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

Pt. 372m (SJ 215 551)

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.

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 13th May 2017.

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

The hill is being listed by the point (Pt. 372m) 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 a minor road to its immediate south and the B5430 road to its north, and has the village of Llanarmon-yn-Iâl towards the west north-west.

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website the summit height of this hill was listed as c 375m, based on what was thought to be the uppermost contour that appeared on contemporary Ordnance Survey 1:25,000 Explorer maps.

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

Since publication of these P30 lists on Geoff Crowder’s v-g.me website there have been a number of Ordnance Survey maps made available online, some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website, whilst others are current and digitally updated such as the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map.  This mapping had many more spot heights not on other publicly available Ordnance Survey maps, and for this hill it showed a 372m spot height on the area of its summit.

The summit spot height of 372m on the Ordnance Survey Vector Map Local is not a dramatic height revision when compared to some revised heights, but it does come 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.

Therefore, this hill’s new listed summit height is 372m and this was derived from data on the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map, this is 3m lower than the interpolated c 375m summit height that was previously given for this hill.

The full details for the hill are:

Group:  Moel y Gamelin

Name:  Pt. 372m

OS 1:50,000 map:  117

Summit Height (New Height):  372m (spot height)

Summit Grid Reference:  SJ 21512 55133 (spot height)

Bwlch Height:  346m (spot height)

Bwlch Grid Reference:  SJ 21519 55047 (spot height)

Drop:  26m (spot height summit and bwlch)

Myrddyn Phillips (December 2020)