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This severely restricts its applications in large areas and over lengthy periods of time. Unfortunately, most of the existing methods employ heuristics for quick positioning in which numerous accumulated errors easily lead to loss of positioning accuracy. While there are critical implementation problems, such as the ability to estimate the position by sensing the unknown indoor environment with sufficient accuracy and low enough latency for stable vehicle control, further development work is necessary. Laser scan matching with grid-based maps is a promising tool for real-time indoor positioning of mobile Unmanned Ground Vehicles (UGVs). This paper discusses the integration of a terrestrial laser scanner into a GPS/INS/pseudolite (terrestrial RF system) integrated terrestrial navigation system, and provides preliminary simulation test results. Sphere centers extracted from different scans are registered based on their topology, and the differences between the scanner's positions and attitudes at different scanning sites, the relative positioning result in a local coordinate frame, are accurately computed and subsequently used for the calibration of the INS.
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Then, the center positions of the spheres are determined by a least squares method. Using a conic search window, a spherical point cloud search is performed.
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To attain centimeter level navigation accuracy in any environment under heavy canopy, spherical objects are placed around the navigation area they remain stationary during navigation. Due to its high accuracy and efficient range measuring capabilities, we propose the integration of a terrestrial laser scanner into a navigation system, primarily for calibrating the INS. Imaging sensors can provide adequate data to support navigation in these situations. However, due to GPS signal blockage and accumulative error attributes of INS, a GPS/INS system cannot continuously maintain such high accuracy navigation during GPS outages, which may frequently happen in terrestrial applications, such as when navigating in forested areas. GPS/INS integration can provide high accuracy (centimeter level) navigation under good satellite geometry and atmospheric conditions.