Road Segmentation in SAR Satellite Images With Deep Fully Convolutional Neural Networks

Remote sensing is extensively used in cartography. As transportation networks grow and change, extracting roads automatically from satellite images is crucial to keep maps up-to-date. Synthetic aperture radar (SAR) satellites can provide high-resolution topographical maps. However, roads are difficult to identify in these data as they look visually similar to targets, such as rivers and railways. Most road extraction methods on SAR images still rely on a prior segmentation performed by the classical computer vision algorithms. Few works study the potential of deep learning techniques, despite their successful applications to optical imagery. This letter presents an evaluation of fully convolutional neural networks (FCNNs) for road segmentation in SAR images. We study the relative performance of early and state-of-the-art networks after carefully enhancing their sensitivity toward thin objects by adding the spatial tolerance rules. Our models show promising results, successfully extracting most of the roads in our test data set. This shows that although FCNNs natively lack efficiency for road segmentation, they are capable of good results if properly tuned. As the segmentation quality does not scale well with the increasing depth of the networks, the design of specialized architectures for roads extraction should yield better performances.