Mapping Mountains – Hill Reclassifications – Y Trichant – The 300m Hills of Wales

Bryn Bras (SN 742 796) – Sub-Trichant reclassified to Trichant

There has been confirmation of a reclassification to the list of Y Trichant – The 300m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Bryn Bras (SN 742 796)

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

Y Trichant – The 300m Hills of Wales – Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13th May 2017.

Y Trichant - The 300m Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Bryn Bras, and it is adjoined to the Pumlumon group of hills, which are situated in the north-western part of Mid and West Wales (Region B, Sub-Region B2), and it is positioned with a minor road to its immediate west and also the A44 road to its north and the A4120 road to its east, and has the village of Ponterwyd towards the north north-east.

When the original 300m height band of Welsh P30 hills was 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 accompanying main P30 list, and was listed with a 372m summit height based on the spot height that appears on the Ordnance Survey 1:50,000 Landranger map.

Extract from the Ordnance Survey 1:50,000 Landranger map

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 372m summit spot height and an estimated c 342m bwlch height based on interpolation of 10m contouring between 340m – 350m that appear on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.

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 and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available maps and showed a 371m spot height for the summit of this hill, and when coupled with the re-interpolated bwlch height of c 371m, its listed drop remained at an estimated 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. 

Therefore, the confirmation of the reclassification of this hill from Sub-Trichant status is due to LIDAR analysis, resulting in a 371.4m summit height and a 339.9m bwlch height, with these values giving this hill 31.5m of drop, which is sufficient for it to be classified as a Trichant.

The full details for the hill are:

Group:  Pumlumon

Name:  Bryn Bras

OS 1:50,000 map:  135, 147

Summit Height:  371.4m (LIDAR)

Summit Grid Reference:  SN 74245 79628 (LIDAR)

Bwlch Height:  339.9m (LIDAR)

Bwlch Grid Reference:  SN 74162 79597 (LIDAR)

Drop:  31.5m (LIDAR)

Myrddyn Phillips (November 2020)