Pt. 277.7m (SO 106 406) – 200m Sub-Twmpau addition
There has been an addition to the list of 200m Twmpau, 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. 277.7m (SO 106 406) |
The criteria for the list that this addition
applies to are:
200m Twmpau
– Welsh hills at or above
200m and below 300m in height that have 30m minimum drop, with an accompanying sub list entitled the 200m
Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or
above 200m and below 300m in height with 20m or more and below 30m of drop, with
the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.
200m Twmpau by Myrddyn Phillips |
The hill is being listed by the point (Pt. 277.7m)
notation, and it is adjoined to the Mynydd Epynt group of hills, which are situated in the central part of South
Wales (Region B, Sub-Region B1), and it is
positioned with a minor road to its west and the A470 road to its east, and has
the small community of Erwyd (Erwood) towards the north north-west.
When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not
included in the accompanying Hills to be
surveyed sub list, as it was considered not to meet the criteria then used
for this sub category.
After the sub list was standardised, and
interpolated heights and drop values also included the details for this hill
were re-evaluated and it was listed with an estimated c 18m of drop, based on
the 275m summit spot height that appears on the contemporary Ordnance Survey
1:25,000 Explorer map and an estimated c 257m bwlch height, based on
interpolation of 10m contouring between 250m – 260m.
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 addition of this hill to 200m Sub-Twmpau
status is due to LIDAR analysis, resulting in a 277.7m summit height and a 255.1m
bwlch height, with these values giving this hill 22.6m of drop, which is
sufficient for it to be classified as a 200m Sub-Twmpau.
The full details for the hill are:
Group: Mynydd Epynt
Name: Pt. 277.7m
OS 1:50,000 map: 148, 161
Summit Height: 277.7m (LIDAR)
Summit Grid Reference: SO 10666 40689 (LIDAR)
Bwlch Height: 255.1m (LIDAR)
Bwlch Grid Reference: SO 10264 40290 (LIDAR)
Drop: 22.6m (LIDAR)
Myrddyn Phillips (August
2024)
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