Mapping Mountains – Summit Relocations – 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales

Cae Ffwyn Uchaf (SN 588 005)

There has been a Summit Relocation to a hill that is listed in the 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height, its location, drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Cae Ffwyn Uchaf

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m 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, with the Introduction to 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 Ffwyn Uchaf and this was derived from the Tithe map, and it is the name this 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 B 4296 immediately to its east with the M 4 and the Afon Lliw beyond, and has the town of Gorseinon towards the south.

As the summit of this hill is not a part of designated open access land permission to visit should be sought, for those wishing to do so it is positioned relatively close to a B road which could give access towards the summit from its east.

When this hill was originally listed as a P30 and published in the 30-99m height band of hills on Geoff Crowder’s v-g.me website, and drop values later added it was listed with c 34m of drop based on the 67m spot height that appears on the Ordnance Survey 1:50,000 Landranger map at SN 586 998 and an estimated c 33m bwlch height.

Extract from the Ordnance Survey 1:50,000 Landranger map

The position of this hill’s summit was re-evaluated when the Ordnance Survey Interactive Coverage Map hosted on the Geograph website became available online, this map showed a 67m spot height positioned at SN 588 005.

Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website

However, it was only with the advent of LIDAR that the high point of this hill could be confirmed, with the summit height produced by LIDAR analysis being 66.6m at SN 58825 00532, with LIDAR giving 65.9m at SS 58625 99765 to the position of the previously listed summit.  The position of the new listed summit position in relation to that previously given comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

LIDAR image of the old listed summit position

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 66.6m and is positioned at SN 58825 00532, this position is close to where the 67m spot height appears on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website, and it is approximately 750 metres north from where the previously listed summit is positioned.  With the caveat that the previously listed summit has a covered reservoir positioned at or close to it, and as this is considered a relatively recent man-made construct it is not considered as a part of this hill’s height.

   

The full details for the hill are:

Group:  Mynydd Penlle’rcastell

Name:  Cae Ffwyn Uchaf

OS 1:50,000 map:  159

Summit Height:  66.6m (LIDAR)

Summit Grid Reference (new position):  SN 58825 00532 (LIDAR)

Bwlch Height:  36.0m (LIDAR, natural bwlch)

Bwlch Grid Reference:  SN 59731 00951 (LIDAR, natural bwlch)

 

Drop:  30.6m (LIDAR)

Dominance:  45.90% (LIDAR)

My thanks to Aled Williams for helping to decipher the Tithe name given to the bounded land where the summit of this hill is situated

Myrddyn Phillips (January 2019)