Mapping Mountains – Hill Reclassifications – Humps

Banc y Graig (SN 699 452) – Hump reclassified to Subhump

This is the thirty sixth 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.

Banc y Graig (SN 699 452)

Many preceding posts detailing these hill reclassifications are retrospective as they were initiated from studying the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map, 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 RHB Yahoo Group forum in relation to this hill was dated 09.09.19.

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, irrespective of their height.  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) instigated by study of contemporary Ordnance Survey maps conducted by Myrddyn Phillips.

The name the hill is listed by is Banc y Graig and it is adjoined to the Elenydd group of hills, and it is positioned with the A482 road to its south-west and the A483 road to its south-east, and has the town of Llanbedr Pont Steffan (Lampeter) towards the west north-west and the town of Llanymddyfri (Llandovery) towards the south-east.

Prior to this reclassification this hill was listed as a Hump with 101m of drop based on the 408m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps and a bwlch height of 307m based on the spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map.  This spot height is also shown on Ordnance Survey data that appears on the Magic Maps website.

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

Extract from the Magic Maps website

The details for this hill were re-assessed using a combination of various scaled Ordnance Survey maps, including the mapping on the OS Maps website.  This is the replacement for OS Get-a-map and has contours at 5m intervals which are proving consistently more accurate compared to the 5m contours that sometimes appear on Ordnance Survey 1:25,000 Explorer maps and used to appear on the online Vector Map Local.

Extract from the OS Maps website

Importantly the 307m spot height that appeared on the Vector Map Local and is still shown on the Magic Maps website is positioned at SN 69521 47114.  This position is not where the 5m contours on the OS Maps website indicate the critical bwlch to be positioned and a better representation of this bwlch height and position is c 309m at SN 69555 47145, and when coupled with the 408m summit height gives this hill an estimated c 99m of drop, which is insufficient for it to be reclassified as a Hump, with the summit of this hill subsequently surveyed with the Trimble GeoXH 6000.

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 14.09.19.

The full details for the hill are:

Name:  Banc y Graig

OS 1:50,000 map:  146

OS 1:25,000 map:  187, 199

Summit Height:  408m (spot height as listed in the Humps, with the Trimble GeoXH 6000 survey giving 408.3m)

Summit Grid Reference:  SN 69981 45212 (hand-held GPS via DoBIH as listed in the Humps, with the Trimble GeoXH 6000 survey giving SN 69992 45216)

Bwlch Height:  c 309m (interpolation)

Bwlch Grid Reference:  SN 69555 47145 (interpolation)

Drop:  c 99m (spot height summit and interpolated bwlch)

Myrddyn Phillips (February 2020)