Tuesday, 15 March 2016

Mapping Mountains – Summit Relocations – 100m Twmpau

Pentre Clawdd Gorse (SJ 311 442)  

There has been a Summit Relocation that was initiated by a survey with the Trimble GeoXH 6000 to the list of 100m Twmpau (thirty welsh metre prominences and upward) with the survey that resulted in this summit relocation being conducted on the 23rd February 2016.

The name of the hill is Pentre Clawdd Gorse and it is positioned in the eastern part of the Moel y Gamelin range of hills, and situated to the east of the A 483 and north-east of the town of Rhiwabon (Ruabon).  Access to the hill 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’s broad north – south summit ridge crest.

Pentre Clawdd Gorse is adjoined to the summit of Wynnstay Park which is approximately one kilometre due south from it, with the latter having a 141m spot height given it on Ordnance Survey 1:25,000 Explorer maps.  The summit of Wynnstay Park was surveyed on the 20th October 2015 resulting in a 141.2m (converted to OSGM15) summit height.  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 P30 Twmpau status with only 29.5m of drop.  However, further map study showed that the summit area of Pentre Clawdd Gorse has two small 140m ring contours on it, and if its summit 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.

As the summit of Pentre Clawdd Gorse was surveyed as 0.8m higher than Wynnstay Park, and as the latter was listed in the Hills to be surveyed sub list that accompanied the original Welsh 100m P30 listings on Geoff Crowder’s v-g.me website, the summit of the qualifying hill has been relocated to that of Pentre Clawdd Gorse.

Therefore the position of the relocated summit is at SJ 31131 44252 and is situated on the highest point of this part of the ancient earthwork known as Wat’s Dyke.  Either side of this earthwork are fields, one given over to grazing and the other which is arable.  This part of Wat’s Dyke has a narrow line of mature trees growing on it which adds perspective and interest to the landscape, although their proximity hampered satellite reception.  This position is not given a spot height on current Ordnance Survey maps and has an uppermost contour ring of 140m, and is approximately 1.4 kilometres northward of the summit of Wynnstay Park.

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 (New Position):  SJ 31131 44252 
Drop:  30.3m (converted to OSGM15)

The Trimble GeoXH 6000 gathering data at the summit of Pentre Clawdd Gorse, with the summit of Wynnstay Park on the left and in the background of this photograph

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

Myrddyn Phillips (February 2016)

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