The Mount (ST 258 848)
There has been a Significant Height Revision to a
hill that is listed in the 100m Twmpau and
Y Trechol – The Dominant Hills of Wales,
with the summit height derived from the OS Trig Database and the bwlch height
derived from interpolation of 5m contouring.
The criteria for the two listings that this height
revision 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 name of the hill is The Mount, and it is
adjoined to the Cymoedd Gwent group of hills, which are situated in the eastern
part of South Wales (Region C, Sub-Region C2), and it has minor roads to its
north-west and north-east and the M4 motorway to its south, and is positioned
between the city of Caerdydd (Cardiff) to the south-west and Casnewydd-ar-Wysg (Newport)
to the north-east.
When the original Welsh 100m P30 list was
published on Geoff Crowder’s v-g.me website this hill was listed with a 124m
summit height, based on the spot height positioned at ST 25276 84738 that
appears on the Ordnance Survey 1:25,000 Explorer map, with an accompanying note
stating that the Ordnance Survey 1:50,000 Landranger map dated 1986 has a 127m
spot height adjoined to a triangulation pillar and which is positioned at ST
25869 84831. As heights on 1:25,000
scale mapping were prioritised in this list over those on 1:50,000 scale
mapping this hill’s summit was listed to where the 124m spot height appears on
the 1:25,000 Explorer map.
 |
| Extract from the Ordnance Survey 1:25,000 Explorer map |
Since publication of these P30 lists on Geoff
Crowder’s v-g.me website the heights on different scaled Ordnance Survey maps
can be cross referenced against a number of sources that are now available
online, and 1:25,000 map data is no longer prioritised for summit heights over
that of 1:50,000 map data, each is now assessed individually. Therefore, the 127m height given to the
triangulation pillar is now prioritised for the summit height of this hill, this
is not a substantial revision compared to some revised heights, but it does
come within the parameters of the Significant Height Revisions used within this
page heading, these parameters are:
The term Significant Height Revisions applies to
any listed hill whose interpolated height and Ordnance Survey or Harvey map
summit spot height has a 2m or more discrepancy when compared to the survey
result produced by the Trimble GeoXH 6000 or analysis of data produced via
LIDAR, also included are hills whose summit map data is missing an uppermost
ring contour when compared to the data produced by the Trimble or by LIDAR
analysis.
Therefore, this hill’s new listed summit height is
127m and this was derived from the 127.247m flush bracket height adjoined to a
triangulation pillar that once stood on the summit of this hill and which was
destroyed in September 1985, this is 3m higher than the previously listed
summit height of 124m which was derived from the spot height that appears on
the Ordnance Survey 1:25,000 Explorer map.
The full details for the hill are:
Group: Cymoedd Gwent
Name: The Mount
OS 1:50,000 map: 171
Summit Height (New height):
127m
Summit Grid Reference:
ST 25868 84839
Bwlch Height: c 66m
Bwlch Grid Reference:
ST 24800 87551
Drop: c 61m
Dominance: 48.03%
Myrddyn Phillips (August 2019)
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