Mapping Mountains – Hill Reclassifications – The Fours - The 400m Hills of England

Reilth Top (SO 284 881) - Four reclassified to 400m Sub-Four

There has been a reclassification to the listing of the The Fours – The 400m Hills of England, with the summit height, col height and their locations, the drop and status of the hill derived from a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and subsequent confirmation by LIDAR analysis conducted by Aled Williams.

Reilth Top (SO 284 881)

The criteria for the list that this reclassification applies to are:

The Fours – The 400m Hills of England.  English hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are three categories of sub hills, with this hill reclassified to the 400m Sub-Four category, the criteria for which are all English hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and the 2^nd edition of the booklet containing this list was published by Mapping Mountains Publications on the 24^th April 2018.

 

The Fours - The 400m Hills of England by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Reilth Top, and it is adjoined to the Cilfaesty group of hills, which are situated in the county of Shropshire close to the Welsh border, and it is positioned encircled by minor roads with the B4385 road to its north and the A488 road to its south-east, and has the town of Bishops Castle towards the east.

When the 1^st edition of the The Fours was published by Europeaklist in December 2013, this hill was included as a Four and listed with an estimated c 30m of drop, based on an estimated c 406m summit height and an estimated c 376m col height, with both heights based on interpolation of 5m contouring that appear on the contemporary Ordnance Survey 1:25,000 Explorer map.

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

Its reclassification is due to a Trimble GeoXH 6000 survey, resulting in a 404.6m summit height and a 375.6m col height, with these values giving this hill 29.0m of drop.

Gathering data at the summit of Reilth Top (SO 284 881)

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 image of Reilth Top (SO 284 881)

Therefore, the confirmation of the reclassification of this hill to 400m Sub-Four status is due to a Trimble GeoXH 6000 summit survey and subsequent LIDAR col analysis, resulting in a 404.6m summit height and a 375.4m col height, with these values giving this hill 29.2m of drop, which is sufficient for it to be classified as a Four.

The full details for the hill are:

Group:  Cilfaesty

Name:  Reilth Top

OS 1:50,000 map:  137

Summit Height:  404.6m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SO 28458 88105 (Trimble GeoXH 6000)

Col Height:  375.4m (LIDAR)

Col Grid Reference:  SO 28878 87840 (LIDAR)

Drop:  29.2m (Trimble GeoXH 6000 summit and LIDAR col)

For the additions, deletions and reclassifications to The Fours – The 400m Hills of England reported on Mapping Mountains since the December 2013 publication of the 1^st edition of this list by Europeaklist please consult the following Change Registers:

The Fours

The Fours – 400m Sub-Four

The Fours – 390m Sub-Four

The Fours – 390m Double Sub-Four

Myrddyn Phillips and Aled Williams (April 2017)