Pen y Coed (SN 569 049)
There has been a Summit Relocation to a hill that is listed in the 30-99m 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 Pen y Coed (SN 569 049) |
The criteria for the list that this summit
relocation applies to are:
30-99m Twmpau - Welsh hills at or above 30m and below 100m in height that have 30m
minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau,
with the criteria for this sub category being all Welsh hills at or above 30m
and below 100m 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.
30-99m Twmpau by Myrddyn Phillips |
The name the hill is now listed by is Pen y Coed and
this was drived from the Tithe map, and
it is adjoined to the Mynydd Sylen group of hills, which are situated in the southern part of South Wales (Region B,
Sub-Region B5), and it is positioned with the
B4306 road to its north-east, a minor road to its south-west, and the M4
motorway to its south-east, and has the town of Pontarddulais towards the
south-east.
When the original 30-99m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not
included in the 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 20m of drop, based on
the 88m summit spot height positioned at SN 56954 04958 that appears on the
contemporary Ordnance Survey 1:25,000 Explorer map and an estimated c 68m bwlch
height, based on interpolation of 5m contouring between 65m – 70m.
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.
LIDAR analysis gives the highest ground on this
hill as 89.3m positioned at SN 56988 04938 and SN 56989 04939. However, this is a part of a raised field
boundary and protocols dictate that as this is deemed a relatively recent
man-made construct such ground is discounted from the height of a hill.
LIDAR summit image of Pen y Coed (SN 569 049) |
The height produced by LIDAR analysis to the highest
remaining natural summit of this hill is 89.2m and this is positioned at SN 56986
04941, and this comes within the parameters of the Summit Relocations used within this
page heading, these parameters are:
The term Summit Relocations applies when the high
point of the hill is found to be positioned; in a different field, to a
different feature such as in a conifer plantation, within a different map contour, to a
different point where a number of potential summit positions are within close proximity,
when natural ground or the natural and intact summit of a hill is confirmed
compared to a higher point such as a raised field boundary or covered reservoir
that is judged to be a relatively recent man-made construct, or a relocation of
approximately 100 metres or more in distance from either the position of a map
spot height or from where the summit of the hill was previously thought to
exist.
Therefore, the height produced by LIDAR analysis
to the remaining natural summit of this hill is 89.2m and is positioned at SN 56986
04941, this
position is relatively close to where the spot height appears on the Ordnance
Survey 1:25,000 Explorer map and is approximately 3 metres north-westward from
where the high point of the raised field boundary is positioned.
The full details for the hill are:
Group: Mynydd Sylen
Name: Pen y Coed
OS 1:50,000 map: 159
Summit Height: 89.2m (LIDAR)
Summit Grid Reference (New Position): SN 56986 04941 (LIDAR)
Bwlch Height: 68.0m (LIDAR)
Bwlch Grid Reference: SN 56691 04800 (LIDAR)
Drop: 21.2m (LIDAR)
Myrddyn Phillips (August
2024)
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