Mapping Mountains – Hill Reclassifications – 100m Twmpau

Pt. 184.3m (SN 202 110) – 100m Twmpau reclassified to 100m Sub-Twmpau

There has been a reclassification to the 100m Twmpau due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

Prior to LIDAR analysis this hill was listed with an estimated c 30m of drop based on the 184m summit height given to a triangulation pillar on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated bwlch height of c 154m based on interpolation of 5m bwlch contouring between 150m – 155m on the Ordnance Survey 1:25,000 Explorer map.

Extract from the Ordnance Survey 1:25,000 Explorer map

As I do not know an appropriate name for this hill it is being listed by the point (Pt. 184.3m) notation, with its previously listed name of Castle Ely Hill being an invention and now considered inappropriate and the Tithe map only giving a generic name of Field.  The hill is adjoined to the Brandy Hill group of hills, which are situated in the south-western part of Mid and West Wales (Region B, Sub-Region B4), and is positioned with the coast to its south and the B 4314 road to its north-east, and has the small community of Rhos-goch (Red Roses) towards its north.

If wanting to visit the hill permission to do so should be sought as it is not a part of designated open access land, for those wishing to do so the nearest public right of way is on a lane / track to the east of the summit.

The reclassification of this hill to 100m Sub-Twmpau status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR image of Pt. 184.3m (SN 20227 11011)

The 1m and 2m DTM LIDAR analysis gives the hill the following details:

Name:  Pt. 184.3m

Summit Height:  184.3m

Summit Grid Reference:  SN 20227 11011

Bwlch Height:  154.7m

Bwlch Grid Reference:  SN 20492 11533

Drop:  29.5m

Therefore, the 184.3m 2m DTM LIDAR analysis for the summit position at SN 20227 11011 and the 154.7m 1m DTM LIDAR analysis for the bwlch position at SN 20492 11533 gives this hill 29.5m of drop, which is not sufficient for its continued 100m Twmpau status.

The full details for the hill are:

Group:  Brandy Hill

Name:  Pt. 184.3m

OS 1:50,000 map:  158

Summit Height:  184.3m (2m DTM LIDAR)

Summit Grid Reference:  SN 20227 11011 (2m DTM LIDAR)

Bwlch Height:  154.7m (1m DTM LIDAR)

Bwlch Grid Reference:  SN 20492 11533 (1m DTM LIDAR)

Drop:  29.5m (LIDAR)

Myrddyn Phillips (September 2018)