Mapping China's ghost cities through the combination of nighttime satellite data and daytime satellite data

One of the side-effects generated by mainland China's urbanization process is "ghost cities"-generally defined as clusters of abandoned buildings or housing structures-but there is a notable lack of studies on the basic characteristics related to this phenomenon, such as size, growth, level, distribution, scale, intensity, pattern and determinants. Through a combination of nighttime satellite data and daytime satellite data as a useful proxy, in this paper, we present the spatial pattern and temporal evolution of China's ghost cities over the last two decades. Nighttime light's rate of change in newly built areas is developed based on DMSP/OLS and Normalized Difference Built-up Index to assess a city's darkness. Results show that the ghost city problem is real, but, at least so far, confined to 22 smaller cities. However, further analysis reveals that nighttime lights change in newly built areas, following an inverted U-curve for big cities representing a reversion from positive to negative values for the trends in recent years. The methodology through the use of the complementary characteristics in time between DMSP/OLS and Landsat data in our study prove to serve as deposing the direct evidences to ascertain and quantify such social-economic phenomenon.