Mapping Mountains – Summit Relocations – Y Trichant – The 300m Hills of Wales

 

Y Llan Wern Fawr (SN 893 300) 

There has been a Summit Relocation to a hill that is listed in the Y Trichant – The 300m Hills of Wales, with the summit height, bwlch height and their location, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Y Llan Wern Fawr (SN 893 300)

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

Y Trichant – The 300m Hills of Wales – Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant, with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13^th May 2017, and the Introduction to the Mapping Mountains publication of the list appearing on the 1^st January 2022. 

Y Trichant - The 300m Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Y Llan Wern Fawr and this was derived from the Tithe map, and it is adjoined to the Mynydd Epynt group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north-west and east, and the A40 road to its south, and has the village of Pontsenni (Sennybridge) towards the east south-east. 

When the original 300m height band of Welsh P30 hills was published on Geoff Crowder’s v-g.me website, this hill was listed with an estimated c 350m summit height based on the small uppermost ring contour that appears on the contemporary Ordnance Survey 1:25,000 Explorer 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 summit image of Y Llan Wern Fawr (SN 893 300)

The height produced by LIDAR analysis for the remaining natural summit of this hill is 350.0m and is positioned at SN 89305 30085, with LIDAR analysis also giving a raised field boundary positioned at SN 89295 30077 a height of 350.1m, and this 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 350.0m and this is positioned at SN 89305 30085, this position is to the remaining natural summit of the hill and is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and is approximately 10 metres from where LIDAR indicates the slightly higher raised field boundary to be positioned. 

 

The full details for the hill are:

Group:  Mynydd Epynt 

Name:  Y Llan Wern Fawr 

OS 1:50,000 map:  160

Summit Height:  350.0m (LIDAR)                                                           

Summit Grid Reference (New Position):  SN 89305 30085 (LIDAR) 

Bwlch Height:  318.0m (LIDAR) 

Bwlch Grid Reference:  SN 89043 30577 (LIDAR) 

Drop:  32.1m (LIDAR) 

 

Myrddyn Phillips (February 2022)