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

Citron Seat (NY 977 102) – 400m Sub-Four deletion

There has been a deletion from the listing of 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 detail on contemporary maps produced from Ordnance Survey data and subsequently confirmed by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Citron Seat (N 977 102)

The criteria for the list that this deletion 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 being deleted from 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 of the hill is listed by is Citron Seat and it is adjoined to the Great Shunner Fell group of hills, which are situated in the Northern and Central Pennines, and it is positioned above the River Greta and the A66 road which are to its north and the village of Bowes which is to its north north-east.

Prior to analysis of data on OS Maps this hill was listed with an estimated c 20m of drop based on the 446m summit spot height given to a triangulation pillar that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 426m col height, based on interpolation of 10m contouring between 420m – 430m.

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

When the 2^nd edition of the The Fours – The 400m Hills of England was published by Mapping Mountains Publications in April 2018, this hill was not included in the accompanying sub list, as it was considered not to meet the criteria used for this sub category, based on analysis of data on the OS Maps website.  This mapping gives contour intervals at 5m which has enabled the height of the col to be narrowed down when compared to the 10m contour intervals given on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps, resulting in it being listed with an estimated c 18m of drop.

Extract from the interactive mapping hosted on the OS 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 summit image of Citron Seat

LIDAR col image of Citron Seat

Therefore, the confirmation of the deletion of this hill from 400m Sub-Four status is due to LIDAR analysis, resulting in a 446.2m summit height and a 428.6m col height, with these values giving this hill 17.7m of drop, which is insufficient for it to be classified as a 400m Sub-Four. 

The full details for the hill are:

Group:  Great Shunner Fell

Name:  Citron Seat

OS 1:50,000 map:  92

Summit Height:  446.2m (LIDAR)

Summit Grid Reference:  NY 97799 10275 (LIDAR)

Col Height:  428.6m (LIDAR)

Col Grid Reference:  NY 97857 09802 (LIDAR)

Drop:  17.7m (LIDAR)

For the additions, deletions and reclassifications to The Fours reported on Mapping Mountains since the December 2013 publication of the 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 (July 2018)