In this article, we introduceiLoc, an innovative visual localization system designed to enhance the autonomy and adaptability of robotic agents in long-term and large-scale applications.iLocspecializes in: 1) extracting stable and consistent descriptors for place recognition, unaffected by changes in viewpoint and illumination; 2) performing swift and precise global relocalization to establish a robot's position within a large and complex environment; and 3) generating real-time tracking trajectories aligned with reference maps, ensuring continual orientation within known spaces. Distinctively,iLocincorporates a transformer-based learning module and an attention-enhanced recognition approach, enabling it to adapt to diverse environmental and viewpoint conditions.iLocleverages a coarse-to-fine global feature matching technique for enhanced localization and integrates robust state estimation combining visual odometry and loop closures through local refinement and pose graph optimization.iLocdemonstrates remarkable proficiency in place recognition, achieving localization over distances of up to 2 km within 0.5 s with average accuracy at 1 m. It maintains stable localization accuracy, even under variable conditions. Its versatile design allows integration across various environments, significantly broadening the scope of universal localization capabilities in robotics.iLocrepresents a substantial step forward in visual-based localization systems, delivering unparalleled speed and accuracy in place recognition. Its ability to adapt and respond to diverse environmental stimuli marks it as a crucial tool in advancing the field of robotic localization.

In the era of advancing autonomous driving and increasing reliance on geospatial information, high-precision mapping not only demands accuracy but also flexible construction. Current approaches mainly rely on expensive mapping devices, which are time consuming for city-scale map construction and vulnerable to erroneous data associations without accurate GPS assistance. In this article, we present AutoMerge, a novel framework for merging large-scale maps that surpasses these limitations, which: 1) provides robust place recognition performance despite differences in both translation and viewpoint; 2) is capable of identifying and discarding incorrect loop closures caused by perceptual aliasing; and 3) effectively associates and optimizes large-scale and numerous map segments in the real-world scenario. AutoMerge utilizes multiperspective fusion and adaptive loop closure detection for accurate data associations, and it uses incremental merging to assemble large maps from individual trajectory segments given in random order and with no initial estimations. Furthermore, AutoMerge performs pose graph optimization after assembling the segments to smooth the merged map globally. We demonstrate AutoMerge on both city-scale merging (120 km) and campus-scale repeated merging (4.5 km × 8). The experiments show that AutoMerge: 1) surpasses the second- and third-best methods by 0.9% and 6.5% recall in segment retrieval; 2) achieves comparable 3-D mapping accuracy for 120-km large-scale map assembly; and 3) and is robust to temporally spaced revisits. To our knowledge, AutoMerge is the first mapping approach to merge hundreds of kilometers of individual segments without using GPS.