Remotely sensed data are acquired by Landsat Thematic
Mapper (TM) and enhanced TM plus (ETM+) that
have similar spectral characteristics. Images acquired near
1990, 2000 and 2010, respectively have been collected. We
also analyzed the magnitude and speed of urban expansion,
estimated the amount of croplands occupied by urban development,
and the economic efficiency of urban expansion.
1 Mapping methods
The scope of the mapping is the built-up areas where the
city governments are located. For the urban-rural transitional
areas, we consider built-up areas within 5 pixels as part of
the urban areas, excluding those just connected by roads [39].