A widely reported story, courtesy of the BBC, appeared last week describing the unusual case of Sandy Island, a south Pacific island between Australia and New Caledonia. Although the island appeared on Google Maps and Google Earth, a research team from Australia were unable to locate it when they went to investigate. Expecting to find a ‘sizeable’ strip of land, the researchers found instead 1,400 m of deep blue sea. In their defence Google commented that they did consult a number of authoritative data sources for their maps, and the island did appear to be a genuine feature.
It seems the island never really existed and was most likely the product of an error that had gone unnoticed and had been perpetuated over the years. This story touched on a number of issues we discussed in The GIS Guide to Public Domain Data including the use of assertive versus authoritative data sources. What does authoritative really mean and how far should we go to get the definitive answer? Should we no longer rely solely on the traditional sources of geographic data when it seems even they can’t be guaranteed, and always get a second opinion? Prof. Michael Goodchild (Univ. of California, Santa Barbara) discusses a hybrid solution in a paper entitled ’Assertion and Authority: The Science of User Generated Geographic Content’ and sees the merits in taking advantage of the expertise and knowledge accumulated by the traditional data providers (national mapping agencies, survey companies and so on) but also taking advantage of independent verification from volunteer groups, research teams and other interested individuals and organisations.
Future developments in data capture and verification will probably mean cases like this should be rare. However given the rate of change in both the physical and man-made environment and the ever-present possibility of mis-interpretation, the ’definitive map’ will probably remain an elusive goal.
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