Pen Moel Hedog (SN 451 469)
There has been a Summit Relocation to a hill that is listed in the Y Trichant – The 300m Hills of Wales, 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 Moel Hedog (SN 451 469) |
The criteria for the list that this summit
relocation applies to are:
Y Trichant
– The 300m Hills of Wales – Welsh
hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the
Sub-Trichant, with the criteria for this sub category being all Welsh hills at
or above 300m and below 400m in height with 20m or more and below 30m of drop. The
list is authored by Myrddyn Phillips with the Introduction to the list and the
renaming of it appearing on Mapping Mountains on the 13th May 2017,
and the Introduction to the Mapping Mountains publication of the list appearing
on the 1st January 2022.
Y Trichant - The 300m Hills of Wales by Myrddyn Phillips |
The name the hill is listed by is Pen Moel Hedog,
and it is adjoined to the Mynydd Bach group of hills, which are situated in the western part of South
Wales (Region B, Sub-Region B1), and
it is positioned with the B4459 road to its west, the A475 road to its south
and a minor road to its east, and has the town of Llanybydder towards the east
south-east.
When the original 300m 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 23m of drop, based on
the 314m summit spot height positioned at SN 45142 46935 that appears on the
contemporary Ordnance Survey 1:25,000 Explorer map, and an estimated c 291m
bwlch height, based on interpolation of 5m contouring between 290m – 295m.
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 313.5m positioned at SN 45168 46943.
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 Moel Hedog (SN 451 469) |
The height produced by LIDAR analysis to the
natural summit of this hill is 312.8m positioned at SN 45159 46968, and this
position in relation to the raised field boundary 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 considered 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 summit height produced by LIDAR
analysis is 312.8m and this is positioned at SN 45159 46968, this position is
not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger
and 1:25,000 Explorer map and is approximately 35 metres north-eastward from
where the 314m spot height appears on the Ordnance Survey 1:25,000 Explorer map
and approximately 25 metres north north-westward from the high point of the
raised field boundary.
The full details for the hill are:
Group: Mynydd Bach
Name: Pen Moel Hedog
OS 1:50,000 map: 146
Summit Height: 312.8m (LIDAR)
Summit Grid Reference (New Position): SN 45159 46968 (LIDAR)
Bwlch Height: 289.8m (LIDAR)
Bwlch Grid Reference: SN 45622 48279 (LIDAR)
Drop: 23.0m (LIDAR)
Myrddyn Phillips
(January 2024)
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