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

Cae Felin Wynt (SS 683 954)

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

LIDAR image of Cae Felin Wynt (SS 683 954)

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 Felin Wynt 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 Fforest Fawr group of hills, which are situated in the western part of South Wales (Region C, Sub-Region C2), and it is positioned with the B5444 and the A4217 roads to its west and the Crymlyn Bog to its east, and has the city of Abertawe (Swansea) towards the west south-west.

When this hill was originally listed in the 100m height band of Welsh P30 hills on Geoff Crowder’s v-g.me website, its summit was listed at SS685956 and it appeared with an accompanying note stating; Two points of same height – other at SS681955.

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

Prior to LIDAR analysis this hill was listed with 43m of drop, based on the prioritised 117m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and which is adjoined to a triangulation pillar positioned at SS 68464 95622 and the 74m bwlch spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.

The second 117m map spot height is positioned at SS 68178 95486 with ground to its east leading to a covered reservoir.  The ground at and also close to where each 117m map spot height appears was analysed via LIDAR resulting in the highest natural ground being positioned close to the north-east corner of the covered reservoir, signifying that the natural summit of this hill is now under this man-made construction.

LIDAR close up image of the summit of Cae Felin Wynt

The height produced by LIDAR analysis to the highest natural ground is 118.9m positioned at SS 68320 95490, with LIDAR contouring indicating that the natural summit of this hill is now under the covered reservoir, but as the remaining natural ground beside the covered reservoir is higher than that beside the old listed summit adjacent to the 117m map heighted trig pillar and is at least 100 metres in distance from it this 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 Ordnance Survey's Vector Map Local hosted on the Geograph website with the highest natural ground circled

Therefore the height produced by LIDAR analysis is 118.9m to natural ground and this is positioned at SS 68320 95490, this position is not given a spot height on Ordnance Survey maps and is approximately 200 metres south-westward from where the previously listed summit position is situated beside the 117m map heighted trig pillar that appears on contemporary Ordnance Survey maps.

The full details for the hill are:

Group:  Fforest Fawr

Name:  Cae Felin Wynt

OS 1:50,000 map:  159

Summit Height:  118.9m (LIDAR, natural ground)

Summit Grid Reference:  SS 68320 95490 (LIDAR, natural ground)

Bwlch Height:  74.2m (LIDAR)

Bwlch Grid Reference:  SS 67837 95105 (LIDAR)

Drop:  44.7m (LIDAR)

Dominance:  37.57% (LIDAR)

Myrddyn Phillips (April 2019)