The two tops of Cefn
Bach have now been surveyed with the Trimble GeoXH 6000, resulting in:
Surveyed on 18.08.15:
389.392m at SO 00293 37291
Surveyed on 30.12.18: 389.391m at SO 00470 38742
Cefn Bach (SO 004 387) - 390m Double Sub-Pedwar deletion
There has been a deletion of a 390m Double Sub-Pedwar by analysis of LIDAR data by Aled
Williams. The 390m Double Sub-Pedwarau is one of three categories of sub hills
that accompany the main Y Pedwarau
list, with the criteria for 390m Double Sub-Pedwar
status being all Welsh hills at or above 390m and below 400m in height with 20m
or more and below 30m of drop.
The hill is situated in the group of hills known
as Mynydd Epynt with its Cardinal Hill being Mynydd Epynt (SN 961 464) and is
placed in the Region of Mid and West Wales (B-2). The hill is positioned between the small
communities of Upper Chapel to the north, Lower Chapel to the south-east and
Merthyr Cynog to the south-west, and between the river valleys of the Ysgir
Fawr to the west and the Honddu to the east.
A narrow lane passes to the north of this hill and a public footpath
leads from this to just below the summit.
The name of the hill is Cefn Bach and it had been
listed in the Y Pedwarau Europeaklist
booklet with c 22m of drop based on its 391m summit spot height at SO 00375
38722 and an estimated bwlch height of c 369m based on bwlch contouring between
360m – 370m. This hill was listed as a 390m Double Sub-Pedwar in deference to
its 391m map heighted twin summit which was listed as the 390m Sub-Pedwar with its 391m spot height at SO 00284 37297, these
two hills are aligned in a north – south direction, with the southerly hill
being listed with 55m of drop based on a 336m bwlch spot height.
Since the Europeaklist publication of the Y Pedwarau the southerly of these two
391m map heighted hills has been surveyed with the Trimble GeoXH 6000 resulting
in a 389.4m (converted to OSGM15) summit height at SO 00293 37291 and a 335.0m
(converted to OSGM15) bwlch height at SO 00287 36949. However, the northerly summit remained
un-Trimbled and the relative height of each summit was only ascertained from
analysis of LIDAR data.
As Aled was analysing other hills in the vicinity
against LIDAR data, he did likewise with the two Cefn Bach hills. 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: 389.2m
Summit
Grid Reference: SO 00471 38745
Bwlch
Height: 368.9m
Bwlch
Grid Reference: SO 00075 38322
Drop: 20.3m
Therefore, the 389.2m LIDAR data produced for the summit position
at SO 00471 38745 and the 368.9m LIDAR data produced for the bwlch position at SO 00075 38322 is insufficient for this hill to
retain its 390m Double Sub-Pedwar status as its summit is below the required height threshold.
The full details for the hill are:
Cardinal Hill: Mynydd Epynt
Summit Height: 389.2m (LIDAR
data)
Name: Cefn Bach
OS 1:50,000 map: 160
Summit Grid Reference: SO 00471 38745
Drop: 20.3m (LIDAR
data)
This now brings the overall total for the 390m Double Sub-Pedwarau to 27 hills
with 13 additions and two deletions to this sub category of hill since
publication of the list by Europeaklist in May 2013. The hill will be taken out of the 390m Double Sub-Pedwar list in
forthcoming publications of the Y Pedwarau. The list of Pedwar hills is available from the Haroldstreet website (January
2014) with all subsequent changes available via the Mapping Mountains site.
The additions, reclassifications and deletions to the 390m Double Sub-Pedwarau since the 1st
edition of the Y Pedwarau was published
by Europeaklist are as follows:
390m DOUBLE SUB-PEDWAR ADDITIONS
390m DOUBLE SUB-PEDWAR DELETIONS
Cefn Bach (SO 004 387) 389.2m summit and 20.3m drop
 |
| Cefn Bach (SO 004 387) the deleted 390m Double Sub-Pedwar |
Myrddyn Phillips and Aled Williams (January 2017)
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