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

Pt. 66m (SH 299 270) - Lesser Dominant reclassified to Dominant

There has been a reclassification to the listing of Y Trechol – The Dominant Hills of Wales due to detail included on the Ordnance Survey enlarged mapping hosted on the Geograph website.  This has resulted in the hill being reclassified from a Lesser Welsh Dominant to a Dominant hill.  With the criteria for inclusion to this list being those Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

The details relating to this hill’s inclusion as a Dominant hill are retrospective as it appeared in the Pen Llŷn group of hills when published on the Mapping Mountains site on the 11^th February 2016.

Prior to this hill’s inclusion as a Dominant hill it was included as a Lesser Welsh Dominant hill based on its summit position being at SH 295 266 where the 64m spot height appears on Ordnance Survey 1:25,000 Explorer maps, with its listed drop being c 31m based on an estimated bwlch height of c 33 and a Dominance of 48.44%, importantly this map showed a 60m ring contour to the north-east of this summit, but with no spot height the 64m map heighted summit was listed as the Lesser Welsh Dominant hill.

In more recent years the Ordnance Survey enlarged mapping hosted on the Geograph website has been made publicly available and this scale of mapping shows many spot heights not on any other publicly available map, and the 60m ring contour to the north-east of the 64m map heighted summit is given a 66m summit spot height on this more detailed and larger scaled map, and therefore the summit position of this hill has changed to the higher map heighted hill and because of this the drop value and Dominance of the hill has also altered, and it is now listed with a 66m summit and 32m bwlch height, with both spot heights taken from the enlarged map on the Geograph website.  These values give the hill 34m of drop and 51.52% Dominance.

The hill is in the Pen Llŷn group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Garn Fadrun (SH 278 351), and it is situated with the small community of Llanengan to the west and the small town of Abersoch to the north-east.

If wanting to visit the hill it can be easily ascended as it is near a number of minor roads, however its summit is not a part of open access land so permission to visit should be sought.

The hill is being listed by the point (Pt. 66m) notation as an appropriate name either known locally or from historical research has not been found by the author, although when the old summit was first listed in the sub list that accompanied the P30 Welsh lists that appeared on Geoff Crowder’s v-g.me website it was listed by an invented name of Bryn Llanengan, named after the village to the north-west of the old summit.

The hill is now listed with a 66m summit and 32m bwlch height, with both spot heights taken from the Ordnance Survey enlarged mapping hosted on the Geograph website.  These values give the hill 34m of drop and 51.52% Dominance.

The full details for the hill are:

Group:  Pen Llŷn

Name:  Pt. 66m

Dominance:  51.52%

OS 1:50,000 map:  123

Summit Grid Reference:  SH 29957 27041

Summit Height:  66m

Drop Summit to Bwlch:  34m

Drop Bwlch to ODN:  32m 

Myrddyn Phillips (March 2017)