Authors: Maffra, Fabiola; Teixeira, Lucas; Chen, Zetao; Chli, Margarita
Place recognition is an essential capability for robotic autonomy. While ground robots observe the world from generally similar viewpoints over repeated visits, other robots, such as small aircraft, experience far more different viewpoints, requiring place recognition for images captured from very wide baselines. While traditional feature-based methods fail dramatically under extreme viewpoint changes, deep learning approaches demand heavy runtime processing. Driven by the need for cheaper alternatives able to run on computationally restricted platforms, such as small aircraft, this letter proposes a novel real-time pipeline employing depth-completion on sparse feature maps that are anyway computed during robot localization and mapping, to enable place recognition at extreme viewpoint changes. The proposed approach demonstrates unprecedented precision-recall rates on challenging benchmarking and own synthetic and real datasets with up to 45° difference in viewpoints. In particular, our synthetic datasets are, to the best of our knowledge, the first to isolate the challenge of viewpoint changes for place recognition, addressing a crucial gap in the literature. All of the new datasets are publicly available to aid benchmarking.