Tuesday, 2 June 2020

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

Pen Ochr y Bwlch (SH 809 172) – 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.

The hill listed as Pen Ochr y Bwlch in the Deweys (SH 809 172)

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 Pen Ochr y Bwlch, and it is adjoined to the Aran group of hills which are situated in the central part of North Wales, and it is positioned with the A494 road to the north and the A470 road to the south, and has the town of Dolgellau towards the west.

The Name: Pen Ochr y Bwlch is a partly invented and transposed name based on the proximity of Ochr y Bwlch which is a prominent name that appears on contemporary Ordnance Survey maps.  Ochr y Bwlch strictly applies to the steep slope immediately above Bwlch Oerddrws which is to the south south-west of this hill’s summit, and does not necessary apply to either the hill name or its summit.  

This hill was not included in the original 1995 Constable publication, but with a 564m summit spot height and bwlch contouring between 530m – 540m that appear on the Ordnance Survey 1:25,000 Explorer map, the interpolated drop value was estimated sufficient for this hill to be 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 of this hill on the 28th April 2000, resulting in 115ft / 35.1m of drop.  These details were forwarded to the list author; Michael Dewey and the hill was added to the list on the 25th May 2000.

Since the inclusion of this hill in the Dewey list the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and gives a 533m spot height on the area of this hill’s bwlch, and when coupled with the 564m summit spot height these values give this hill 31m of drop according to contemporary Ordnance Survey maps.

The Trimble GeoXH 6000 gathering data at the summit of the hill named Pen Ochr y Bwlch in the Deweys

The Trimble GeoXH 6000 gathering data at the bwlch of the hill named Pen Ochr y Bwlch in the Deweys

This hill was subsequently surveyed by GNSS receiver by Myrddyn Phillips using a Trimble GeoXH 6000 on the 8th March 2014, resulting in a 564.3m summit height and a 530.5m bwlch height, with these values giving this hill 33.8m of drop and confirming its Dewey status.

The full details for the hill are:

Name:  Pen Ochr y Bwlch

OS 1:50,000 map:  124, 125

OS 1:25,000 map:  23

Summit Height:  564.3m (Trimble GeoXH 6000)

Summit Grid Reference:  SH 80957 17269 (Trimble GeoXH 6000)

Bwlch Height:  530.5m (Trimble GeoXH 6000)

Bwlch Grid Reference:  SH 81133 17386 (Trimble GeoXH 6000)

Drop:  33.8m (Trimble GeoXH 6000 summit and bwlch)

Myrddyn Phillips (June 2020)

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