Saturday, 27 June 2020

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

Pt. 369.4m (SJ 047 509) – 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 and its location confirmed by LIDAR analysis conducted by Myrddyn Phillips, and the bwlch height and its location, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data.

LIDAR image of Pt. 369.4m (SJ 047 509)

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 hill is being listed by the point (Pt. 369.4m) notation as an appropriate name for it either through local enquiry and / or historic research has not been found by the author, 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 B5105 road to its north and minor roads to it immediate west and south-east, with the A494 road further to its south-east, and has the village of Clawddnewydd towards the east north-east.

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 an estimated c 29m of drop, based on an estimated c 370m summit height and the 341m bwlch spot height that appears on the Ordnance Survey 1:25,000 Explorer map.

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 confirmation of the addition of this hill to Sub-Trichant status is due to LIDAR analysis which only covers the summit area and detail derived from contemporary maps produced from Ordnance Survey data, resulting in a 369.35m summit height and a 341m bwlch height, with these values giving this hill 28m 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:  Pt. 369.4m

OS 1:50,000 map:  116

Summit Height:  369.4m (LIDAR)

Summit Grid Reference:  SJ 04708 50996 (LIDAR)

Bwlch Height:  341m (spot height)

Bwlch Grid Reference:  SJ 04933 51669 (spot height)

Drop:  28m (LIDAR summit and spot height bwlch)

Myrddyn Phillips (June 2020)

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