An automatic co-registration approach for optical and SAR data in urban areas

Abstract

© 2016 Informa UK Limited, trading as Taylor & Francis Group. With the increasing applications of multisource remote sensing, the synergistic use of optical and Synthetic Aperture Radar (SAR) remote sensing images is becoming increasingly popular. Although numerous approaches have been proposed to register satellite images between two optical images or between two SAR images, these approaches cannot be directly applied to register optical and SAR images due to the differences of imaging mechanism between optical and SAR remote sensing. Therefore, the co-registration between optical and SAR images remains challenging, especially in urban areas where surface geometric configuration is much more complex. This study aims to propose a fast and automatic approach for optical and SAR data co-registration based on an assumption of affine transformation between the two images. With a set of initial homologous points generated automatically, an optimization is applied towards the initial homologous points on the SAR images subject to an affine transformation model and a given threshold of root mean square errors (RMSEs) for the co-registration. Three various data sets of optical and SAR images, including SPOT-5 and ENVISAT ASAR, Landsat TM and ENVISAT ASAR, and SPOT-5 and ALOS PALSAR, were employed to test and validate the effectiveness of the proposed method. Experimental results demonstrate the promising effectiveness of the proposed approach with a significant reduction of RMSE compared with the initial homologous points. The proposed approach is especially applicable in urban areas where the uncertain errors of homologous points in SAR images are higher due to the speckles and foreshortening, layover and shadows from tall buildings.