Adjustment with Sparse Gcps and the High-resolution Satellite 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 West China Topographic Mapping (WChTM) which has been approved by the State Council of China in year 2006. In western part of China up to 2.02 million km are not mapped at 1:50,000 scale, it includes Sorthern-XinJiang desert area, Qing-Tibet Plateau area and Heng-duan mountain ranges. This unmapped area covers about 20% of all areas of China; contains total number of about 5,032 sheets of 1:50,000 scale topographic maps. The unmapped area related to the project covers most unmans area of China, the very harsh natural conditions (average terrain elevation is more than 4000m) and difficult transportation conditions provide a very difficult situation for outside field-works such as GCP measurement. In many areas, it’s even impossible for collecting enough GCPs, therefore, new advanced technologies in field of photogrammetry and remote sensing, such as the block-adjustment with sparse GCPs and mapping with high-resolution satellite imagery are very necessary. In this paper, we present an approach for block-adjustment based on Rational Function Model (RFM) with sparse GCPs by using satellite Images. To test the proposed approach, it has been applied to SPOT-5 images over 2 test-fields, one is in Baoji City, Chanxi, China, and another covers eastern part of Tibet Plateau, China. All test-fields are with variable terrain geomorphologic type and several tens of GCPs and check points measured by DGPS. The block-adjustment results show that with SPOT-5 HRS images and small number of GCPs we can achieve 5-9m in planimetric and 2-3m in height direction. In another test we use 23 scenes of IRS-P5 images, the test area covers Beijing area and about 21,000 square kilometers. In this test-field, we used DGPS to measure 66 GCPs and the block-adjustment result shows that only with 5 GCPs we could achieve 2.0 m in planimetric and 2.5m in height direction. From these experiments, it’s shown that with the proposed block-adjustment approach, by using SPOT-5 HRS/HRG and IRS-P5 imagery with small number of GCPs, satisfactory image orientation results can be achieved with a little bit better accuracy than those requirements from the Chinese Surveying and Mapping regulations for 1:50000 topographic maps.