Offline-Online Hierarchical 3D Global Relocalization With Synthetic LiDAR Sensing and Descriptor-Space Retrieval

TL;DR

This paper introduces a hierarchical offline-online framework for 3D global relocalization that significantly reduces online computation time while maintaining high accuracy, suitable for large-scale environments.

Contribution

The proposed method decouples the search space into offline and online phases, enabling faster relocalization with comparable accuracy compared to existing approaches.

Findings

Achieves an average relocalization time of 3 seconds.

Attains an average localization accuracy of 8 cm.

Provides an order-of-magnitude improvement in computational efficiency.

Abstract

3D global relocalization is one of the key capabilities for mobile robots in practical applications. However, in large scale spaces, existing methods often suffer from prolonged online relocalization time due to factors such as the massive pose search space and high computational overhead. To address these issues, this paper proposes an offline-online hierarchical framework that decouples the search space. In the offline phase, candidate positions and their corresponding geometric descriptor indices are generated in the map by simulating LiDAR scans within the grid map. In the online phase, a coarse pose estimate is first obtained via global retrieval, followed by point cloud registration to output precise 6-DoF pose estimates. Real-world experiments demonstrate that the proposed method achieves an average relocalization time of 3 s and an average localization accuracy of 8 cm in 3D environments. Compared with existing global relocalization methods, the proposed method achieves an order-of-magnitude improvement in computational efficiency while delivering comparable relocalization accuracy.