Saturday, 14 November 2015

Mapping Mountains – Summit Relocations – 100m Twmpau

The Pimple (SJ 299 472)

There has been a Summit Relocation to the list of the 100m Twmpau (thirty welsh metre prominences and upward) initiated by a survey with the Trimble GeoXH 6000, with the following details being retrospective as the survey that resulted in this summit relocation was conducted on the 20th October 2015.

Accompanying the main P30 list is a sub list entitled the 100m Sub-Twmpau that takes in all Welsh hills at or over 100m and below 200m in height that have 20m or more and below 30m of drop.  It is this sub category that this hill in now included in, as prior to the survey with the Trimble GeoXH 6000 it had not been listed in the sub list adjoined to the original P30 lists on Geoff Crowder’s website.

The survey was conducted in the eastern part of the Bryniau Clwyd range of hills, above the small community of Pentre Bychan which is adjacent to the larger community of Rhosllanerchrugog, and the hill can be accessed from its west where a public footpath traverses the course of the valley where its bwlch is positioned.  However, permission should be sought for those wishing to visit as the summit is not on open access land.  When I visited I asked permission to do so and was kindly directed to the best ascent route.

The name of the hill is The Pimple; this is a locally known name that was given me when I made enquiries during the survey for its bwlch position.  The hill remains unnamed on current Ordnance Survey maps and its locally known name relates directly to the past industrial heritage of the hill, as its summit is made of mining waste that is now stabilised and grassed over.  The uppermost part of the summit is relatively small in area and squat in shape, and hence its name, as it resembles a pimple as it sits upon another elevated part of the hill.

Although prior to the survey with the Trimble GeoXH 6000 the hill was not classified, its summit position was indicated to be at SJ 30075 47320, this is where a 154m spot height appears on current Ordnance Survey maps.   This spot height is positioned in a field which when I visited, had been ploughed and probably seeded.  However there is also high ground to the south-west of where the 154m spot height appears on the ground and each respective high point was surveyed, with the following results:

South-western high point (The Pimple):  153.5m (converted to OSGM15) at SJ 29984 47262

North-eastern high point (154m spot height in field):  153.1m (converted to OSGM15) at SJ 30071 47279

Therefore the position of the relocated summit is at SJ 29984 47262 and is the top of a relatively small and squat mound made of old mining spoil that is now stabilised and grassed over.  This position is not given a spot height on current Ordnance Survey maps but the Trimble result gave it as 0.4m higher when compared to the position where the 154m spot height appears on the ground and approximately 115 metres south-westward from it.

The full details for the hill are:

Cardinal Hill:  Moel y Gamelin

Summit Height:  153.5m (converted to OSGM15)

Name:  The Pimple

OS 1:50,000 map:  117

Summit Grid Reference (New Position):  SJ 29984 47262
Drop:  25.2m (converted to OSGM15)

The Trimble GeoXH 6000 gathering data at the new summit position of The Pimple, with the old position of the summit in the ploughed field in the background of this photograph

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

Myrddyn Phillips (October 2015)

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