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

Cae (SN 560 038) – Lesser Dominant deletion

There has been a Significant Name Change to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Cae (SN 560 038)

The criteria for the list that this addition 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.  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, and the list is now available in its entirety on Mapping Mountains in Google Doc format. 

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Cae and this was derived from the Tithe map, and it is adjoined to the Mynydd Sylen group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and is positioned between the stream valleys of the Afon Morlais to its west and the Afon Gwili to its east, and has the towns of Llanelli to the south-west and Pontarddulais to the east.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the main P30 list with a 119m summit height, based on the spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map. 

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with an estimated c 40m of drop, based on the 119m summit spot height and an estimated c 79m bwlch height, based on interpolation of 5m contouring between 75m – 80m, resulting in a dominance value of 33.61%, which was sufficient for Lesser Dominant status.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.  

Therefore, the deletion of this hill from Lesser Dominant status is due to LIDAR analysis, resulting in a 119.0m summit height and an 80.0m bwlch height, with these values giving this hill 39.0m drop and 32.79% dominance, which is insufficient for Lesser Dominant status.

The full details for the hill are:

Group:  Mynydd Sylen

Name:  Cae

OS 1:50,000 map:  159

Summit Height:  119.0m (LIDAR)

Summit Grid Reference:  SN 56069 03819 (LIDAR)

Bwlch Height:  80.0m (LIDAR)

Bwlch Grid Reference:  SN 55961 04021 (LIDAR)

  

Drop:  39.0m (LIDAR)

Dominance:  32.79% (LIDAR)

Myrddyn Phillips (November 2018)