Crug y Gorllwyn (SN 321 340)
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 Crug y Gorllwyn (SN 321 340) |
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 Crug y Gorllwyn,
and it is adjoined to the Mynydd Pencarreg group of hills, which are situated in the south-western part of
South Wales (Region B, Sub-Region B1), and
it is positioned with minor roads to its north, west and south, and the B4333
road to its east, and has the town of Castell Newydd Emlyn (Newcastle Emlyn)
towards the north.
When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included
in the Hills to be surveyed sub list
with a summit height of 326m, based on the spot height adjoined to a
triangulation pillar positioned at SN 32185 34085 that appears on the
contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.
Extract from the Ordnance Survey 1:25,000 Explorer map |
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 28m of drop, based on the 326m summit
spot height and the 298m bwlch spot height that appeared on the Ordnance Survey
Vector Map Local hosted on the Geograph website and which was entitled the
Interactive Coverage 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 327.5m positioned at SN 32249 34121 and SN 32258 34125. However, this is a part of a covered
reservoir 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 Crug y Gorllwyn (SN 321 340) |
The height produced by LIDAR analysis to the summit
of this hill is 326.2m positioned at SN 32186 34079, and this position in
relation to covered reservoir 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 326.2m and this is positioned at SN 32186 34079, this position is beside
the triangulation pillar and is approximately 63 metres south-westward from the
high point of the covered reservoir.
The full details for the hill are:
Group: Mynydd Pencarreg
Name: Crug y Gorllwyn
OS 1:50,000 map: 145
Summit Height: 326.2m (LIDAR)
Summit Grid Reference (New Position): SN 32186 34079 (LIDAR)
Bwlch Height: 297.1m (LIDAR)
Bwlch Grid Reference: SN 32843 35432 (LIDAR)
Drop: 29.1m (LIDAR)
Myrddyn Phillips (May 2024)
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