Mapping Mountains – Hill Reclassifications – Y Trichant

Bwlch y Cefn Bank (SO 123 608) – Pedwar reclassified to Trichant

There has been a reclassification to the listing of Y Trichant due to analysis of LIDAR data by Aled Williams and subsequently confirmed via a survey with the Trimble GeoXH 6000.  Y Trichant is the title for the hills in the 300m height band of the Twmpau (thirty welsh metre prominences and upward) and takes in all Welsh hills at or above 300m and below 400m in height that have a minimum 30m of drop, with the introduction to the re-naming of this list appearing on Mapping Mountains on the 13^th May 2017.

Prior to analysis of LIDAR data this hill was listed as a Pedwar with c 52m of drop based on the 400m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps and an estimated bwlch height of c 348m based on interpolation of bwlch contouring between 340m – 350m.  The criteria for Pedwar status are all Welsh hills at or above 400m and below 500m in height that have a minimum 30m of drop, the list is a joint compilation between Myrddyn Phillips and Aled Williams and it commenced publication on Mapping Mountains on the 30^th January 2017. 

The name of the hill is Bwlch y Cefn Bank and it is situated in the Elfael range of hills with its Cardinal Hill being Gilwern Hill (SO 098 582) and is placed in the Region of Mid and West Wales (Region B, Sub-Region B1).  The hill is positioned above the A 44 road which is to its east and to its north, and the Afon Ieithon (River Ithon) which is to its north-west, with the small community of Llandegley to the north north-east of the hill.

As the summit of the hill is not a part of designated open access land permission to visit should be sought, for those wishing to do so the land to the north-east and the south-west of the hill is a part of designated open access land, and a public footpath crosses between each just to the south-east of this hill’s summit.

The reclassification of Bwlch y Cefn Bank to Trichant status 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:

Bwlch y Cefn Bank

Summit Height:  399.0m

Summit Grid Reference:  SO 12367 60871

Bwlch Height:  347.1m

Bwlch Grid Reference:  SO 12752 60893

Drop:  51.9m

Therefore, the 399.0m LIDAR data produced for the summit position at SO 12367 60871 and the 347.1m LIDAR data produced for the bwlch position at SO 12752 60893 gives this hill 51.9m of drop, and as the summit height is below 400m and in the 300m height band it is sufficient for this hill to be reclassified to Trichant status, with the details from the Trimble GeoXH 6000 survey being 399.9m (converted to OSGM15) summit at SO 12369 60880 and 347.2m (converted to OSGM15) bwlch at SO 12752 60893, giving this hill a summit height below 400m.

The full details for the hill are:

Cardinal Hill:  Gilwern Hill 

Summit Height:  399.9m (converted to OSGM15)

Name:  Bwlch y Cefn Bank

OS 1:50,000 map:  148

Summit Grid Reference:  SO 12369 60880

Drop:  52.7m (converted to OSGM15)

Bwlch y Cefn Bank (SO 123 608) is now included in the Y Trichant listing of hills

My thanks to Aled Williams for sending the details of this hill to me

For details on the survey that confirmed this hill's Trichant status

Myrddyn Phillips (September 2017)