Present and Future of SLAM in Extreme Underground Environments

TL;DR

This paper reviews the current state of underground SLAM, focusing on lidar-based solutions, multi-robot systems, and real-world challenges, while highlighting open problems and providing open-source resources.

Contribution

It offers a comprehensive analysis of SubT competition SLAM systems, emphasizing practical challenges, system maturity, and future research directions.

Findings

Lidar-centric SLAM dominates underground applications

Multi-robot systems enhance exploration capabilities

Open-source datasets and implementations are available for research

Abstract

This paper reports on the state of the art in underground SLAM by discussing different SLAM strategies and results across six teams that participated in the three-year-long SubT competition. In particular, the paper has four main goals. First, we review the algorithms, architectures, and systems adopted by the teams; particular emphasis is put on lidar-centric SLAM solutions (the go-to approach for virtually all teams in the competition), heterogeneous multi-robot operation (including both aerial and ground robots), and real-world underground operation (from the presence of obscurants to the need to handle tight computational constraints). We do not shy away from discussing the dirty details behind the different SubT SLAM systems, which are often omitted from technical papers. Second, we discuss the maturity of the field by highlighting what is possible with the current SLAM systems and what we believe is within reach with some good systems engineering. Third, we outline what we believe are fundamental open problems, that are likely to require further research to break through. Finally, we provide a list of open-source SLAM implementations and datasets that have been produced during the SubT challenge and related efforts, and constitute a useful resource for researchers and practitioners.