Abstract: An efficient and fully automatic approach to detect terrain changes and update old DEM simultaneously with outdated DEM and up-to-date aerial stereoscopic pair is presented.The related tests are done with geo-spatial data from two regions in China,and experimental results of both change detection and updating are satisfactory.Compared with existing procedure in production,the approach excels at efficiency markedly,requires less for source data,produces more products,and it is more robust and automatic.