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

Coed y Garth (SH 660 165) – Lesser Dominant deletion

There has been a deletion to the listing of Y Trechol – The Dominant Hills of Wales due to analysis of data produced by LIDAR and which was initially conducted by Chris Crocker and George Gradwell, and subsequently by Myrddyn Phillips, with the details relating to this hill taken from the latter’s analysis.

The criteria for inclusion to the Dominant list are all Welsh P30 hills whose prominence equal or exceed half that of their absolute height, whilst the criteria for the Lesser Dominant list are those additional Welsh P30s whose prominence is 33% or more and below 50% of their absolute height.

Prior to analysis of data produced via LIDAR this hill was listed with 35.63% Dominance based on the 87m summit spot height that appears on the Harvey 1:25,000 Cadair Idris Superwalker map and the 56m bwlch spot height on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website, with these values giving this hill 31m of drop.

The name of the hill is Coed y Garth and it is positioned in the Cadair Idris group and is placed in the North Wales Region (Region A, Sub-Region A3), and is situated between the small communities of Arthog to the south-west and Abergwynant to the east north-east.

As the hill is situated in conifer plantation a route to its summit may prove problematic, for those wishing to visit access from the track that crosses its bwlch to the north-east may offer the quickest approach.

The deletion of Coed y Garth from Lesser Dominant status is due to analysis of data produced by LIDAR initially conducted by Chris Crocker and George Gradwell, and subsequently by Myrddyn Phillips, with the details from the latter’s analysis being presented below.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The analysis of data produced via LIDAR gives the hill the following details:

Coed y Garth

Summit Height:  83.4m

Summit Grid Reference:  SH 66061 16545

Bwlch Height:  56.2m

Bwlch Grid Reference:  SH 66291 16811

Drop:  27.1m

Dominance:  not applicable

Therefore, the 83.372m data produced via LIDAR for the summit position at SH 66061 16545 and the 56.238m data produced via LIDAR for the bwlch position at SH 66291 16811 gives this hill 27.134m of drop, with the drop value insufficient for qualification to the Dominant list.

The full details for the hill are:

Group:  Cadair Idris

Name:  Coed y Garth

Dominance:  not applicable

OS 1:50,000 map:  124

Summit Grid Reference:  SH 66061 16545 

Summit Height:  83.4m (data via LIDAR)

Drop Summit to Bwlch:  27.1m (data via LIDAR)

Drop Bwlch to ODN:  56.2m (data via LIDAR)

My thanks to Chris Crocker and George Gradwell for initial LIDAR analysis and bringing the details of this hill to my attention

Myrddyn Phillips (April 2018)