Mapping Mountains – Significant Height Revisions – The Welsh P15s

 

Cae Cenfas Ucha (SN 751 118) 

There has been a Significant Height Revision 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 Cae Cenfas Ucha (SN 751 118)

The criteria for the list that this height revision 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 name the hill is listed by is Cae Cenfas Ucha and this was derived from the Tithe map, and it is adjoined to the Mynydd Du group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and it is positioned with a minor road to its west and south, and the A4068 road to its east, and has the community of Y Gurnos towards the south-east.

When the listing that became known as The Welsh P15s was being compiled, this hill was not included as with an uppermost 170m contour and bwlch contouring between 160m – 170m that appear on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, it was judged not to meet the criterion for the main P15 or the accompanying P14 sub list. 

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 Cae Cenfas Ucha (SN 751 118)

The summit height produced by LIDAR analysis is 182.8m and when compared to detail on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, 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 182.8m and this was derived from LIDAR analysis.  This is 12.8m higher than the uppermost 170m contour on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

 ills of Wales, and are reproduced below@

The full details for the hill are: 

Group:  Mynydd Du 

Name:  Cae Cenfas Ucha 

OS 1:50,000 map:  160

Summit Height (New Height):  182.8m (LIDAR)                                                           

Summit Grid Reference:  SN 75108 11870 (LIDAR) 

Bwlch Height:  164.5m (LIDAR) 

Bwlch Grid Reference:  SN 75202 12488 (LIDAR) 

Drop:  18.3m (LIDAR) 

 

Myrddyn Phillips (May 2024)