Mapping Mountains – Hill Reclassifications – 200m Twmpau

Blaen Pibydd (SN 286 337 & SN 286 336) – 200m Twmpau reclassified to 200m Sub-Twmpau

There has been a reclassification to the list of 200m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail produced by Joe Nuttall in his surface analysis progamme, with subsequent LIDAR analysis conducted by the DoBIH team and independently by Myrddyn Phillips. 

LIDAR image of Blaen Pibydd (SN 286 337 & SN 286 336)

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

200m Twmpau – Welsh hills at or above 200m and below 300m in height that have 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 or 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. 

The 200m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Blaen Pibydd and this was derived from the Tithe map, and it is adjoined to the Mynydd Pencarreg group of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned encircled by minor roads, with the B4299 road farther to its south-east, and has the town of Castellnewydd Emlyn (Newcastle Emlyn) towards the north north-east.

When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the main P30 list with an accompanying note stating; Included by contour configuration.

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with an estimated c 30m of drop, based on the 224m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 194m bwlch height, based on interpolation of 5m contouring between 190m – 195m.                                                               

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 reclassification of this hill to 200m Sub-Twmpau status is due to LIDAR analysis, resulting in a 223.9m summit height and a 195.0m bwlch height, with these values giving this hill 28.8m of drop, which is insufficient for it to be classified as a 200m Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Pencarreg 

Name:  Blaen Pibydd 

OS 1:50,000 map:  145

Summit Height:  223.9m (LIDAR) 

Summit Grid Reference:  SN 28692 33707 & SN 28695 33701 & SN 28696 33697 & SN 28694 33695 (LIDAR) 

Bwlch Height:  195.0m (LIDAR) 

Bwlch Grid Reference:  SN 28588 33103 (LIDAR) 

Drop:  28.8m (LIDAR) 

 

Myrddyn Phillips (September 2023)