Y Foel (SJ 026 407)
There has been a Summit Relocation to a hill that is listed
in the Y Pedwarau and the Y Trichant, with the summit height and
its position confirmed by LIDAR analysis conducted by Myrddyn Phillips.
 |
| LIDAR summit image of Y Foel (SJ 026 407) |
The criteria for the two listings
this summit relocation affects are:
Y Pedwarau - Welsh hills at or above 400m and below 500m in height that have 30m minimum drop. Accompanying the main Y Pedwarau list are five categories of sub hills, with this summit relocation applying to a hill listed in the 390m Sub-Pedwar category, with the criteria for this sub category being all Welsh hills at or above 390m and below 400m in height that have a minimum 30m of drop. The list is co-authored by Myrddyn Phillips and Aled Williams, with the Introduction to the Mapping Mountains publication of this list appearing on the 30th January 2017.
Y Trichant – 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.
The name of the hill is Y Foel and it is adjoined to the
Arenig group of hills, which are situated in the central part of North Wales (Region A,
Sub-Region A3), and
it is positioned with the A494 road to the north-west and the Afon Dyfrdwy
(River Dee) and the B4401 road to the south-east, and has the small community
of Cynwyd towards the east.
When the original 300m height band of Welsh P30
hills were published on Geoff Crowder’s v-g.me website the summit height of
this hill was listed as 392m which was based on the spot height adjoined to a triangulation
pillar positioned at SJ 02550 40750 on the Ordnance Survey 1:50,000 Landranger
and 1:25,000 Explorer map. The latter
map also records a 391m spot height adjoined to a small ancient enclosure
positioned to the east south-east of the triangulation pillar.
 |
| 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.
Unfortunately LIDAR only covers the land adjoined
to the ancient enclosure and not that adjoined to the triangulation pillar,
however the flush bracket adjoined to the trig pillar is recorded as 391.972m,
therefore ground at its base will be approximately 391.6m – 391.7m in height.
The summit height produced by LIDAR analysis for
land adjoined to the ancient enclosure is 392.85m at SJ 02666 40700 and its
position in relation to that previously given comes within the parameters of the Summit
Relocations used within this page heading, these parameters are:
The term Summit Relocations applies to any listed
hill whose summit meets the following criteria; where there are a number of
potential summit positions within close proximity and the highest point is not
where previously given, 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, or when the summit of the hill is
in a different field compared to where previously given, or when the natural
and intact summit of a hill is confirmed compared to a higher point such as a
raised field boundary that is judged to be a relatively recent man-made
construct.
Therefore, the summit
height produced by LIDAR analysis is 392.85m and is positioned at SJ 02666
40700, this position is given a 391m spot height on the Ordnance Survey 1:
25,000 Explorer map and is approximately 130 metres east south-eastward from
where the previously listed summit is positioned which is land at the base of
the triangulation pillar which is given a 392m spot height on contemporary
Ordnance Survey maps.
The full details for the hill are:
Group: Arenig
Name: Y Foel
OS 1:50,000 map: 125
Summit Height: 392.85m
(LIDAR)
Summit Grid Reference (New Position): SJ 02666 40700 (LIDAR)
Bwlch Height: 327m (spot height)
Bwlch Grid Reference:
SJ 01843 40765 (spot height)
Drop: 66m (LIDAR
summit and spot height bwlch)
Myrddyn Phillips and Aled Williams (November 2019)
No comments:
Post a Comment