IMPROVING THE RELIABILITY OF A GPS/INS NAVIGATION SOLUTION FOR MM VEHICLES BY PHOTOGRAMMETRY

Integration of INS and GPS is necessary for continuous georeferencing in Mobile Mapping (MM); improved mathematical models, such as tightly coupled solutions, make very efficient use of the available information, especially with poor GPS solutions. However, experience shows trajectory errors still arise. If data from the two system components do not agree for whatever reason, deciding which data is wrong may not be easy and depends on filter implementation. The availability of data from other sensors can help to identify the erroneous data source. In this paper, use of photogrammetry to verify the consistency of GPS/INS data is proposed. First, the GPS-aided inertial navigation solution implemented is introduced, discussing its extension to photogrammetry-aided solution. Some reliability tests are reviewed. Finally, the concept and implementation details of an automatic procedure providing a photogrammetric check of the GPS/INS data is described. In short, the idea is rather simple: to compare the image locations of a set of object points, computed from the stereo pair at time ti, with those of the same points projected on the images at ti+1, based on the exterior orientation computed by the navigation solution at time ti+1. Although no test of the method has been made yet, experience shows that tracking points on the road surface in MM image sequences is feasible; implementation details take care of redundancy as well as of speed of computation: in principle the check can be applied to every consecutive pair of the sequence