Mapping Mountains – Significant Height Revisions – The Fours – The 400m Hills of England

Ether Knott (NY 268 171) 

There has been a Significant Height Revision to a hill that is listed in 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 LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Ether Knott (NY 268 171)

The criteria for the list this height revision affects 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, the 400m Sub-Four category, the 390m Sub-Four category and the 390m Double Sub-Four category.  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 Ether Knott, and it is adjoined to the High Raise group of hills, which are situated in the central fells of the Lake District, and it is positioned with the B5289 road to its west and a minor road to its east, and has the village of Grange towards the west.

When the 1^st edition of the The Fours was published by Europeaklist in 2013, this hill was listed with a 419m summit height based on the spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

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

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 Ether Knott (NY 268 171)

When the 2^nd edition of the The Fours – The 400m Hills of England was published by Mapping Mountains Publications in April 2018, the height of this hill was revised to 419.8m based on available LIDAR.  Latest LIDAR analysis gives the highest ground on this hill as 420.1m positioned at NY 26833 17157 and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 420.1m and this was derived from LIDAR analysis, this is 0.3m higher than its previously listed height and 1.1m higher than the 419m spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

 

The full details for the hill are:

Group:  High Raise

Name:  Ether Knott

OS 1:50,000 map:  89, 90

Summit Height (New Height):  420.1m (LIDAR)

Summit Grid Reference:  NY 26833 17157 (LIDAR)

Col Height:  322.4m (LIDAR)

Col Grid Reference:  NY 26877 15910 (LIDAR)

Drop:  97.7m (LIDAR)

 

Myrddyn Phillips and Aled Williams (December 2022)