Mapping Mountains – Hill Reclassifications – Humps

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)

Mapping Mountains – Summit Relocations – 200m Twmpau and Y Trechol – The Dominant Hills of Wales

Mynydd Gelliwastad (SN 678 015)

There has been a Summit Relocation to a hill that is listed in the 200m Twmapu and Y Trechol – The Dominant Hills of Wales, with the summit height, drop and status of the hill being confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Mynydd Gelliwastad

The criteria for the two lists that this summit relocation applies to are:

200m Twmpau - Welsh hills at or above 200m and below 300m in height with 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

The name of the hill is Mynydd Gelliwastad, and it is adjoined to the Mynydd Penlle’rcastell group of hills, which are situated in the western part of South Wales (Region C, Sub-Region C1), and has the Lower Clydach River, the B 4603 and the A 4067 towards its east and the M 4 towards its south, and has the village of Clydach towards its east.

As the summit of the hill is a part of designated open access land it can be approached from most directions with public footpaths accessing this land from the north and the west.

Prior to LIDAR analysis this hill was listed with c 100m of drop based on the 213m height given to a triangulation pillar positioned at SN 67799 01456 that appears on Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps, and an estimated bwlch height of c 113m based on interpolation of 5m contours between 110m – 115m.

Close up LIDAR image of the summit of Mynydd Gelliwastad

LIDAR image of the bwlch of Mynydd Gelliwastad

The summit height produced by LIDAR analysis is 213.9m at SS 67852 01598 and its position in relation to that previously given comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies to any listed hill whose summit meets the following criteria; where there are a number of potential summit positions within close proximity and the highest point is not where previously given, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist, or when the summit of the hill is in a different field compared to where previously given, or when the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary that is judged to be a relatively recent man-made construct.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 Explorer map is being prioritised in favour of the 1:50,000 Landranger map for detailing these relocations.

Extract from the Ordnance Survey 1:25,000 Explorer map showing the new summit position in relation to the old listed summit position at the trig pillar

The summit height produced by LIDAR analysis is 213.9m and is positioned at SN 67852 01598, this position is not given a spot height on contemporary Ordnance Survey maps but appears within an uppermost 210m contour ring.  This position is approximately 100 metres north from where the previously listed summit is positioned.  

 

The full details for the hill are:

Group:  Mynydd Penlle’rcastell

Name:  Mynydd Gelliwastad

OS 1:50,000 map:  159

Summit Height:  213.9m (LIDAR)

Summit Grid Reference (new position):  SN 67852 01598 (LIDAR)

Bwlch Height:  114.8m (LIDAR)

Bwlch Grid Reference:  SN 67677 02435 (LIDAR) 

 

Drop:  99.1m (LIDAR)

Dominance:  46.33% (LIDAR)

Myrddyn Phillips (January 2019)

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)