Mapping Mountains – Hill Reclassifications – The 500-Metre Tops of England and Wales – Deweys

Mynydd Graig Goch (SH 497 485) – Dewey deletion

This is one in a series of retrospective Hill Reclassification posts that detail hills whose status has altered in the listing of the Deweys and where I have had direct association with the status change.  These posts will tie in with a forthcoming Change Register giving detail to this list and its alterations since publication in the Mountain tables book.

Mynydd Graig Goch (SH 497 485)

The 500-Metre Tops of England and Wales are affectionately known after their hill list compiler; Michael Dewey.  This list mixes metric and imperial height in its criteria to bookend up to the 2000ft height band and takes in all hills in England, Isle of Man and Wales that are 500m and above and below 2000ft (609.6m) in height that have 30m minimum drop.

This list formed one of a number of lists that appeared in the Mountain tables book published by Constable in 1995 and at the time of publication comprised 373 hills with 164 in England, 5 in the Isle of Man and 204 in Wales.  The Deweys have undergone extensive revision since first publication with the initial stages forming the basis of this revision given below:

1995    Mountain tables published by Constable with 373 hills listed as Deweys.

April 2000    Strider (LDWA quarterly booklet) publishes contact details for David Purchase and Myrddyn Phillips who have found and list 24 and 14 possible new 500m tops respectively.

It was expanded versions of the above two lists that formed the basis of the next publication:

25^th May 2000    List of Possible 500 Metre Tops by Michael Dewey listing 44 hills.

David Purchase expands his Additional Dewey 500m Hills and Myrddyn Phillips produces lists of English 500m hills to measure and Welsh 500m hills to measure.

These lists formed the basis of the next publication:

29^th June 2000    Possible/Probable 500’s by Michael Dewey listing 77 hills.  Michael adopts following protocol; if one person proposes that a top should qualify as a 500 by personal survey, and is then confirmed by a second person, it should then be promoted to the main list.

April 2002    The 500+ Tops of England and Wales – The ‘New Deweys’ published in the Strider booklet and listing 66 new qualifying hills.

25^th May 2006    Rob Woodall republishes Michael’s main and possible/probable lists on the RHB Yahoo group file database. 

 

Mountain tables by Michael Dewey

The details for this deletion appear below:

The name the hill was listed by in the Deweys is Mynydd Graig Goch, and it is adjoined to the Moel Hebog group of hills which are situated in the north-western part of north Wales, and it is positioned with the B4418 road to its north, the A487 road to its west and the A498 and A4085 roads to its east, and has the village of Pen-y-groes towards the north north-west.

This hill was included in the original 1995 Constable publication and listed with a 609m summit height which appeared as a spot height on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps, and latterly with an estimated c 71m of drop with an estimated bwlch height of c 539m.

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

As its 609m summit spot height was near the benchmark height of 2000ft (609.6m) it was prioritised for a GNSS survey by John Barnard who approached Leica Geosystems suggesting that a joint survey with the fledgling team of G&J Surveys could take place.  Leica Geosystems were enthusiastic for this to happen and the hill was surveyed on the 11^th August 2008.

Mynydd Graig Goch was surveyed by James Whitworth of Leica Geosystems using a Leica SmartRover 1200 and two hours of data were gathered in testing conditions, resulting in a summit height at that time of 609.72m.  These data were reprocessed by Ordnance Survey resulting in a summit height of 609.75m which when converted using OSGM15 results in a summit height of 609.8m, which is higher than 2000ft  (609.6m) and therefore exceeds the height for Dewey classification and qualifies for that of Hewitt status.

The Leica SmartRover 1200 gathering data at the summit of Mynydd Graig Goch

These details were forwarded to the list author; Michael Dewey and the hill was deleted from the list in August 2008 and its newly acquired summit height and its ramifications was announced via a press conference on the 19^th September 2008.

The full details for the hill are:

Name:  Mynydd Graig Goch

OS 1:50,000 map:  115, 123

OS 1:25,000 map:  17, 254

Summit Height:  609.8m (Leica SmartRover 1200)

Summit Grid Reference:  SH 49732 48518 (Leica SmartRover 1200)

Bwlch Height:  c 538 (interpolation)

Bwlch Grid Reference:  SH 50960 48794 (interpolation)

Drop:  c 72m (Leica SmartRover 1200 summit and interpolated bwlch)

Myrddyn Phillips (September 2020)