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)

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

Lurden Top (SD 989 121) – 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 Lurden Top (SD 989 121)

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 Lurden Top, and it is adjoined to the Way Stone Edge group of hills, which are situated in the Pennines of northern England, and it is positioned with the A672 road to its west and the A640 road to its south-east, and has the town of Rochdale towards the 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 15m of drop, based on the 429m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 414m col height, based on interpolation of 5m contouring between 410m – 415m. 

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 429.0m summit height and a 415.5m col height, with these values giving this hill 13.6m of drop, which is insufficient for it to be classified as a Sub-Four. 

 

The full details for the hill are:

Group:  Way Stone Edge

Name:  Lurden Top

OS 1:50,000 map:  109

Summit Height:  429.0m (LIDAR)

Summit Grid Reference:  SD 98937 12165 (LIDAR)

Col Height:  415.5m (LIDAR)

Col Grid Reference:  SD 99146 12314 (LIDAR)

Drop:  13.6m (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 (November 2025)            

Mapping Mountains – Summit Relocations – 200m Twmpau

 

Long Cae Maes (SO 312 933) 

There has been a Summit Relocation to a hill that is listed in the 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 Long Cae Maes (SO 312 933)

The criteria for the list that this summit relocation 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 Long Cae Maes, and this was derived from the Tithe map, and it is adjoined to the Stiperstones group of hills, which are situated in the north-eastern part of South Wales (Region B, Sub-Region B2), and it is positioned with minor roads to its north, west and east, with the A489 road to its south-west, and has the village of Yr Ystog (Churchstoke) towards the 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 25m of drop, based on the 247m summit spot height positioned at SO 31294 93315 that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 222m bwlch height, based on interpolation of 5m contouring between 220m – 225m. 

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 analysis gives the highest ground on this hill as 248.0m positioned at SO 31293 93303.  However, this is a part of a raised field boundary and protocols dictate that as this is deemed a relatively recent man-made construct such ground is discounted from the height of a hill. 

LIDAR summit image of Long Cae Maes (SO 312 933)

The height produced by LIDAR analysis to the natural summit of this hill is 247.9m and this is positioned at SO 31286 93304, 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 de-twinning of a summit, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist.

Therefore, the summit height produced by LIDAR analysis is 247.9m and this is positioned at SO 31286 93304, this position is relatively close to where the 247m spot height appears on the Ordnance Survey 1:25,000 Explorer map and is approximately 7 metres westward from the high point of the raised field boundary. 

 

The full details for the hill are: 

Group:  Stiperstones 

Name:  Long Cae Maes 

OS 1:50,000 map:  137

Summit Height:  247.9m (LIDAR) 

Summit Grid Reference (New Position):  SO 31286 93304 (LIDAR) 

Bwlch Height:  221.4m (LIDAR) 

Bwlch Grid Reference:  SO 31081 93871 (LIDAR) 

Drop:  26.5m (LIDAR) 

 

Myrddyn Phillips (November 2025)

 

 

Mapping Mountains – Significant Name Changes – The Welsh P15s

 

Coed Felin Lodge (SN 663 932) 

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 Coed Felin Lodge (SN 663 932)

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 Banc Llechwedd Mawr group of hills, which are situated in the north-western part of South Wales (Region B, Sub-Region B1), and it is positioned with the B4353 road to its south-west and the A487 road to its east, and has the town of Machynlleth towards the north-east.

When the listing that became known as The Welsh P15s was being compiled, this hill was not included in either the main list or the accompanying sub list, and was subsequently documented under the name of Felin Lodge Wood, which is a prominent name that appears adjacent to the summit on the Ordnance Survey 1:25,000 Explorer map. 

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

The intricacies of language and prioritising one in favour of another for listing a hill is fraught with complication, with originating Cymraeg names being anglicised and also originating English names being cymricised, examples such as these are more common in border country and especially so for anglicised forms.  There is no steadfast rule that fits all, but as a standard a name that has its origins in the Welsh language and where this is substantiated by either historic documentation and/or contemporary usage should be prioritised in favour of a contemporary anglicised or English version of the name.  Likewise, if a name exists where an element of it is in English and if this name applies to a hill that is situated in a Welsh speaking part of Wales it is standard practice to use a full Welsh term for the name.  It is also standard practice to use a Welsh name for a hill if another name exists that has originated in a different language.

Therefore, the name this hill is now listed by in the The Welsh P15s is Coed Felin Lodge, and this was derived from the Ordnance Survey 1:25,000 Explorer map with the language protocol also implemented. 

 

The full details for the hill are: 

Group:  Banc Llechwedd Mawr 

Name:  Coed Felin Lodge 

Previously Listed Name:  Felin Lodge Wood 

OS 1:50,000 map:  135

Summit Height:  70.9m (LIDAR)                                                           

Summit Grid Reference:  SN 66384 93253 (LIDAR)                                                  

Bwlch Height:  52.1m (LIDAR) 

Bwlch Grid Reference:  SN 66457 93532 (LIDAR) 

Drop:  18.8m (LIDAR) 

 

Myrddyn Phillips (November 2025)

 

Mapping Mountains – Significant Height Revisions – 100m Twmpau

 

Bryn Llwyn (SN 672 998) 

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

LIDAR image of Bryn Llwyn (SN 672 998)

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

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

100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Bryn Llwyn, and it is adjoined to the Tarren y Gesail group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and it is positioned with a minor road to its north and the A493 road to its south-east, and has the village of Cwrt towards the east.

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 27m of drop, based on an estimated c 173m summit height and an estimated c 146m bwlch height, with both heights based on interpolation of 10m contouring that appears on the Ordnance Survey 1:25,000 Explorer map. 

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

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

LIDAR summit image of Bryn Llwyn (SN 672 998)

The summit height produced by LIDAR analysis is 175.4m and is positioned at SN 67202 99820, 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 175.4m and this was derived from LIDAR analysis, this is 2.4m higher than the previously listed c 173m summit height which was estimated from interpolation of the uppermost 170m ring contour that appears on the Ordnance Survey 1:25,000 Explorer map.

 

ills of Wales, and are reproduced below@

The full details for the hill are: 

Group:  Tarren y Gesail 

Name:  Bryn Llwyn 

OS 1:50,000 map:  135

Summit Height (New Height):  175.4m (LIDAR) 

Summit Grid Reference:  SN 67202 99820 (LIDAR) 

Bwlch Height:  145.4m (LIDAR) 

Bwlch Grid Reference:  SN 66942 99795 (LIDAR) 

Drop:  30.0m (LIDAR) 

 

Myrddyn Phillips (November 2025)