Monday, 28 September 2015

Mapping Mountains – Summit Relocations – 200m Twmpau


Winllan Hill (SJ 217 214)  

This is the eighteenth post under the heading of Summit Relocations, with the following details being retrospective as the Trimble survey that resulted in this summit relocation was conducted over two days; on 28th / 29th  August 2015.

The eighteenth summit relocation initiated from a survey with the Trimble GeoXH 6000 was conducted in the company of Mark Trengove on the lower easterly hills of Y Berwyn, above the small community of Llansanffraid-ym-Mechain which is situated just north-west of where the Afon Cain flows in to the Afon Efyrnwy (River Vyrnwy).

The hill is listed as a 200m Twmpau (thirty welsh metre prominences and upward) as prior to the survey with the Trimble GeoXH 6000 it was listed with c 48m of drop based on the current Ordnance Survey map height of 216m and an estimated bwlch height of c 168m.

There is good access to the summit of the hill with a number of public footpaths converging on its high point from a variety of directions, with its summit positioned beside a fence and under a large overhanging tree, with the high point only a few metres from where a public footpath crosses the field that it is situated in.

The name of the hill is Winllan Hill and prior to the survey with the Trimble GeoXH 6000 the position of the summit was listed as that of its 216m spot height which is situated at SJ 21686 21409.  This spot height is positioned on a slight rise which resembles part of an ancient earthen embankment associated with an old hill fort, and although there is evidence of these existing on neighbouring hills there is no evidence on current maps that one existed on Winllan Hill.

The position of the relocated summit is at SJ 21709 21460 and is the top of a field with the highpoint situated under a large overhanging tree beside a fence that runs in an east – west direction over the summit.  This position is not given a spot height on current Ordnance Survey maps but the Trimble result gave it as 4.3m higher when compared to the position where the 216m spot height appears on current Ordnance Survey maps and approximately 50 metres northward from it.
 

The full details for the hill are:

Cardinal Hill:  Rhialgwm

Summit Height:  220.3m (converted to OSGM15)

Name:  Winllan Hill

OS 1:50,000 map:  126

Summit Grid Reference (New Position):  SJ 21709 21460
  
Drop:  c 52m


The Trimble GeoXH 6000 gathering data at the new summit position of Winllan Hill, with Mark (wearing blue top) standing on the old position of the summit in the left background of this photograph

For details on the survey that relocated the summit of this hill please click {here}

Myrddyn Phillips (August 2015)



No comments: