Mapping Mountains – Hill Reclassifications – 200m Twmpau

Pt. 232.1m (SH 675 157) – 200m Sub-Twmpau addition

There has been an addition to the 200m Twmpau list due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

200m Twmpau - Welsh hills at and above 200m and below 300m in height with 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at and above 200m and below 300m 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 18m of drop based on the 233m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 215m bwlch spot height that appears on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website.

Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website

As the name of this hill has not been confirmed by the author the hill is being listed by the point (Pt. 232.1m) notation and it is adjoined to the Cadair Idris group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and the hill is positioned with the A 493 road to its north-west and has the town of Dolgellau towards its east north-east.

The summit of the hill is a part of designated open access land with the most probable and convenient access to the hill via a public footpath approaching this land from a minor road towards the south-west of the summit.

The addition of this hill to 200m 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. 

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

Name:  Pt. 232.1m

Summit Height:  232.1m

Summit Grid Reference:  SH 67577 15753

Bwlch Height:  210.0m

Bwlch Grid Reference:  SH 67357 15854

Drop:  22.1m

LIDAR image of Pt. 232.1m

Therefore, the 232.1m LIDAR analysis for the summit position at SH 67577 15753 and the 210.0m LIDAR analysis for the bwlch position at SH 67357 15854 gives this hill 22.1m of drop, which is sufficient for it to be classified as a 200m Sub-Twmpau.

The full details for the hill are:

Group:  Cadair Idris

Name:  Pt. 232.1m

OS 1:50,000 map:  124

Summit Height:  232.1m (LIDAR)

Summit Grid Reference:  SH 67577 15753 (LIDAR)

Bwlch Height:  210.0m (LIDAR)

Bwlch Grid Reference:  SH 67357 15854 (LIDAR)

Drop:  22.1m (LIDAR)

Myrddyn Phillips (June 2018)