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

Moel Truan (SJ 113 468)

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 name the hill is listed by is Moel Truan 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 the B5429 road to its north, the A494 road to its west and the A5104 road to its south, and has the town of Corwen towards the south-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 340m which was the uppermost contour that appeared on contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps.

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

After the P30 lists were standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with an estimated c 342m summit height based on interpolation of its uppermost 340m ring contour.

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 mapping on the WalkLakes website, and it is this mapping that gives this hill a 344m summit spot height.

Extract from the WalkLakes website

The summit spot height of 344m on the WalkLakes website 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 344m and this was derived from data on the WalkLakes website, this is 2m higher than the interpolated c 342m summit height that was previously given for this hill.

The full details for the hill are:

Group:  Moel y Gamelin

Name:  Moel Truan

OS 1:50,000 map:  116

Summit Height (New Height):  344m (spot height)

Summit Grid Reference:  SJ 11316 46806 (spot height)

Bwlch Height: 296m (spot height)

Bwlch Grid Reference:  SJ 12338 47708 (spot height)

Drop:  48m (spot height summit and bwlch)

Myrddyn Phillips (October 2020)