Cae Cefn (ST 059 748)
There has been a Significant Height Revision to a
hill that was listed in the 100m Twmpau,
with the summit height and its location confirmed by a Leica GS15 survey
conducted by John Barnard, Graham Jackson and Myrddyn Phillips which took place
on the 4th November 2013, and the bwlch height and its location, the
drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn
Phillips.
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| The Leica GS15 gathering data at the summit of Cae Cefn |
The criteria for the list 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.
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| LIDAR image of Cae Cefn (ST 059 748) |
The name the hill is now listed as is Cae Cefn and
this derived from the Tithe map, 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 A48 road to its south-east and
minor roads to its west, north and east, has the city of Caerdydd (Cardiff)
towards the east and the town of Y Bont-faen (Cowbridge) to the west.
When the original 100m height band of Welsh P30
hills were published on Geoff Crowder’s v-g.me website this hill was listed
with a 140m summit height based on the spot height that appears on the Ordnance
Survey 1:25,000 Explorer map. However,
as the 140m spot height is placed at the top of a covered reservoir and as
these structures are considered recent man-made constructs and as Tair Onnen
vied for being the higher hill, both hills were surveyed using a Leica GS15,
resulting in:
Cae Cefn (ST 05910 74886): 136.2m (natural ground at base of covered reservoir)
Tair Onnen (ST 03660 73979): 137.3m
When LIDAR became available the details for these
two hills were re-assessed. The LIDAR
(Light Detection & Ranging) technique produced highly accurate height data
that is now freely available for much of England and Wales. The LIDAR summit details are given below:
Cae Cefn (ST 05915 74885): 136.4m (natural ground at base of covered
reservoir)
Tair Onnen (ST 03661 73979): 137.4m
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| Extract from the Ordnance Survey 1:25,000 Explorer map |
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| Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website |
The height produced by the Leica GS15 survey is
136.2m and is positioned at ST 05910 74886, this revised height comes 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 other GNSS equipment, 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
136.2m and this is to natural ground at the base of a covered reservoir and
positioned at ST 05910 74886, this is 3.8m
lower than the previously listed summit height of 140m which was based on the
spot height that appears on the Ordnance Survey 1:25,000 Explorer map.
The full details for the hill are:
Group: Bro Morgannwg
Name: Cae Cefn
OS 1:50,000 map: 170
Summit Height (New Height):
136.2m (Leica GS15)
Summit Grid Reference:
ST 05910 74886 (Leica GS15)
Bwlch Height: 116.25m
(LIDAR)
Bwlch Grid Reference:
ST 04273 74542 (LIDAR)
Drop: 19.9m (Leica
GS15 summit and LIDAR bwlch)
Myrddyn Phillips (October 2019)
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