Mapping Mountains – Hill Reclassifications – Y Trechol – The Dominant Hills of Wales

Cae Ffwyn Uchaf (SN 588 005) – Dominant reclassified to Lesser Dominant

There has been a reclassification to the listing of 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 list that this reclassification applies to are:

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.

Prior to LIDAR analysis this hill was listed with 50.75% dominance based on a c 34m drop value, with a 67m summit spot height on the Ordnance Survey 1:50,000 Landranger map and an estimated bwlch height of c 33 based on interpolation of bwlch contouring between 30m – 35m.

The bounded land where the summit of this hill is situated is named Cae Ffwyn Uchaf on the Tithe map and this is the name 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 B4296 immediately to its east with the M4 and the Afon Lliw beyond, and has the town of Gorseinon towards the south.

 

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 the summit is positioned relatively close to a B road which could give access towards the summit from its east.

The reclassification of Cae Ffwyn Uchaf to Lesser Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips.   The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The DTM LIDAR analysis gives the hill the following details:

Name:  Cae Ffwyn Uchaf

Summit Height:  66.6m

Summit Grid Reference:  SN 58825 00532

Bwlch Height:  36.0m (natural bwlch)

Bwlch Grid Reference:  SN 59731 00951 (natural bwlch)

Drop:  30.6m

Dominance:  45.90%

LIDAR bwlch image of Cae Ffwyn Uchaf

Therefore, the 66.6m LIDAR analysis for the summit position at SN 58825 00532 and the 36.0m LIDAR analysis for the bwlch position at SN 59731 00951 gives this hill 30.6m of drop and 45.90% dominance, which is insufficient for its continued Dominant status, with LIDAR also giving a 65.9m height at SS 58625 99765 which is to the old listed summit of this hill.

 

LIDAR image of the old listed summit at SS 58625 99765

The full details for the hill are:

Group:  Mynydd Penlle’rcastell

Name:  Cae Ffwyn Uchaf

OS 1:50,000 map:  159

Summit Grid Reference:  SN 58825 00532 (LIDAR)

Summit Height:  66.6m (LIDAR)

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

Drop Summit to Bwlch:  30.6m (LIDAR)

Drop Bwlch to ODN:  36.0m (LIDAR, natural bwlch)

Dominance:  45.90% (LIDAR)

Myrddyn Phillips (February 2019)