Multi-Image Matching for DTM Generation from SPOT-5 HRS/HRG and IRS-P5 Imagery - For the Project of West China Topographic Mapping at 1:50,000 Scale

High-resolution satellite images (HRSI) at sub-5m footprint such as IKONOS, IRS-P5 (CartoSat-1) and SPOT-5 HRG/HRS images are becoming increasingly available to the earth observation community and their respective clients. HRSI is one of the main data sources for the Project of Western China Topographic Mapping (WChTM) which has been approved by the State Council of China in year 2006. New advanced technologies in field of photogrammetry and remote sensing, such as the block-adjustment with sparse GCPs, automatic DSM/DTM generation and 3D mapping with HRSI are very necessary to the project. In this paper, we present a matching approach for automatic DSM/DTM generation from HRSI. It can provide dense, precise and reliable results. The method matches multiple images simultaneously and it uses a coarse-to-fine hierarchical solution with an effective combination of several image matching algorithms and automatic quality control. The DSMs/DTMs are generated by combination of matching results of feature points, grid points and edges. The new characteristics provided by the high-resolution imaging systems, i.e. the multiple-view terrain coverage and the high quality image data, are also efficiently utilized in this approach. The proposed approach has been applied to SPOT-5 HRS/HRG images over a testfield in Zone of headstream of Three rivers, eastern Tibet Plateau, China with variable terrain geomorphologic type. The accuracy study was based on the comparison between as many as 160 accurate GPS check points, more than 1400 manually measured check points and the automatically extracted DTMs. The RMS errors for the whole area are 2-7 m, while for flat/hilly areas the accuracy is about 2-3 m or even better. The proposed approach has also been applied to 23 IRS-P5 stereo pairs over Beijing city, the resulted 12.5 m DTM reproduced quite well not only the general features of the terrain relief but also small geomorphological and other features visible in the IRS-P5 images. From these experiments, it’s shown that with the proposed automatic DTM generation approach, by using SPOT-5 HRS/HRG and IRS-P5 imagery, satisfactory 1:50000 DTMs can be completed with a better accuracy than those requirements from Chinese Surveying and Mapping regulations.