Thursday, 17 November 2016

Mapping Mountains – Hill Reclassifications – Yr Uchafion

Craig Gwaun Taf (SO 005 207) - Uchaf addition

There has been a new addition to the listing of Yr Uchafion instigated from a survey conducted with the Trimble GeoXH 6000.  Yr Uchafion is the draft title for a list of the Welsh 500m P15s that takes in all hills in Wales at or above 500m that have a minimum of 15m of drop, the list is a joint compilation with Aled Williams.  Details relating to this list were published on the Mapping Mountains site in November 2015.

The hill is situated in the Bannau Brycheiniog group of hills in the heartland of the Brecon Beacons National Park in the northern part of south Wales and is situated southward of Corn Du and south-westward of Pen y Fan, with the latter hill being its Cardinal Hill, and is positioned above the towns of Aberhonddu (Brecon) to its north north-east and Merthyr Tudful (Merthyr Tydfil) to its south south-east.  The hill group of Bannau Brycheiniog are referred to in English as the Brecon Beacons and are positioned between the hills of Mynydd Epynt to their north and the hills of the south Wales valleys to their south.

The hill can be easily accessed from the car park at Pont ar Daf to its south south-west with the path leading toward the bwlch just north of its summit; Bwlch Duwynt, being on the Beacons Way and one of the main paths leading to the summit of south Wales’ highest mountain; Pen y Fan.  The hill can also be ascended from near to the Lower Neuadd Reservoir to its south-east where a path heads west to gain height on to the hill’s southerly ridge; this can then be followed to its summit.

The name of the hill is Craig Gwaun Taf and the survey conducted with the Trimble GeoXH 6000 was instigated through communication with Joe Nuttall, who had analysed the height of this hill’s summit and bwlch with LIDAR dataLIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales, and Joe has been diligently checking a number of hills for qualification to his parents 2,000ft list.  These lists are based on a minimum qualifying drop value of 15m and Joe found that LIDAR data gave Craig Gwaun Taf a drop of 15.783m.

However, as mentioned in the first paragraph of this post; if Craig Gwaun Taf has a minimum of 15m of drop it would also be included in the listing of Welsh hills at or over 500m in height that has a minimum of 15m of drop, and has the working title of Yr Uchafion.

Craig Gwaun Taf is given an 824m summit spot height on current Ordnance Survey maps that derives from the 2,704ft height on the series of old Six-Inch maps and has current bwlch contouring between 800m – 810m, with an 815m spot height on the area of the bwlch on the Ordnance Survey enlarged mapping on the Geograph website.  These figures give this hill an approximate c 13m of drop based on interpolation of bwlch contours, or only 9m of drop if based on the 815m Geograph spot height.  However, when Joe Nuttall analysed this hill with LIDAR data he found that it gave the summit as 825.885m and the bwlch as 810.102m, giving a drop value of 15.783m, sufficient for both Uchaf and Nuttall qualification.

The summit consists of a grassy hummock a few metres to the east of the ridge path that crosses the hill, and the 826.4m (converted to OSGM15) height produced by the Trimble is an average of three summit data sets.  On the day of the Trimble survey the bwlch consisted of an elongated shallow puddle stretching across the valley to valley traverse, and the 810.3m (converted to OSGM15) height produced by the Trimble is an average of two bwlch data sets taken from the same position, with a further two data sets also taken on the area of the bwlch, with one data set taken at either end of the shallow puddle.

This now revises the total in Yr Uchafion which will be updated accordingly and the hill is now listed as an Uchaf.

The full details for the hill are:

Cardinal Hill:  Pen y Fan

Summit Height:  826.4 (converted to OSGM15)

Name:  Craig Gwaun Taf

OS 1:50,000 map:  160

Summit Grid Reference:  SO 00548 20720 
Drop:  16.1m (converted to OSGM15)

The reclassifications to Yr Uchafion / The Welsh 500m P15s reported on Mapping Mountains are ills of wales as follows:



Craig Gwaun Taf (SO 005 207, the extended ridge on the right) the new Uchaf

Myrddyn Phillips and Aled Williams (November 2016)

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