Mapping Mountains – Hill Reclassifications – 700m Twmpau

Craig Eigiau (SH 713 654) – 700m Sub-Twmpau addition

There has been an addition to the listing of the 700m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Leica RX1250 survey conducted by Alan Dawson, with a previous Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and Aled Williams having taken place.

Craig Eigiau (SH 713 654)

The criteria for the list that this addition applies to are: 

700m Twmpau - Welsh hills at or above 700m and below 800m in height with 30m minimum drop, with an accompanying sub list entitled the 700m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 700m and below 800m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.  The list is authored by Myrddyn Phillips and is available to download in Google Doc format from Mapping Mountains.

700m Twmpau by Myrddyn Phillips

The name the hill is listed by is Craig Eigiau and it is adjoined to the Carnedd Llywelyn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with a minor road to its east and the B5106 road farther to its east, and has the small community of Tal-y-bont towards the north-east.

When the list that later became known as the 700m Twmpau was first compiled, this hill was not included in the accompanying sub list as it was listed with an estimated c 19m of drop, based on the 735m summit spot height that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 716m bwlch height, based on interpolation of 10 contouring between 710m - 720m. 

Extract from the Ordnance Survey 1:25,000 Explorer map

However, it was not until the Trimble GeoXH 6000 survey that the details for this hill could be accurately re-assessed.  This survey resulted in the hill being included as a 700m Sub-Twmpau.  The hill has now been surveyed by Alan Dawson with the Leica RX1250 and it is the height and position produced from this survey that is being prioritised.

The Trimble GeoXH 6000 gathering data at the summit of Craig Eigiau

Therefore, the addition of this hill to 700m Sub-Twmpau status is due to a Trimble GeoXH 6000 survey and a subsequent Leica RX1250 survey, resulting in a 735.0m summit height and a 714.1m bwlch height, with these values giving this hill 20.9m of drop, which is sufficient for it to be classified as a 700m Sub-Twmpau.

The full details for the hill are:

Group:  Carnedd Llywelyn

Name:  Craig Eigiau

OS 1:50,000 map:  115

Summit Height:  735.0m (converted to OSGM15, Leica RX1250)

Summit Grid Reference:  SH 71315 65425 (Leica RX1250) 

  

Bwlch Height:  714.1m (converted to OSGM15, Leica RX1250)

Bwlch Grid Reference:  SH 71191 65460 (Leica RX1250) 

Drop:  20.9m (Leica RX1250)

Myrddyn Phillips (July 2017)