Road Topology Extraction from Satellite images by Knowledge Sharing

Anil Kumar

Abstract

Motivated by human visual system machine or computer vision technology has been revolutionized in last few decades and make a strong impact in wide range of applications such as object recognition, face recognition and identification etc. However, despite much encouraging advancement, there are still many fields which lack to utilize the full potential of computer vision techniques. One such field is to analyze the satellite images for geo-spatial applications. In past, building and launching the satellites in to space was expensive, and was big hurdle in acquir- ing low cost images from satellites. However, with technological innovations, the inexpensive satellites are capable of sending terabytes of images of our planet on the daily basis that can provide insights on global-scale economic, social and industrial processes. The significant applications of satellite imagery are urban planning, crop yield forecasting, mapping and change detection. The most obvious application of satellite imagery is to extract topological road network from the satellite images, as it plays an important role in planning the mobility between multiple geographical locations of interest. The extraction of road topology from the satellite images is formulated as binary segmentation problem in vision community. Despite of huge satellite imagery, the fundamental hurdle in applying computer vision algorithms based on deep learning architectures is unavailability of labeled data and causes the poor results. Another challenge in extraction of the roads from satellite imagery is visual ambiguity in identifying the roads and occlusion by various objects. This challenge causes many standard algorithms in computer vision research to perform poorly and is the major concern. In this thesis we develop deep learning based models and techniques that allows us to address the above challenges. In the first part of our work, we make an attempt to perform road segmentation with the less labeled data and existing unsupervised feature learning techniques. In particular, we use self-supervised technique to learn visual representations with an artificial supervision, followed by fine tuning of model with labeled dataset. We use semantic image in-painting as an artificial/auxiliary task for supervision. The enhancement of road segmentation is in direct relation with the features captured by model through inpainting of the erased regions in the image. To further enhance the feature learning, we propose to inpaint the difficult regions of the image and develop a novel adversarial training scheme to learn mask used for erasing the image. The proposed scheme gradually learns to erase regions, which are difficult to inpaint. Thus, this increase in difficulty level of image in-painting leads to better road segmentation. Additionally, we study the proposed approach on scene parsing and land classification in satellite images.

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