Monday, 14 March 2016

Mapping Mountains – Hill Reclassifications – 100m Twmpau


Pentre Clawdd Gorse (SJ 311 442) - 100m Twmpau addition  

There has been an addition to the 100m Twmpau (thirty welsh metre prominences and upward) hill list instigated by a survey with the Trimble.   The hill is situated just to the east of the A 483 and to the north-east of Rhiwabon (Ruabon) in the eastern part of the Moel y Gamelin range of hills.

The Trimble GeoXH 6000 survey that resulted in this hill’s addition to the 100m Twmpau list was conducted in the afternoon of the 23th February 2016 on a beautiful winter’s day in good, dry and sunny conditions.

The hill is named Pentre Clawdd Gorse and access to it is relatively easy as its summit is positioned on Wat’s Dyke, this ancient earthwork stretches from the Dee estuary in the north to Shropshire in the south, and public footpaths follow its course over this hill.

Pentre Clawdd Gorse is adjoined to the summit of Wynnstay Park which is an approximate one kilometre due south from it and which has a 141m spot height given it on current Ordnance Survey maps.  The summit of Wynnstay Park was surveyed on the 20th October 2015 resulting in a summit height of 141.2m (converted to OSGM15).  On the same day the bwlch positioned at SJ 307 437 was also surveyed resulting in a bwlch height of 111.7m (converted to OSGM15).  If this was the critical bwlch for Wynnstay Park the hill just failed to make it to P30 Twmpau status with only 29.5m of drop.  However, further map inspection showed that the summit area of Pentre Clawdd Gorse had two 140m small ring contours on it, and if one proved to be at least 0.5m higher than the summit of Wynnstay Park the bwlch positioned at SJ 307 437 would be adjoined to Pentre Clawdd Gorse and the hill would be a new P30.

The survey with the Trimble GeoXH 6000 resulted in a summit height of 142.0m (converted to OSGM15), and therefore as Pentre Clawdd Gorse is 0.8m higher than Wynnstay Park the 111.7m (converted to OSGM15) high bwlch positioned at SJ 307 437 is that for the higher hill. 


The full details for the hill are:

Cardinal Hill:  Moel y Gamelin

Summit Height:  142.0m (converted to OSGM15)

Name:  Pentre Clawdd Gorse

OS 1:50,000 map:  117

Summit Grid Reference:  SJ 311 442

Drop:  30.3m (converted to OSGM15)


The summit of Pentre Clawdd Gorse (SJ 311 442) the new addition to the 100m Twmpau list

For details on the survey that resulted in this hill being added to the 100m Twmpau list please click {here} for summit and {here} for the bwlch survey.

Myrddyn Phillips (February 2016)

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