Pt. 657.9m (SH 856 209) – Welsh Highland
Sub deletion
There has been a deletion from 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. 657.9m (SH 856 209) |
The criteria for the list that this deletion applies to are:
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Welsh Highlands - Uchafion Cymru by Myrddyn Phillips and Aled Williams |
The hill is being listed by the point (Pt. 657.9m)
notation and it is adjoined to the Aran Fawddwy group of hills, which are situated in the south-western part of
North Wales (Region A, Sub-Region A3), and
it is positioned with the A494 road to its north-west and minor roads to its
south and east, and has the village of Dinas Mawddwy towards the south.
When the initial P10 sub list was completed in
June 2020 this hill was listed with an estimated c 8m of drop, based on the 657m
summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and
an estimated c 649m 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 |
When the sub list was updated with details from
basic levelling surveys conducted by Myrddyn Phillips the details for this hill
were re-evaluated and it was listed with 10.8m of drop, based on a basic
levelling survey conducted on the 19.05.98 which gave this hill 35.3ft of drop,
resulting in the addition of this hill to the sub list.
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 657.9m summit
height and a 648.1m 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: Aran Fawddwy
Name: Pt. 657.9m
OS 1:50,000 map: 124,
125
Summit Height: 657.9m
(LIDAR)
Summit Grid Reference:
SH 85683 20921 (LIDAR)
Bwlch Height: 648.1m (LIDAR)
Bwlch Grid Reference:
SH 85705 20958 (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 (October 2023)
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