The results of the July hill-height surveys by the Munro Society (TMS) have now been published. Three hills were surveyed on 4, 6 and 8 July – all in the remote Fisherfield area and all either just above or just below the 3,000-foot / 914.4-metre line that defines qualification for the list of Munros.
The surveys were conducted by John Barnard, Graham Jackson and Myrddyn Phillips of G & J Surveys, along with a supporting team of fellow TMS members, with sponsorship provided by Lord Haworth of Fisherfield. The new heights were then processed by the Ordnance Survey (OS).
Ruadh Stac Mor had an existing OS height of 918m, with its summit marked by a trig point. The precise height of the flush bracket was given by the OS as 918.65m and TMS surveyors measured it at 918.67m. So in terms of both its mapped height and hill-list status, there is no change: it remains a 918m Munro.
Beinn Dearg Mor, previously regarded as a 910m Corbett, was surveyed as 906.28m. So again its status remains the same – it’s still a Corbett. Exactly when the OS changes the mapped height from 910m to 906m remains to be seen.
Beinn a’Chlaidheimh was mapped as 916m and listed as a Munro. The surveyors came up with a figure of 913.96m, which would – if accepted by the Scottish Mountaineering Club (SMC) – see its status change from Munro to Corbett, making it one of three 914m Corbetts along with Foinaven in Sutherland and Beinn Dearg in Torridon.
However, the SMC – which publishes the list of Munros and ultimately decides what is and isn’t in – asked TMS to include the following statement in its press release: “The Scottish Mountaineering Club has been notified of these survey results and has undertaken to consider the implications for Munro’s and Corbett’s tables when the Ordnance Survey update its map of the area.”
What now happens with regard to Beinn a’Chlaidheimh is unclear. There is evidence that it is below 3,000ft (913.96m converts to about 2,998 feet 6 inches), but in an unusual move the SMC has decided not to immediately accept the change – whereas they did immediately remove Munro status from Sgurr nan Ceannaichean when it was reduced from 915m to 913m in a similar survey in 2009.
How long this consideration period might be and what form it will take remains to be seen. For now, though, Beinn a’Chlaidheimh is still a Munro, albeit one with a curious status.
As regards the other two hills, there was never much chance of Ruadh Stac Mor losing the 3m or 4m that would bring it close to the critical line, given that its summit is marked by a ground-survey trig point. The new figure, just 2cm higher, is effectively identical to the old one as it is within the 10cm margin for error.
The Beinn Dearg Mor height-loss of around 4m is interesting, as it – along with the figure for Beinn a’Chlaidheimh – continues a trend of height-loss that began with TMS’s survey of Foinaven in 2007 (down from 914m to 911m) and was also evident in the 2009 surveys. Could there now be enough of a trend to suggest that a considerable number of OS aerial-survey heights are on the high side by this kind of margin? Probably not, but – assuming the methodology used by G & J Surveys to be valid – it does seem to reinforce the idea that resurveys generally reduce heights rather than adding to them.
As for the technical side of things, the press release from TMS says that “Summit positions were identified using a Leica NA730 Professional Automatic level tripod system and a 1m extendable E-staff. Absolute heights were measured using a Leica Geosystems 530 GPS receiver which locks on to 12 satellites and receives two signals from each satellite, thus reducing inaccuracies from atmospheric conditions.”
A spokesperson from TMS said: “In measuring the heights of mountains just below and just above 3,000ft (914.4m), we believe we are following in the tradition of accurate measurement established by Sir Hugh Munro who first produced the Munro’s Tables in 1891. Munro and his friends relied on aneroid barometers, the technology of the time; in 2011 we use satellite technology to achieve yet greater accuracy, but we seek the same objective. Munro never set down complete criteria for Munro status before his death in 1919, but it has always been accepted that 3,000ft (914.4m) was the primary requirement.”
More background can be found in yesterday's preview piece.
Donate to us: support independent, intelligent, in-depth Scottish journalism from just 3p a day
Related posts: