Department;
of;
Remote;
Sensing;
and;
Geographical;
Information;
Science,;
China;
Xuzhou,;
Jiangsu;
221008,;
China;
Key;
Laboratory;
for;
Virtual;
Geographic;
Environment;
of;
Ministry;
of;
Education,;
Nanjing;
Normal;
University,;
Nanjing,;