Friday, 27 January 2017

Mapping Mountains – Summit Relocations – Y Pedwarau and Y Pellennig

Esgair Cerrig (SN 952 432)

This is the thirtieth post under the heading of Summit Relocations, with the survey that resulted in the following details taking place on the 28th December 2016 in good, clear and bright conditions.

The thirtieth major summit relocation partly initiated from a survey with the Trimble GeoXH 6000 was conducted in the Mynydd Epynt hills, this hill range is situated in the south-eastern part of Mid and West Wales (Region B, Sub-Region B2), and the hill is positioned above the small community of Llangamarch (Llangammarch Wells) to its north north-west and the small town of Llanwrtyd (Llanwrtyd Wells) to its west north-west. 

The name of the hill is Esgair Cerrig and this was derived from local enquiry (see Significant Name Changes) and access to it is restricted due to it being positioned within the confines of the Sennybridge Artillery Range Training Area.

Esgair Cerrig is listed as a Pedwar (‘Y Pedwarau’ Europeaklist May 2013 and Haroldstreet January 2014), these are the Welsh 400m hills with 30m minimum drop, and also as a Pellennig, these are the Welsh hills whose summit is 2.5km or more from the nearest paved public road and the hill has a minimum drop of 15m.  This hill’s summit position was previously given as SN 956 435 and this is where the current 456m spot height appears on Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps. 

However, prior to the survey with the Trimble GeoXH 6000 this hill’s summit was analysed using LIDAR data by Aled Williams.  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:

Esgair Cerrig

Summit Height:  456.3m

Summit Grid Reference:  SN 95226 43298

The analysis of LIDAR data pinpointed this hill’s position and its height was confirmed with the Trimble survey:

Esgair Cerrig

Summit Height:  456.4m (converted to OSGM15)

Summit Grid Reference:  SN 95224 43297 

Therefore the position of the relocated summit is at SN 95224 43297 and is featureless ground consisting of grass and reed grass beside a bomb crater, this position is within the uppermost 450m ring contour on Ordnance Survey maps although no spot height is given to it, the relocated summit is approximately 490 metres south-westward from where the previously listed summit is positioned.

The full details for the hill are:

Cardinal Hill:  Clepyn Melyn

Summit Height:  456.4m (converted to OSGM15)

Name:  Esgair Cerrig

OS 1:50,000 map:  147, 160

Summit Grid Reference (New Position):  SN 95224 43297 
Drop:  35.6m (converted to OSGM15)

The Trimble GeoXH 6000 gathering data at the summit of Esgair Cerrig, with the old position of the summit in the centre background of this photograph

Myrddyn Phillips and Aled Williams (January 2017)

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