I. Introduction
Simultaneous Localization and Mapping (SLAM) has been extensively investigated with numerous sensor modalities, e.g., sonar, camera and LiDAR, in the last decades. However, for outdoor large-scale SLAM, ensuring its robust operation is still very challenging especially in adverse weather conditions. Recently, the emerging Frequency-Modulated Continuous Wave (FMCW) radar sensors which can work in various weathers have been increasingly adopted for self-diving cars and autonomous robots. Therefore, an interesting yet open question is whether these radars can be used for robust SLAM in large-scale environments in extreme weather conditions, such as heavy snowfall.