Sunday, 7 May 2017

Mapping Mountains – Hill Reclassifications – Yr Uchafion

Foel Wyddon (SN 788 836) - Uchaf addition

There has been a new addition to the ranks of Yr Uchafion instigated from analysis of LIDAR data by Aled Williams.  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 in height that have a minimum drop of 15m, the list is a joint compilation between Myrddyn Phillips and Aled Williams, with the details relating to this list being published on the Mapping Mountains site in November 2015.

This hill is given a 535m summit spot height on Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps and has bwlch contouring between 520m – 530m, with an estimated drop based on these map figures of c 13m which is insufficient for qualification as an Uchaf, and therefore prior to the analysis of LIDAR data the hill was not classified.

The hill is adjoined to the Pumlumon group of hills with its Cardinal Hill being Pumlumon Fawr (SN 789 869) and is placed in the Region of Mid and West Wales (Region B, Sub-Region B2), and is situated with the small community of Ponterwyd to its south-west.

The hill is positioned on designated open access land and can be easily accessed via a public footpath on a track from Eisteddfa Gurig which is to the east north-east of the summit.

The name of the hill is Foel Wyddon and its addition to Uchaf status is due to analysis of LIDAR data by Aled Williams.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

Aled’s analysis of LIDAR data gives the hill the following details:

Foel Wyddon

Summit Height:  535.9m (converted to OSGM15)

Summit Grid Reference:  SN 78812 83668

Bwlch Height:  520.9m (converted to OSGM15)

Bwlch Grid Reference:  SN 78784 83859

Drop:  15.0m

Therefore, the 535.9m (converted to OSGM15) LIDAR data produced for the summit position at SN 78812 83668 and the 520.9m (converted to OSGM15) LIDAR data produced for the bwlch position at SN 78784 83859 gives this hill 15.0m of drop, which is sufficient for it to be classified as an Uchaf.

The full details for the hill are:

Cardinal Hill:  Pumlumon Fawr

Summit Height:  535.9m (converted to OSGM15) (LIDAR data)

Name:  Foel Wyddon

OS 1:50,000 map:  135

Summit Grid Reference:  SN 78812 83668 
Drop:  15.0m (converted to OSGM15) (LIDAR data)

The overall total for Yr Uchafion / The Welsh 500m P15s is now 631 hills with the total for the 500m Sub-Uchaf category remaining at 25.

For the additions, reclassifications and deletions to Yr Uchafion / The Welsh 500m P15s reported on Mapping Mountains please consult the following Change Registers:

Foel Wyddon (SN 788 836) now added as an Uchaf.  Photo: Aled Williams

Myrddyn Phillips and Aled Williams (May 2017)

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