Mapping Mountains – Hill Reclassifications – Yr Uchafion

Cefn Wylfre (SO 145 510) – 490m Sub-Uchaf addition

There has been an addition 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 with the introduction to the list being published on Mapping Mountains 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 addition of this hill affecting the 490m Sub-Uchaf category, with the criteria for inclusion to this sub category being all Welsh hills at or above 490m and below 500m in height that have a minimum 15m of drop.

Prior to analysis of LIDAR data this hill was not classified as its estimated drop was c 15m based on its 489m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 474m based on bwlch contouring between 470m – 480m.

The hill is situated in the Elfael group of hills with its Cardinal Hill being Glascwm Hill (SO 169 525) and is placed in the Region of Mid and West Wales (Region B, Sub-Region B1), with the small communities of Glascwm towards the north north-east, Hundred House towards the north-west and Cregrina towards the west north-west.

The hill is a part of designated open access land and for those wishing to visit there are a number of tracks leading toward the hill from the west and the south, and it can also be combined with its higher neighbours if wanting a longer walk.

The name of the hill is Cefn Wylfre and its addition to the 490m Sub-Uchaf category 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:

Cefn Wylfre

Summit Height:  490.1m

Summit Grid Reference:  SO 14585 51034

Bwlch Height:  474.9m

Bwlch Grid Reference:  SO 14819 51062

Drop:  15.2m

Therefore, the 490.1m LIDAR data produced for the summit position at SO 14585 51034 and the 474.9m LIDAR data produced for the bwlch position at SO 14819 51062 gives this hill 15.2m of drop which when coupled with its height is sufficient for it to be classified as a 490m Sub-Uchaf.

The full details for the hill are:

Cardinal Hill:  Glascwm Hill

Summit Height:  490.1m (LIDAR data)

Name:  Cefn Wylfre

OS 1:50,000 map:  148

Summit Grid Reference:  SO 14585 51034  

 

Drop:  15.2m (LIDAR data)

The overall total for Yr Uchafion / The Welsh 500m P15s remains at 631 hills with the total for the 490m Sub-Uchaf category increasing by one to 63 hills.

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

The Welsh 500m P15s (Yr Uchafion)

The Welsh 500m P15s (Yr Uchafion) – 500m Subs

The Welsh 500m P15s (Yr Uchafion) – 490m Subs

The Welsh 500m P15s (Yr Uchafion) – Double Subs

Myrddyn Phillips and Aled Williams (October 2017)