Tuesday, 12 May 2020

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

Blaydike Moss (SD 852 772) – 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.

LIDAR summit image of Blaydike Moss (SD 852 772)

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 Blaydike Moss, and it is adjoined to the Ingleborough group of hills which are situated in the Yorkshire Dales in England, and it is positioned with the B6479 road to its south-west and the B6160 road to its east, and has the village of Horton in Ribblesdale towards the south-west.

This hill was not included in the original 1995 publication, but with a 510m summit spot height and col contouring between 470m – 480m that appear on the Ordnance Survey 1:25,000 Explorer map, this hill has a minimum of 30m of drop according to contemporary Ordnance Survey maps and therefore was an automatic entry to the listing of Deweys. 

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

The above was noted by Myrddyn Phillips and these details were forwarded to the list author; Michael Dewey, and the hill was added to the list on the 3rd 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 477m spot height on the area of this hill’s col, and when coupled with the 510m summit spot height these values give this hill 33m of drop.  The 477m spot height is also shown on Ordnance Survey data that appears on the Magic Maps website.

Extract from the Magic Maps website

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

LIDAR col image of Blaydike Moss

The summit and col heights for this hill were subsequently ascertained from LIDAR analysis conducted by Myrddyn Phillips, resulting in a 510.1m summit height and 476.6m col height, with these values giving this hill 33.5m of drop, confirming its Dewey status. 

The full details for the hill are:

Name:  Blaydike Moss

OS 1:50,000 map:  98

OS 1:25,000 map:  2, 30

Summit Height:  510.1m (LIDAR)

Summit Grid Reference:  SD 85261 77264 (LIDAR)

Col Height:  476.6m (LIDAR)

Col Grid Reference:  SD 84317 77373 (LIDAR)

Drop:  33.5m (LIDAR)

Myrddyn Phillips (May 2020)

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