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

 

Pt. 353.6m (SJ 249 539) 

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 detail on contemporary maps produced from Ordnance Survey data and from LIDAR analysis and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips. 

Pt. 353.6m (SJ 249 539)

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. 

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

The hill is being listed by the point (Pt. 353.6m) notation as an appropriate name for it either through local enquiry and / or historic research has not been found by the author, and it is adjoined to the Moel y Gamelin group of hills, which are situated in the north-eastern part of North Wales (Region A, Sub-Region A2), and it is positioned with minor roads to its north, east and south, the B5430 road to its west and the A525 road farther to its south, and has the village of Bwlchgwyn towards the east south-east. 

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

When the original 300m height band of Welsh P30 hills was published on Geoff Crowder’s v-g.me website, this hill was listed under the transposed and invented name of Gwern Hill with a 353m summit height, based on the spot height that appeared on the Ordnance Survey 1:50,000 Landranger map of the day and which was positioned at SJ 251 543.  This 353m height is based on an old imperial Surface Height of 1158.3ft (353.1m) that appears on the Ordnance Survey series of Six-Inch maps. 

Extract from the Ordnance Survey series of Six-Inch maps

The summit of this hill was subsequently listed as a twin top with the prioritised summit position relocated when the Ordnance Survey Vector Map local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available maps and for this hill a 353m spot height appeared positioned at SJ 250 539. 

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 image of Pt. 353.6m (SJ 249 539)

LIDAR analysis confirms the top positioned at SJ 249 539 as being higher than 353.1m and as this summit has now been surveyed with the Trimble GeoXH 6000 it is this result that is being prioritised for listing purposes, 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. 

The Trimble GeoXH 6000 gathering data at the summit of Pt. 353.6m

Therefore, the summit height produced by the Trimble GeoXH 6000 survey is 353.6m and this is positioned at SJ 24997 53989, this position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and is approximately 380 metres southward from where the previously listed summit is positioned. 

 

The full details for the hill are:

Group:  Moel y Gamelin 

Name:  Pt. 353.6m 

OS 1:50,000 map:  117

Summit Height:  353.6m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference (New Position):  SJ 24997 53989 (Trimble GeoXH 6000) 

Bwlch Height:  c 322m (interpolation) 

Bwlch Grid Reference:  SJ 24041 53999 (interpolation) 

Drop:  c 32m (Trimble GeoXH 6000 summit and interpolated bwlch) 

 

Myrddyn Phillips (November 2021)