Saturday, 3 October 2015

Mapping Mountains – Significant Height Revisions – 200m Twmpau

Winllan Hill (SJ 217 214)  

This is the nineteenth post under the heading of Significant Height Revisions, and the following details are retrospective as the Trimble survey that resulted in this height revision was conducted over two days; 28th / 29th August 2015.

The nineteenth major height revision initiated from a survey with the Trimble GeoXH 6000 was conducted in the lower easterly hills of Y Berwyn, above Llansanffraid-ym-Mechain which is situated beside where the Afon Cain flows in to the Afon Efyrnwy (River Vyrnwy).

The hill was surveyed in the late evening in the company of Mark Trengove after nourishing our appetite in the Bradford Arms in Llanymynech.

The hill is listed as a 200m Twmpau (thirty welsh metre prominences and upward) as prior to the survey with the Trimble it was listed as 216m high based on the spot height on the area of the summit on current Ordnance Survey maps, and an estimated drop value of c 48m, based on bwlch contour interpolation which gives the height of the bwlch as c 168m.

Access to the hill is good as public footpaths from the south, west, north and east head towards its summit and parking is easily found when approaching the hill from the west and north, this is also likely to be the case if approaching the hill from the east and south.  The high point of the hill is beside a fence and under a large overhanging tree, and is 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 height of the hill was taken as 216m, after the spot height that appears on current Ordnance Survey maps, however there is significantly higher land to the north of where this spot height appears on the ground.

Therefore this hill’s new summit height is 220.3m (converted to OSGM15) which is 4.3m higher than its previously listed height of 216m which was based on the current Ordnance Survey spot height.

The full details for the hill are:

Cardinal Hill:  Rhialgwm

Summit Height (New Height):  220.3m (converted to OSGM15)

Name:  Winllan Hill

OS 1:50,000 map:  126

Summit Grid Reference:  SJ 21709 21460 
Drop:  c 52m

Gathering data from the summit of Winllan Hill which resulted in this hill's significant height revision

For details on the survey that significantly revised the summit height of this hill please click {here}

Myrddyn Phillips (August 2015)

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