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

Boncyn Nadroedd (SJ 027 540) – 390m Double Sub-Pedwar reinstatement

There has been a reinstatement of a hill 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 Boncyn Nadroedd (SJ 027 540)

The criteria for the list that this reinstatement 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 reinstated to the 390m Double Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 390m and below 400m 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 Boncyn Nadroedd and it is adjoined to the Mynydd Hiraethog group of hills which are situated in the north-eastern part of North Wales (Region C1, Sub-Region C1A), and it is positioned with minor roads to its north, west and east, and has the town of Rhuthun (Ruthin) towards the east north-east.

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list that accompanied the main P30 list, as it was considered not to meet the criteria then used for this sub category.

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with an estimated c 23m of drop, based on an estimated c 390m summit height and an estimated c 367m bwlch height, with each based on interpolation of 10m contouring that appears on the Ordnance Survey 1:25,000 Explorer map, and these were the details that it appeared under after the 390m sub categories were added to this list. 

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

The details for this hill were re-assessed when the OS Maps website became available online.  This is the replacement for OS Get-a-map and has contours at 5m intervals which are proving consistently more accurate compared to the 5m contours that sometimes appear on Ordnance Survey 1:25,000 Explorer maps and used to appear on the online Vector Map Local.  This re-assessment resulted in the estimated bwlch height for this hill being amended to c 368m, with this based on interpolation of 5m contouring between 365m – 370m. 

Extract from the Magic Maps website

The details for this hill were also re-assessed against Ordnance Survey data hosted on the Magic Maps website as well as the WalkLakes website, and what was thought to be a tiny uppermost 390m summit ring contour is given a 389m spot height on these two interactive maps, implying that what was taken as a small ring contour on the Ordnance Survey 1:25,000 Explorer map, is in fact a spot height missing its 389m height, resulting in the deletion of this hill from 390m Double Sub-Pedwar status. 

Extract from the WalkLakes website

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

Therefore, the reinstatement of this hill to 390m Double Sub-Pedwar status is due to LIDAR analysis, resulting in a 390.0m summit height and a 368.4m bwlch height, with these values giving this hill 21.6m of drop, which is sufficient for it to be classified as a 390m Double Sub-Pedwar. 

 

The full details for the hill are:

Group:  Mynydd Hiraethog 

Name:  Boncyn Nadroedd 

OS 1:50,000 map:  116

Summit Height:  390.0m (LIDAR) 

Summit Grid Reference:  SJ 02735 54033 (LIDAR) 

Bwlch Height:  368.4m (LIDAR) 

Bwlch Grid Reference:  SJ 02555 54073 (LIDAR) 

Drop:  21.6m (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 (October 2026) 

Monthly Synopsis

 

Synopsis of all major changes detailed on Mapping Mountains during the last calendar month.  These can include new, confirmation and retrospective changes

 

Hill Reclassifications: 

Hound Tor (SX 628 890) - Sub-Four addition

Braich Bryn Engan (SH 723 569) - Welsh P15 addition

Llechwedd Deiliog (SH 785 398) - 500m Sub-Twmpau addition

Soussons Down (SX 676 803) - Sub-Four exclusion

 

Significant Height Revisions: 

Pt. 574.9m (SH 663 500) - 500m Twmpau and The Welsh Highlands

Aston Hill (SO 296 900) - Y Trichant - The 300m Hills of Wales

Summit Relocations: 

Carnedd Llechwedd Llyfn (SH 857 444) - 600m Twmpau, The Welsh Highlands - Uchafion

 Cymru and Y Pellennig - The Remotest Hills of Wales

Buttern Hill (SX 652 885) - The Fours - The 400m Hills of England

Daufraich (SM 661 236) - 30-99m Twmpau and Y Pellennig - The Remotest Hills of Wales

Significant Name Changes: 

Aber y Llyn (SH 792 584) - The Welsh P15s

Mapping Mountains – Summit Relocations – Y Pellennig – The Remotest Hills of Wales and 30-99m Twmpau

 

Daufraich (SM 661 236) 

There has been a Summit Relocation to a hill that is listed in the Y Pellennig – The Remotest Hills of Wales and the 30-99m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Trimble GeoXH 6000 survey and its de-twinning reliant upon LIDAR analysis conducted by Myrddyn Phillips. 

Daufraich (SM 661 236)

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

Y Pellennig –The Remotest Hills of Wales - Welsh hills whose summit is at least 2.5km from the nearest paved public road and the hill has a minimum 15m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is available as a downloadable e-booklet or print-booklet version on Mapping Mountains Publications with the up-to-date master list available on Mapping Mountains to download in Google Doc format. 

Y Pellennig - The Remotest Hills of Wales by Myrddyn Phillips and Aled Williams

30-99m Twmpau – Welsh hills at or above 30m and below 100m in height that have 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

30-99m Twmpau by Myrddyn Phillips

The name the hill is listed by is Daufraich and it is adjoined to the Garn Fawr group of hills, which are situated in the south-western part of South Wales (Region C2, Sub-Region C2A), and it is positioned on an island to the west of mainland Wales with a minor road on the mainland to its east, and has the city of Tyddewi (St David’s) on the mainland also towards the east.

When the original 30-99m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

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 21m of drop, based on the twin 21m summit spot heights positioned at SM 66198 23680 and SM 66173 23699 that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

The summit area of Daufraich

Looking from the higher to the lower summit of Daufraich

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 Daufraich (SM 661 236)

The height produced by the Trimble GeoXH 6000 survey to the summit of this hill is 21.7m and is positioned at SM 66199 23673, with LIDAR giving the other top as 21.4m positioned at SM 66200 23673, and this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

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

LIDAR image of Daufraich (SM 661 236)

Therefore, the new listed summit height of this hill is 21.7m and this is positioned at SM 66199 23673 and this was derived from a Trimble GeoXH 6000 survey, this matches the approximate position of one of the spot heights and has resulted in the de-twinning of this hill.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Garn Fawr

Name:  Daufraich

OS 1:50,000 map:  157

Summit Height:  21.7m (converted to OSGM15) 

Summit Grid Reference (New Position):  SM 66199 23673 

Bwlch Height:  N/A (island) 

Bwlch Grid Reference:  N/A (island) 

Drop:  21.7m 

Remoteness:  6.450km

 

Myrddyn Phillips and Aled Williams (September 2026)

Mapping Mountains – Hill Reclassifications – The Fours – The 400m Hills of England

Soussons Down (SX 676 803) – Sub-Four exclusion

There has been an exclusion from the listing of 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 Soussons Down (SX 676 803)

The criteria for the list that this exclusion 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 Soussons Down, 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 B4312 road to its north-west and minor roads to its south and east, and has the small community of Postbridge towards the west 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 an estimated c 16m of drop, based on the 420m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 404m col height, based on interpolation of 10m contouring between 400m – 410m. 

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 exclusion of this hill from Sub-Four status is due to LIDAR analysis, resulting in a 421.3m summit height and a 406.6m col height, with these values giving this hill 14.7m of drop, which is insufficient for it to be classified as a Sub-Four. 

 

The full details for the hill are:

Group:  High Willhays

Name:  Soussons Down

OS 1:50,000 map:  191

Summit Height:  421.3m (LIDAR)

Summit Grid Reference:  SX 67662 80357 (LIDAR)

Col Height:  406.6m (LIDAR)

Col Grid Reference:  SX 67766 80718 (LIDAR)

Drop:  14.7m (LIDAR)

 

For the additions, deletions and reclassifications to The Fours – The 400m Hills of England reported on Mapping Mountains since the December 2013 publication of the 1^st edition of this list by Europeaklist please consult the following Change Registers:

 

The Fours

 

Sub-Fours

 

Myrddyn Phillips and Aled Williams (September 2026)               

Mapping Mountains – Significant Height Revisions – Y Trichant – The 300m Hills of Wales

 

Aston Hill (SO 296 900) 

There has been a Significant Height Revision to a hill that is listed in the Y Trichant – The 300m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Aston Hill (SO 296 900)

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

Y Trichant – The 300m Hills of Wales – Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant, with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13^th May 2017, and the Introduction to the Mapping Mountains publication of the list appearing on the 1^st January 2022. 

Y Trichant - The 300m Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Aston Hill, and it is adjoined to the Cilfaesty group of hills, which are situated in the north-eastern part of South Wales (Region C2, Sub-Region C2B), and it is positioned encircled by minor roads, with the B4385 road farther to its north-east, and has the town of Bishop’s Castle towards its south-east.

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was listed with a 379m summit height based on the spot height positioned at SO 29659 90041 that appears on the Ordnance Survey 1:25,000 Explorer map. 

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

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

LIDAR summit image of Aston Hill (SO 296 900)

The summit height produced by LIDAR analysis is 380.0m positioned at SO 29663 90049, 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 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 380.0m and this was derived from LIDAR analysis, this is 1.0m higher than the previously listed summit height of 379m, which was based on the spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map, and importantly indicates that this map is missing an uppermost 380m ring contour.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Cilfaesty

Name:  Aston Hill

OS 1:50,000 map:  137

Summit Height (New Height):  380.0m (LIDAR)

Summit Grid Reference:  SO 29663 90049 (LIDAR)  

Bwlch Height:  341.8m (LIDAR)

Bwlch Grid Reference:  SO 28966 89594 (LIDAR)

Drop:  38.2m (LIDAR)

 

Myrddyn Phillips (September 2026)