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

Cefn Uchaf (SN 958 800) – Trichant reclassified to Sub-Trichant

There has been confirmation of a reclassification to a hill that is listed in the 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 conducted by Myrddyn Phillips. 

LIDA image of Cefn Uchaf (SN 958 800)

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 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 now listed by is Cefn Uchaf, and this was derived from the Tithe map, and it is adjoined to the Hirddywel group of hills, which are situated in the northern part of South Wales (Region B, Sub-Region B2), and it is positioned with minor roads to its north, west and south, with the A470 road farther to its north-west and the B4518 road farther to its east, and has the town of Llanidloes 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 included in the accompanying Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 list. 

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

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 30m of drop, based on the 358m summit spot height and the 328m 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.

However, it was not until a Trimble GeoXH 6000 survey and subsequent LIDAR analysis 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 to Sub-Trichant status is due to LIDAR analysis, resulting in a 357.7m summit height and a 329.3m bwlch height, with these values giving this hill 28.4m of drop, which is insufficient for it to be classified as a Trichant. 

 

The full details for the hill are: 

Group:  Hirddywel 

Name:  Cefn Uchaf 

OS 1:50,000 map:  136

Summit Height:  357.7m (LIDAR)                                                           

Summit Grid Reference:  SN 95819 80021 (LIDAR) 

Bwlch Height:  329.3m (LIDAR) 

Bwlch Grid Reference:  SN 95421 80193 (LIDAR) 

Drop:  28.4m (LIDAR) 

 

Myrddyn Phillips (September 2025)