Mynydd Gelliwastad (SN 678 016) – Hump reclassified to Subhump
This is the thirty fourth in a series of Hill Reclassification posts that detail hills whose status has either been altered in the listing of the Humps (HUndred Metre Prominences) through map study and / or surveys that I have instigated, or it is the recommendation that their status is altered.
Many preceding posts detailing these hill reclassifications to the Humps are retrospective as they were initiated from studying the Ordnance Survey Interactive Coverage Map hosted on the Geograph website, or from surveying with the Trimble GeoXH 6000, or from LIDAR analysis, and for this reclassification that affected the Humps the email I posted on the Tump Yahoo Group forum in relation to this hill was dated 31.10.18.
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 hill reclassification appear below:
There has been a reclassification to the listing of the Humps (HUndred Metre Prominences) instigated by LIDAR analysis conducted by Myrddyn Phillips.
This hill has a convoluted history of classification within the Humps with it initially listed as a Subhump with c 96m of drop based on the 213m spot height adjoined to a triangulation pillar positioned at SN 67799 01456 and an estimated bwlch height of c 117m based on bwlch contouring at 10m intervals. This hill was then reclassified to a Hump (see Humps Reclassification post) based on the 213m trig pillar height and interpolation of 5m bwlch contours on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website which refined the estimated height of the bwlch to c 113m, with these values giving this hill c 100m of drop and its reclassification to Hump status was accepted on the 19.07.12.
However, the advent of LIDAR has meant greater accuracy for summit and bwlch heights and their positions, with LIDAR analysis giving this hill a 213.9m summit height positioned at SN 67852 01598 and a 114.8m bwlch height positioned at SN 67677 02435, with these values giving this hill 99.1m of drop, which is insufficient for it to retain its Hump status.
|LIDAR summit image of Mynydd Gelliwastad|
|LIDAR bwlch image of Mynydd Gelliwastad|
The reclassification of this hill from Hump to Subhump status was accepted and its new classification augmented in to the listing of the Humps on the 31.10.18.
The full details for the hill are:
Name: Mynydd Gelliwastad
OS 1:50,000 map: 159
OS 1:25,000 map: 165
Summit Height: 214.0m (LIDAR) (as listed in the Humps)
Summit Grid Reference: SN 67855 01603 (LIDAR) (as listed in the Humps)
Bwlch Height: 114.8m (LIDAR)
Bwlch Grid Reference: SN 6767 0243 (LIDAR) (as listed in the Humps)
Drop: 99.1m (LIDAR)
Myrddyn Phillips (February 2019)