Thursday, 11 May 2017

Mapping Mountains – Hill Reclassifications – Yr Uchafion

Banc yr Ŵyn (SN 771 923) – Double Sub-Uchaf deletion

There has been a reclassification to the listing 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, and details relating to this list were published on the Mapping Mountains site in November 2015.

Accompanying the main Yr Uchafion list are three sub lists; 500m Sub-Uchaf, 490m Sub-Uchaf and the Double Sub-Uchaf categories, with the reclassification of this hill affecting the Double Sub-Uchaf category, with the criteria for inclusion to this sub category being Welsh hills at or above 490m and below 500m in height that have 14m or more and below 15m of drop.

Prior to analysis of LIDAR data by Aled the hill was listed with c 14m of drop based on the 491m summit spot height that appears on the Ordnance Survey enlarged mapping hosted on the Geograph website and an estimated bwlch height of c 477m based on bwlch contouring between 470m – 480m.

The hill is situated in the Pumlumon group with its Cardinal Hill being Pen y Darren (SN 764 942) and is placed in the Region of Mid and West Wales (Region B, Sub-Region B2), and in Welsh terms it is a long way away from any small community.

As the hill is immersed in conifer plantation a route to its summit cannot be advised, although if wanting to visit waiting for the trees to be felled may be the most sensible and easiest option.

The name of the hill is Banc yr Ŵyn and its deletion from the ranks of Double Sub-Uchaf is due to the analysis of LIDAR data by Aled.  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 for the bwlch (summit not covered) gives the hill the following details:

Banc yr Ŵyn

Summit Height:  491m

Summit Grid Reference:  SN 77182 92335

Bwlch Height:  478.1m

Bwlch Grid Reference:  SN 77031 92373

Drop:  13m

Therefore, the 491m summit spot height at SN 77182 92335 and the 478.1m LIDAR data produced for the bwlch position at SN 77031 92373 gives this hill 13m of drop which is insufficient for it to retain its status as a Double Sub-Uchaf.

The full details for the hill are:

Cardinal Hill:  Pen y Darren

Summit Height:  491m

Name:  Banc yr Ŵyn

OS 1:50,000 map:  135

Summit Grid Reference:  SN 77182 92335 
Drop:  13m (OS summit spot height and LIDAR bwlch data)

The overall total for Yr Uchafion / The Welsh 500m P15s is now 631 hills with the total for the Double Sub-Uchaf category now being 5.

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

Myrddyn Phillips and Aled Williams (May 2017)

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