Cefn yr Ystrad (SO 086
137)
There has been a Summit Relocation to a hill that
is listed in the Yr Uchafion and the 600m Twmpau with the summit height and its
location being confirmed by a Trimble GeoXH 6000 survey conducted by Myrddyn
Phillips and Aled Williams on the 19th April 2019.
The criteria for the two listings that this summit
relocation applies to are:
Yr Uchafion – Welsh hills at or above 500m in height that
have 15m minimum drop. The list is
co-authored by Myrddyn Phillips and Aled Williams, with the Introduction to this list appearing on Mapping Mountains on the 4th November 2015.
600m Twmpau – Welsh hills at or above 600m and below 700m in
height that have 30m minimum drop, with an accompanying sub category entitled
the 600m Sub-Twmpau consisting of all
Welsh hills at or above 600m and below 700m in height that have 20m or more and
below 30m of drop. With the word Twmpau
being an acronym standing for thirty
welsh metre prominences and upward. The list is authored
by Myrddyn Phillips.
The name of the hill is Cefn yr Ystrad 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 is positioned with the
A465 road to its south, with the Pontsticill Reservoir to its west and the
Talybont Reservoir towards its north, and has the towns of Aberhonddu (Brecon)
towards its north and Merthyr Tudful towards its south.
 |
| Extract from the Ordnance Survey 1:25,000 Explorer map |
When this hill was first included in the listings
that would later become known as the Yr
Uchafion and 600m Twmpau the
summit position was given to where the 617m map heighted triangulation pillar
is situated. The summit position for
this hill was later changed to ground beside the ancient cairn which is named Carn
y Bugail. This summit relocation was
based on Abney level surveys that indicated ground at the base of the ancient
cairn was 0.8m higher than the flush bracket adjoined to the triangulation
pillar.
Thee points were surveyed with the Trimble GeoXH
6000 and these results are given below:
Upright rock beside ancient cairn: 616.888m at SO 08810 13628
Grass at base of ancient cairn: 616.311m at SO 08793 13627
Small embedded rock beside trig pillar: 617.442 at SO 08696 13729
 |
| Gathering data on the upright rock beside the ancient cairn of Carn y Bugail |
The 617.4m summit height produced by the Trimble
GeoXH 6000 survey and its position in relation to the previously listed summit
position on ground at the base of the ancient cairn comes within the
parameters of the Summit Relocations used within this page heading, these
parameters are:
 |
| Gathering data at the base of the ancient cairn |
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.
 |
| Gathering data at the highest embedded rock beside the triangulation pillar |
The summit height produced by the Trimble GeoXH
6000 survey is 617.4m and is positioned at SO 08696 13729, this position is
approximately 140 metres north-west from where the old listed summit is
positioned.
The full details for the hill are:
Group: Cymoedd Gwent
Name: Cefn yr Ystrad
OS 1:50,000 map: 160
Summit Height: 617.4m
(converted to OSGM15)
Summit Grid Reference (new position): SO 08696 13729
Bwlch Height: 439.9m (converted
to OSGM15)
Bwlch Grid Reference:
SO 05261 17241
Drop: 177.5m (converted
to OSGM15)
Myrddyn Phillips and Aled Williams (August 2019)
No comments:
Post a Comment