)

Drop:  20.2m (LIDAR)


Myrddyn Phillips (June 2018)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Pt. 254.9m (SH 690 175) – 200m Sub-Twmpau addition (19th reclassification)


There has been confirmation of an addition to the 200m Twmpau list due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

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

This hill was not listed in the Hills to be surveyed sub list when the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website as it did not meet the criteria then used for this category of hill; however this list has now been standardised and interpolated heights and drop values also included, resulting in this hill being listed with c 22m of drop, based on the 256m summit spot height that appears on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website and an estimated bwlch height of c 234m based on bwlch contouring between 230m – 240m.

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

As the name of the ffridd taking in this hill’s summit has not been confirmed the hill is being listed by the point (Pt. 254.9m) notation and it is adjoined to the Cadair Idris group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and the hill is positioned with the A 493 road to its north and has the town of Dolgellau towards its east.

As the hill is not a part of designated open access land permission to visit should be sought, for those wishing to do so a public footpath crosses to the south of the summit and this can be accessed from open access land to the west.

The confirmation of the addition of this hill to 200m Sub-Twmpau status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The 1m DTM LIDAR analysis gives the hill the following details:


Name:  Pt. 254.9m

Summit Height:  254.9m

Summit Grid Reference:  SH 69086 17596

Bwlch Height:  231.5m

Bwlch Grid Reference:  SH 68969 17478

Drop:  23.5m


LIDAR image of Pt. 254.9m

Therefore, the 254.9m LIDAR analysis for the summit position at SH 69086 17596 and the 231.5m LIDAR analysis for the bwlch position at SH 68969 17478 gives this hill 23.5m of drop, which confirms its addition to 200m Sub-Twmpau status.


The full details for the hill are:

Group:  Cadair Idris

Name:  Pt. 254.9m

OS 1:50,000 map:  124

Summit Height:  254.9m (LIDAR)

Summit Grid Reference:  SH 69086 17596 (LIDAR)

Bwlch Height:  231.5m (LIDAR)

Bwlch Grid Reference:  SH 68969 17478 (LIDAR)

Drop:  23.5m (LIDAR)


Myrddyn Phillips (June 2018)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Tŵr Glas (SH 672 164) – 200m Sub-Twmpau reclassified to 200m Twmpau (18th reclassification)


There has been confirmation of a reclassification to the 200m Twmpau list due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

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

This hill was listed in the Hills to be surveyed sub list when the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website as it did not meet the criteria then used for the main P30 list; however this list has now been standardised and interpolated heights and drop values also included, resulting in this hill being listed with an estimated c 30m of drop, based on the 227m summit spot height that appears on Harvey maps and an estimated bwlch height of c 197m based on bwlch contouring between 190m – 200m.  The details for this hill were later amended when the Ordnance Survey Interactive Coverage Map hosted on the Geograph website became available online and it was then listed with an estimated c 32m of drop based on the 228m summit spot height appearing on this map and re-interpolation of bwlch contouring giving an estimated bwlch height of c 196m.

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

The name of the hill is Tŵr Glas and it is adjoined to the Cadair Idris group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), it is positioned overlooking the A 493 road which is to its north-west and has the small community of Arthog towards the south-west and the town of Dolgellau towards the east.

The summit and southern section of the hill is a part of designated open access land with a public footpath approaching the hill from the west probably being the most convenient ascent route, this follows the lower northern section of the hill before entering the open access land toward the east of the summit.

The confirmation of the reclassification of Tŵr Glas to 200m Twmpau status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The 1m DTM LIDAR analysis gives the hill the following details:


Name:  Tŵr Glas

Summit Height:  227.4m

Summit Grid Reference:  SH 67218 16437

Bwlch Height:  193.6m

Bwlch Grid Reference:  SH 67439 16279

Drop:  33.8m


LIDAR image of Tŵr Glas

Therefore, the 227.4m LIDAR analysis for the summit position at SH 67218 16437 and the 193.6m LIDAR analysis for the bwlch position at SH 67439 16279 gives this hill 33.8m of drop, which confirms its reclassification to 200m Twmpau status.


The full details for the hill are:

Group:  Cadair Idris

Name:  Tŵr Glas

OS 1:50,000 map:  124

Summit Height:  227.4m (LIDAR)

Summit Grid Reference:  SH 67218 16437 (LIDAR)

Bwlch Height:  193.6m (LIDAR)

Bwlch Grid Reference:  SH 67439 16279 (LIDAR)

Drop:  33.8m (LIDAR)


Myrddyn Phillips (June 2018)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Gribin (SH 675 168) – 200m Sub-Twmpau reclassified to 200m Twmpau (17th reclassification)


There has been confirmation of a reclassification to the 200m Twmpau list due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

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

This hill was listed in the Hills to be surveyed sub list when the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website as it was thought not  to meet the criteria then used for the main P30 list; however this list has now been standardised and interpolated heights and drop values also included, resulting in this hill being listed with an estimated c 39m of drop, based on an estimated c 211m summit height and an estimated bwlch height of c 172m based on bwlch map contouring between 170m – 180m.  The details for this hill were later amended when the Ordnance Survey Interactive Coverage Map hosted on the Geograph website became available online and it was then listed with a 211m summit height based on the spot height appearing on this map.

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

The name of the hill is Gribin and it is adjoined to the Cadair Idris group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), it is positioned overlooking the A 493 road which is to its north and has the small community of Arthog towards the south-west and the town of Dolgellau towards the east.

The summit and upper southern section of the hill is a part of designated open access land and a public footpath leads toward this from the west south-west of the hill, with another option for an ascent following a public footpath from the north-east of the hill.

The confirmation of the reclassification of Gribin to 200m Twmpau status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

The 1m DTM LIDAR analysis gives the hill the following details:


Name:  Gribin

Summit Height:  209.3m

Summit Grid Reference:  SH 67559 16814

Bwlch Height:  169.7m

Bwlch Grid Reference:  SH 67588 16670

Drop:  39.6m


LIDAR image of Gribin

Therefore, the 209.3m LIDAR analysis for the summit position at SH 67559 16814 and the 169.7m LIDAR analysis for the bwlch position at SH 67588 16670 gives this hill 39.6m of drop, which confirms its reclassification to 200m Twmpau status.


The full details for the hill are:

Group:  Cadair Idris

Name:  Gribin

OS 1:50,000 map:  124

Summit Height:  209.3m (LIDAR)

Summit Grid Reference:  SH 67559 16814 (LIDAR)

Bwlch Height:  169.7m (LIDAR)

Bwlch Grid Reference:  SH 67588 16670 (LIDAR)

Drop:  39.6m (LIDAR)


Myrddyn Phillips (May 2018)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Pt. 296.1m (SH 694 169) – 200m Sub-Twmpau addition (16th reclassification)


There has been confirmation of an addition to the 200m Twmpau list due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

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

This hill was not listed in the Hills to be surveyed sub list when the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website as it did not meet the criteria then used for this category of hill; however this list has now been standardised and interpolated heights and drop values also included, resulting in this hill being listed with 26m of drop, based on the 297m summit spot height and the 271m bwlch spot height that appear on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website.

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

As the name of the ffridd taking in this hill’s summit has not been confirmed the hill is being listed by the point (Pt. 296.1m) notation and it is adjoined to the Cadair Idris group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and the hill is positioned with the A 493 road to its north and has the town of Dolgellau towards its east.

As the hill is a part of designated open access land an ascent from a variety of directions is feasible, with a minor road towards its east and a public footpath towards its north and a bridleway towards its south probably giving the easiest option for ascent.

The confirmation of the addition of this hill to 200m Sub-Twmpau status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The 1m DTM LIDAR analysis gives the hill the following details:


Name:  Pt. 296.1m

Summit Height:  296.1m

Summit Grid Reference:  SH 69444 16921

Bwlch Height:  271.0m

Bwlch Grid Reference:  SH 69406 17012

Drop:  25.0m


LIDAR image of Pt. 296.1m

Therefore, the 296.1m LIDAR analysis for the summit position at SH 69444 16921 and the 271.0m LIDAR analysis for the bwlch position at SH 69406 17012 gives this hill 25.0m of drop, which confirms its addition to 200m Sub-Twmpau status.


The full details for the hill are:

Group:  Cadair Idris

Name:  Pt. 296.1m

OS 1:50,000 map:  124

Summit Height:  296.1m (LIDAR)

Summit Grid Reference:  SH 69444 16921 (LIDAR)

Bwlch Height:  271.0m (LIDAR)

Bwlch Grid Reference:  SH 69406 17012 (LIDAR)

Drop:  25.0m (LIDAR)


Myrddyn Phillips (May 2018)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Pt. 296.6m (SH 693 171) – 200m Sub-Twmpau addition (15th reclassification)


There has been confirmation of an addition to the 200m Twmpau list due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

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

This hill was not listed in the Hills to be surveyed sub list when the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website as it did not meet the criteria then used for this category of hill; however this list has now been standardised and interpolated heights and drop values also included, resulting in this hill being listed with 25m of drop, based on the 297m summit spot height and the 272m bwlch spot height that appear on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website.

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

As the name of the ffridd taking in this hill’s summit has not been confirmed the hill is being listed by the point (Pt. 296.6m) notation and it is adjoined to the Cadair Idris group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and the hill is positioned with the A 493 road to its north and has the town of Dolgellau towards its east.

As the hill is a part of designated open access land an ascent from most directions is feasible, with a minor road towards its east and a public footpath towards its north and a bridleway towards its south probably giving the easiest option for ascent.

The confirmation of the addition of this hill to 200m Sub-Twmpau status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 


The 1m DTM LIDAR analysis gives the hill the following details: 

Name:  Pt. 296.6m

Summit Height:  296.6m

Summit Grid Reference:  SH 69333 17107

Bwlch Height:  272.2m

Bwlch Grid Reference:  SH 69427 17196

Drop:  24.4m


LIDAR image of Pt. 296.6m

Therefore, the 296.6m LIDAR analysis for the summit position at SH 69333 17107 and the 272.2m LIDAR analysis for the bwlch position at SH 69427 17196 gives this hill 24.4m of drop, which confirms its addition to 200m Sub-Twmpau status.


The full details for the hill are:

Group:  Cadair Idris

Name:  Pt. 296.6m

OS 1:50,000 map:  124

Summit Height:  296.6m (LIDAR)

Summit Grid Reference:  SH 69333 17107 (LIDAR)

Bwlch Height:  272.2m (LIDAR)

Bwlch Grid Reference:  SH 69427 17196 (LIDAR)

Drop:  24.4m (LIDAR)


Myrddyn Phillips (May 2018)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Craig y Castell (SH 694 173) – 200m Sub-Twmpau reclassified to 200m Twmpau (14th reclassification)


There has been confirmation of a reclassification to the 200m Twmpau list due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

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

This hill was listed in the Hills to be surveyed sub list when the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website as it did not meet the criteria then used for the main P30 list; however this list has now been standardised and interpolated heights and drop values also included, resulting in this hill being listed with an estimated c 33m of drop, based on the 297m summit spot height that appears on Harvey maps and an estimated bwlch height of c 264m based on bwlch contouring between 260m – 270m.  The details for this hill were later amended when the Ordnance Survey Interactive Coverage Map hosted on the Geograph website became available online and it was then listed with 34m of drop based on the 298m summit and 264m bwlch spot heights that appear on this map.

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

The name of the hill is Craig y Castell and it is adjoined to the Cadair Idris group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and the hill is positioned overlooking the A 493 road to its north-west and has the town of Dolgellau towards its east.

As the upper section of the hill is a part of designated open access land an ascent from most directions is feasible, with a minor road towards its south-east and a public footpath towards its north probably giving the easiest option for ascent.

The confirmation of the reclassification of Craig y Castell to 200m Twmpau status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The 1m DTM LIDAR analysis gives the hill the following details:


Name:  Craig y Castell

Summit Height:  297.1m

Summit Grid Reference:  SH 69405 17302

Bwlch Height:  263.5m

Bwlch Grid Reference:  SH 69186 17218

Drop:  33.6m

LIDAR image of Craig y Castell

Therefore, the 297.1m LIDAR analysis for the summit position at SH 69405 17302 and the 263.5m LIDAR analysis for the bwlch position at SH 69186 17218 gives this hill 33.6m of drop, which confirms its reclassification to 200m Twmpau status.


The full details for the hill are:

Group:  Cadair Idris

Name:  Craig y Castell

OS 1:50,000 map:  124

Summit Height:  297.1m (LIDAR)

Summit Grid Reference:  SH 69405 17302 (LIDAR)

Bwlch Height:  263.5m (LIDAR)

Bwlch Grid Reference:  SH 69186 17218 (LIDAR)

Drop:  33.6m (LIDAR)


Myrddyn Phillips (May 2018)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Craig y Merwydd (SH 644 134) – 200m Sub-Twmpau reclassified to 200m Twmpau (13th reclassification)


There has been confirmation of a reclassification to the 200m Twmpau list due to LIDAR analysis conducted by Myrddyn Phillips and subsequently confirmed via a survey with the Trimble GeoXH 6000, with the criteria for this list being:

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

This hill was listed in the Hills to be surveyed sub list when the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website as it did not meet the criteria then used for the main P30 list; however this list has now been standardised and interpolated heights and drop values also included, resulting in this hill being listed with an estimated c 32m of drop, based on the 296m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 264m based on bwlch contouring between 260m – 270m.  This drop value was later amended to c 33m based on the larger scaled contours on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website.

The name of the hill is Craig y Merwydd (composition given as Craigymerwydd on contemporary maps) and it is adjoined to the Cadair Idris group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and the hill is positioned overlooking the A 493 road to its north-west and has the small community of Arthog to the north.

Craig y Merwydd (SH 644 134)

Extract from the Ordnance Survey series of Six-Inch maps

As the upper section of the hill is a part of designated open access land an ascent from most directions is feasible, with a minor road to its immediate south giving the easiest option.

The confirmation of the reclassification of Craig y Merwydd to 200m Twmpau status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 


The 1m DTM LIDAR analysis gives the hill the following details:


Name:  Craig y Merwydd

Summit Height:  295.5m

Summit Grid Reference:  SH 64413 13459

Bwlch Height:  261.0m

Bwlch Grid Reference:  SH 64606 13315

Drop:  34.5m


LIDAR image of Craig y Merwydd

Therefore, the 295.5m LIDAR analysis for the summit position at SH 64413 13459 and the 261.0m LIDAR analysis for the bwlch position at SH 64606 13315 gives this hill 34.5m of drop, with the details from the Trimble GeoXH 6000 survey being 295.7m (converted to OSGM15) summit at SH 64413 13459 and 261.2m (converted to OSGM15) bwlch at SH 64605 13317, giving this hill 34.6m of drop, which confirms its reclassification to 200m Twmpau status.


The full details for the hill are:

Group:  Cadair Idris

Name:  Craig y Merwydd

OS 1:50,000 map:  124

Summit Height:  295.7m (converted to OSGM15)

Summit Grid Reference:  SH 64413 13459

Bwlch Height:  261.2m (converted to OSGM15)

Bwlch Grid Reference:  SH 64605 13317

Drop:  34.6m (converted to OSGM15)



The Trimble GeoXH 6000 gathering data at the summit of Craig y Merwydd

For details on the survey of Craig y Merwydd

Myrddyn Phillips (May 2018)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Gwastad Meirionydd (SH 589 071) – 200m Sub-Twmpau addition (12th reclassification)

There has been an addition to the 200m Twmpau due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

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

Prior to LIDAR analysis this hill was listed with 19m of drop based on the 214m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and the bwlch spot height of 195m that appears on the Ordnance Survey 1:25,000 Explorer map.

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

The name of the hill is Gwastad Meirionydd and it is adjoined to the Cadair Idris group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and the hill is positioned between the coast to its north-west and the Afon Dysynni to its south-east and has the small communities of Llwyngwril to the north and Llanegryn to the south-east.

If wanting to visit the hill permission to do so should be sought as it is not a part of designated open access land, however the track to its west and north is a bridleway and is not too far from the high point of the hill.

The addition of Gwastad Meirionydd to 200m Sub-Twmpau status is due to LIDAR analysis of the bwlch conducted by Myrddyn Phillips, with the summit of the hill not covered by LIDAR.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The 2m DTM LIDAR analysis gives the hill the following details:


Gwastad Meirionydd

Summit Height:  214m

Summit Grid Reference:  SH 589 071

Bwlch Height:  191.5m

Bwlch Grid Reference:  SH 59229 08003

Drop:  23m

LIDAR image of Gwastad Meirionydd

Therefore, the 191.5m LIDAR analysis for the bwlch position at SH 59229 08003 when coupled with the 214m summit height gives this hill 23m of drop, which is sufficient for 200m Sub-Twmpau status.


The full details for the hill are:

Group:  Cadair Idris

Name:  Gwastad Meirionydd

Summit Height:  214m

Summit Grid Reference:  SH 589 071

Bwlch Height:  191.5m (LIDAR)

Bwlch Grid Reference:  SH 59229 08003 (LIDAR)

OS 1:50,000 map:  124

Drop:  23m


Myrddyn Phillips (May 2018)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Ffridd Tyddyn Mawr (SH 654 140) – 200m Sub-Twmpau addition (11th reclassification)

Survey post for Ffridd Tyddyn Mawr

Significant Name Changes post for Ffridd Tyddyn Mawr


There has been a confirmation of an addition to the 200m Twmpau with the summit height, drop and status of the hill confirmed by a survey with the Trimble GeoXH 6000, which was conducted by Myrddyn Phillips and took place on the 17th February 2018, and LIDAR analysis for the bwlch.

The criteria for this listing are:

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

The hill did not appear in the original Welsh P30 lists on Geoff Crowder’s v-g.me website as it did not meet the criteria then adopted for the Hills to be surveyed sub list.  The hill was subsequently listed in the sub category after this was standardised and interpolated drop values added, and was included when the updates to the 200m Welsh P30s were published for the Cadair Idris group of hills on Mapping Mountains on the 7th July 2014.

Prior to the survey with the Trimble GeoXH 6000 the hill was listed with 20m of drop, based on the 274m summit spot height and 254m bwlch spot height that appear on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website.

The bounded land where the summit of this hill is situated is named Ffridd Tyddyn Mawr and it is adjoined to the Cadair Idris group of hills, which is situated in the south-western part of North Wales (Region A, Sub-Region A3), and is positioned above the double lakes of Llynnau Cregennan which are to its north north-east and the small community of Arthog which is to its west north-west.

As the upper section of the hill is a part of designated open access land permission to visit does not need to be sought, for those wishing to visit the hill it can be approached from the lakeside car park adjacent to Llynnau Cregennan where a series of gates give access from one walled and bounded ffridd to the next.

The confirmation that Ffridd Tyddyn Mawr is a 200m Sub-Tumpau was due to the survey with the Trimble GeoXH 6000 and LIDAR analysis, resulting in a 273.2m (converted to OSGM15) summit height and a 251.2m (LIDAR) bwlch height, with these values giving the hill 22.0m of drop which is sufficient for its classification to this sub list.


The full details for the hill are:

Group:  Cadair Idris

Summit Height:  273.2m (converted to OSGM15)

Name:  Ffridd Tyddyn Mawr

OS 1:50,000 map:  124

Summit Grid Reference:  SH 65486 14081  

Drop:  22.0m (Trimble summit and LIDAR bwlch)


Ffridd Tyddyn Mawr (SO 654 140) now confirmed as a 200m Sub-Twmpau addition


Myrddyn Phillips (March 2018)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Erw Penlan (SO 045 495) – 200m Sub-Twmpau addition (10th reclassification)

Survey post for Erw Penlan

Significant Name Changes post for Erw Penlan


There has been a confirmation of an addition to the 200m Twmpau (thirty welsh metre prominences and upward) ranks of hills due to a survey with the Trimble GeoXH 6000, with the survey that confirmed this addition being conducted on the 13th June 2017.

The criteria for 200m Twmpau status is all Welsh hills at or above 200m and below 300m in height with 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop, and it is the inclusion of this hill in the 200m Sub-Twmpau that has been confirmed. 

The hill did not appear in the original Welsh P30 lists on Geoff Crowder’s v-g.me website as it did not meet the criteria then adopted for the Hills to be surveyed sub list.  The hill was later classified and listed in the sub category after this was standardised and interpolated drop values added, and was included when the updates to the 200m Welsh P30s were published for the Mynydd Epynt group of hills on Mapping Mountains on the 25th August 2014.  The listing this hill is now a part of is named Twmpau (thirty welsh metre prominences and upward) and its height, drop and status was confirmed by a survey with the Trimble GeoXH 6000.   

Prior to the survey with the Trimble GeoXH 6000 the hill was listed by the name of Coetgae Fawr with an estimated c 21m of drop, based on the 213m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 192m based on interpolation of bwlch contouring between 190m – 200m.

The name that this hill is being listed by is Erw Penlan (see Significant Name Changes) and it is adjoined to the Mynydd Epynt range, which is situated in the south-eastern part of Mid and West Wales (Region B, Sub-Region B2) with its Cardinal Hill being Clepyn Melyn (SN 961 464), and it is positioned above the A 483 road which is to the hill’s north and east, with the town of Llanfair-ym-Muallt (Builth Wells) positioned to its north.

As the hill does not form a part of designated open access land permission to visit should be sought, for those wishing to do so a public footpath connects between minor country lanes to the north and south of the hill’s summit and proceeds around the upper western part of the hill.


The full details for the hill are:


Cardinal Hill:  Clepyn Melyn

Summit Height:  212.1m (converted to OSGM15)

Name:  Erw Penlan

OS 1:50,000 map:  147

Summit Grid Reference:  SO 04597 49535  

Drop:  20.9m (converted to OSGM15)


Erw Penlan (SO 045 495) now confirmed as a 200m Sub-Twmpau addition


Myrddyn Phillips (August 2017)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Y Pincin (SH 723 581) – 200m Twmpau addition (9th reclassification)

Survey post for Y Pincin


There has been a confirmation of an addition to the 200m Twmpau (thirty welsh metre prominences and upward) ranks of hills due to a survey with the Trimble GeoXH 6000, with these details being retrospective as the survey that confirmed this addition was conducted on the 24th December 2013.

The criteria for 200m Twmpau status is all Welsh hills at or above 200m and below 300m in height with 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop. 

This hill did not appear in the original Welsh P30 lists when published on Geoff Crowder’s v-g.me website even though the hill is given a 264m summit spot height on the Ordnance Survey 1:25,000 Explorer map and has bwlch contouring between 220m – 230m.  Its addition to the P30 ranks was announced shortly before the hill was surveyed with the Trimble GeoXH 6000, and prior to this survey the hill was listed with c 36m of drop.

The name of the hill is Y Pincin and it is situated in the Carneddau range with its Cardinal Hill being Creigiau Gleision (SH 729 615) and is positioned immediately above the A5 road which is to its south and the small community of Capel Curig.

The upper section of the hill is a part of designated open access land, with a public footpath leaving Capel Curig to the west of the hill and heading toward the summit.  Although this hill makes an enjoyable walk and scramble in its own right, a more fulfilling experience can be had when combining it with its higher neighbours toward the north.


The full details for the hill are:

Cardinal Hill:  Creigiau Gleision

Summit Height:  263.5m (converted to OSGM15)

Name:  Y Pincin

OS 1:50,000 map:  115

Summit Grid Reference:  SH 72357 58126

Drop:  34.7m (converted to OSGM15)


Y Pincin (SH 723 581) has now been confirmed as a 200m Twmpau by a survey with the Trimble GeoXH 6000



Myrddyn Phillips (August 2017)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Dinas Mawr (SH 808 539) – 200m Sub-Twmpau reclassified to 200m Twmpau (8th reclassification)

Survey post for Dinas Mawr


There has been a confirmation of a reclassification to the 200m Twmpau (thirty welsh metre prominences and upward) ranks of hills due to a survey with the Trimble GeoXH 6000, with these details being retrospective as the survey that confirmed this reclassification was conducted on the 24th December 2013.

The criteria for 200m Twmpau status is all Welsh hills at or above 200m and below 300m in height with 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop. 

This hill was listed in the Hills to be surveyed sub list accompanying the original Welsh P30 lists on Geoff Crowder’s v-g.me website and was only reclassified to P30 status when the sub list was standardised and interpolated drop values were accepted for qualification to the main P30 list.

Prior to the survey with the Trimble GeoXH 6000 the hill was listed with 33m of drop based on the 254m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 221m bwlch spot height that appears on the Ordnance Survey enlarged mapping hosted on the Geograph website.

The name of the hill is Dinas Mawr and it  is situated in the Mynydd Hiraethog range with its Cardinal Hill being Mwdwl Eithin (SH 917 540) and is positioned immediately above the A5 road which is to its south, and is placed between the small communities of Capel Garmon to the north north-east and Penmachno to the south south-west.

The upper section of the hill is a part of designated open access land and this can be accessed from public footpaths originating from the A5 road south-west of the summit or from a minor lane to the east of the summit.


The full details for the hill are:

Cardinal Hill:  Mwdwl Eithin

Summit Height:  254.0m (converted to OSGM15)

Name:  Dinas Mawr

OS 1:50,000 map:  116

Summit Grid Reference:  SH 80884 53931

Drop:  33.9m (converted to OSGM15)


Dinas Mawr (SH 808 539) this hill's reclassification to 200m Twmpau status is now confirmed by a survey with the Trimble GeoXH 6000


Myrddyn Phillips (August 2017)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Pen y Gaer (SO 139 976) – 200m Twmpau reclassified to Trichant (7th reclassification)

Survey post for Pen y Gaer


There has been a reclassification of a 200m Twmpau (thirty welsh metre prominences and upward) to the listing of Y Trichant due to surveying with the Trimble GeoXH 6000.

The details relating to this hill’s inclusion in the listing of Y Trichant are retrospective as the survey with the Trimble took place on the 11th January 2015 and the Hill Reclassifications post for its 300m Twmpau status was published on Mapping Mountains on the 12th January 2015.

The criteria for 200m Twmpau status is all Welsh hills at or above 200m and below 300m in height with 30m minimum drop, whilst Y Trichant is the title for the hills in the 300m height band of the Twmpau and takes in all Welsh hills at or above 300m and below 400m in height with 30m minimum drop, with the introduction to the re-naming of this list appearing on Mapping Mountains on the 13th May 2017.

Prior to the survey with the Trimble GeoXH 6000 the hill was listed with 87m of drop based on the 299m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and the 212m bwlch spot height that appears on the Ordnance Survey enlarged mapping hosted on the Geograph website.

The hill is situated in the Carnedd Wen range with its Cardinal Hill being Stingwern Hill (SJ 132 014and is placed in the North Wales Region (Region A, Sub-Region A4), and is positioned with the small community of Bettws Cedewain to the west south-west and Aber-miwl (Abermule) to the south-east.

As the summit of the hill is not a part of designated open access land permission to visit its high point should be sought.  For those seeking this and wishing to visit there is a public footpath just to the north of the summit which can be accessed from either the north-east or the south-west.

The name of the hill is Pen y Gaer and it is only the third hill that I know of whose status has been altered due to the Ordnance Survey remodelling known as OSGM15.  This remodelling has increased the accurately known height of hills in Wales by approximately 2-4cm, and the other two hills whose status was altered because of OSGM15 are Calf Top (SD 664 856) and Carn Ysgubor (SM 699 246).


Surveyed height of Pen y Gaer pre OSGM15 = 299.974m

Surveyed height of Pen y Gaer post OSGM15 = 300.002m



The full details for the hill are:

Cardinal Hill:  Stingwern Hill

Summit Height:  300.0m (converted to OSGM15)

Name:  Pen y Gaer

OS 1:50,000 map:  136

Summit Grid Reference:  SO 13997 97677

Drop:  88m



Pen y Gaer (SO 139 976) reclassified from a 200m Twmpau to a Trichant



Myrddyn Phillips (June 2017)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Moelfryn (SH 569 511) – 200m Twmpau reclassified to 200m Sub-Twmpau (6th reclassification)


There has been a reclassification to the listing of Twmpau (thirty welsh metre prominences and upward) hills due to analysis of LIDAR data by Aled Williams.  The hill was listed in the 200m height band of P30 Twmpau hills and it has now been reclassified to a 200m Sub-Twmpau, with the criteria for 200m Twmpau status being all Welsh hills at or above 200m and below 300m in height with 30m minimum drop, and the 200m Sub-Twmpau being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop.

The hill was originally listed in the sub list that accompanied the P30 lists when published on Geoff Crowder’s v-g.me website under the title of ‘Hills to be surveyed.’  When this list was re-evaluated the hill was reclassified to a P30 with c 30m of drop based on its 277m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps and an estimated bwlch height of c 247m.  However, the 277m spot height may be erroneous as this summit is immersed in conifer plantation and the only spot height preceding it that has appeared on Ordnance Survey maps is the imperial height of 901ft (274.6m) which originated on the Six-Inch series.  Therefore there seems no evidence to support how a spot height has changed by 2.4m when the summit is unsighted and blanketed in trees.

The hill is situated in the north-eastern part of the Beddgelert Forest and is adjoined to Crib Nantlle and the Moel Hebog group of hills, with its Cardinal Hill being Pt. 734m (SH 525 502) and is placed in the Region of North Wales (Region A, Sub-Region A1), and is situated between the small communities of Rhyd-ddu to its north and Beddgelert to its south south-east.

As the hill is immersed in conifer plantation any ascent may prove problematical, but forest tracks are marked on the map to the north-east and south-west of the summit, with the former indicated as giving nearer access.

The name of the hill is Moelfryn and its reclassification to a 200m Sub-Twmpau is due to the analysis of LIDAR data by Aled Williams.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

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


Moelfryn

Summit Height:  269.0m

Summit Grid Reference:  SH 56900 51151

Bwlch Height:  246.1m

Bwlch Grid Reference:  SH 56416 51301

Drop:  22.9m


Therefore, the 269.0m LIDAR data produced for the summit position at SH 56900 51151 and the 246.1m LIDAR data produced for the bwlch position at SH 56416 51301 gives this hill 22.9m of drop.  However as the DTM model may have struggled to model the summit hillock the detail from the Ordnance Survey Six-Inch map is being taken for the summit.


The full details for the hill are:


Cardinal Hill:  Pt. 734m (SH 525 502)

Summit Height:  275m (height rounded up from Six-Inch map)

Name:  Moelfryn

OS 1:50,000 map:  115

Summit Grid Reference:  SH 56900 51151  

Drop:  29m (summit height from Six-Inch map and bwlch height from LIDAR data)



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

Myrddyn Phillips (May 2017)







Mapping Mountains - Hill Reclassifications - 200m Twmpau


Mynydd y Drum (SN 807 097) - 200m Twmpau reclassified to 200m Sub-Twmpau (5th reclassification)

Survey post for Mynydd y Drum


There has been a reclassification to the listing of Twmpau (thirty welsh metre prominences and upward) hills due to analysis of LIDAR data by Kevin McGovern and also independently by Aled Williams, and subsequently confirmed via a survey with the Trimble GeoXH 6000.  The hill has been reclassified from a 200m Twmpau to a 200m Sub-Twmpau, with the criteria for the former being all hills in Wales at or above 200m and below 300m in height that have a minimum drop of 30m, and the criteria for the sub category being all hills in Wales at or above 200m and below 300m in height with 20m or more and below 30m of drop.

The hill had been listed with an estimated drop of c 53m based on an estimated bwlch height of c 244m and the 297m summit height positioned at SN 807 098 derived from the spot height that appears on the Ordnance Survey 1:25,000 Explorer map numbers 12 and 165, whilst the Ordnance Survey 1:50,000 Landranger map number 160 gives a 298m summit spot height at the same position.  This latter spot height is derived from the 978.1ft (298.1ft) height on the Ordnance Survey old Six-Inch map.

When this hill was originally listed in the Welsh P30 lists on the v-g.me website it had an accompanying note which stated ‘3 points of 300m on 1985 map may probably no longer exist (quarrying)’.  The hand written Master List stated ‘Due to opencast workings the three points of 300c at GR 830 112 on 1985 1:50,000 map probably no longer exist’.  These three points are in the vicinity of where a 984ft (299.9m) height appears on the Ordnance Survey old Six Inch map and in all likelihood signified where the summit of this hill was once positioned.  Since this time the opencast workings which take in the northern and eastern part of the larger hill known as Mynydd y Drum have destroyed the old 984ft (299.9m) summit, but in its place are two separate hills comprising the spoil from the mine workings, with this Hill Reclassifications post concentrating on the remaining ‘natural’ and now lower of these three summits. 

Prior to analysis of LIDAR data Mynydd y Drum was listed with one summit, but due to opencast mining a further two summits have been created which are artificial and comprise the remains of waste spoil, the hill which this Hill Reclassifications post details is the remaining ‘natural’ summit, which is now lower in height compared to the two artificial summits, this has resulted in new bylchau heights and positions and also drop values for these three hills, all of these will be detailed in this and the two previous Hill Reclassifications posts, with the other two hills being Teisen Priodas (SN 820 108) and MRF Tip (SN 828 114).

The hill is adjoined to the Fforest Fawr group with its Cardinal Hill being Fan Gyhirych (SN 880 191) and is placed in the Region of South Wales (Region C, Sub-Region C2), and is positioned between the small town of Ystradgynlais to the north-west and the village of Blaendulais (Seven Sisters) to the south-east.

The upper part of the hill is situated within open access land and can be easily accessed from a number of public footpaths that emanate from Cwm Tawe (Swansea Valley) to the north-west and from Cwm Dulais (Dulais valley) from the south-east.

The name of the hill is Mynydd y Drum and its reclassification to a 200m Sub-Twmpau is due to the analysis of LIDAR data by Kevin McGovern and also independently by Aled Williams.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

Kevin’s analysis of LIDAR data gives the hill the following details:


Mynydd y Drum

Summit Height:  296.1m (converted to OSGM15)

Summit Grid Reference:  SN 80720 09754

Bwlch Height:  271.8m (converted to OSGM15)

Bwlch Grid Reference:  SN 81526 10520

Drop:  24.3m


Therefore, the 296.1m LIDAR data produced for the summit position at SN 80720 09754 and the 271.8m LIDAR data produced for the bwlch position at SN 81526 10520 is sufficient for this hill to be reclassified from a 200m Twmpau to a 200m Sub-Twmpau with 24.3m of drop, with the details from the Trimble GeoXH 6000 survey being 296.2m (converted to OSGM15) summit at SN 80718 09753 and 271.4m bwlch (converted to OSGM15) at SN 81526 10519), giving this hill 24.8m of drop.

This now revises the total in the 200m Twmpau and the list will be updated accordingly.


The full details for the hill are:

Cardinal Hill:  Fan Gyhirych

Summit Height:  296.2m (converted to OSGM15, Trimble data)

Name:  Mynydd y Drum

OS 1:50,000 map:  160

Summit Grid Reference:  SN 80718 09753 
  
Drop:  24.8m (converted to OSGM15, Trimble data)


Mynydd y Drum (SN 807 097) now reclassified to a 200m Sub-Twmpau

My thanks to Mark Jackson for bringing the details of this hill to my attention, and to Kevin McGovern and Aled Williams for their analysis of LIDAR data.


Myrddyn Phillips (March 2017)







Mapping Mountains - Hill Reclassifications - 200m Twmpau

Y Ceiliog Mawr (SH 594 598) - 200m Twmpau addition (4th reclassification)


There has been a new addition to the 200m Twmpau (thirty welsh metre prominences and upward) hill list instigated through analysis of LIDAR data by Aled Williams.  The hill is one that Aled first proposed as a prospective P30 Twmpau approximately two years ago and it then waited to be Trimbled, but as it looked a daunting prospect the Trimble surveyor shied away from his duties, and in the meantime as LIDAR data is proving highly accurate I am using the data that Aled has obtained.

The hill is situated in the Glyderau group of hills with its Cardinal Hill being Y Garn (SH 630 595) and is placed in the Region of North Wales (Region A, Sub-Region A1).  The hill is positioned above Llyn Peris which is to its south and the small community of Nant Peris to its south-east and the town of Llanberis to its west.  The hill is a part of the old Dinorwig Slate Quarries, and can be accessed from tracks leading into the hill from the south-east and from the west.

The hill is known locally as Y Ceiliog Mawr which translates into English as the big cockerel.  I am thankful to Eric Jones for the information relating to this name and the history of the hill which comes from the following two passages on the Geograph website:


The Ceiliog Mawr is an igneous intrusion within the Dinorwig Quarries.  Several attempts were made to remove the intrusion but a considerable section of it remains.  "Ceiliog Mawr" means big cockerel.

Buildings associated with the Dinorwig HEP station have been built around the foot of a slightly modified 'cockerel'.  Three attempts were made in the past to 'slaughter the cockerel'.  In 1896 Mr Brinckman, the general manager, decided that the days of the cockerel were numbered.  On the day, the quarrymen were invited to witness what "a real explosion was like".  The cream of the Welsh aristocracy, and dozens of cameramen, were also invited to watch the demise of the cockerel.  The fateful moment came and the button pressed on the battery firer (the only occasion in the history of the quarry for a battery firer to be used).  A huge pall of smoke emerged from the rock.  When it cleared, Y Ceiliog Mawr stood unscathed.  A visit by the Prince and Princess of Wales in May 1902 was an excuse for another go, this time using two tons of explosive, only to leave more egg on the managers' face.  Finally, in 1905, 10 shafts were dug into the outcrop at a cost of £437-12-2 and explosives set at the bottom of each.  Again, only a few loose rocks were dislodged.  Ever since, the Ceiliog Mawr has been an icon of Dinorwig Quarry.


Current Ordnance Survey 1:50,000 and 1:25,000 mapping does not give this hill any ring contours, as is the norm for areas of land that have been quarried.  The hill is of interest (and quite daunting) as it is only now listed as a 200m Twmpau through the quarrying activities of past years, as it has been left as a stone monolith separated from its connecting bwlch by over 37m of vertical height.


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


Y Ceiliog Mawr

Summit Height:  220.3m

Summit Grid Reference:  SH 59467 59848

Bwlch Height:  182.8m

Bwlch Grid Reference:  SH 59538 59823

Drop:  37.5m


Therefore, the 220.3m LIDAR data produced for the summit position at SH 59467 59848, and the 182.8m LIDAR data produced for the bwlch position at SH 59538 59823 is sufficient for this hill to be included in the list of 200m Twmpau hills with 37.5m of drop, and therefore Y Ceiliog Mawr is included in the listing of Twmpau which will be updated accordingly.


The full details for the hill are:


Cardinal Hill:  Y Garn

Summit Height:  220.3m (LIDAR data)

Name:  Y Ceiliog Mawr

OS 1:50,000 map:  115

Summit Grid Reference:  SH 59467 59848

Drop:  37.5m (LIDAR data)



My thanks to Aled for supplying the details of his LIDAR analysis of this hill.

Y Ceiliog Mawr - the new 200m Twmpau.  Photo © Aled Williams

To view an old and a relatively recent photograph of Y Ceiliog Mawr {here} {here}


Myrddyn Phillips (December 2016)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Gallt y Celyn (SH 811 542) - 200m Sub-Twmpau reclassified to 200m Twmpau (3rd reclassification)

Summit survey post for Gallt y Celyn

Bwlch survey post for Gallt y Celyn

Significant Name Changes post for Gallt y Celyn


There has been a reclassification within the 200m Twmpau (thirty welsh metre prominences and upward) hill list instigated by a survey with the Trimble GeoXH 6000.   The hill has a convoluted history of reclassification and is situated just to the north of the A 5 and southward of the small community of Capel Garmon and south-eastward of the town of Betws-y-coed, and is positioned in the Mynydd Hiraethog range of hills.

The Trimble GeoXH 6000 survey that resulted in this hill’s reclassification from a 200m Sub-Twmpau to a 200m Twmpau was conducted in the afternoon of the 23th February 2016 on a beautiful winter’s day in good, dry and sunny conditions.

The hill is unnamed on current Ordnance Survey maps but is given as a part of Gallt y Celyn on the Tithe map and therefore this name is deemed appropriate to use.
Access to the hill is relatively easy as there is a public footpath approaching from the north which can be accessed from Capel Garmon, and also one from the south-east which can be accessed from a steep minor lane that heads north from the A 5.  The summit of the hill is only a short distance from where these footpaths meet and is on open access land.

The hill has a convoluted history of inclusion and exclusion from the 200m P30 Welsh list as it was originally included in the ‘Hills to Survey’ Sub-List that accompanied the main P30 lists on Geoff Crowder’s v-g.me website.  This Sub-List was reliant upon the details on Ordnance Survey maps being correct and did not take in contour interpolation for inclusion within the main P30 list.  After the Sub-List was standardised and contour interpolation used, the hill was reclassified to a P30 with c 30m of drop, based on a 258m summit spot height and an estimated bwlch height of c 238m.  To complicate matters this hill had twin tops, both given a 258m spot height on Ordnance Survey maps, these tops were surveyed with the Trimble on the 24th December 2013 with the following results:


257.610m (converted to OSGM15) at SH 81121 54259.

257.093m (converted to OSGM15) at SH 81007 54476.


Although the twin tops had been separated the bwlch was not surveyed and as it was estimated to be c 238m high, the drop for this hill was accepted as being just under the qualifying minimum drop of 30m and therefore the hill re-joined the ranks of Subs.

It was always my intention to survey the bwlch and determine once and for all the classification of the hill, and on the 23rd February I found myself immersed in a water laden bog gathering the allotted five minutes of data.  This survey resulted in a bwlch height of 227.5m (227.529m, converted to OSGM15), which gave this hill 30.1m (30.081m) of drop, and therefore it re-joins the ranks of P30 Twmpau hills.


The full details for the hill are:

Cardinal Hill:  Mwdwl Eithin

Summit Height:  257.6m (converted to OSGM15)

Name:  Gallt y Celyn

OS 1:50,000 map:  116

Summit Grid Reference:  SH 811 542

Drop:  30.1m (converted to OSGM15)


Gallt y Celyn (SH 811 542) in the centre foreground of this photograph and which has now been re-instated as a 200m P30 Twmpau.  Photograph taken from the summit of Dinas Mawr (SH 808 539)

For details on the survey that resulted in this hill being reclassified from a 200m Sub-Twmpau to a 200m Twmpau please click {here} for summit and {here} for the bwlch survey.

Myrddyn Phillips (February 2016)







Mapping Mountains - Hill Reclassifications - 200m Twmpau

Bwlch Clump (SJ 170 108) - 200m Twmpau reclassified to 200m Sub-Twmpau (2nd reclassification)

Survey post for Bwlch Clump

Summit Relocations post for Bwlch Clump

Significant Name Changes post for Bwlch Clump


There has been a reclassification within the 200m Twmpau (thirty welsh metre prominences and upward) hill list instigated by a survey with the Trimble GeoXH 6000.   The hill has twin map heighted summits and is situated to the south-east of Dyffryn Meifod and to the north-west of the Maesmawr valley and forms part of the Carnedd Wen range of hills.

These details are retrospective, as the Trimble GeoXH 6000 survey that resulted in this hill’s reclassification from a P30 Twmpau hill to a 200m Sub- Twmpau hill was conducted in the afternoon of the 20th January 2016 on a beautiful crisp winter day in good, dry and sunny conditions.

The lower section of the hill can be accessed from public footpaths to its west and east.  However, its summit does not appear on open access ground, therefore permission to visit the high point should be sought.

The hill was originally included in the main 200m P30 list that appeared on Geoff Crowder’s v-g.me website as a single summit under the current 1:25,000 Explorer map height of 262m (SJ 173 109), and listed under the partly invented name of Pen y Bryn Wood (Bryn Wood being the name of the wood to the north-east of the originally listed hill’s summit).  The hill gained a twin summit when the Ordnance Survey enlarged map on the Geograph website included a 262m spot height for the adjacent hill at SJ 170 108, which was named as Bwlch Clump on this map.  According to map contours the drop between each was not sufficient for both to be included as P30s, with interpolation suggesting c 19m of drop.

Therefore the purpose of this survey was to ascertain which of the two summits is higher and separate their twin top status, and see if the drop between each was sufficient for the lower Trimbled summit to be included as a Sub-Twmpau and ascertain if the higher summit retained its P30 status, as the listed drop value for this hill was c 30m, which was based on bwlch contour interpolation.


The survey results for this once twin topped P30 are:


Pt . 262.8m (originally listed as Pen y Bryn Wood)

262.8m (converted to OSGM15) summit at SJ 17354 10914

243.5m (converted to OSGM15) bwlch at SJ 17190 10797

19.4m drop



Bwlch Clump

263.9m (converted to OSGM15) summit at SJ 17063 10813

234.9m (converted to OSGM15) bwlch at SJ 17089 10581

29.1m drop


Therefore the survey with the Trimble GeoXH 6000 confirms that Bwlch Clump is 1.1m higher than Pt. 262.8m, and that Pt. 262.8m has 19.4m of drop and is not listed as a Sub-Twmpau, and that Bwlch Clump has 29.1m of drop and is therefore reclassified to a 200m Sub-Twmpau.


The full details for the new status of this hill are:


Cardinal Hill:  Carnedd Wen

Summit Height:  263.9m (converted to OSGM15)

Name:  Bwlch Clump

OS 1:50,000 map:  125

Summit Grid Reference:  SJ 17063 10813

Drop:  29.1m (converted to OSGM15)


Pt. 262.8m - now reclassified from a twin topped P30 to a non Sub-Twmpau.  How the mighty fall!!!

Bwlch Clump - now reclassified from a twin topped P30 to a 200m Sub-Twmpau

For details on the survey that resulted in this hill being reclassified from a 200m Twmpau to a 200m Sub-Twmpau please click {here}


Myrddyn Phillips (January 2016)







Mapping Mountains - Hill Reclassifications - 200m Twmpau

Broniarth (SJ 166 120) - 200m Sub-Twmpau addition (1st reclassification)

Survey post for Broniarth


There has been a confirmation of a new addition to the Sub category within the 200m Twmpau (thirty welsh metre prominences and upward) hill list instigated by a survey with the Trimble GeoXH 6000.   The hill is situated between the small community of Meifod to its north-west and that of Maesmawr to its south-east and is part of the Carnedd Wen range of hills.

These details are retrospective, as the Trimble GeoXH 6000 survey that resulted in this hill’s confirmation as a 200m Sub- Twmpau was conducted on the 20th January 2016 on a beautiful crisp winter day in good, dry and sunny conditions.

The hill can be easily accessed from its south where a narrow lane crosses from south-west to north-east across its southerly flank.  This would be a short visit of no more than a few minutes, so combining the hill with some of its neighbours is recommended.  However, permission should be sought for those wishing to visit as the summit is not on open access land.

The hill is unnamed on current Ordnance Survey 1:25,000 Explorer maps but is part of land known locally as Broniarth and which appears on some Ordnance Survey maps as an extended name of either Broniarth or Broniarth Hill.

This is a confirmation of this hill’s addition to the 200m Sub-Twmpau ranks as current Ordnance Survey enlarged mapping on the Geograph website has a 247m spot height on this hill’s bwlch, with the summit having a 268m spot height on the Ordnance Survey 1:25,000 Explorer map and the enlarged map hosted on the Geograph website.  These values give the hill 21m of drop, which compares favourably with the Trimble survey of 21.5m of drop.

The survey with the Trimble GeoXH 6000 resulted in a 267.9m (converted to OSGM15) summit height and a 246.5m (converted to OSGM15) bwlch height, giving this hill 21.5m of drop and confirming its entry in to the 200m Sub-Twmpau ranks.


The full details for the hill are:

Cardinal Hill:  Carnedd Wen

Summit Height:  267.9m (converted to OSGM15)

Name:  Broniarth

OS 1:50,000 map:  125

Summit Grid Reference:  SJ 16648 12055

Drop:  21.5m (converted to OSGM15)


Broniarth (SJ 166 120) 200m Sub-Twmpau status now confirmed by the Trimble GeoXH 6000

For details on the survey that resulted in this hill being confirmed as a 200m Sub-Twmpau please click {here}

Myrddyn Phillips (January 2016)





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