Thursday, 25 June 2015

Mapping Mountains – Hill Reclassifications – 30m–99m Twmpau

Carreg yr Eryr (SH 526 378) - 30-99m Sub-Twmpau reclassified to 30-99m Twmpau 

There has been a new addition to the listing of Twmpau (thirty welsh metre prominences and upward) hills due to a recent survey with the Trimble GeoXH 6000.  The hill is listed in the 30m-99m height band of Twmpau hills and is situated on the outskirts of Morfa Bychan overlooking Black Rock Sands to its east and Castell Cricieth to its west.

The first time Carreg yr Eryr ever appeared in a hill list was in 2003 when the original Welsh P30 hills under 500m in height were published on Geoff Crowder’s website.  It was then listed in the Sub-List which was named ‘Hills to Survey’.  The reason for this was that Carreg yr Eryr was not given a summit and bwlch spot height that gave it a minimum of 30m of drop on the then current Ordnance Survey map, because of this it was listed as a Sub.  When this list was first published on Geoff’s website it did not include a drop value for each hill, although the qualification for the main list and the Sub-List was based on drop.  These drop values were added at a later date.

When these drop values were added to the list I also decided to include hills in the Main P30 Twmpau list through interpolation of map contours, although some of these details were passed onto Geoff, the great majority were not.  When drop figures were added to the list I gave Carreg yr Eryr c 30m of drop and promoted it into the ranks of P30 hills.  This drop value was estimated from its 53m summit spot height and an estimated bwlch height of c 23m based on the 1:25,000 map bwlch contouring between c 20m – c 30m.  Since this hill was promoted into the P30 ranks the Ordnance Survey enlarged map on the Geograph website has been made available, and this map has contour intervals of 5m and gives the bwlch contouring between c 20m and c 25m, with an estimated bwlch height of c 23m, so the hill remained listed as a P30.  Even though the hill had been promoted in my list the details were never made public, so it was now time to have it Trimbled and to confirm its status via the Mapping Mountains blog.

The full details for the hill are:

Cardinal Hill:  Moel Hebog

Summit Height:  53.3m (converted to OSGM15)

Name:  Carreg yr Eryr

OS 1:50,000 map:  124

Summit Grid Reference:  SH 526 378

Drop:  30.9m (converted to OSGM15)

Carreg yr Eryr (SH 526 378) P30 status now confirmed by the Trimble GeoXH 6000

For details on the survey that confirmed this hill's 30m-99m Twmpau status please click {here}

Myrddyn Phillips (June 2015)

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