Automated registration of high-resolution satellite images

Automatic registration of remotely sensed imagery is an important technique in GIS as geographical databases need to undergo frequent updating due to rapid changes in the physical environment. While satellite imagery, with its recently enhanced spatial, spectral and temporal resolution, allows for accurate and reliable detection and characterisation of patterns of change, a key factor that dictates the validity and reliability of change detection results is the quality of image registration. There is a need to develop robust registration procedures for multitemporal, multi-spectral and/or multiresolution imagery captured from different sensors to facilitate the change detection process. This paper discusses an approach for automated image registration based on a hierarchical image matching strategy. Following an initial feature-point extraction phase, the method uses the similarity of grey levels to find homologous point candidates across the images. A hierarchical image pyramid is used to enhance both the success rate and reliability of matching while reducing the computational complexity. The adopted approach also uses contextual information to achieve locally consistent matches. Implementation and testing of the proposed method has involved imagery from different sensors. Here, results are reported for IKONOS and QuickBird data over test sites in Hobart, Australia and Thimphu, Bhutan. The potential of operational automatic image registration in the process of change detection is illustrated by means of these test results.