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

Thack Moor (NY 611 462) – 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.

Thack Moor (NY 611 462)

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 Thack Moor, and it is adjoined to the Black Fell group of hills which are situated in the northern Pennines of England, and it is positioned with the A686 road to its south-east and the A689 road to its north-east, and has the small town of Alston towards the east and the small community of Renwick towards the south south-west.

This hill was included in the original 1995 Constable publication and listed with a 609m summit height which is adjoined to a triangulation pillar given the flush bracket height of 609.600m in the OS Trig Database, and which appears as a spot height on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps.

As its 609m summit spot height was near the benchmark height of 2000ft (609.6m) it was prioritised for a GNSS survey and this took place on the 22^nd August 2012.  The summit of this hill was surveyed by John Barnard, Graham Jackson and Myrddyn Phillips using a Leica 530 with two hours of data gathered, resulting in a summit height at the time of 609.645m.

The first Leica 530 survey of Thack Moor

As this result was so close to the benchmark height of 2000ft (609.6m) it was decided to re-visit and gather a further four hours of data.  The second survey was conducted on the 3^rd March 2013 by John Barnard, Graham Jackson and Myrddyn Phillips using a Leica GS15, with Bob Smith editor of the Grough website joining us to write a feature on the survey, and by Aled Williams who also joined us on the summit.  The survey result at that time came to 609.625m which when converted using OSGM15 resulted in a summit height of 609.65m, which is higher than the maximum 2000ft (609.6m) height for Dewey status.

The second Leica GS15 survey of Thack Moor

These details were forwarded to the list author; Michael Dewey and the hill was deleted from his list in April 2013.

The full details for the hill are:

Name:  Thack Moor

OS 1:50,000 map:  86

OS 1:25,000 map:  31

Summit Height:  609.65m (converted to OSGM15, Leica GS15)

Summit Grid Reference:  SN 61166 46278 (Leica GS15)

Col Height:  c 549m (interpolation)

Col Grid Reference:  NY 63681 45681 (interpolation)

Drop:  c 61m (Leica GS15 summit and interpolated col)

Myrddyn Phillips (October 2020)