Comin Gwauncaegurwen (SN 721 131)
There has been a Significant Height Revision to a
hill that is listed in the 200m Twmpau, with the summit height, bwlch height
and their locations, the drop and status of the hill derived from detail produced by JoeNuttall in his surface analysis programme, with subsequent LIDAR analysis
conducted by the DoBIH team and independently by Myrddyn Phillips.
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LIDAR image of Comin Gwauncaegurwen (SN 721 131) |
The criteria for the list that this height revision 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.
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200m Twmpau by Myrddyn Phillips |
The name the hill is listed by is Comin
Gwauncaegurwen and this was derived from the Tithe map with the language
protocol also used, 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 the A4068 road to its north, the A4069 road to its west
and a minor road to its south-west, and has the village of Brynaman towards the
north-west.
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Extract from the Ordnance Survey 1:50,000 Landranger map |
Since the original publication of the Welsh P30
lists on Geoff Crowder’s v-g.me website there have been a number of maps made
available online. Some of these are
historic such as the series of Six-Inch maps on the National Library of
Scotland website. Whilst others were digitally
updated such as the Ordnance Survey Vector Map Local that was hosted on the
Geograph website and which was entitled the Interactive Coverage Map, whilst
others are current and digitally updated such as the interactive mapping on the
Magic Maps and WalkLakes websites.
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Extract from the interactive mapping hosted on the WalkLakes website |
One of the mapping resources now available online
is the WalkLakes website which hosts an interactive map originated from the
Ordnance Survey Open Data programme.
This map has many spot heights not on other publicly available maps and
a 258m spot height is given on the summit area of this hill. Latterly the contemporary Ordnance Survey
1:25,000 Explorer map now has an uppermost 250m contour for this hill.
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Extract from the contemporary online 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.
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LIDAR summit image of Comin Gwauncaegurwen (SN 721 131) |
LIDAR analysis gives the highest ground on this
hill that could now be deemed natural as 258.4m positioned at SN 72135 13154,
and when compared to detail on contemporary Ordnance Survey maps when the Welsh
P30 lists were originated 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 258.4m and this was derived from LIDAR analysis, this is 34.4m higher
than the uppermost 220m contour on the old Ordnance Survey 1:50,000 Landranger
and 1:25,000 Outdoor Leisure map and 8.4m higher than the uppermost 250m contour
that appears online on the contemporary Ordnance Survey 1:25,000 Explorer map.
ills of Wales, and are reproduced below@
The full details for the hill are:
Group: Mynydd Du
Name: Comin Gwauncaegurwen
OS 1:50,000 map: 160
Summit Height (New
Height): 258.4m (LIDAR)
Summit Grid
Reference: SN 72135 13154 (LIDAR)
Bwlch Height: 218.5m (LIDAR)
Bwlch Grid
Reference: SN 72505 12523 (LIDAR)
Drop: 39.9m (LIDAR)
Myrddyn Phillips (March
2024)