Ben Nevis and geologically driven changes in elevation

Abstract

With a great deal of fanfare in March 2016 an Ordnance Survey press release announced 1345 m as the newly rounded height for Ben Nevis, the highest mountain in Scotland. After a series of complex calculations and surveying, new measurements underpinned by geophysical data revealed that the highest point in the United Kingdom had gone up to by only a few cm since 1949, when it was last measured. This time they were able to use GPS readings from satellites maintained by the US military to pin this down to millimetre precision. The height rose to 1344.527 metres (or 4411 feet and 1½ inches), but Britain's national mapping agency does not reveal exactly what the old height was. Oddly the seventh series 1: 63 360 map (Sheet 47‐Glencoe) published in 1960 was still using 4406 feet, 1343 m. This antiquated height was transferred from the 4406.3 ft inscribed on the six‐inch 1 : 10 560 (Inverness‐shire—Mainland sheet CLI) map published in 1902, relative to the Liverpool datum originally used by the Ordnance Survey. This was probably the base of the cairn upon which the triangulation pillar is built, and not even the nearby summit of Ben Nevis itself. Indeed the OS explains in a video on its website why modern 1 : 50 000 editions show two heights, with brackets around that for the natural high point, to make this distinction clear.