Mapping Mountains – Significant Height Revisions – 200m Twmpau and Y Trechol - The Dominant Hills of Wales

Pen y Berth (SJ 081 127)  

There has been a Significant Height Revision to a hill that is listed in the 200m Twmpau (thirty welsh metre prominences and upward) as well as Y Trechol - The Dominant Hills of Wales, and which was initiated by a survey with the Trimble GeoXH 6000, with these details being retrospective as the survey that resulted in this height revision was conducted on 19^th October 2014.

The criteria for the two listings that this height revision affects are:


200m Twmpau - these are the Welsh hills at or above 200m and below 300m in height that have a minimum drop of 30m. 

Y Trechol - The Dominant Hills of Wales - these are the 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 name of the hill is Pen y Berth and it is situated in the Y Berwyn range of hills and the survey with the Trimble GeoXH 6000 was conducted in the company of Mark Trengove on a colourful autumnal day in October.

The hill can be accessed from 1km east of the small community of Dolanog on a track that heads north-west and then east to sneak up to the summit from the opposing side of the hill.  The summit area of the hill is given two 280m uppermost ring contours aligned east and west of one another on Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps, with each contour ring given a 282m spot height on the Ordnance Survey enlarged mapping hosted on the Geograph website.

The following results are those obtained with the Trimble GeoXH 6000 for the two points surveyed:

Eastern 282m spot height:  283.7m (converted to OSGM15) at SJ 08322 12748

Western 282m spot height at SJ 08012 12780 not surveyed

Easterly high point of western 280m ring contour:  287.5m (converted to OSGM15) at SJ 08126 12730

The land at SJ 08126 12730 was visually judged to be higher than the land at SJ 08012 12780, therefore the latter position was not surveyed.  The height given this hill on the Ordnance Survey enlarged mapping hosted on the Geograh website is 282m, with the height resulting from the survey with the Trimble GeoXH 6000 being 287.5m (converted to OSGM15).

Therefore this hill’s new summit height is 5.5m higher than its previously listed height which came from the 282m spot height on the Ordnance Survey enlarged mapping hosted on the Geograph website.

The full details for the hill are:

Cardinal Hill:  Carreg y Big

Summit Height (New Height):  287.5m (converted to OSGM15)

Name:  Pen y Berth

OS 1:50,000 map:  125

Summit Grid Reference:  SJ 08126 12730 

 

Drop:  134.2m (converted to OSGM15)

Dominance:  46.68%

Pen y Berth (SJ 081 127) a hill whose height has been significantly revised

For details on the survey that significantly revised the summit height of this hill

Myrddyn Phillips (August 2015)