Christian Heipke
3.3 Test flights
The test flights were carried out by the Norwegian companies Fotonor AS and Fjellanger Wideree (FW) Aviation AS.
Fotonor used an Ashtech GPS receiver and the Applanix POS/DG AIMU equipment tightly coupled to a wide angle
Leica RC30, the latter mounted on the gyro-stabilised platform PAV30. The PAV30 data and thus rotations of the cam-
era and the IMU relative to the plane body were recorded and introduced into further processing. FW also had an
Ashtech GPS receiver and the AEROcontrol II system fitted to a wide angle RMK Top from Z/I Imaging GmbH on
board. A second gyro system was used by IGI to register possible movements of the camera with respect to the plane
body during the flight. In order to obtain redundant observations for the differential GPS data processing, a number of
GPS reference stations at various distances from the test field were in operation during data acquisition. The reference
stations were also equipped with GPS receivers from Ashtech.
All flights were carried out on October 7, 1999 with an end overlap and a side overlap of 60 % each using black and
white film material. In the morning Fotonor AS flew the Applanix-Leica equipment, in the afternoon FW acquired data
with the IGI-Z/I system. In total, approximately 250 images per company, were acquired. Each company flew two so-
called calibration flights, the first one in 1:5000, the second one in 1:10000, followed by the actual test flight in 1:5000.
The 1:5000 calibration flight consists of two strips in east/west direction and two strips in north/south direction, see
figure 1. The two directions are necessary for dynamic GPS/IMU alignment. Each pair of strips was flown in opposite
direction to each other in order to be able to determine and to separate GPS shift parameters and the angles of mis-
alignment between the IMU gyro axes and those of the image coordinate system, also called boresight misalignment.
The 1:10000 calibration flight comprises five parallel strips and two cross strips and covers the complete test field, see
figure 2. Apart from the possibility to check the GPS shifts and the boresight misalignment in another image scale the
second scale is needed to resolve the high correlation between the vertical GPS shift and possible errors of the cali-
brated focal length of the camera.
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Figure 1: Calibration flight, image scale 1:5000 Figure 2: Calibration flight, image scale 1:10000
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Following the calibration flights, the actual test flight in the scale
1:5000 covering the complete test field was carried out, see figure
3. It comprises 7 parallel strips and 1 cross strip. Originally, it
was planed to carry out another calibration flight at the end of the
mission in order to assess possible time-dependent effects of the
GPS shifts and the boresight misalginment, but due to weather
conditions this flight could only be flown by Fotonor. In order to
create identical conditions for both systems, this flight is not
further considered in the test.
RR —<K Figure 3:
Á Bun d Test flight, image scale 1:5000
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000. 375
