Mapping Mountains – Hill Reclassifications – Welsh Highlands – Uchafion Cymru

Pt. 516.9m (SN 754 620) – Welsh Highland Sub reclassified to Welsh Highland P15 

There has been a reclassification to the listing of the Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Aled Williams. 

Pt. 516.9m (SN 754 620)

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

Welsh Highlands – Uchafion Cymru – Welsh hills at or above 500m in height with 15m minimum drop, with an accompanying sub list entitled the Welsh Highland Subs, the criteria for which is all Welsh hills at or above 500m in height with 10m or more and below 15m of drop.  This list is authored by Myrddyn Phillips and Aled Williams with the Introduction to the list published on Mapping Mountains in November 2015 and the latest update relating to the list published on Mapping Mountains in January 2023.

Welsh Highlands - Uchafion Cymru by Aled Williams and Myrddyn Phillips

The hill is being listed by the point (Pt. 516.9m) notation 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 a minor road to its north north-west and south, and has the small community of Pontrhydfendigaid towards the north-west and the town of Tregaron towards the west south-west.

When the original list that later became known as the Welsh Highlands – Uchafion Cymru was first compiled, this hill was not included as a Welsh Highland P15 as with no spot height adjoined to its uppermost 510m ring contour and bwlch contouring between 500m – 510m, the drop value could not be interpolated accurately to include it in this list. 

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

Since the original compilation of this list 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 that was 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.

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had a 517m summit spot height and a 502m bwlch spot height, with these values giving this hill 15m of drop and therefore it was included as a Welsh Highland P15. 

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map

The hill was subsequently surveyed with the Trimble GeoXH 6000, resulting in a 516.3m summit height and a 501.4m bwlch height.  However, as the area of the bwlch is situated in conifer plantation it was decided to use an interpolated height and position from OS Maps.  This mapping gave contour intervals at 5m and showed a small 500m ring contour where the 502m spot height appears on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website, data were collected from near this position resulting in a 501.4m height, but when doing so the authors were aware that land to the north-east was judged slightly higher and this is what the 5m contouring on the OS Maps website indicated.  Therefore, the hill was listed with an estimated c 14m of drop, resulting in its reclassification to Welsh Highland Sub status. 

Extract from the interactive mapping that was hosted on the OS Maps 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. 

LIDAR image of Pt. 516.9m (SN 754 620)

Therefore, the reclassification of this hill from Welsh Highland Sub status is due to a LIDAR analysis, resulting in a 516.9m summit height and a 501.0m bwlch height, with these values giving this hill 15.8m of drop, which is sufficient for it to be reinstated and classified as a Welsh Highland P15. 

 

The full details for the hill are: 

Group:  Esgair Wen

Name:  Pt. 516.9m

OS 1:50,000 map:  146, 147

Summit Height:  516.9m (LIDAR)

Summit Grid Reference:  SN 75493 62086 (LIDAR)

Bwlch Height:  501.0m (LIDAR)

Bwlch Grid Reference:  SN 75576 61971 (LIDAR)   

Drop:  15.8m (LIDAR) 

 

For the additions, deletions and reclassifications to the Welsh Highlands – Uchafion Cymru reported on Mapping Mountains please consult the following Change Registers:

 

Welsh Highland P15s

 

Welsh Highland Subs

 

Aled Williams and Myrddyn Phillips (November 2023)