Mapping Mountains – Hill Reclassifications – 100m Twmpau

Close (SJ 094 090) – 100m Twmpau reclassified to 100m Sub-Twmpau

There has been a reclassification 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 Close (SJ 094 090)

The criteria for the list that this reclassification 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.  The list is authored by Myrddyn Phillips, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

100m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Close, and this was derived from the Tithe map, and it is adjoined to the Esgeiriau Gwynion group of hills, which are situated in the southern part of North Wales (Region A, Sub-Region A3), and it is positioned with minor roads to its north, west and north-east, and the A495 road to its south-east, and has the town of Llanfair Caereinion towards the south south-east.

When the original 100m 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.

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 an estimated c 36m of drop, based on the 199m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 163m bwlch height, based on interpolation of 5m contouring between 160m – 165m. 

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 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 197.4m summit height and a 168.6m bwlch height, with these values giving this hill 28.8m of drop, which is insufficient for it to be classified as a 100m Twmpau. 

 

The full details for the hill are: 

Group:  Esgeiriau Gwynion 

Name:  Close 

OS 1:50,000 map:  125

Summit Height:  197.4m (LIDAR) 

Summit Grid Reference:  SJ 09460 09012 (LIDAR) 

Bwlch Height:  168.6m (LIDAR) 

Bwlch Grid Reference:  SJ 08798 09899 & SJ 08797 09900 (LIDAR) 

Drop:  28.8m (LIDAR) 

 

Myrddyn Phillips (January 2025)