Supervised Change Detection Using Prechange Optical-SAR and Postchange SAR Data

Change detection using satellite/aerial images is used to quantify the impacts of many natural and man-made disasters. At the occurrence of such events, both pre-change optical and Synthetic Aperture Radar (SAR) images can be obtained by going back in time. However, the availability of the post-change optical image is often hindered by the presence of artifacts like clouds. To circumnavigate this, we propose a novel change detection data setting which uses both optical and SAR images pre-change, yet only SAR imagery post-change. For this challenging scenario, we propose a Siamese network that processes the pre-change and post-change SAR inputs using a shared set of weights, while the pre-change optical input is processed using a network that do not share the weights with the SAR inputs. The encoded weights from the three networks are fused and finally decoded using a common decoder to obtain the change map. Our model effectively fuses multi-sensor information and can obtain satisfactory result despite the absence of the post-change optical image. Experimental results on a multi-sensor urban dataset demonstrate the effectiveness of the proposed approach. Code is available athttps://gitlab.lrz.de/ai4eo/cd/-/tree/main/optSarSarCd