Mapping Mountains – Hill Reclassifications – 100m Twmpau

Bryn y Llan or Highermost Gredington (SJ 453 383) - 100m Sub-Twmpau addition

There has been an addition to the listing of the 100m Twmpau (thirty welsh metre prominences and upward) due to analysis of the Ordnance Survey enlarged mapping on the Geograph website by Myrddyn Phillips and which has now been refined and confirmed by analysis of LIDAR data by Aled Williams.  With the criteria for the 100m Twmpau being all Welsh hills 100m or more and below 200m in height with 30m minimum drop.

Accompanying the Twmpau list is a sub list entitled the Sub-Twmpau.  With the criteria for 100m Sub-Twmpau qualification being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with this addition affecting this sub category of hill.

Prior to analysis of the Ordnance Survey enlarged mapping on the Geograph website and the subsequent analysis of LIDAR data the hill was not classified.  Analysis of the Ordnance Survey enlarged map gave the hill an estimated drop of c 23m based on the 114m summit spot height and an estimated bwlch height of c 91m, with these values being sufficient for the hill to be classified as a 100m Sub-Twmpau.

The hill is a part of the Maelor Saesneg group of hills, this part of Wales is the land to the east of the Afon Dyfrdwy (River Dee) and originated as a cantref of the Kingdom of Powys, with its Cardinal Hill being Pt. 157m (SJ 549 440) and is placed in the Region of North Wales (Region A, Sub-Region A4), and is situated with the small community of Hanmer to the north and Cumber’s Bank to the north north-west.

According to the map the summit of the hill is situated in mixed woodland and as it is not a part of open access land permission to visit the high point should be sought.  There is access toward the summit on public footpaths from the north originating from Hanmer that follows the eastern shore of Hanmer Mere, and from the south-west following the boundary of the woodland in its upper section.

The name of the hill is Bryn y Llan or Highermost Gredington and this was derived from the Tithe map by Aled Williams, and its addition to 100m Sub-Twmpau status is due to analysis of the Ordnance Survey enlarged mapping on the Geograph website by Myrddyn Phillips and confirmation of its status via LIDAR data analysed 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:

Bryn y Llan or Highermost Gredington

Summit Height:  115.1m

Summit Grid Reference:  SJ 45301 38375

Bwlch Height:  91.0m

Bwlch Grid Reference:  SJ 51088 36435

Drop:  24.1m

Therefore, the 115.1m LIDAR data produced for the summit position at SJ 45301 38375 and the 91.0m LIDAR data produced for the bwlch position at SJ 51088 36435 gives this hill 24.1m of drop, which is sufficient for its inclusion as a 100m Sub-Twmpau, therefore this hill is included in this sub category and the total in the Twmpau will be updated accordingly.

The full details for the hill are:

Cardinal Hill:  Pt. 157m (SJ 549 440)

Summit Height:  115.1m (LIDAR data)

Name:  Bryn y Llan or Highermost Gredington

OS 1:50,000 map:  126

Summit Grid Reference:  SJ 45301 38375 

  

Drop:  24.1m (LIDAR data)

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

Myrddyn Phillips (April 2017)