@unpublished{TUW-199542, author = {Van Dam, Tonie and B{\"o}hm, Johannes and Angermann, Detlef}, title = {Position Paper Session 2: Environmental modeling based on external data; Deficiencies, standards, and issues}, year = {2011}, note = {talk: Third GGOS Unified Analysis Workshop, Z{\"u}rich; 2011-09-16 -- 2011-09-17} }