Saturday, 22 April 2017

Mapping Mountains – Hill Reclassifications – Yr Uchafion


Pt. 522.0m (SJ 136 363) - 500m Sub-Uchaf deletion

There has been a deletion from 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 between Myrddyn Phillips and Aled Williams, with details relating to this list being 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 deletion of this hill affecting the 500m Sub-Uchaf classification, with the criteria for qualification to this sub category being all Welsh hills at or above 500m in height that have 14m or more and below 15m of drop.

Prior to analysis of LIDAR data the hill was listed with 14m of drop based on the 522m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps and the 508m bwlch spot height that appears on the Ordnance Survey 1:25,000 Explorer map.

The hill is situated in the Y Berwyn group of hills with its Cardinal Hill being Moel Fferna (SJ 116 397) and is placed in the Region of North Wales (Region A, Sub-Region A4), and is positioned with the small communities of Llanarmon Dyffryn Ceiriog to its south south-east and Pandy to its east.

The hill is situated on open access land and can be accessed from the south or north-east, with public footpaths making their way up to higher ground from the stream valleys containing the Afon Ceiriog and the Afon Teirw respectively.

Although a number of local names for the hill exist it is being catalogued by the point (Pt. 522.0m) notation and its deletion from the 500m Sub-Uchaf category is due to the 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:


Pt. 522.0m

Summit Height:  522.0m (converted to OSGM15)

Summit Grid Reference:  SJ 13615 36369

Bwlch Height:  508.2m (converted to OSGM15)

Bwlch Grid Reference:  SJ 13888 36062

Drop:  13.8m


Therefore, the 522.0m (converted to OSGM15) LIDAR data produced for the summit position at SJ 13615 36369 and the 508.2m (converted to OSGM15) LIDAR data produced for the bwlch position at SJ 13888 36062 gives this hill 13.8m of drop which is insufficient for its retention as a 500m Sub-Uchaf.


The full details for the hill are:

Cardinal Hill:  Craig Berwyn

Summit Height:  522.0m (converted to OSGM15) (LIDAR data)

Name:  Pt. 522.0m

OS 1:50,000 map:  125

Summit Grid Reference:  SJ 13615 36369
   
Drop:  13.8m (converted to OSGM15) (LIDAR data)


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

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 (April 2017)



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