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

Mynydd Bach (SN 992 359) – Trichant reclassified to Sub-Trichant

There has been 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 by LIDAR analysis.

LIDAR image of Mynydd Bach (SN 992 359)

This was initiated by Joe Nuttall who produced a summit analysis programme that used LIDAR with an alternative height map (DEM) allowing identification of summits and cols and thereby drops.  The resulting spreadsheet that Joe produced contains over 29600 hills.

This spreadsheet is being evaluated by DoBIH Editors and others, and for this particular hill it was Jim Bloomer who initially assessed its height and that of its adjacent peak via LIDAR analysis.

Myrddyn Phillips then evaluated this hill’s details via LIDAR analysis and confirmed its height and hence its reclassification to Sub-Trichant status.

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 Mynydd Bach, 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 minor roads to its east, north and west and farther afield it has the A40 road to its south and the B4520 road to its east, and has the hamlet of Merthyr Cynog towards the north 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 listed as a 387m map heighted twin summit with its adjacent hill positioned at SN 992 359.   

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

However, it was not until LIDAR became available that the details for these two hills 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.

The LIDAR result for each hill appears below:

Lan    385.9m summit at SN 98815 36321

Mynydd Bach    385.3m summit at SN 99215 35955

As Lan is higher than Mynydd Bach it is retained as the Trichant, whilst the drop is sufficient for Mynydd Bach to be classified as a Sub-Trichant.

LIDAR image of Lan (SN 988 363) and Mynydd Bach (SN 992 359)

Therefore, the reclassification of this hill to Sub-Trichant status is due to LIDAR analysis, resulting in a 385.3m summit height and a 362.9m bwlch height, with these values giving this hill 22.3m of drop, which is sufficient for it to be classified as a Sub-Trichant.

The full details for the hill are:

Group:  Mynydd Epynt

Name:  Mynydd Bach

OS 1:50,000 map:  160

Summit Height:  385.3m (LIDAR)

Summit Grid Reference:  SN 99215 35955 (LIDAR)

Bwlch Height:  362.9m (LIDAR)

Bwlch Grid Reference:  SN 98996 36093 (LIDAR)

Drop:  22.3m (LIDAR)

Myrddyn Phillips (September 2020)