Mapping Mountains – Significant Name Changes – Y Pedwarau – The 400m Hills of Wales

Pt. 428.2m (SN 731 497) 

There has been a Significant Name Change that is retrospective to a hill listed in 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 detail on contemporary Ordnance Survey maps, with confirmation of the status from subsequent LIDAR analysis. 

LIDAR image of Pt. 428.2m (SN 731 497) 

The criteria for the list that this retrospective name change 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 classified as a 400m Sub-Pedwar.  The criteria for 400m Sub-Pedwar status 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 hill 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 is positioned with minor roads to its north, west, south and east, and has the village of Llanddewi Brefi towards the north-west.

The hill appeared in the original Welsh 400m P30 list compiled by Myrddyn Phillips and published on Geoff Crowder’s v-g.me website, under the transposed and invented name of Carn Nant-yr-ast East Top, with an accompanying note stating; Name from hill to the West.

Carn Nant-yr-ast East Top

427m

SN732497

146/147

187

Name from hill to the West

When Myrddyn Phillips first compiled this list he thought it appropriate to either invent a name for a hill, or use a name that appeared near to the summit of the hill on Ordnance Survey maps of the day.  His preference was to use farm names and put Pen, Bryn or Moel in front of them or as in this instance use a directional name based on supplanting the name of a near hill and adding a directional component to it.  This is not a practice that he now advocates as with time and inclination place-name data can be improved either by asking local people or by examining historic documents, through this form of research an appropriate name for the hill can usually be found. 

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

However, on occasion even when research is conducted an appropriate name for the hill may not be found, and on such occasions the listing protocol is to use the point notation, and this is the protocol adopted when Myrddyn Phillips and Aled Williams became co-authors of this list and the 1^st edition of the Y Pedwarau was published by Europeaklist in May 2013.  This hill was then listed under the point (Pt. 427m) notation with an estimated c 30m of drop, based on the 427m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 397m bwlch height, based on interpolation of 10m contouring between 390m – 400m.

Therefore, the name this hill is now listed by in the Y Pedwarau – The 400m Hills of Wales is Pt. 428.2m, and this is being used as the authors have not found an appropriate name for the hill either through historic research and/or local enquiry.

 

The full details for the hill are: 

Group:  Esgair Wen 

Name:  Pt. 428.2m 

Previously Listed Name:  Carn Nant-yr-ast East Top 

OS 1:50,000 map:  146, 147 

Summit Height:  428.2m (LIDAR) 

Summit Grid Reference:  SN 73159 49742 (LIDAR) 

Bwlch Height:  399.0m (LIDAR) 

Bwlch Grid Reference:  SN 72736 49808 & SN 72739 49810 (LIDAR) 

Drop:  29.2m (LIDAR) 

 

Myrddyn Phillips and Aled Williams (August 2026)                                                  

Mapping Mountains – Significant Name Changes – The Welsh P15s

 

Bryn Coch Ucha (SH 732 554) 

There has been a Significant Name Change to a hill that is listed in The Welsh P15s, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Bryn Coch Ucha (SH 732 554)

The criteria for the list that this name change applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The hill is adjoined to the Moel Siabod group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A5 road to its north, the A4086 road to its north-west and the A470 road to its south, and has the village of Betws-y-coed towards the east north-east.

When the listing that became known as The Welsh P15s was being compiled, this hill was listed under the point (Pt. c 364m) notation, with an estimated c 15m of drop, based on an estimated c 364m summit height and an estimated c 349m bwlch height, with both heights based on interpolation of 10m contouring. 

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

As the summit of this hill comprises bounded land the details for it were examined on the Tithe map.  The term Tithe map is generally given to a map of a Welsh or English parish or township and which was prepared after the 1836 Tithe Commutation Act.  This act allowed tithes to be paid in cash rather than goods.  The Tithe maps gave names of owners and occupiers of land in each parish and importantly for place-name research they also included the name of enclosed land.  This enclosed land is usually based on a field system, however not every field is given a name, but many are and especially so in Wales. 

Extract from the Tithe map

The enclosed land where the summit of this hill is situated is given the number 59 on the Tithe map, this can be cross referenced against the apportionments; it is these apportionments that give the name of the owner or occupier of the land as well as the name of the land.  The land where the summit of this hill is situated is named Bryn Coch Ucha in the apportionments, with the details on the Tithe map appearing in the parish named as Llanrwst and in the county named as Caernarfonshire. 

Extract from the apportionments

Therefore, the name this hill is now listed by in the The Welsh P15s is Bryn Coch Ucha, and this was derived from the Tithe map. 

 

The full details for the hill are: 

Group:  Moel Siabod 

Name:  Bryn Coch Ucha 

Previously Listed Name:  Pt. c 364m 

OS 1:50,000 map:  115

Summit Height:  367.2m (LIDAR)                                                           

Summit Grid Reference:  SH 73243 55426 (LIDAR)                                                  

Bwlch Height:  348.8m (LIDAR) 

Bwlch Grid Reference:  SH 73032 55281 (LIDAR) 

Drop:  18.4m (LIDAR) 

                                                           

Myrddyn Phillips (August 2026)

 

Mapping Mountains – Hill Reclassifications – 200m Twmpau

 

Penllan Oat Piece (SO 103 633) – 200m Sub-Twmpau addition

There has been of an addition to the list of 200m 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 Penllan Oat Piece (SO 103 633)

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

200m Twmpau – Welsh hills at or above 200m and below 300m in height that have 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.  The list is authored by Myrddyn Phillips, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

200m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Penllan Oat Piece, and this was derived from the Tithe map, and it is adjoined to the Hirddywel group of hills, which are situated in the eastern part of South Wales (Region B, Sub-Region B2), and it is positioned with the A44 road to its north, the A483 road to its west and minor roads to its south-west and south-east, and has the town of Llandrindod towards the west south-west.

When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the accompanying 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 17m of drop, based on the 259m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 242m bwlch height, based on interpolation of 10m contouring between 240m – 250m. 

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

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

Therefore, the addition of this hill to 200m Sub-Twmpau status is due to LIDAR analysis, resulting in a 260.3m summit height and a 240.0m bwlch height, with these values giving this hill 20.3m of drop, which is sufficient for it to be classified as a 200m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Hirddywel 

Name:  Penllan Oat Piece 

OS 1:50,000 map:  148

Summit Height:  260.3m (LIDAR) 

Summit Grid Reference:  SO 10357 63307 (LIDAR) 

Bwlch Height:  240.0m (LIDAR) 

Bwlch Grid Reference:  SO 10742 63832 (LIDAR) 

Drop:  20.3m (LIDAR) 

 

Myrddyn Phillips (August 2026)

 

Mapping Mountains – Significant Height Revisions – The Fours – The 400m Hills of England

Water Hill (SX 671 812) 

There has been a Significant Height Revision to a hill that is listed in the The Fours – The 400m Hills of England, with the summit height, col height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Water Hill (SX 671 812)

The criteria for the list that this height revision applies to are:

The Fours – The 400m Hills of England - English hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list is a sub list entitled the Sub-Fours, the criteria for which are all English hills at or above 400m and below 500m in height that have 15m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is available to download in Google Doc format from the Mapping Mountains site.

The Fours - The 400m Hills of England by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Water Hill, and it is adjoined to the High Willhays group of hills, which are situated in the south-west of England, and it is positioned with the B3212 road to its south-east, and has the village of Princetown towards the south-west.

When the Introduction to the first group of hills for the updated and revised listing of the The Fours – The 400m Hills of England was published by Mapping Mountains on the 10^th September 2022, it was announced that the accompanying sub lists were being revised with the two 390m categories dispensed with and the criteria and name of the 400m Sub-Fours revised.  The one accompanying sub list is now named the Sub-Fours with its criteria being all English hills 400m and above and below 500m in height that have 15m and more and below 30m of drop.

Prior to this revision this hill was listed with 16m of drop, based on the 489m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and the 473m col spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

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

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

LIDAR summit image of Water Hill (SX 671 812)

LIDAR analysis gives the summit height of this hill as 490.1m positioned at SX 67155 81293 and when compared to its originally listed height this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey, Harvey or other interactive map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR.  Also included are hills whose summit map data is missing an uppermost ring contour when compared with the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 490.1m and this was derived from LIDAR analysis, this is 1.1m higher than the originally listed 489m summit height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and importantly this height signifies that an uppermost 490m ring contour is missing from these maps. 

 

The full details for the hill are:

Group:  High Willhays

Name:  Water Hill

OS 1:50,000 map:  191

Summit Height (New Height):  490.1m (LIDAR)

Summit Grid Reference:  SX 67155 81293 (LIDAR)

Col Height:  473.4m (LIDAR)

Col Grid Reference:  SX 67079 81668 (LIDAR)

Drop:  16.6m (LIDAR)

 

Myrddyn Phillips and Aled Williams (August 2026) 

Mapping Mountains – Significant Height Revisions – The 500-Metre Tops of England and Wales – Deweys

Mynydd Nodol (SH 865 393) 

There has been a Significant Height Revision to a hill that is listed in the The 500-Metre Tops of England and Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Trimble GeoXH 6000 summit survey conducted by Myrddyn Phillips and LIDAR bwlch analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips. 

Mynydd Nodol (SH 865 393)

The criteria for the list that this height revision applies to are:

The 500-Metre Tops of England and Wales are affectionately known after their hill list compiler; Michael Dewey.  This list mixes metric and imperial height in its criteria to bookend up to the 2000ft height band and takes in all hills in England, Isle of Man and Wales that are 500m and above and below 2000ft (609.6m) in height that have 30m minimum drop. 

Mountain tables by Michael Dewey

Michael Dewey died on the 5^th November 2022.  His wife; Gillian wished for this list to be carried on and made provision for it to be co-authored by Myrddyn Phillips.  Michael will always be the compiler and originator, it’s just that he’s now got a co-author to safeguard and carry this list on.

The name the hill is listed by is Mynydd Nodol and it is adjoined to the Arenig Fawr group of hills, which are situated in the central part of North Wales, and it is positioned with Llyn Celyn and the A4212 road to its north and a minor road to its south, and has the town of Y Bala towards the south-east.

When the original list of Deweys appeared in the Mountain tables book published by Constable in 1995, this hill was listed with a non-interpolated summit height of 530+m, based on the uppermost 530m ring contour that appeared on the contemporary 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 the survey with the Trimble GeoXH 6000 and 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. 

The Trimble GeoXH 6000 gathering data at the summit of Mynydd Nodol (SH 865 393)

The survey with the Trimble GeoXH 6000 gives the summit of this hill as 540.0m positioned at SH 86514 39339, and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey, Harvey or other interactive map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or other GNSS equipment or analysis of data produced via LIDAR.  Also included are hills whose summit map data is missing an uppermost ring contour when compared with the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 540.0m and this was derived from a Trimble GeoXH 6000 survey, this is 10.0m higher than the originally listed summit height of 530+m, which was based on the non-interpolated uppermost 530m ring contour that appeared on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and 1m height than the 539m summit spot height that now appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and importantly this height signifies that an uppermost 540m ring contour is missing from these maps. 

 

The full details for the hill are:

Group:  Arenig Fawr

Name:  Mynydd Nodol

OS 1:50,000 map:  124, 125

Summit Height (New Height):  540.0m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 86514 39339 (Trimble GeoXH 6000)  

Bwlch Height:  370.8m (LIDAR)

Bwlch Grid Reference:  SH 85660 39014 (LIDAR)

Drop:  169.2m (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

Myrddyn Phillips (August 2026)