Broughton Burrows (SS 413 927)
There has been a Summit Relocation to a hill that
is listed in the 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales, with
the summit height and drop of the hill being confirmed by LIDAR analysis
conducted by Myrddyn Phillips.
LIDAR image of Broughton Burrows |
The criteria for the two lists that this summit
relocation applies to are:
30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 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.
Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose
prominence equal or exceed half that of their absolute height. With the criteria for Lesser Dominant status being those addition Welsh P30 hills whose
prominence is 33.33% or more and below 50% of their absolute height. The list is authored by Myrddyn Phillips with
the Introduction to the start of the Mapping Mountains publication of this list
appearing on the 3rd December 2015.
LIDAR image of Broughton Burrows showing the summit and connecting bwlch |
The name of the hill is Broughton Burrows, and it
is adjoined to the Gŵyr group of
hills, which are situated in the western part of South Wales (Region C, Sub-Region C1), and it is positioned at
the western end of the Gŵyr, and has the small community of Llangynydd towards
the south-east.
Although the summit of this hill is not a part of
open access land, and as such permission to visit should be sought, there is
general acceptance for people to visit, with the nearest public footpath encircling
the summit of the hill which comprises a dune system.
Close up LIDAR summit image of Broughton Burrows |
Prior to LIDAR analysis and the inspection of 5m contouring
on OS Maps, which is the recent replacement for OS Get-a-map, this hill was
listed with c 32m of drop and 65.31% dominance based on the 49m spot height that
appears on the Ordnance Survey 1:25,000 Explorer map and an interpolated bwlch
height of c 17m based on what was thought to be bwlch contouring between 15m –
20m. However, as this hill is a part of
a dune system this map did not show continuous contours on either the summit or
bwlch area of this hill.
Extract from OS Maps |
The summit height produced by LIDAR analysis is 61.9m
at SS 41391 92781 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. As heights on different
scaled Ordnance Survey maps are not consistent the height given on the 1:25,000
Explorer map is being prioritised in favour of the 1:50,000 Landranger map for
detailing these relocations.
The summit height produced by LIDAR analysis is 61.9m
and is positioned at SS 41391 92781, this position is not given a spot height
on contemporary Ordnance Survey maps and is approximately 450 metres south-east
from where the 49m spot height appears on the Ordnance Survey 1:25,000 Explorer
map.
The Ordnnance Survey Interactive Coverage map hosted on the Geograph website showing the summit position in relation to where the 49m spot height appears |
The full details for the hill are:
Group: Gŵyr
Name: Broughton
Burrows
OS 1:50,000 map: 159
Summit Height: 61.9m
(LIDAR)
Summit Grid Reference (new position): SS 41391 92781 (LIDAR)
Bwlch Height: 17.4m
(LIDAR)
Bwlch Grid Reference:
SS 41739 92663 (LIDAR)
Drop: 44.5m (LIDAR)
Dominance: 71.95%
(LIDAR)
Myrddyn Phillips (December 2018)
No comments:
Post a Comment