Snowdonian Mountain Resurvey Could Rewrite Map

Ever since detailed maps of Snowdonia have been produced, the 3,002-foot Tryfan has been a member of the 14 peaks, the list of 3,000-foot Welsh mountains. But recently some experts have asked, "Does Tryfan really measure up?" The matter will be settled in June when three amateur mountain surveyors haul professional GPS equipment and computers to the summit.

John Barnard, Graham Jackson and Myrddyn Phillips have a serious track record in surveying mountains, and their measurements are accepted by Ordnance Survey, the national mapping agency.

In 2008 Mynydd Graig Goch on the Nantlle Ridge was designated as a 2,000 foot mountain as a result of their work. Last summer they proved that one of the accepted 3,000-foot Scottish Munros was no such thing. Now they have Tryfan in their sights.

Myrddyn says: "We are interested in whether or not it is indeed above the 3,000-foot mark. It would certainly make the challenge of visiting every Welsh 3,000 foot summit in a single journey easier if it wasn't!"

Mark Greaves, Ordnance Survey Geodetics Analyst, has been working closely with the expedition. He comments: "The professionalism shown by Myrddyn and the team means we have no hesitation in supporting their work. Once their survey is complete we will verify the accuracy of their data and, providing it meets our standards - which I'm sure it will, the revision will be made to the relevant maps and mapping data."

Ordnance Survey makes around 5,000 changes a day to the digital mastermap of Britain used by businesses and the Government. Mark adds: "Most of those changes take place in urban areas, which is where Ordnance Survey has to concentrate our resources."

Most mountain heights are calculated using aerial photography, which provides a height accurate to around 4 metres. The GPS equipment now being used to measure Tryfan is accurate to just a few centimetres.