Monday, 29 June 2020

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


Foel Cynfal (SH 749 395) – Dewey addition

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.

Foel Cynfal (SH 749 395)

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:

25th 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:

29th 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.

25th 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 addition appear below:

The name the hill is listed by in the Deweys is Foel Cynfal, and it is adjoined to the Arenig group of hills which are situated in the central part of North Wales, and it 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 Trawsfynydd towards the south-west.

This hill was not included in the original 1995 Constable publication, with no summit spot height on the publicly available Ordnance Survey maps and with an uppermost 540m ring contour and bwlch contouring between 510m – 520m that appear on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, this hill was noted as an outside possibility for a potential new Dewey.

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

The above detail was noted by Myrddyn Phillips who then conducted a basic levelling survey (BLS) of this hill on the 15th July 2000, resulting in 93½ft / 28.5m of drop.  These details were forwarded to the list author; Michael Dewey along with other recent results produced from basic levelling surveys.

Although surveyed as having less than the minimum 30m of drop required to enter this list, the hill was inadvertently included by Michael Dewey.  Its inclusion was subsequently noted during proof reading when an updated copy of the list was received by Myrddyn Phillips.  Although its inclusion in this list was an error, it was for a short period of time listed as a Dewey and therefore the details of this hill are appearing in this Hill Reclassification post and the forthcoming Change Register.

The Trimble GeoXH 6000 gathering data at the summit of Foel Cynfal

The Trimble GeoXH 6000 gathering data at the bwlch of Foel Cynfal

As the margin of uncertainty for the BLS method of surveying over terrain such as that on this hill is approximately +/- 2m and as the resulting 28.5m of drop was near the minimum 30m qualifying drop value, this hill was prioritised for a GNSS survey, and this took place on the 1st July 2017.  The summit and bwlch of this hill were surveyed by Myrddyn Phillips and Aled Williams using a Trimble GeoXH 6000, resulting in a 545.5m summit height and a 517.4m bwlch height, with these values giving this hill 28.1m of drop, and confirming its non-Dewey status.

The full details for the hill are:

Name:  Foel Cynfal

OS 1:50,000 map:  124

OS 1:25,000 map:  18

Summit Height:  545.5m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 74998 39546 (Trimble GeoXH 6000)

Bwlch Height:  517.4m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SH 74884 39528 (Trimble GeoXH 6000)

Drop:  28.1m (Trimble GeoXH 6000)

Myrddyn Phillips (June 2020)

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