Mapping Mountains – Hill Reclassifications – Humps

Cefn yr Ogof (SH 916 773) – Subhump reclassified to Hump

This is the tenth in a series of Hill Reclassification posts that detail hills whose status has been altered in the listing of the Humps (HUndred Metre Prominences) through map study and / or surveys that I have instigated.

Cefn yr Ogof (SH 916 773)

This and forthcoming posts are retrospective as many of these hill reclassifications were initiated from studying the Ordnance Survey enlarged mapping that is hosted on the Geograph website, and for the reclassifications that affected the Humps the email I posted on the RHB Yahoo Group forum in relation to this hill was dated 23.05.12.

The listing of Humps was published in book format by Lulu in 2009 and entitled More Relative Hills of Britain, its author; Mark Jackson gives credit to a number of people who contributed toward the formation of this list, these include; Eric Yeaman, Alan Dawson, Clem Clements, Rob Woodall, Bernie Hughes, Pete Ridges and others.  When the list was published in book format there were 2987 Humps listed with their criteria being any British hill that has 100m or more of drop, accompanying the main list is a sub category entitled Subhumps, with the criteria being any British hill that has 90m or more and below 100m of drop.

More Relative Hills of Britain by Mark Jackson

The details for the reclassification appear below:

There has been a reclassification to the listing of the Humps (HUndred Metre Prominences) due to consulting the Ordnance Survey enlarged mapping that is hosted on the Geograph website, with these details being posted on the RHB Yahoo Group forum on 23.05.12.

Prior to this notification Mark Jackson had listed this hill as a Subhump with c 97m of drop based on the 204m summit spot height given to a triangulation pillar on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated bwlch height of c 107m based on bwlch contouring at 10m intervals.  Subsequently bwlch contour interpolation was helped by the use of 5m contour intervals on the Ordnance Survey enlarged mapping hosted on the Geograph website and therefore the estimated bwlch height could be better refined to c 103m – c 104m, and when coupled with this hill’s 204m summit spot height these values give this hill c 100m – c 101m of drop, which is sufficient for it to be reclassified to Hump status.

Extract from the Ordnance Survey enlarged mapping hosted on the Geograph website showing the 5m contour intervals at the bwlch of this hill

The hill is adjoined to the Rhos group of hills and is situated overlooking the A 547 and A 55 roads and the coast which are to its north and the Afon Dulas which is to its west, with the village of Llanddulas to the north-west of the hill.

The addition of this hill to Hump status was accepted by Mark Jackson and its new classification augmented in to the listing of the Humps on the 19.07.12.

Cefn yr Ogof was subsequently surveyed by John Barnard, Graham Jackson and Myrddyn Phillips on the 23.01.14 using a Leica GS15 and a Trimble GeoXH 6000, resulting in this hill having a 204.5m (converted to OSGM15) summit height and a 102.9m (converted to OSGM15) bwlch height, with these values giving this hill 101.6m of drop.

Gathering data with the Leica GS15 at the summit of Cefn yr Ogof

The full details for the hill are:

Name:  Cefn yr Ogof

Summit Height:  204.5m (converted to OSGM15)

OS 1:50,000 map:  116

OS 1:25,000 map:  264

Summit Grid Reference:  SH 91684 77301

Drop:  101.6m (converted to OSGM15)

Myrddyn Phillips (September 2017)