Mapping Mountains – Summit Relocations – 200m Twmpau

Cae Gwar Tŷ (SN 656 640) 

There has been a Summit Relocation to a hill that is listed in the 200m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data and LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Cae Gwar Tŷ (SN 656 640)

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

200m Twmpau – Welsh hills at or above 200m and below 300m in height that have 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or above 200m and below 300m 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. 

The 200m Twmpau y Myrddyn Phillips

The name the hill is now listed by is Cae Gwar Tŷ and this was derived from the Tithe map, and it is adjoined to the Mynydd Bach group of hills, which are situated in the western part of South Wales (Region B, Sub-Region B1), and it is positioned with the A485 road to its west and south, and a minor road to its east, and has the town of Tregaron towards the south south-east.

When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was listed with a summit height of 266m based on the spot height adjoined to a triangulation pillar positioned at SN 65517 64195 that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

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

One of the mapping resources now available online is on the Magic Maps website which hosts an interactive map originated from Ordnance Survey data.  Until recently this mapping had many spot heights not on other publicly available maps and for this hill it had a 266m spot height positioned at SH 656 640. 

Extract from the interactive mapping hosted on the Magic Maps website

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.

The height produced by LIDAR analysis to the summit of this hill is 266.1m positioned at SN 65639 64649, and this position comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies to when the high point is positioned in a different field, to a different feature such as a conifer plantation, within a different map contour, a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is considered a relatively recent man-made construct, 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.

Therefore, the summit height produced by LIDAR analysis is 266.1m which is positioned at SN 65639 64649, this position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and is approximately 160 metres south-eastward from where the previously listed summit is positioned.  However, this position is in close proximity to where the 266m spot height appeared on the interactive mapping hosted on the Magic Maps website. 

 

The full details for the hill are:

Group:  Mynydd Bach 

Name:  Cae Gwar Tŷ 

OS 1:50,000 map:  146

Summit Height:  266.1m (LIDAR) 

Summit Grid Reference (New Position):  SN 65639 64049 (LIDAR) 

Bwlch Height:  c 232m (interpolation) 

Bwlch Grid Reference:  SN 64663 64467 (interpolation) 

Drop:  c 34m (LIDAR summit and interpolated bwlch) 

 

Myrddyn Phillips (December 2022)