Llechwedd Diflas (SN 789 930) – Welsh
Highland Sub deletion
There has been a deletion 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.
|
LIDAR image of Llechwedd Diflas (SN 789 930) |
The criteria for the list that this deletion applies to are:
|
Welsh Highlands - Uchafion Cymru by Aled Williams and Myrddyn Phillips |
The name the hill is listed by is Llechwedd Diflas
and it is adjoined to the Pumlumon group of hills, which are situated in the northern part of South
Wales (Region B, Sub-Region B1), and
it is positioned with minor roads to its south south-west and east north-east, and
has the village of Penffordd-las (Staylittle) towards the east.
When the initial P10 sub list was completed in
June 2020 this hill was listed with an estimated c 10m of drop, based on the
514m summit spot height that appears on the contemporary Ordnance Survey
1:25,000 Explorer map, and an estimated c 504m bwlch height, based on
interpolation of 5m contouring that appeared on online mapping.
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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
Highland Sub status is due to LIDAR analysis, resulting in a 513.4m summit
height and a 503.8m bwlch height, with these values giving this hill 9.5m of
drop, which is insufficient for it to be classified as a Welsh Highland
Sub.
The full details for the hill are:
Group: Pumlumon
Name: Llechwedd Diflas
OS 1:50,000 map: 135
Summit Height: 513.4m
(LIDAR)
Summit Grid Reference:
SN 78935 93043 (LIDAR)
Bwlch Height: 503.8m
(LIDAR)
Bwlch Grid Reference:
SN 79224 92986 (LIDAR)
Drop: 9.5m
(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 (December 2023)
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