Friday, 10 July 2020

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

Ffridd Uchaf (SH 993 500) – 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 confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Ffridd Uchaf (SH 993 500)

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 13th May 2017.

The name the hill is listed by is Ffridd Uchaf and this was derived from the Tithe map, and it is adjoined to the Mynydd Hiraethog group of hills which are situated in the north-eastern part of North Wales (Region A, Sub-Region A2), and it is positioned with the B4501 road to its west and the B5105 road to its south, and has the village of Llanfihangel Glyn Myfyr towards the south.

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s 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. 

When 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 375m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger map and the 351m bwlch spot height that appeared at SH 99666 50565 on the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map.

Extract from the Ordnance Survey 1:50,000 Landranger 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 376.4m summit height and a 350.5m bwlch height, with these values giving this hill 25.9m of drop, which is sufficient for it to be classified as a Sub-Trichant.

The full details for the hill are:

Group:  Mynydd Hiraethog

Name:  Ffridd Uchaf

OS 1:50,000 map:  116

Summit Height:  376.4m (LIDAR)

Summit Grid Reference:  SH 99378 50074 (LIDAR)

Bwlch Height:  350.5m (LIDAR)

Bwlch Grid Reference:  SH 99671 50547 (LIDAR)

Drop:  25.9m (LIDAR)

Myrddyn Phillips (July 2020)

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