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

Hafod Las (SN 738 506) – Trichant reinstatement 

There has been a reinstatement 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 conducted by Myrddyn Phillips. 

LIDAR image of Hafod Las (SN 738 506)

The criteria for the list that this reinstatement 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 Hafod Las and it is adjoined to the Esgair Wen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north, west, south and east, and has the village of Llanddewibrefi towards the north-west.

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 main P30 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 an estimated c 31m of drop, based on the 385m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and the 1:25,000 Explorer map and an estimated c 354m bwlch height, based on interpolation of 10m contouring between 350m – 360m that appears on the Ordnance Survey 1:25,000 Explorer map. 

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

Since the publication of the P30 lists of Geoff Crowder’s v-g.me website there have been a number of Ordnance Survey maps made available online, some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website, whilst others are current and digitally updated such as the old Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage 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 for this hill it had a 354m bwlch spot height positioned at SN 73649 50811, and when coupled with the 385m summit spot height gave this hill 31m of drop.

The details for this hill were subsequently re-assessed against the mapping on the OS Maps website.  This is the replacement for OS Get-a-map and until recent times had contours at 5m intervals which were proving consistently more accurate compared to the 5m contours that sometimes appear on the Ordnance Survey 1:25,000 Explorer map and used to appear on the online Vector Map Local.  This mapping had bwlch contouring between 355m – 360m with the position of the 354m bwlch spot height shown on the Ordnance Survey Vector Map Local below the 355m contour line.  This re-assessment resulted in the bwlch height being estimated as c 356m and its drop value listed as an estimated c 29m, resulting in its reclassification to Sub-Trichant status.

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 reinstatement of this hill to Trichant status is due to LIDAR analysis, resulting in a 386.1m summit height and a 355.0m bwlch height, with these values giving this hill 31.1m of drop, which is sufficient for it to be classified as a Trichant. 

 

The full details for the hill are: 

Group:  Esgair Wen 

Name:  Hafod Las 

OS 1:50,000 map:  146, 147

Summit Height:  386.1m (LIDAR)                                                           

Summit Grid Reference:  SN 73822 50654 (LIDAR) 

Bwlch Height:  355.0m (LIDAR) 

Bwlch Grid Reference:  SN 73628 50858 & SN 73632 50858 (LIDAR) 

Drop:  31.1m (LIDAR) 

 

Myrddyn Phillips (January 2026)