Mapping urban dynamics (1992-2018) in Southeast Asia using consistent nighttime light data from DMSP and VIIRS

The long-term urban dynamics at regional and global scales is essential to understanding the urbanization processes and environmental consequences for providing better scientific insights and effective decision-making. The time series of consistent nighttime light (NTL) data generated by integrating the Defense Meteorological Satellite Program-Operational Linescane System (DMSP-OLS) and the Suomi National Polar-Orbiting Partnership Visible Infrared Imaging Radiometer Suite (NPP-VIIRS) provide a longer consistent record of the nightscape beyond a single dataset for monitoring urban dynamics. In this study, we developed a new framework based on the spatial variation of NTL gradient (SVNG) to map urban dynamics in Southeast Asia using the consistent NTL data (1992-2018). First, we identified the potential urban clusters in the region using the cluster-based segmentation approach in 2018. Second, we applied the SVNG framework in each potential urban cluster to extract the initial annual urban extent from corresponding time-series NTL images (1992-2018). Finally, we performed a temporal consistency check on the initial urban extent to obtain the final urban sequence in Southeast Asia. The evaluation on the spatiotemporal patterns and consistency of urban dynamics using other urban products indicates that the SVNG framework can effectively capture the urban dynamics in areas with different development levels and patterns. Moreover, we investigated urban dynamics in Southeast Asia at the local, national, and regional scales. This study opens new research avenues for monitoring and understanding the long-term urban dynamics and the pathways of urban growth from local to global scales.