Saturday, 4 June 2016

Mapping Mountains – Hill Reclassifications – 30–99m Twmpau

Daufraich (SM 661 236) - Double Sub-Twmpau addition

There has been an addition to the Sub category within the 30–99m Twmpau (thirty welsh metre prominences and upward) hill list instigated by a survey with the Trimble GeoXH 6000.   The hill is better described as an island and is situated to the west of St David’s in south-west Wales, and forms part of the chain of islands known as the Bishops and Clerks.

The Trimble GeoXH 6000 survey that resulted in this hill’s inclusion as a 30–99m Sub-Twmpau was conducted on the 14th May 2016 in the early afternoon on a fine day in good, dry and sunny conditions.  The trip to this and other islands was organised by Adrian Rayner and the survey took place in the company of Adrian, Rob Woodall, Bob Kerr and Jon Glew, with Sheila Glew, Akako and Sarah Kerr remaining on the RIB whilst we were on the island.

Not surprisingly the island can only be accessed by boat, and although landing is relatively easy the way to the summit involves a scramble, and although not difficult it is exposed, with the prospect of an undignified dunking in the sea a distinct probability if one foot hold proves a wee bit slippy.

The name of the island is Daufraich and it comprises two parts, with its easterly high point being given the map height of 20m, and its westerly high point being given two positions of 21m high on current Ordnance Survey maps.  We only had time to land on the westerly part of the island which proved visually higher than the easterly part.  I also only had time for one survey, and consensus of opinion was that the highest part of the island was where the south-eastern 21m spot height appears on the ground, with the ground where the north-western 21m spot height is positioned being assessed as slightly lower.

Daufraich was not included in the Sub-List which accompanied the original listing of 30m -99m hills that appeared on Geoff Crowders website, as that Sub-List comprised ‘Hills to Survey’ and as this island was under 30m in height it was not included as the only hills that were, were those deemed to have chance of qualifying for the main P30 list after having been surveyed.  However, this Sub-List has now been standardised and includes all hills that are known to have at least 20m of drop and below 30m of drop.

The survey with the Trimble GeoXH 6000 resulted in a 21.7m (converted to OSGM15) summit height, which as an island is also this hill’s drop value, and therefore confirming its entry in to the 30–99m Sub-Twmpau ranks.

The full details for the hill are:

Cardinal Island:  Bishops and Clerks

Summit Height:  21.7m (converted to OSGM15)

Name:  Daufraich

OS 1:50,000 map:  157

Summit Grid Reference:  SM 66199 23673

Drop:  21.7m (converted to OSGM15)

Daufraich (SM 661 236) the new Double Sub-Twmpau

Myrddyn Phillips (May 2016)

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