Pt. 557.6m (SO 023 822) – 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.
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LIDAR image of Pt. 557.6m (SO 023 822) |
The criteria for the list that this deletion applies to are:
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Welsh Highlands - Uchafion Cymru by Aled Williams and Myrddyn Phillips |
The hill is being listed by the point (Pt. 557.6m)
notation, and it is adjoined to the Hirddywel group of hills, which are situated in the northern part of South
Wales (Region B, Sub-Region B2), and
it is positioned with minor roads to its north-west, south-west and north-east,
and the B4518 and A470 roads to its west and the A483 road to its east, and has
the town of Llanidloes towards the west north-west.
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Extract from the Ordnance Survey 1:25,000 Explorer map |
When the initial P10 sub list was completed in
June 2020 this hill was listed with an estimated c 11m of drop, based on the 558m
summit spot height that appears on the contemporary Ordnance Survey 1:25,000
Explorer map and an estimated c 547m bwlch height, based on the 1796ft (547.4m)
height that appears on the Ordnance Survey series of Six-Inch maps.
|
Extract from the Ordnance Survey series of Six-Inch maps |
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 557.6m summit
height and a 547.8m bwlch height, with these values giving this hill 9.8m of
drop, which is insufficient for it to be classified as a Welsh Highland Sub.
The full details for the hill are:
Group: Hirddywel
Name: Pt. 557.6m
OS 1:50,000 map: 136
Summit Height: 557.6m
(LIDAR)
Summit Grid Reference:
SO 02324 82248 (LIDAR)
Bwlch Height: 547.8m
(LIDAR)
Bwlch Grid Reference:
SO 02100 81851 (LIDAR)
Drop: 9.8m
(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 (January 2024)
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