SRTM‐assisted block adjustment for stereo pushbroom imagery

This paper proposes a stereo‐image block‐adjustment algorithm without ground control points ( GCP s) by adopting a Shuttle Radar Topography Mission ( SRTM ) digital elevation model ( DEM ) as a height assistant. Using dense, evenly distributed tie points on images used in the block adjustment, the initial height values of tie points are derived directly from the SRTM DEM . In the subsequent block‐adjustment iterative computation, the height correction value for tie points is rigorously restricted by the SRTM DEM elevation. A total of 509 ZY ‐3 satellite stereo‐images across 190 000 km 2 of China's Hubei Province were used for this block‐adjustment experiment. The results show that the vertical root mean square errors ( RMSE s) are improved from 7·2 to 2·3 m without GCP s, while the RMSE s in flat and mountainous terrain are improved to 1·5 and 2·8 m, respectively, fulfilling the vertical accuracy requirement of China's 1:25 000 scale mapping.