Wednesday, 2 September 2015

Mapping Mountains – Summit Relocations – 100m Twmpau

Gravel Pit Field (SJ 225 167)

There has been a Summit Relocation to the listing of 100m Twmpau (thirty welsh metre prominences and upward) hills due to a survey with the Trimble GeoXH 6000, and these details are retrospective as the survey that resulted in this summit relocation was conducted on 8th August 2015.

The survey was conducted in the lower hills of the Carnedd Wen range, between the small communities of Deuddwr and Collfryn, these are situated between the A495 to the west and the A483 to the east.

The hill was surveyed in the company of Alex Cameron during a multi hill bagging day when the sun beat down and we visited nine P30 Twmpau hills with seven of them being Trimbled.

The name of the land where the summit of this hill is situated is Gravel Pit Field and this was derived from the Tithe map, with the hill having been listed as The Mount in the original P30 lists that appeared on Geoff Crowder’s website, this was a name taken from the farm which is situated southward of this hill's summit. 

Prior to the survey with the Trimble GeoXH 6000 the position of the summit was listed as that of its triangulation pillar which is submerged in a hedge beside a narrow country lane.  This trig pillar has a 153.951m flush bracket height adjoined to it and is given the rounded up height of 154m on current Ordnance Survey maps, with its flush bracket given the position of SJ 22556 16673 in the OS Trig Database.  However, higher ground exists on the opposite side of the lane in a field.

The position of the relocated summit is at SJ 22598 16703 and is the top of featureless ground a few metres from a hedge in a field, this is not given a spot height on current Ordnance Survey maps but the survey result with the Trimble gave it as 0.99m higher than the flush bracket on the triangulation pillar and approximately 50 metres north-eastward from where it stands in a hedge.

The full details for the hill are:

Cardinal Hill:  Carnedd Wen

Summit Height:  154.9m (converted to OSGM15)

Name:  Gravel Pit Field

OS 1:50,000 map:  126

Summit Grid Reference (New Position):  SJ 22598 16703 
Drop:  c 47m

The Trimble GeoXH 6000 gathering data at the new summit position of Gravel Pit Field, with the old position of the summit opposite the gate in the centre right of this photograph

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

Myrddyn Phillips (August 2015)

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