Mapping Mountains – Hill Reclassifications – Y Pedwarau – The 400m Hills of Wales

Pen y Garfan (SN 727 512) – 400m Sub-Pedwar addition

There has been confirmation of a retrospective addition to the listing of the Y Pedwarau – The 400m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Pen y Garfan (SN 727 512)

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

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are five categories of sub hills, with this hill being included in the 400m Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Pen y Garfan, and it is adjoined to the Esgair Wen 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-east, west and south, and has the village of Llanddewibrefi towards the north-west.

When the original 400m height band of Welsh P30 hills compiled by Myrddyn Phillips was 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 428m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and an estimated c 403m bwlch height, based on interpolation of 10m contouring between 400m – 410m, and these are the details given the hill when the 1^st edition of the Y Pedwarau, now co-authored by Myrddyn Phillips and Aled Williams was published by Europeaklist in May 2013. 

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 400m Sub-Pedwar status is due to LIDAR analysis, resulting in a 427.4m summit height and a 400.9m bwlch height, with these values giving this hill 26.4m of drop, which is sufficient for it to be classified as a 400m Sub-Pedwar.                                         

 

The full details for the hill are:

Group:  Esgair Wen

Name:  Pen y Garfan

OS 1:50,000 map:  146, 147

Summit Height:  427.4m (LIDAR)

Summit Grid Reference:  SN 72700 51270 (LIDAR)

Bwlch Height:  400.9m (LIDAR)

Bwlch Grid Reference:  SN 71962 51672 (LIDAR)   

Drop:  26.4m (LIDAR) 

 

For the additions, reclassifications and deletions to Y Pedwarau – The 400m Hills of Wales reported on Mapping Mountains since the May 2013 publication of the list by Europeaklist please consult the following Change Registers:

 

Y Pedwarau

 

Y Pedwarau – 400m Sub-Pedwarau

 

Y Pedwarau – 390m Sub-Pedwarau

 

Y Pedwarau – 390m Double Sub-Pedwarau

 

Myrddyn Phillips and Aled Williams (April 2026) 

Mapping Mountains – Hill Reclassifications – Y Pedwarau – The 400m Hills of Wales

 

Crug Siarls (SN 702 483) – 390m Sub-Pedwar deletion

There has been a deletion from the listing of the Y Pedwarau – The 400m Hills of Wales, 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 Crug Siarls (SN 702 483)

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

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are five categories of sub hills, with this hill being deleted from the 390m Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 390m and below 400m in height that have 30m minimum drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Crug Siarls, and it is adjoined to the Esgair Wen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its west and south, the B4343 road farther to its west, and the A482 road farther to its south-west, and has the town of Llanbedr Pont Steffan (Lampeter) towards the west.

When the original 300m height band of Welsh P30 hills compiled by Myrddyn Phillips was published on Geoff Crowder’s v-g.me website, this hill was included in the main P30 list with a 391m summit height, based on the 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

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 54m of drop, based on the 391m summit spot height and the 337m 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, and these are the details giiven the hill when the 1^st edition of the Y Pedwarau, now co-authored by Myrddyn Phillips and Aled Williams was published by Europeaklist in May 2013.

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

Therefore, the deletion of this hill from 390m Sub-Pedwar status is due to LIDAR analysis, resulting in a 389.7m summit height and a 336.8m bwlch height, with these values giving this hill 52.9m of drop, with the summit height insufficient for it to be classified as a 390m Sub-Pedwar.                                         

 

The full details for the hill are:

Group:  Esgair Wen

Name:  Crug Sials

OS 1:50,000 map:  146, 147

Summit Height:  389.7m (LIDAR)

Summit Grid Reference:  SN 70220 48343 (LIDAR)

Bwlch Height:  336.8m (LIDAR)

Bwlch Grid Reference:  SN 69635 48220 (LIDAR)   

Drop:  52.9m (LIDAR) 

 

For the additions, reclassifications and deletions to Y Pedwarau – The 400m Hills of Wales reported on Mapping Mountains since the May 2013 publication of the list by Europeaklist please consult the following Change Registers:

 

Y Pedwarau

 

Y Pedwarau – 400m Sub-Pedwarau

 

Y Pedwarau – 390m Sub-Pedwarau

 

Y Pedwarau – 390m Double Sub-Pedwarau

 

Myrddyn Phillips and Aled Williams (February 2026) 

Mapping Mountains – Hill Reclassifications – Y Pedwarau – The 400m Hills of Wales

 

Mynydd Mallaen (SN 741 437) – 400m Sub-Pedwar addition

There has been confirmation of a retrospective addition to the listing of the Y Pedwarau – The 400m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Mynydd Mallaen (SN 741 437)

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

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are five categories of sub hills, with this hill being included in the 400m Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Mynydd Mallaen, and it is adjoined to the Mynydd Mallaen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with a minor road to its north, west and east, the A482 road farther to its south-west, and the A483 road farther to its south-east, and has the village of Llanwrda towards the south.

When the original 400m height band of Welsh P30 hills compiled by Myrddyn Phillips was published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with 24m of drop, based on the 437m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and the 413m 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, and these are the details adjoined to the hill when the 1^st edition of the Y Pedwarau, now co-authored by Myrddyn Phillips and Aled Williams was published by Europeaklist in May 2013. 

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 400m Sub-Pedwar status is due to LIDAR analysis, resulting in a 437.4m summit height and a 412.6m bwlch height, with these values giving this hill 24.8m of drop, which is sufficient for it to be classified as a 400m Sub-Pedwar.                                         

 

The full details for the hill are:

Group:  Mynydd Mallaen

Name:  Mynydd Mallaen

OS 1:50,000 map:  146, 147, 160

Summit Height:  437.4m (LIDAR)

Summit Grid Reference:  SN 74126 43705 (LIDAR)

Bwlch Height:  412.6m (LIDAR)

Bwlch Grid Reference:  SN 73863 44207 (LIDAR)   

Drop:  24.8m (LIDAR) 

 

For the additions, reclassifications and deletions to Y Pedwarau – The 400m Hills of Wales reported on Mapping Mountains since the May 2013 publication of the list by Europeaklist please consult the following Change Registers:

 

Y Pedwarau

 

Y Pedwarau – 400m Sub-Pedwarau

 

Y Pedwarau – 390m Sub-Pedwarau

 

Y Pedwarau – 390m Double Sub-Pedwarau

 

Myrddyn Phillips and Aled Williams (December 2025)

Mapping Mountains – Hill Reclassifications – Y Pedwarau – The 400m Hills of Wales

Cefn y Bryn (SN 705 429) – 400m Sub-Pedwar addition

There has been an addition to the listing of the Y Pedwarau – The 400m Hills of Wales, 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 y Bryn (SN 705 429)

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

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are five categories of sub hills, with this hill being included in the 400m Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Cefn y Bryn, 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 west and south, and the A482 road farther to its west, and has the village of Llanwrda towards the south.

When the original 400m height band of Welsh P30 hills was published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with an estimated c 19m of drop, based on the 410m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and an estimated c 391m bwlch height, based on interpolation of 10m contouring between 390m – 400m. 

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 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.

Another resource now available online is the interactive mapping hosted on the Welsh Government website and entitled the DataMapWales.  This mapping has 5m contours and its detail matches that produced from the OS Terrain 5 product, which compliments much of that produced from LIDAR, and for this hill it has a 410m summit spot height and bwlch contouring between 385m – 390m. 

Extract from the DataMapWales

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 400m Sub-Pedwar status is due to LIDAR analysis, resulting in a 410.3m summit height and a 389.9m bwlch height, with these values giving this hill 20.4m of drop, which is sufficient for it to be classified as a 400m Sub-Pedwar.                                         

 

The full details for the hill are:

Group:  Mynydd Mallaen

Name:  Cefn y Bryn

OS 1:50,000 map:  146, 147, 160

Summit Height:  410.3m (LIDAR)

Summit Grid Reference:  SN 70571 42996 (LIDAR)

Bwlch Height:  389.9m (LIDAR)

Bwlch Grid Reference:  SN 70984 43313 (LIDAR)    

Drop:  20.4m (LIDAR) 

 

For the additions, reclassifications and deletions to Y Pedwarau – The 400m Hills of Wales reported on Mapping Mountains since the May 2013 publication of the list by Europeaklist please consult the following Change Registers:

 

Y Pedwarau

 

Y Pedwarau – 400m Sub-Pedwarau

 

Y Pedwarau – 390m Sub-Pedwarau

 

Y Pedwarau – 390m Double Sub-Pedwarau

 

Myrddyn Phillips and Aled Williams (December 2025) 

Mapping Mountains – Hill Reclassifications – Y Pedwarau – The 400m Hills of Wales

 

Mynydd Perthi (SN 953 727) – 400m Sub-Pedwar addition

There has been an addition which is retrospective to the listing of the Y Pedwarau – The 400m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Trimble GeoXH 6000 survey and LIDAR analysis conducted by Myrddyn Phillips and Aled Williams. 

LIDAR image of Mynydd Perthi (SN 953 727)

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

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are five categories of sub hills, with this hill being included in the 400m Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Mynydd Perthi and it is adjoined to the Hirddywel group of hills, which are situated in the northern part of South Wales (Region B, Sub-Region B2), and it is positioned with the A470 road to its south-west and a minor road to its south-east, and has the town of Rhaeadr Gwy (Rhayader) towards the south south-east.

When the original 400m height band of Welsh P30 hills compiled by Myrddyn Phillips was published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

When the 1^st edition of the Y Pedwarau co-authored by Myrddyn Phillips and Aled Williams was published by Europeaklist in May 2013, the details for this hill were reassessed and it was listed with 26m of drop, based on the 458m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 432m 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 the survey with the Trimble GeoXH 6000 and subsequent LIDAR analysis 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. 

The Trimble GeoXH 6000 gathering data at the summit of Mynydd Perthi

Therefore, the confirmation of the addition of this hill to 400m Sub-Pedwar status is due to a Trimble GeoXH 6000 summit survey and LIDAR bwlch analysis, resulting in a 457.0m summit height and a 430.5m bwlch height, with these values giving this hill 26.5m of drop, which is sufficient for it to be classified as a 400m Sub-Pedwar.                                         

 

The full details for the hill are:

Group:  Hirddywel

Name:  Mynydd Perthi

OS 1:50,000 map:  136, 147

Summit Height:  457.0m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 95321 72719 (Trimble GeoXH 6000)

Bwlch Height:  430.5m (LIDAR)

Bwlch Grid Reference:  SN 95572 72577 (LIDAR)   

Drop:  26.5m (Trimble GeoXH 6000 summit and LIDAR bwlch) 

 

For the additions, reclassifications and deletions to Y Pedwarau – The 400m Hills of Wales reported on Mapping Mountains since the May 2013 publication of the list by Europeaklist please consult the following Change Registers:

 

Y Pedwarau

 

Y Pedwarau – 400m Sub-Pedwarau

 

Y Pedwarau – 390m Sub-Pedwarau

 

Y Pedwarau – 390m Double Sub-Pedwarau

 

Myrddyn Phillips and Aled Williams (November 2025)