Photo based volunteered geographic information initiatives: A comparative study of their suitability for helping quality control of corine land cover

Volunteered Geographic Information has become exponentially available over the Web in the last years. This availability can hide a vast geographical richness and provides us with both a great opportunity to explore new ways to use it and also big challenges related with its unstructured nature. This paper conducts a preliminary analysis of the adequacy of photos from the Flickr and Panoramio initiatives in order to use them as a source of field data in the quality control of the Land Use/Cover databases production. It evaluates its temporal and spatial distributions over Continental Portugal and also its distribution over Land Use/Cover classes using as a reference the European Corine Land Cover database. It concludes that this source is very valuable but needs to be combined with other sources due to its uneven spatial distribution.