For the 2000 period, all cities were interpreted
in 1999–2002. For the 2010 period, all cities were interpreted
in 2008–2010. Specifically 488 cities were interpreted
in 2009.
2 Accuracy analysis
The mapping products cover a long temporal period and
large spatial scale. It is difficult to validate the results by
field checking for each city. However, interpretation results
from high resolution images available from Google Earth
can be used instead of field works. When interpreting the
urban areas, we used high resolution data (within 2.5 m) for
reference. In order to understand the quality of this work,
we asked several other experienced interpreters to interpret
5% of the cities that were randomly selected based on the
high resolution imagery in Google Earth.