Sunday, 12 February 2017

Mapping Mountains – Hill Reclassifications – Yr Uchafion

Cefn Cwm Coel (SN 891 647) - Uchaf reclassified to 500m Sub-Uchaf

Please note; this hill has subsequently been surveyed with the Trimble GeoXH 6000, resulting in a 503.0m summit and 489.6m bwlch height, with these values giving this hill 13.4m of drop.  Therefore, this hill has been deleted from 500m Sub-Uchaf status, with the details below remaining as originally written for future reference.

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 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.

Cefn Cwm Coel (SN 891 647)

The listing of Yr Uchafion includes three sub lists; the 500m Sub-Uchaf, 490m Sub-Uchaf and the Double Sub-Uchaf category.  The reclassification of this hill is from Uchaf to 500m Sub-Uchaf, with the criteria for this sub category being all Welsh hills at or above 500m in height that have 14m or more and below 15m of drop.

The hill is situated in the Elenydd group of hills with its Cardinal Hill being Carn yr Hyrddod (SN 790 704) 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 east and is positioned above the Claerwen Reservoir to its west and the Graig-ddu Reservoir to its east.

The hill can be accessed from its east south-east, starting from a picnic place where a public footpath heads west through conifer and then deciduous woodland contouring round the south-western part of the Graig-ddu Reservoir.  A track then leads up the lower slopes of the hill to open access land and a faint path marked on the Ordnance Survey 1:25,000 Explorer map then heads toward the summit.

The hill was listed as an Uchaf with 15m of drop which is the minimum required for inclusion in the main list, this 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 504m, with the latter map also giving a bwlch spot height of 489m.

The name of the hill is Cefn Cwm Coel and its reclassification from an Uchaf to a 500m Sub-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.  As LIDAR data does not cover this hill’s summit, only the bwlch data can be analysed.

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

Cefn Cwm Coel

Summit Height:  504m

Summit Grid Reference:  SN 89101 64730

Bwlch Height:  489.6m (LIDAR data)

Bwlch Grid Reference:  SN 88436 65371

Drop:  14m (LIDAR data for bwlch)

Therefore, the 504m summit spot height on Ordnance Survey maps at SN 89101 64730 and the 489.6m LIDAR data produced for the bwlch position at SN 88436 65371 gives this hill 14m 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:  Carny yr Hyrddod

Summit Height:  504m

Name:  Cefn Cwm Coel

OS 1:50,000 map:  147

Summit Grid Reference:  SN 89101 64730 
Drop:  14m (LIDAR data for bwlch)

This now brings the overall total for Yr Uchafion / The Welsh 500m P15s to 628 hills and the overall total for the 500m Sub-Uchaf category to 26.

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



Cefn Cwm Coel (LIDAR data for bwlch) (SN 891 647) Uchaf reclassified to 500m Sub-Uchaf with 14m of drop


Myrddyn Phillips and Aled Williams (February 2017)

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