Uni-Mapper: Unified Mapping Framework for Multi-Modal LiDARs in Complex and Dynamic Environments

The unification of disparate maps is crucial for enabling scalable robot operation across multiple sessions and collaborative multi-robot scenarios. However, achieving a unified map robust to sensor modalities and dynamic environments remains a challenging problem. Variations in LiDAR types and dynamic elements lead to differences in point cloud distribution and scene consistency, hindering reliable descriptor generation and loop closure detection essential for accurate map alignment. To address these challenges, this paper presents Uni-Mapper, a dynamic-aware 3D point cloud map merging framework for multi-modal LiDAR systems. It comprises dynamic object removal, dynamic-aware loop closure, and multi-modal LiDAR map merging modules. A voxel-wise free space hash map is built in a coarse-to-fine manner to identify and reject dynamic objects via temporal occupancy inconsistencies. The removal module is integrated with a map-centric descriptor, which extracts local features from preserved static points, ensuring robustness multimodal LiDARs in dynamic environments. In the final stage, multiple pose graph optimizations are conducted for both intrasession and inter-map loop closures. We adopt a centralized anchor-node strategy to mitigate intra-session drift errors during map merging. Our framework is evaluated on diverse realworld datasets with dynamic objects and heterogeneous LiDARs, showing superior performance in loop detection across sensor modalities, robust mapping in dynamic environments, and accurate multi-map alignment over existing methods. Project Page: https://sparolab.github.io/research/uni_mapper.