Friday, 4 September 2015

Mapping Mountains – Summit Relocations – 100m Twmpau

Cae Boncyn (SJ 238 193) 

There has been a Summit Relocation initiated by a survey with the Trimble GeoXH 6000 to the listing of 100m Twmpau (thirty welsh metre prominences and upward), with the following details being 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, centred between the small towns of Llansanffraid-ym-Mechain to the hill’s north-west, Llanymynech to the hill’s north-east and Four Crosses to the hill’s south-east, with all three communities being situated beside or close to the Afon Efyrnwy (River Vyrnwy).

The hill was surveyed in the company of Alex Cameron during a multi hill bagging day in lovely sunshine as we visited nine P30 Twmpau hills with seven of them being Trimbled.

The hill is unnamed on current Ordnance Survey maps, having been listed as Bryn y Gelli in the original P30 lists that appeared on Geoff Crowder’s website.  This was an invented name partly taken from the farm which is situated just to the south-west of the summit.  However, when we visited the hill we asked Mel Jones at Gelli Farm for permission to do so and also made enquiries concerning the name of the hill, Mel produced a field map of Gelli Farm with the field where the summit of the hill is situated named as Cae Boncyn, unsurprisingly this is also the name that Mel gave us for the highest field.

Prior to the survey with the Trimble GeoXH 6000 the position of the summit was listed as that of its 142m spot height which is situated at SJ 23882 19312.  This spot height is positioned in an adjacent field to where the highest part of the hill is situated, the distance between these two positions is not great but a relocation of a summit to a different field is important and therefore this information warrants a post under the heading of Summit Relocations.

The position of the relocated summit is at SJ 23849 19306 and is the top of a small hillock, hence the Boncyn part of its name, this is not given a spot height on current Ordnance Survey maps but the survey result produced by the Trimble gave it as 142.1m (converted to OSGM15) and approximately 30-40 metres westward from the position of the spot height on Ordnance Survey maps.

The full details for the hill are:

Cardinal Hill:  Carnedd Wen

Summit Height:  142.1m (converted to OSGM15)

Name:  Cae Boncyn

OS 1:50,000 map:  126

Summit Grid Reference (New Position):  SJ 23849 19306
Drop:  44m

The Trimble GeoXH 6000 gathering data at the new summit position of Cae Boncyn, with the old position of the summit in the adjacent field beyond the wooden fence in the background of this photo

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

Myrddyn Phillips (August 2015)

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