Wednesday, 15 February 2017

Mapping Mountains – Hill Reclassifications – Yr Uchafion

Blaen y Clawdd Du (SN 878 752) - Uchaf addition

There has been a new entry 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 that have a minimum drop of 15m, 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 listing of Yr Uchafion includes three sub lists; the 500m Sub-Uchaf, 490m Sub-Uchaf and the Double Sub-Uchaf category.  The classification of this hill is from unclassified to Uchaf, as the hill was previously catalogued with insufficient drop even to attain 500m Sub-Uchaf status.

The hill is situated in the Elenydd group of hills with its Cardinal Hill being Draws Drum (SN 790 811) and is placed in the Region of Mid and West Wales (Region B, Sub-Region B2).  The hill is situated with the small community of Llangurig to the north-east and is positioned between the stream valleys of the Afon Elan to the south and the Nant y Trafel Gwyn which flows into the Nant y Dernol to the east.

The hill can be accessed from a forestry road to its north, although this may require a bit of tree bashing to reach its high point unless the track is left for open hillside at the northerly connecting bwlch, or it can be accessed from the south-west where a narrow mountain road gives the opportunity of starting the ascent from approximately 390m high.

The hill was previously catalogued with 13m of drop and therefore thought of as being unclassified, this value was based on detail from Ordnance Survey maps, with the 1:50,000 Landranger, the 1:25,000 Explorer and the enlarged map hosted on the Geograph website all giving a summit spot height of 517m, with the latter map also giving a bwlch spot height of 504m.

The name of the hill is Blaen y Clawdd Du and its classification as an Uchaf 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:

Blaen y Clawdd Du

Summit Height:  516.8m

Summit Grid Reference:  SN 87845 75282

Bwlch Height:  501.2m

Bwlch Grid Reference:  SN 87916 75115

Drop:  15.6m

Therefore, the 516.8m LIDAR data produced for the summit position at SN 87845 75282 and the 501.2m LIDAR data produced for the bwlch position at SN 87916 75115 gives this hill 15.6m of drop which is sufficient for it to be included as an Uchaf  as its drop value is more than the minimum of 15m required.

The full details for the hill are:

Cardinal Hill:  Draws Drum

Summit Height:  516.8m (LIDAR data)

Name:  Blaen y Clawdd Du

OS 1:50,000 map:  135, 136, 147

Summit Grid Reference:  SN 87845 75282 
Drop:  15.6m (LIDAR data)

This now brings the overall total for Yr Uchafion / The Welsh 500m P15s to 629 hills with the overall total for the 500m Sub-Uchaf category remaining at 26.

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


Blaen y Clawdd Du (LIDAR data) (SN 878 752) added as an Uchaf with 15.6m of drop



Myrddyn Phillips and Aled Williams (February 2017)

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