WORKING WITH GPS/INS

One of the basic problems of photogrammetry is the reconstruction of the elements of the exterior orientation. Over the last 40 years, triangulation techniques have been developed and improved, in order to determine these elements of the exterior orientation by computation. A different approach is taken by the method of direct geo-referencing. This technique allows to transfer sensor or object data immediately into a local or global co-ordinate system, which makes their further processing possible. Such a system exists of receivers of the global positioning system (GPS) on board and on the ground (reference stations) and an inertial system combined with a sensor, which determines angles and accelerations of the sensor with high precision. Since the year 2000 Hansa Luftbild German Air Surveys is operating the modular system AEROcontrol ™ (IGI, Kreuztal; Germany) in the combination with several sensors. In total more than 40 projects have been finished till 2003 with analogue and digital cameras. (besides the LiDAR projects which will be far more than 100). Over time, pros and cons of the system have been witnessed, experiences in terms of reliability have been made. The technical procedure for flight preparation, flight mission and post-processing has been improved. Quality checks in ortho photo projects have shown the precision of the exterior orientation parameter. Using the GPS/INS data as additional information in triangulation for areas of very low contrast (desert, e.g.) has been very helpful. The technique of GPS/INS is clearly in a production stage for several applications, but also limitations have been found. KURZFASSUNG: Eines der grundlegenden Probleme der Photogrammetrie ist die Wiederherstellung der Aufnahmegeometrie durch die Elemente de