Mapping Mountains – Hill Reclassifications – 30-99m Twmpau

Redding (ST 087 776) – 30-99m Sub-Twmpau reclassified to 30-99m Twmpau

There has been confirmation of a reclassification to the list of 30-99m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Redding

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m 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 name of the bounded land where the summit of this hill is situated is Redding, and this was derived from the Tithe map and it is this name that the hill is now being listed by.  The hill is adjoined to the Cymoedd Morgannwg group of hills, which are situated in the central part of South Wales (Region C, Sub-Region C2), and it has the M4 towards its north-west and the A4232 road to its east, and has the city of Caerdydd (Cardiff) towards its east.

This hill was included in the accompanying Hills to be surveyed sub list when the original Welsh 30-99m P30 hills were published on Geoff Crowder’s v-g.me website, as it did not meet the criteria then used for the main P30 list.  The sub list has now been standardised and interpolated drop values and interpolated summit heights have also been included in the main P30 and sub list.

When interpolated heights were used in this list this hill was listed with an estimated c 30m of drop, based on the 81m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 51m based on interpolation of bwlch contouring between 50m – 55m.

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

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website became available online; this mapping is entitled the Interactive Coverage Map, and its larger scale enabled a better assessment of bwlch contouring, this resulted in the same estimated c 51m bwlch height giving this hill the same estimated drop value of c 30m.

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. 

The confirmation of this hill’s reclassification to 30-99m Twmpau status is due to LIDAR analysis, resulting in an 80.3m summit height and a 49.05m bwlch height, with these values giving this hill 31.3m of drop.

The full details for the hill are:

Group:  Cymoedd Morgannwg

Name:  Redding

OS 1:50,000 map:  170

Summit Height:  80.3m (LIDAR, natural summit)

Summit Grid Reference:  ST 08782 77683 (LIDAR, natural summit)

Bwlch Height:  49.05m (LIDAR)

Bwlch Grid Reference:  ST 08551 79827 (LIDAR)

Drop:  31.3m (LIDAR)

Myrddyn Phillips (June 2019)