Mapping Mountains – Hill Reclassifications – 100m Twmpau

 

Pt. 152.7m (SH 510 416) – 100m Sub-Twmpau addition

There has been confirmation of an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Pt. 152.7m (SH 510 416)

The criteria for the list that this addition applies to are:

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 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. 

100m Twmpau by Myrddyn Phillips

The hill is being listed by the point (Pt. 152.7m) notation as an appropriate name for it either through local enquiry and/or historic research has not been found by the author, and it is adjoined to the Moel Hebog group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A487 road to its north, the B4411 road to its west, the A497 road to its south and a minor road to its east, and has the town of Cricieth towards the south south-west.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with 20m of drop, based on the 153m summit spot height and the 133m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the confirmation of the addition of this hill to 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 152.7m summit height and a 131.8m bwlch height, with these values giving this hill 20.9m of drop, which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Moel Hebog 

Name:  Pt. 152.7m 

OS 1:50,000 map:  124

Summit Height:  152.7m (LIDAR) 

Summit Grid Reference:  SH 51049 41671 & SH 51051 41671 (LIDAR) 

Bwlch Height:  131.8m (LIDAR) 

Bwlch Grid Reference:  SH 51301 41590 (LIDAR) 

Drop:  20.9m (LIDAR) 

 

Myrddyn Phillips (May 2024)