Mapping Mountains – Summit Relocations – 200m Twmpau

Cae Cownog (SJ 111 135 & SJ 112 135) 

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 LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Cae Cownog (SJ 111 135 and SJ 112 135)

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.  The list is authored by Myrddyn Phillips, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

200m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Cae Cownog and this was derived from the Tithe map, and it is adjoined to the Foel Cedig group of hills, which are situated in the central part of North Wales (Region A, Sub-Region A3), and it is positioned encircled by minor roads, with the B4393 road farther to its north, the B4382 road farther to its south-west and the A495 road farther to its south-east, and has the village of Meifod towards the east.

When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the accompanying Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

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 21m of drop, based on the 212m summit spot height positioned at SJ 11210 13508 that appears on the contemporary Ordnance Survey 1:25,000 Explorer map and the 191m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

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 212.6m positioned at SJ 11200 13509.  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 Cae Cownog (SJ 111 135 and SJ 112 135)

The height produced by LIDAR analysis to the natural summit of this hill is 212.5m and this is positioned at SJ 11199 13511 and SJ 11200 13515, and this 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 either on Ordnance Survey maps or interactive mapping, 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 212.5m and this is positioned at SJ 11199 13511 and SJ 11200 13515, this position is relatively close to where the spot height appears on the Ordnance Survey 1:25,000 Explorer map, and is approximately 10 metres west north-westward from the high point of the raised field boundary. 

 

The full details for the hill are: 

Group:  Foel Cedig 

Name:  Cae Cownog 

OS 1:50,000 map:  125

Summit Height:  212.5m (LIDAR) 

Summit Grid Reference (New Position):  SJ 11199 13511 & SJ 11200 13515 (LIDAR) 

Bwlch Height:  191.0m (LIDAR) 

Bwlch Grid Reference:  SJ 11120 13695 (LIDAR) 

Drop:  21.6m (LIDAR) 

 

Myrddyn Phillips (November 2024)