Friday, 7 July 2017

Mapping Mountains – Hill Reclassifications – 30-99m Twmpau

Dinas Dinlle (SH 436 564) – 30-99m Twmpau addition

There has been an addition to the Twmpau (thirty welsh metre prominences and upward) list with this hill being included in the 30-99m height band.  Accompanying all the 100m height band of hills within the Twmpau are sub lists with the one attached to this list being entitled the 30-99m Sub-Twmpau.

The details relating to this hill’s addition are retrospective as its P30 status is due to detail on the Ordnance Survey enlarged mapping hosted on the Geograph website and which was first spotted by Chris Watson, its status has subsequently been confirmed from a survey with the Trimble GeoXH 6000 which was conducted on the 26th December 2013.

The criteria for 30-99m Twmpau status is all Welsh hills at or above 30m and below 100m in height with 30m minimum drop, whilst the criteria for 30-99m Sub-Twmpau status is all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop.

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

The hill is positioned in the Moel Hebog range and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Mynydd Mawr (SH 539 546) 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 some of its western 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 30-99m Twmpau 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 give 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 c 32m of drop. 

The full details for the hill are:

Cardinal Hill:  Mynydd Mawr

Summit Height:  34.7m (converted to OSGM15)

Name:  Dinas Dinlle

OS 1:50,000 map:  115, 123

Summit Grid Reference:  SH 43676 56438

Drop:  c 32m

Dinas Dinlle (SH 436 564) confirmed as a 30-99m Twmpau

Myrddyn Phillips (July 2017)

No comments: