Mapping Mountains – Hill Reclassifications – Y Trechol – The Dominant Hills of Wales

Pt. 65.9m (ST 352 947) – Dominant reclassified to Lesser Dominant

There has been a reclassification to the listing of Y Trechol – The Dominant 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 Pt. 65.9m (ST 352 947)

The criteria for the list that this reclassification applies to are:

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

As I do not know an appropriate name for this hill either from historic research or local enquiry it is being listed by the point (Pt. 65.9m) notation, and it is adjoined to the Cymoedd Gwent group of hills, which are situated in the eastern part of South Wales (Region C, Sub-Region C2), and it is positioned with the A4042 road to the west and the A449 road to the east, and has the town of Caerllion (Caerleon) towards the south.

When the original 30-99m height band of Welsh P30 hills published on Geoff Crowder’s v-g.me website were standardised with interpolated heights and drop values this hill was listed with a 66m summit height based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 36m based on interpolation of 10m contouring between 30m – 40m, with these values giving this hill an estimated c 30m of drop.

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

When the original Dominants list was compiled this hill was listed as a Dominant based on detail on the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map.  This mapping has additional spot heights not available on any other form of Ordnance Survey publicly available map and in the case of this hill it has a bwlch spot height and 5m contouring.  The bwlch spot height is 33m and when coupled with the 66m summit spot height it gives this hill 33m of drop and 50.00% dominance. 

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website

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.

The reclassification of Pt. 65.9m from Dominant to Lesser Dominant status is due to LIDAR analysis, resulting in a 65.9m summit height and a 34.3m bwlch height, with these values giving this hill 31.6m of drop and 47.93% dominance.

The full details for the hill are:

Group:  Cymoedd Gwent

Name:  Pt. 65.9m

OS 1:50,000 map:  171

Summit Grid Reference:  ST 35225 94717 (LIDAR)

Summit Height:  65.9m (LIDAR)

Bwlch Grid Reference:  ST 35297 94949 (LIDAR)

Drop Summit to Bwlch:  31.6m (LIDAR)

 

Drop Bwlch to ODN:  34.3m (LIDAR)

Dominance:  47.93% (LIDAR)

Myrddyn Phillips (September 2019)