Mapping Mountains – Summit Relocations – Y Trechol – The Dominant Hills of Wales

Castell y Garn (SM 880 212)

There has been a Summit Relocation to a hill that appears in the Y Trechol – The Dominant Hills of Wales list, with the hill’s height, drop and dominance confirmed by LIDAR analysis conducted by Myrddyn Phillips.

The criteria for the list that this summit relocation 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 addition Welsh P30 hills whose prominence is 33% or more and below 50% of their absolute height.  The list is authored by Myrddyn Phillips and the Introduction to the Mapping Mountains publication of this list appeared on the 3^rd December 2015.

The name of the hill is Castell y Garn (Roch Castle in English) and it is adjoined to the Carn Llidi group of hills, which are situated in the south-western part of Mid and West Wales (Region B, Sub-Region B4), and is positioned with a minor road to its immediate south and the A 487 road to its south-west, and has the small community of Y Garn (Roch) towards the west.

As the summit of the hill is not on designated open access land permission to visit should be sought, for those wishing to do so the high point given by LIDAR analysis is to a rock outcrop that is beside a castle which functions as a hotel.

The summit location for this hill was originally given in the Dominant list to a 121m map heighted hill that has a triangulation pillar at its high point with a 122.685m flush bracket height and which is situated at SM 87859 16326.  Since the initial compilation of this list was completed the Ordnance Survey Interactive Coverage Map hosted on the Geograph website has been made available online and this map gives a 122m summit spot height to the hill listed as Castell y Garn and therefore the summit location for the listed Dominant hill was transferred to the higher map heighted hill, and this summit relocation has now been confirmed by LIDAR analysis.

The summit height produced by 1m DTM LIDAR analysis is 122.8m and is positioned at SM 88048 21231, this position is given a 122m spot height on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website and is approximately 4.8km north from where the previously listed summit position is situated.

LIDAR image of Castell y Garn

The full details for the hill are:

Group:  Carn Llidi

Name:  Castell y Garn

Summit Height:  122.8m (LIDAR)

OS 1:50,000 map:  157

Summit Grid Reference (New Position):  SM 88048 21231 (LIDAR)

  

Drop:  57.3m (LIDAR)

Dominance:  46.69% (LIDAR) 

Myrddyn Phillips (September 2018)