See, Linda, Mooney, Peter, Foody, Giles M., Bastin, Lucy, Comber, A., Estima, Jacinto, Fritz, Steffen, Kerle, Norman, Jiang, Bin, Laakso, Mari, Liu, Hai-Ying, Mil?inski, Grega, Nikši?, Matej, Painho, Marco, Podor, Andrea, Olteanu-Raimond, Ana-Maria, Rutzinger, Martin, "Crowdsourcing, citizen science or volunteered geographic information? The current state of crowdsourced geographic information", ISPRS International Journal of Geo-Information, 2016