Mapping Mountains – Hill Reclassifications – The Welsh P15s

 

Pt. 83.1m (SN 539 026) – Welsh Sub-P15 deletion

There has been a deletion to the list of 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 Pt. 83.1m (SN 539 026)

The criteria for the list that this deletion 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 being listed by the point (Pt. 83.1m) notation, and it is adjoined to the Mynydd Sylen group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and it is positioned with the A476 road to its north-west and minor roads to its immediate south and east, and has the town of Llanelli towards the south-west.

When the listing that became known as The Welsh P15s was being compiled, this hill was included in the P14 sub list with an estimated c 14m of drop, based on an estimated c 86m summit height based on interpolation of the uppermost 85m ring contour that appears on the Ordnance Survey 1:25,000 Explorer map, and the 72m 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 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 deletion of this hill from Welsh Sub-P15 status is due to LIDAR analysis, resulting in an 83.1m summit height and a 70.6m bwlch height, with these values giving this hill 12.6m 0f drop, which is insufficient for it to be classified as a Welsh Sub-P15. 

 

The full details for the hill are: 

Group:  Mynydd Sylen 

Name:  Pt. 83.1m 

OS 1:50,000 map:  159

Summit Height:  83.1m (LIDAR)                                                           

Summit Grid Reference:  SN 53910 02627 (LIDAR)                                                  

Bwlch Height:  70.6m (LIDAR) 

Bwlch Grid Reference:  SN 54258 03092 (LIDAR) 

Drop:  12.6m (LIDAR) 

 

Myrddyn Phillips (January 2025)