Mapping Mountains – Hill Reclassifications – Humps

Mynydd Gelliwastad (SN 677 014) – Subhump reclassified to Hump

This is the eighth 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.

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 08.05.12.

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 08.05.12.

Prior to this notification Mark Jackson had listed this hill as a Subhump with c 96m of drop based on the 213m 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 117m 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 113m, and when coupled with this hill’s 213m summit spot height these values give this hill c 100m 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 Penlle’rcastell range of hills and is situated overlooking the M4 motorway which is to its south and the Lower Clydach River which is to its east, with the village of Clydach also positioned to the east of the hill.

The reclassification of this hill from Subhump 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.

The full details for the hill are:

Name:  Mynydd Gelliwastad

Summit Height:  213m

OS 1:50,000 map:  159

OS 1:25,000 map:  165

Summit Grid Reference:  SN 67799 01456

Drop:  c 100m

Myrddyn Phillips (September 2017)