[1] Univ Maryland, Dept Geog Sci, 2181 LeFrak Hall, College Pk, MD 20740 USA
[2] Univ Maryland, Coll Informat Studies iSchool, College Pk, MD 20740 USA
[3] NAS Ukraine & SSA Ukraine, Space Res Inst, UA-03680 Kiev, Ukraine
[4] Natl Tech Univ Ukraine, Igor Sikorsky Kyiv Polytech Inst, UA-03056 Kiev, Ukraine