New data gathered from the remote islet Rockall by adventurer Nick Hancock during his record-breaking 45-day occupation this summer has shown it is lower than officially recorded.
However, after multiple hi-tech tests, the position of the rock in the Atlantic Ocean has been confirmed to be the same as was calculated back in 1977.
The latest coordinates are said to have pinpointed its position to two centimetres accuracy.
During his occupation in June and July, Edinburgh-based chartered surveyor Nick installed a fixed permanent survey marker on the summit plateau of the rock. He carried out 24-hour data collection sessions, connecting to satellites and Ordnance Survey radio stations and the results have been published.
The aim was to update the current United Kingdom Hydrographical Office (UKHO) records relating to the position and height of Rockall collated in 1977.
The new data sets were processed by Leica Geosystems and also by Ordnance Survey (OS) for final processing using high-accuracy scientific techniques and software. Data from OS Net stations were included, as well as data from the Faroes, Northern Ireland and Iceland.
Results from four data sessions collected by Nick showed very good precision, with a comparison of coordinates agreeing to below 5mm. A quality check on the final coordinates indicated that they were accurate to better than 2cm in all dimensions.
The difference between the new data and the previous collections is only about 1.3m in an east/west direction and 0.3m in a north/south direction. Experts say it is clear that both the UKHO and Nick’s new survey arrived at much the same answer, which is testament to the quality of the 1977 Doppler survey. That means Nick can’t claim to have significantly ‘moved’ Rockall.
The height of Rockall was previously estimated at about 18 metres above sea level to the summit by the Royal Geographical Society in their first map of Rockall. It was previously 19.2 metres but the summit was removed by the Royal Engineers in 1971.
The height of Rockall has now been officially recalculated using Nick’s data. It is now registered as having a mean height above sea level of about 17.15m, which is 0.85 metres lower than previously thought.
His new data shows the height difference between the summit plateau and Hall’s Ledge, where his RockPod was on the rock, as 3.13 metres. That means the ledge is approximately 14 metres above mean sea level.
Mark Greaves, the OS satellite positioning expert, said: “Nick’s occupation of Rockall for such a long time is a fantastic achievement and Ordnance Survey was happy to be involved with advice and data processing facilities. The satellite positioning data that Nick recorded on Rockall was of high quality and it enabled the island’s position to be determined to just a few centimetres. This provided a very useful check on the official chart position of Rockall.”
Nick said: “I had hoped that my survey results might significantly relocate Rockall, but being able to finally establish the true height of the rock means that my time spent there has even greater long-term significance than just breaking the previous occupation records and raising funds for Help for Heroes.”