The authors would like to acknowledge European Space Agency (ESA) gratefully for providing Envisat ASAR data, the Delft geospatial Institute (DEOS) for precise orbit data, and the JAXA for the ALOS DSM data, and ERSI for ENVI/SARscape software. We thank the editors and anonymous reviewers for their constructive comments and time spent reviewing the manuscript.
The present work was supported by the natural science foundation of Hunan province of China (Grant No. 2021JJ30076, 2022JJ50261, 2021JJ40023) and the foundation of the Hunan educational committee (Grant No. 21A0502).