POSITIONING ACCURACY IMPROVEMENT OF TERRESTRIAL MOBILE MAPPING SYSTEMS USING A BUNDLE BLOCK ADJUSTMENT

摘要

Recently, several low-cost terrestrial Mobile Mapping Systems (MMSs) have been developed for the construction of 3D city models and mapping. A terrestrial MMS combining GNSS and IMU are able to perform the direct geo-referencing and then to use forward intersections to determine a number of spatial coordinates of image points. However, according to many experiments, the accuracy of positioning results with a low cost Terrestrial MMS using only the direct geo-referencing and forward intersections is not stable because of the bad base-depth ratio in the terrestrial Photogrammetry. the GNSS signal obstruction in city regions, and less redundancy for extra examination which leads also to unreliability of positioning results. This research uses the exterior orientations obtained from a terrestrial MMS w ith the help of ground control points and introduces them into a bundle block adjustment in order to improve the positioning accuracy. Based on our experiments using a set of real MMS data, a bundle block adjustment with exterior orientations as weighted control can only increase the positioning accuracy from 4.8 m to 3.1 m. Our experiments have shown that the accuracy in the level of 12 cm can be achieved by extra adding several pairs of ground control points.