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

 

Lan Ffynnon Las and Disgwylfa (SN 998 433) – Sub-Trichant deletion

There has been a deletion 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 Lan Ffynnon Las and Disgwylfa (SN 998 433)

The criteria for the list that this deletion 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. 

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

The name the hill is listed by is Lan Ffynnon Las and Disgwylfa and this was derived from the Tithe map, and it is adjoined to the Mynydd Epynt group of hills, which are situated in the south-eastern part of Mid and West Wales (Region B, Sub-Region B2), and it is positioned with the B4519 road to its west and the B4520 road to its east, and has the hamlet of Capel Uchaf (Upper Chapel) towards the south south-east. 

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

After the P30 lists were standardised, and interpolated heights and drop values also included, this hill was listed with an estimated c 20m of drop based on the 393m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 373m bwlch height based on interpolation of 10m contouring between 370m – 380m. 

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 deletion of this hill from Sub-Trichant status is due to LIDAR analysis, resulting in a 391.9m summit height and a 372.0m bwlch height, with these values giving this hill 19.9m of drop, which is insufficient for it to be classified as a Sub-Trichant. 

 

The full details for the hill are: 

Group:  Mynydd Epynt 

Name:  Lan Ffynnon Las and Disgwylfa 

OS 1:50,000 map:  147, 160

Summit Height:  391.9m (LIDAR)                                                           

Summit Grid Reference:  SN 99803 43305 (LIDAR) 

Bwlch Height:  372.0m (LIDAR) 

Bwlch Grid Reference:  SN 99999 43777 (LIDAR) 

Drop:  19.9m (LIDAR) 

 

Myrddyn Phillips (January 2021)