Cefn Bach (SO 208 038) - 400m Sub-Pedwar addition
There has been a new 400m Sub-Pedwar added to the list by analysis
of LIDAR data by Aled Williams. The 400m Sub-Pedwarau are the Welsh hills at or above 400m and below 500m in height with
a drop between 20m and below 30m.
The hill is situated in the group of hills known
as the Y Cymoedd with its Cardinal Hill being Mynydd Carn y Cefn (SO 187 085) and
is placed in the Region of South Wales (C-2).
The hill is positioned above the town of Abertyleri (Abertillery) to its
east and between the river valleys of the Afon Ebwy (Ebbw River) to the west
and the Afon Ebwy Fach (Ebbw Fach River) to the east, and can be easily
accessed from a track from its south, and from the continuation of the track
from the west.
The name of the hill is Cefn Bach and prior to the
analysis of LIDAR data the hill was catalogued as having only 7m of drop based
on a 416m summit spot height at SO 20738 04263 and a 409m bwlch spot height at
SO 20369 04523, with the latter spot height appearing on the Ordnance Survey
enlarged mapping on the Geograph website.
The contouring near the area of the bwlch is different between the
Ordnance Survey 1:25,000 Explorer map and the enlarged Geograph map and the
summit position indicated by LIDAR is on the edge of the uppermost contour on
current 1:25,000 maps, with the contouring disappearing at this same position
on the enlarged Geograph map, indicating that the present day summit is the
relic of mine spoil, this is confirmed when analysing older maps.
As Aled was analysing other hills in the vicinity
against LIDAR data, he did likewise with Cefn Bach. LIDAR (Light Detection & Ranging) is highly
accurate height data that is now freely available for much of England and
Wales.
Aled’s analysis of LIDAR data gives the hill the
following details:
Cefn
Bach
Summit
Height: 427.2m
Summit
Grid Reference: SO 20819 03887
Bwlch
Height: 406.2m
Bwlch
Grid Reference: SO 20893 03917
Drop: 21.0m
Therefore, the 427.2m LIDAR data produced for the summit
position at SO 20819 03887 and the 406.2m LIDAR data
produced for the bwlch position at SO 20893 03917 is sufficient for this hill
to be reclassified to a 400m Sub-Pedwar with 21.0m of drop, and therefore Cefn Bach
is included in the listing of 400m Sub-Pedwar hills and the list of Y Pedwarau will
be updated accordingly. The list of
Pedwar hills is available from the Haroldstreet website (January 2014) with all
subsequent changes available via the Mapping Mountains site.
The full details for the hill are:
Cardinal Hill: Mynydd
Carn y Cefn
Summit Height: 427.2m
(LIDAR data)
Name: Cefn Bach
OS 1:50,000 map: 171
Summit Grid Reference: SO 20819 03887
Drop: 21.0m (LIDAR data)
The list of additions, reclassifications and deletions from
the 400m Sub-Pedwar list since the 1st edition of the Y Pedwarau was
published by Europeaklist are as follows:
400m SUB-PEDWAR ADDITIONS
Cefn Bach (LIDAR data) (SO 208 038) 21.0m drop
Pt. 422.3m (converted to OSGM15) (SO 073 822) Pedwar reclassified to 400m Sub-Pedwar with 29.0m drop
Pt. 407.7m (converted to OSGM15) (SO 180 692) Pedwar reclassified to 400m Sub-Pedwar with 28.3m drop
400m SUB-PEDWAR RECLASSIFICATIONS
Pt. 499.5m (converted to OSGM15) (SH 665 310) 400m Sub-Pedwar reclassified to Pedwar with 30.3m drop
400m SUB-PEDWAR DELETIONS
Myrddyn Phillips and Aled Williams (December 2016)
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