Mapping Mountains – Summit Relocations – 200m Twmpau

Coed Ffridd Fawr (SH 869 033) 

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 initiated by Joe Nuttall who produced a summit analysis programme using LIDAR, and then by LIDAR analysis initially conducted by Jim Bloomer and subsequently by Myrddyn Phillips. 

LIDAR image of Coed Ffridd Fawr (SH 869 033)

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 by Myrddyn Phillips

The name the hill is now listed by is Coed Ffridd Fawr and it is adjoined to the Carnedd Wen group of hills which are situated in the south-eastern part of North Wales (Region A, Sub-Region A4), and it is positioned with a minor road to its north and the A470 road to its south, and has the village of Llanbryn-mair towards the east 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 included in the Hills to be surveyed sub list that accompanied the main P30 list, as it was considered not to meet the criteria then used for the main P30 category and it was listed with a summit height of 242m based on a spot height that appears on the Ordnance Survey 1:25,000 Explorer map positioned just to the north of a boundary fence on open hillside at SH 869 033.

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

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. 

LIDAR summit image of Coed Ffridd Fawr (SH 869 033)

LIDAR analysis confirms the highest part of this hill to be positioned in forestry that has recently been felled and is a part of Coed Ffridd Fawr, this comes within the Summit Relocations used within this page heading, and 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 244.0m and this is positioned at SH 86944 03372, this position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and although not a dramatic summit relocation in distance, it is a significant summit relocation from open hillside to being positioned in a recently felled conifer plantation.

 

ills of Wales, and are reproduced below@

The full details for the hill are: 

Group:  Carnedd Wen 

Name:  Coed Ffridd Fawr 

OS 1:50,000 map:  135, 136

Summit Height:  244.0m (LIDAR) 

Summit Grid Reference (New Position):  SH 86944 03372 (LIDAR) 

Bwlch Height:  213.5m (LIDAR) 

Bwlch Grid Reference:  SH 87416 03786 (LIDAR) 

Drop:  30.5m (LIDAR) 

 

Myrddyn Phillips (November 2021)