Mapping Mountains – Hill Reclassifications – Major Mountains of Britain and Ireland

Moel Siabod (SH 705 546) – Major deletion

There has been a deletion to the list of the Major Mountains of Britain and Ireland, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and Aled Williams, with the bwlch position based on LIDAR analysis conducted by Aled Williams.

Moel Siabod (SH 705 546)

The criteria for the list that this deletion applies to are:

The Major Mountains of Britain and Ireland - British and Irish hills that have 600m or more of drop.  This list was first published in a downloadable leaflet format by Europeaklist in February 2010.  Its author; Mark Trengove originally listed 119 qualifying hills, with these comprising 82 hills in Scotland, 25 hills in Ireland, 7 hills in Wales, 4 hills in England and 1 hill in the Isle of Man, with a further five Scottish hills listed that fail to qualify by 10m or less of drop.

The Major Mountains of Britain and Ireland by Mark Trengove

The name the hill is listed by is Moel Siabod, and it is positioned with the A5 road to its north-east, the A4086 road to its north-west and the A498 road to its west, and has the small community of Capel Curig towards its north north-east.

When this list was originally published this hill was not included as it was documented with 595m of drop, based on the 872m summit spot height that is adjoined to a triangulation pillar and the 277m spot height that appears on the area of the bwlch on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.  However, the 277m spot height appears on a road which is above the position of the critical bwlch.

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

Since the original publication of this list 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 old Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map.

The details for this hill were re-assessed 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 it had a 272m bwlch spot height positioned at SH 66071 55625, and when coupled with the 872m summit spot height gave this hill 600m of drop.

Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website

However, it was not until the survey with the Trimble GeoXH 6000 that the details for this hill could be accurately re-assessed.  This resulted in a 872.2m summit height, with the author of the list present during this survey, and a 272.3m bwlch height, with the latter position based on LIDAR analysis.  With these vales giving this hill 599.9m of drop.  

Gathering data at the critical bwlch of Moel Siabod

Gathering data at the summit of Moel Siabod

Therefore, the deletion of this hill from Major status was accepted by Mark Trengove and announced in his photo blog on the Relative Hills of Britain Facebook page on the 14.03.18, with this deletion augmented in to the listing of the Major Mountains of Britain and Ireland resulting in the total reverting to 119 qualifying hills.

The full details for the hill are:

Name:  Moel Siabod

OS 1:50,000 map:  115

OS 1:25,000 map:  18

Summit Height:  872.2m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 70524 54631

Bwlch Height:  272.3m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SH 66044 55603

Drop:  599.9m

Myrddyn Phillips (April 2018)