Mapping Mountains – Significant Height Revisions – Welsh Highlands – Uchafion Cymru

Pt. 505.8m (SN 785 598) 

There has been a Significant Height Revision to a hill that is listed in 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. 

LIDAR image of Pt. 505.8m (SN 785 598)

The criteria for the list that this height revision 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. 505.8m) 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-west and south, and has the small community of Pontrhydfendigaid towards the north-west and the town of Tregaron towards the west. 

Extract from the Ordnance Survey series of Six-Inch maps

When the initial P10 sub list was completed in June 2020 this hill was listed with an estimated c 9m of drop, based on the 1649ft (502.6m) height that appeared on the Ordnance Survey series of Six-Inch maps and an estimated c 494m bwlch height, based on interpolation of 5m contouring that appeared on online mapping. 

Extract from the Ordnance Survey 1:50,000 Landranger map

The height that appeared on the Ordnance Survey series of Six-Inch maps was at odds with the 506m spot height that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and which is positioned at SN 78576 59903, however this spot height was not supported by contemporary contour information on large scaled Ordnance Survey maps. 

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 Pt. 505.8m (SN 785 598)

LIDAR analysis gives the highest ground on this hill as 505.8m positioned at SN 78575 59899, 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 or Harvey 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 to the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 505.8m and this was derived from LIDAR analysis, this is 3.2m higher than the previously listed summit height which was derived from the 1649ft (502.6m) height that appeared on the Ordnance Survey series of Six-Inch maps.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Esgair Wen

Name:  Pt. 505.8m

OS 1:50,000 map:  146, 147

Summit Height (New Height):  505.8m (LIDAR)

Summit Grid Reference:  SN 78575 59899 (LIDAR)

Bwlch Height:  492.4m (LIDAR)

Bwlch Grid Reference:  SN 78513 60070 (LIDAR)   

Drop:  13.5m (LIDAR) 

 

Myrddyn Phillips and Aled Williams (November 2023)