Mapping Mountains – Summit Relocations – 100m Twmpau and Y Trechol – The Dominant Hills of Wales

Cae Ddu Main (SN 622 983)

There has been a Summit Relocation to a hill that is listed in the 100m Twmpau and also now in Y Trechol – The Dominant Hills of Wales, with the summit height, its location, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Cae Ddu Main

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

100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m 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 bounded land where the summit of this hill is situated is Cae Ddu Main and this was derived from the Tithe map, and it is this name that the hill is now listed by.  The hill 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 is positioned with the A483 road to its immediate west and the A48 and M4 to its north, and has the village of Penlle’r-gaer to its north.

If wanting to visit the hill permission to do so should be sought as the summit area is not a part of designated open access land, for those wishing to do so an approach from the north may be feasible.

When the original Welsh 100m P30 list was published on Geoff Crowder’s v-g.me website the summit location of this hill was given to the 102m spot height that is positioned at SS 619 984 on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps.  However, the 1:25,000 Explorer map has a small uppermost 105m ring contour to the east of the 102m spot height.

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

The summit relocation to land within the 105m ring contour has now been confirmed by LIDAR analysis and this land is confirmed as higher than that at the 102m spot height to its west.

The summit height produced by LIDAR analysis is 106.9m to remaining natural ground, and its position in relation to that originally 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.

The summit height produced by LIDAR analysis is 106.9m to remaining natural ground and is positioned at SS 62212 98337, this position is approximately 290 metres east from where the summit was originally listed at the position of the 102m spot height.

The full details for the hill are:

Group:  Mynydd Penlle’rcastell

Name:  Cae Ddu Main

OS 1:50,000 map:  159

Summit Height:  106.9m (LIDAR, remaining natural high point)

Summit Grid Reference (new position):  SN 62212 98337 (LIDAR, remaining natural high point)

Bwlch Height:  69.1m (LIDAR, natural bwlch)

Bwlch Grid Reference:  SN 62051 00000 (LIDAR, natural bwlch) 

Drop:  37.8m (LIDAR)

Dominance:  35.34% (LIDAR)

Myrddyn Phillips (February 2019)