Oeepe Test on Integrated Sensor Orientation - Status Report

The topic of image orientation by combined aerial triangulation with GPS/IMU, also called integrated sensor orientation, has received much attention lately. One of the main questions of fundamental relevance is, if and under which conditions the direct determination of the parameters of exterior orientation via GPS and IMU can be a complete substitute for aerial triangulation. A more practical question deals with the possibilities of an optimum combination of the different methods using a minimum of ground control points. The European Organisation for Experimental Photogrammetric Research (OEEPE) has embarked on a test investigating these issues. The main focus of the test is on the obtainable accuracy of integrated sensor orientation for large scale topographic mapping as determined at exterior orientation elements and at independent points on the ground. In this paper we present the current status of the test. At present, the first phase of the test in nearly finished, and we have received results from 11 test participants. Phase 2 will start within the next months. 1 TEST OBJECTIVES AND EXPECTED RESULTS The European Organisation for Experimental Photogrammetric Research (OEEPE) has embarked on a test investigating integrated sensor orientation using GPS and IMU in comparison and in combination with aerial triangulation. The test has been set up as a multi-site test. The Institute for Photogrammetry and Engineering Surveys (IPI), University of Hanover acts as pilot centre for the test. Data acquisition and pre-processing including the organisation of test flights and the necessary field work was carried out by the Department of Mapping Sciences (IKF), Agricultural University of Norway in Ås. The main focus of the test is on the obtainable accuracy for large scale topographic mapping using photogrammetric film cameras. The accuracy of the results will be assessed by investigating the exterior orientation elements of an image block and in particular with the help of independent check points on the ground in the following scenarios: aerial triangulation, GPS/IMU observation for the projection centres only, combination of aerial triangulation with GPS/IMU. The test is expected to demonstrate to which extent integrated sensor orientation using GPS and IMU with and without aerial triangulation is an accurate and efficient method for the determination of the exterior orientation parameters for large scale topographic mapping. A comparative analysis will show in which way the mentioned potential error sources and an integrated bundle block adjustment, with or without using a minimum of ground control points have an influence upon the accuracy of the derived orientation parameters and ground control coordinates. Furthermore, the potential and problems of integrated sensor orientation will be assessed based on the comments of the participants. A detailed investigation into the transformation of the raw GPS and IMU measurements into flight trajectories and attitude values (roll, pitch, and yaw as a function of time), however, is out of the scope of this test. Rather, the flight trajectories and the attitude values as computed by the GPS/IMU systems, are considered to be the input of the test, and are to be processed together with the image data. 2 ACQUISITION OF TEST DATA Two companies producing suitable GPS/IMU equipment agreed to participate in the test, namely Applanix of Toronto, Canada, using their system POS/AV 510-DG (Hutton J., Lithopoulos E. 1998; Applanix 2000), and IGI mbH of Kreuztal (formerly of Hilchenbach), Germany, with the system AEROcontrol II (IGI mbH 1999). More details of the test can be found in Heipke et al. (2000). The test flights were carried out by the Norwegian companies Fotonor AS and Fjellanger Widerøe (FW) Aviation AS over the test field Fredrikstad in the south of Norway. The test field is maintained by IKF. In the following we shortly report on the status of the test as of January 2001. The test imagery was acquired in October 1999. For each GPS/IMU system calibration flights in two different scales (1:5.000 and 1:10.000) followed by a flight over the actual test block in 1:5.000 were carried out. All three flights were carried out over the Fredrikstad test field, for further details see table 1 and 2 and Heipke et al. 2000).