Pt. 103.2m (SS 923 719)
There has been a Summit Relocation to a hill that
is listed in the 100m Twmpau and Y Trechol – The Dominant Hills of Wales,
with the summit height, bwlch height and their locations, the drop and status
of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.
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| LIDAR summit image of Pt. 103.2m (SS 923 719) |
The criteria for the two listings that this summit
relocation applies to are:
100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m
minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all
Welsh hills at or above 100m and below 200m 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 additional Welsh P30 hills whose
prominence is between one third and half that 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.
The hill is being listed by the Point (Pt. 103.2m)
notation as I do not know an appropriate name for it either from historic
research or local enquiry, and it is adjoined to the Bro Morgannwg group of
hills, which are situated in the southern part of South Wales (Region C,
Sub-Region C2), and it is positioned with the B4265 to its north-east and minor
roads to its north and west, and has the small community of Y Wig (Wick) towards
the north.
When the original Welsh 100m P30 list was
published on Geoff Crowder’s v-g.me website this hill was listed with a 102m
summit height, based on the spot height positioned at SS 921 719 that appears
on the Ordnance Survey 1:25,000 Explorer map.
 |
| Extract from the Ordnance Survey 1:25,000 Explorer map |
The details for this hill were re-evaluated when
the Ordnance Survey Vector Map Local hosted on the Geograph website and which
is entitled the Interactive Coverage Map became available online, and as this
map gives a 103m spot height positioned at SS 92333 71971, the summit of this
hill was relocated.
 |
| Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website |
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.
 |
| Close up LIDAR summit image of Pt. 103.2m (SS 923 719) |
The summit height produced by LIDAR analysis is 103.2m
positioned at SS 92366 71993 with LIDAR also giving a 103.4m height positioned
at SS 92370 72054 to a raised field boundary that is excluded from the height
of this hill as it is considered a recent man-made construct. The above detail 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 103.2m to ground meeting the criteria used within this list and
this is positioned at SS 92366 71993, this is relatively close to where the 103m spot
height appears on the Ordnance Survey Vector Map Local hosted on the Geograph
website and is positioned approximately 170 metres east north-eastward from
where the 102m spot height appears on the Ordnance Survey 1:25,000 Explorer map
and approximately 60 metres from where the highest part of the raised field
boundary is situated, and as the latter is
considered a relatively recent man-made construct it is not taken as a part of
the height of this hill.
The full details for the hill are:
Group: Bro Morgannwg
Name: Pt. 103.2m
OS 1:50,000 map: 170
Summit Height: 103.2m
(LIDAR, natural summit)
Summit Grid Reference (new position): SS 92366 71993 (LIDAR, natural summit)
Bwlch Height: 59.4m
(LIDAR)
Bwlch Grid Reference:
SS 97154 74620 & SS 97156 74616 & SS 97158 74613 (LIDAR)
Drop: 43.8m (LIDAR)
Dominance: 42.43%
(LIDAR)
Myrddyn Phillips (September 2019)
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