Friday, 24 February 2017

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

Dinas Dinlle (SH 436 564) - Dominant addition

There has been an addition 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 and which was first spotted by Chris Watson, and subsequently confirmed via a survey with the Trimble GeoXH 6000.  This has resulted in the hill being added to the Dominant list.  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 was added to the list shortly after its initial compilation and later appeared in the Moel Hebog group of hills when published on Mapping Mountains on the 28th January 2016.

Prior to Chris Watson raising the probability of this hill being a P30 and its subsequent inclusion as a Dominant hill it had remained unclassified, as the Ordnance Survey 1:50,000 Landranger map gave a 31m summit spot height and bwlch contouring between 0m – 10m, whilst the 1:25,000 Explorer map gave an uppermost 30m ring contour and the same bwlch contouring, which implied that the hill did not have the required 30m of drop to be considered for Dominant status.

The hill is positioned in the Moel Hebog group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) and is situated on the outskirts of the small community that takes its name from the hill; Dinas Dinlle, and is positioned with the sea to its immediate west which has eroded much of its slopes over recent years.  If wanting to visit the hill it can be easily accessed from the car park adjacent to the sea front from where a path heads up its northern slopes.

The name of the hill is Dinas Dinlle and as its name implies the upper section of the hill comprises an ancient hill fort, it was included as a Dominant hill as the Ordnance Survey enlarged mapping hosted on the Geograph website has contours at 5m intervals giving the hill an uppermost contour of 35m and bwlch contouring between 0m – 5m, these values gave the hill an estimated drop of c 31m – c 32m.  The summit of the hill has subsequently been surveyed with the Trimble GeoXH 6000 as being 34.7m (converted to OSGM15) high and with an estimated bwlch height of c 3m this gives the hill 92.16% Dominance.

The full details for the hill are:

Group:  Moel Hebog

Name:  Dinas Dinlle

Dominance:  92.16%

OS 1:50,000 map:  115, 123

Summit Grid Reference:  SH 43676 56438

Summit Height:  34.7m (converted to OSGM15)

Drop Summit to Bwlch:  c 32m

Drop Bwlch to ODN:  c 3m

Dinas Dinlle (SH 436 564) now classified as a Dominant hill

Myrddyn Phillips (February 2017)

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