Mapping Mountains – Hill Reclassifications – 700m Twmpau

Pt. 714.3m (SH 827 359) – 700m Sub-Twmpau addition

There has been an addition to the listing of the 700m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Aled Williams. 

LIDAR image of Pt. 714.3m (SH 827 359)

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

700m Twmpau - Welsh hills at or above 700m and below 800m in height with 30m minimum drop, with an accompanying sub list entitled the 700m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 700m and below 800m 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 list is authored by Myrddyn Phillips and is available to download in Google Doc format from Mapping Mountains.

The 700m Twmpau by Myrddyn Phillips

The hill is being listed by the point (Pt. 714.3m) notation and it is adjoined to the Arenig Fawr group of hills, which are situated in the central part of North Wales (Region A, Sub-Region A2), and it is positioned with a minor roads to the north, south-west and east, and the A4212 road farther to its north, and has the town of Y Bala towards the east.

When the list that later became known as the 700m Twmpau was first compiled, this hill was not included in the accompanying sub list due to an eye and spirit level survey conducted by John and Anne Nuttall that resulted in 60ft (18.3m) of drop, and it was originally listed with a 712m summit height based on the spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and a 694m bwlch height. 

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 addition of this hill to 700m Sub-Twmpau status is due to LIDAR analysis, resulting in a 714.3m summit height and a 693.6m bwlch height, with these values giving this hill 20.7m of drop, which is sufficient for it to be classified as a 700m Sub-Twmpau.

 

The full details for the hill are:

Group:  Arenig Fawr

Name:  Pt. 714.3m

OS 1:50,000 map:  124, 125

Summit Height:  714.3m (LIDAR) 

Summit Grid Reference:  SH 82741 35938 (LIDAR) 

Bwlch Height:  693.6m (LIDAR) 

Bwlch Grid Reference:  SH 82725 36128 (LIDAR) 

Drop:  20.7m (LIDAR)

 

Myrddyn Phillips (July 2023)