The Generation And Accuracy Analysis Of Dem Without Control Point

The multi-temporal images and DEMs are main data source for obtaining the deformation information. Researching the technique of absolute orientating without ground control points (GCPs), and generating complete DEMs from several independent models of the same period, has very important significance. Firstly, it would be helpful to reduce the field works of constructing and maintenance of GCPs and save money. Secondly, it can make full use of those quite old pre-disaster data, although it is impossible to setup valid GCPs for them before disaster occurrence. In addition, it can create conditions for monitoring terrain changes with multi-temporal DEMs.PUWAIGOU, a typical debris-flow valley along Chengdu-Kunming railway, southwest China, is adopted as experimental area to research the generation and accuracy analysis of DEM without GCP. With aerial photographs of the year 1987 and 1957, and GCPs of the year 2003 as basic data, DEMs of the year 1987 are generated with GCPs on JX4 Digital Photogrammetric Workstation, and DEMs of the year 1957 are generated with and without GCPs respectively. Then by comparing the two kinds of DEM edge match difference, analysis the difference of the two kinds of absolute orientation accuracy is possible.The experimental results show that for the same pair of aerial photographs of the year 1987 and 1957, the edge match difference of DEM without GCPs is smaller than those with GCPs ones, and the edge match difference precision of DEM without GCPs increases by an average of 35.9%, which is classified into two types: forward overlapping (49.7%), side overlapping (15.2%). The results also suggest that for the same pair of aerial photographs without stable reliable GCPs, the edge match difference precision of DEM without GCPs can significantly improve (87.8%). Such information will form a foundation for further research on DEM absolute orientation without GCPs in future.