Thursday, 9 February 2017

Mapping Mountains – Hill Reclassifications – Yr Uchafion

Pen Maen Wern (SN 864 620) - Uchaf deletion

There has been a deletion 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 deletion of this hill is from Uchaf to unclassified as it has insufficient drop to qualify for the 500m Sub-Uchaf category.

The hill is situated in the Elenydd group of hills with its Cardinal Hill being Drygarn Fawr (SN 862 584) 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 the Elan Village to its north north-east and is positioned above the Claerwen Reservoir to its north and the Caban-coch Reservoir to its east.

The hill can be accessed from its east where a track heads up onto its lower slopes from the end of a minor road that makes its way to the farm buildings named Rhiwnant.  A narrow path leaves this track and heads westward toward the standing stone atop the 505m map heighted summit at SN 881 613.  From here it is less than 2km to the summit of Pen Maen Wern.

The hill was listed as an Uchaf based on a rudimentary levelling survey conducted by Myrddyn Phillips on 26.06.05 which gave the hill 50ft (15.2m) of drop.  However, the hill’s inclusion in this list was dependent upon its prominence being taken to the top of the standing stone that adorns its summit, as the drop value from its connecting bwlch to ground at the base of the ancient monolith was measured as being 45ft (13.7m), with the height of the standing stone measured as being 5ft (1.52m) high.  Therefore this hill’s inclusion as an Uchaf was dependent upon the height of the ancient standing stone being taken into account.  As this stone has been in situ for over 2,000 years it is considered permanent in nature and therefore it is considered as being a part of the hill.

The name of the hill is Pen Maen Wern and its deletion as an 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 gives the hill the following details:

Pen Maen Wern

Summit Height:  543.2m

Summit Grid Reference:  SN 86433 62011

Bwlch Height:  529.9m

Bwlch Grid Reference:  SN 85875 61850

Drop:  13.3m

Therefore, the 543.2m LIDAR data produced for the summit position at SN 86433 62011 and the 529.9m LIDAR data produced for the bwlch position at SN 85875 61850 gives this hill 13.3m of drop which is insufficient for it to retain its Uchaf status as its drop is below the minimum of 15m required.

The full details for the hill are:

Cardinal Hill:  Drygarn Fawr

Summit Height:  543.2m (LIDAR data)

Name:  Pen Maen Wern

OS 1:50,000 map:  147

Summit Grid Reference:  SN 86433 62011 
Drop:  13.3m (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 25.

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




Pen Maen Wern (LIDAR data) (SN 864 620) Uchaf deletion with 13.3m of drop

Myrddyn Phillips and Aled Williams (February 2017)

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