Mapping Mountains – Hill Reclassifications – Marilyns

Graig Wen (SH 739 394) – Submarilyn addition

This is one in a series of retrospective Hill Reclassification posts that detail hills whose status has altered in the listing of the Welsh Marilyns.  These reclassification posts will give details of hills where I have had direct association with their change of status, and they will tie in with a forthcoming Change Register giving detail to this list and its alterations since publication in the TACit Tables booklet

The listing of Welsh Marilyns was published in booklet format by TACit Tables in February 1997 and entitled The Hewitts and Marilyns of Wales.  The Marilyns were originally listed as an all British compilation and were published by Cicerone Press in 1992 in the book entitled The Relative Hills of Britain.  The list compiler for the Marilyns is Alan Dawson.

When the Welsh Marilyns list was published in booklet format there were 156 qualifying hills with a further 27 Welsh Submarilyns also included.  The criteria for Marilyn status being any hill that has a drop of at least 150m, irrespective of their height, with the criteria for Submarilyn being any hill that has 140m or more and below 150m of drop.

The Hewitts and Marilyns of Wales by Alan Dawson

The details for the hill reclassification appear below:

The name of the hill is Graig Wen, and it is situated in the Arenig group of hills in the north-western part of Wales, and is positioned with the B4391 road to its north, the A470 road to its west and the A4212 road to its south, and has the village of Ffestiniog towards the north-west and Trawsfynydd towards the south-west.

Prior to this hill’s addition to Submarilyn status it was listed with an estimated c 139m of drop, based on the 556m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger map and an estimated bwlch height of c 417m.

The Trimble GeoXH 6000 set-up position at the summit of Graig Wen 

As its c 139m listed drop was near the benchmark value of 140m it was prioritised for a GNSS survey and this took place on the 1^st July 2017 and the 23^rd December 2017.  The summit was surveyed on the 1^st July by Myrddyn Phillips and Aled Williams and the col was surveyed on the 23^rd December by Myrddyn Phillips, using a Trimble GeoXH 6000 with collection times of five and six minutes respectively.  These surveys resulted in a 555.6m summit height and a 414.6m bwlch height, with these values giving this hill 141.0m of drop.

The Trimble GeoXH 6000 gathering data at the bwlch of Graig Wen

The addition of this hill to Submarilyn status was accepted by the list author; Alan Dawson, and its new classification augmented in to the listing of Marilyns in December 2017.

The full details for the hill are:

Name:  Graig Wen

OS 1:50,000 map:  124

OS 1:25,000 map:  18

Summit Height:  555.6m (converted to OSGM15)

Summit Grid Reference:  SH 73910 39474

Bwlch Height:  414.6m (converted to OSGM15)

Bwlch Grid Reference:  SH 76316 40341

Drop:  141.0m

Myrddyn Phillips (March 2020)