Semi-automatic Geo-referencing Images in Mobile Mapping

This paper presents a purely photogrammetric strategy to orient short image sequences in a MM van equipped with two GPS receivers and a pair of synchronized cameras but currently still lacking an IMU. The motivation for this is twofold: bridge over short GPS outages, so increasing the vehicle productivity; improving the consistency of image georeferencing between consecutive image pairs, which in relative terms is poor due to the limited accuracy of the GPS-supported camera parameters determination. Drawing on techniques developed for structure and motion reconstruction from image sequences, a general method has been tailored to the specific conditions of the MM imaging geometry, trying to ensure reliability of the matches and stability of the solution. Though currently not all constraints between synchronous image pair are yet enforced, the first results suggest that the technique may be working satisfactory, ensuring that the error propagation is within the specifications for GPS outages of about 100 m..