Mapping Mountains – Hill Reclassifications – 200m Twmpau

 

Parc Pal (SN 354 246) – 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 LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Parc Pal (SN 354 246)

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 Parc Pal 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 A484 road farther to its north-east, the B4299 road farther to its west and the B4298 and A40 roads father to its south, and has the town of Caerfyrddin (Carmarthen) towards the south-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 Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 category.

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 29m of drop, based on the 227m summit spot height adjoined to a triangulation pillar that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 198m bwlch height, based on interpolation of 5m contouring between 195m – 200m. 

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

Since the original publication of the Welsh P30 lists on Geoff Crowder’s v-g.me website there have been a number of maps made available online.  Some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website.  Whilst others were digitally updated such as the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map, whilst others are current and digitally updated such as the interactive mapping on the Magic Maps and WalkLakes websites.

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had a 228m summit spot height and when coupled with the estimated c 198m bwlch height, these values gave this hill an estimated c 30m of drop.

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 227.2m summit height and a 198.6m bwlch height, with these values giving this hill 28.6m 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:  Parc Pal 

OS 1:50,000 map:  145, 159

Summit Height:  227.2m (LIDAR) 

Summit Grid Reference:  SN 35443 24619 & SN 35456 24637 & SN 35458 24640 (LIDAR) 

Bwlch Height:  198.6m (LIDAR) 

Bwlch Grid Reference:  SN 37285 25364 (LIDAR) 

Drop:  28.6m (LIDAR) 

 

Myrddyn Phillips (June 2022)