Mapping Mountains – Summit Relocations – 200m Twmpau

 

Cae Tŷ Cefn Ysgubor (SJ 111 080) 

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 Tŷ Cefn Ysgubor (S 111 080)

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 Tŷ Cefn Ysgubor, and this was derived from the Tithe map, and it is adjoined to the Esgeiriau Gwynion group of hills, which are situated in the southern part of North Wales (Region A, Sub-Region A3), and it is positioned with the B4382 road to its north, the A495 road to its north-west and the A458 road to its south, and has the town of Llanfair Caereinion towards the south-west.

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 main P30 list with a 233m summit height, based on the spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map.

After the accompanying 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 36m of drop, based on the 233m summit spot height positioned at SJ 11187 08043 and the 197m 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.  The drop value of this hill has subsequently increased due to a bwlch swap with Erw Hir (SJ 102 076). 

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 235.7m positioned at SJ 11202 08044.  However, this is to the top of a covered reservoir 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 Tŷ Cefn Ysgubor (SJ 111 080)

The height produced by LIDAR analysis to the natural summit of this hill is 233.0m and this is positioned at SJ 11158 08048 and SJ 11173 08045, 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 233.0m and this is positioned at SJ 11158 08048 and SJ 11173 08045, and this position is approximately 44 metres westward from the high point of the covered reservoir. 

 

The full details for the hill are: 

Group:  Esgeiriau Gwynion 

Name:  Cae Tŷ Cefn Ysgubor 

OS 1:50,000 map:  125

Summit Height:  233.0m (LIDAR) 

Summit Grid Reference (New Position):  SJ 11158 08048 & SJ 11173 08045 (LIDAR) 

Bwlch Height:  160.2m (LIDAR) 

Bwlch Grid Reference:  SJ 09294 08676 & SJ 09295 08677 (LIDAR) 

Drop:  72.7m (LIDAR) 

 

Myrddyn Phillips (January 2025)