Mapping Mountains – Summit Relocations – 200m Twmpau

Blaen Pibydd (SN 286 337 and SN 286 336) 

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 produced by JoeNuttall in his surface analysis programme, with subsequent LIDAR analysis conducted by the DoBIH team and independently by Myrddyn Phillips. 

LIDAR image of Blaen Pibydd (SN 286 337 and SN 286 336)

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 Blaen Pibydd and this was derived from the Tithe map, and it is adjoined to the Mynydd Pencarreg group of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned encircled by minor roads, with the B4299 road farther to its south-east, and has the town of Castellnewydd Emlyn (Newcastle Emlyn) towards the north north-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 224m, based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map which is positioned at SN 28673 33662. 

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 analysis gives the highest ground on this hill as 224.4m positioned at SN 28648 33672.  However, this is a part of a raised field boundary and protocols dictate that as this is deemed a relatively recent man-made construct such ground is discounted from the height of a hill. 

LIDAR summit image of Blaen Pibydd (SN 286 337 and SN 286 336)

The height produced by LIDAR analysis to the natural summit of this hill is 223.9m positioned at SN 28692 33707 and SN 28695 33701 and SN 28696 33697 and SN 28694 33695, and this position in relation to the raised field boundary comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour, to a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit of a hill 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 223.9m and this is to the natural summit of the hill which is positioned at SN 28692 33707 and SN 28695 33701 and SN 28696 33697 and SN 28694 33695, although relatively close to where the 224m spot height is positioned, none of these positions are given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and they are approximately 45 metres north-eastward from where the high point of the raised field boundary is positioned. 

 

The full details for the hill are: 

Group:  Mynydd Pencarreg 

Name:  Blaen Pibydd 

OS 1:50,000 map:  145

Summit Height:  223.9m (LIDAR) 

Summit Grid Reference (New Position):  SN 28692 33707 & SN 28695 33701 & SN 28696 33697 & SN 28694 33695 (LIDAR) 

Bwlch Height:  195.0m (LIDAR) 

Bwlch Grid Reference:  SN 28588 33103 (LIDAR) 

Drop:  28.8m (LIDAR) 

 

Myrddyn Phillips (September 2023)