Mapping Mountains – Significant Height Revisions – Y Trichant – The 300m Hills of Wales

 

Pt. 360.1m (SN 604 447) 

There has been a Significant Height Revision to a hill that is listed in the Y Trichant – The 300m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data and LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Pt. 360.1m (SN 604 447)

The criteria for the list this height revision affects 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 now listed by the Point (Pt. 360.1m) notation, as an appropriate name for it either from historic research or local enquiry has not been found, and it is adjoined to the Elenydd group of hills, which are situated in the central part of the Mid and West Wales Region (Region B, Sub-Region B2), and it is positioned with a minor road to its north-east and the A482 road to its south-west, and has the town of Llanbedr Pont Steffan (Lampeter) towards the north-west. 

When the original 300m height band of Welsh P30 hills was published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list with a summit height of 357m, based on the spot height that appears on the 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 analysis gives the summit height of this hill as 360.1m and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are: 

The term Significant Height Revisions applies to any listed hill whose interpolated summit height and Ordnance Survey or Harvey map summit spot height, has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR.  Also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

LIDAR summit image of Pt. 360.1m (SN 604 447)

Therefore, the new listed summit height for this hill is 360.1m and this was derived from LIDAR analysis, this is 3.1m higher than the previously listed summit height of 357m which appears as a spot height on the contemporary Ordnance Survey 1:25,000 Explorer map. 

 

The full details for the hill are: 

Group:  Elenydd 

Name:  Pt. 360.1m 

OS 1:50,000 map:  146

Summit Height (New Height):  360.1m (LIDAR)                                                           

Summit Grid Reference:  SN 60451 44797 (LIDAR) 

Bwlch Height:  c 324m (interpolation) 

Bwlch Grid Reference:  SN 61574 45299 (interpolation) 

Drop:  c 36m (LIDAR summit and interpolated bwlch) 

 

Myrddyn Phillips (October 2021)