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

 

Bryn y Gadair (SN 956 942) – Sub-Trichant addition

There has been confirmation of an addition 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 derived from LIDAR analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips. 

LIDAR image of Bryn y Gadair (SN 956 942)

The criteria for the list that this addition 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 13^th May 2017, and the Introduction to the Mapping Mountains publication of the list appearing on the 1^st January 2022. 

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

The name the hill is listed by is Bryn y Gadair, and it is adjoined to the Pumlumon group of hills, which are situated in the northern part of South Wales (Region B, Sub-Region B1), and it is positioned with the A470 road to its north-east and a minor road to its south, and has the village of Carno towards the north.

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

After 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 24m of drop, based on the 396m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and the 372m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

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 confirmation of the addition of this hill to Sub-Trichant status is due to LIDAR analysis, resulting in a 396.8m summit height and a 370.7m bwlch height, with these values giving this hill 26.1m of drop, which is sufficient for it to be classified as a Sub-Trichant. 

 

The full details for the hill are: 

Group:  Pumlumon 

Name:  Bryn y Gadair 

OS 1:50,000 map:  136

Summit Height:  396.8m (LIDAR)                                                           

Summit Grid Reference:  SN 95697 94281 (LIDAR) 

Bwlch Height:  370.7m (LIDAR) 

Bwlch Grid Reference:  SN 95476 94151 (LIDAR) 

Drop:  26.1m (LIDAR) 

 

Myrddyn Phillips (November 2022)