The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Voi. XXXVII. Part Bl. Beijing 2008 
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200 400 600 800 1000 200 400 600 800 1000 
(a) (b) 
Figure 5. The radial systematic lens distortion in the image 
from calibration report (a) and in-situ calibration (b) 
(pm) 
24 u m 
Figure 6. Systematic image errors determined by introduced 
additional parameters to the reference adjustment 
4. BORESIGHT MISALIGNMENT 
The image orientation determined by GPS-supported bundle 
block adjustment, with improved image coordinate and focal 
length in approach 5 was used for the determination of the 
boresight misalignment. The orientations from the GPS- 
supported bundle block adjustment were compared to the 
orientations obtained from GPS/IMU processing. The shift 
parameters were determined by comparing the projection 
centers from the reference adjustment to the GPS/IMU-derived 
projection centers as well as to lever arm measurements. 
In general, the IMU is fixed to the camera body as close as 
possible and is aligned parallel to the camera. In our installation, 
the camera was installed perpendicular to the flight direction, 
resulting in a 90° rotation between the x axis of camera and that 
of the IMU. The orientations from the reference bundle block 
adjustment were transferred into roll, pitch and yaw and the 
boresight angles were determined as 0.18476° for roll, 1.29884° 
for pitch and 0.34447°for yaw. The determined shift values 
were -0.384 m for X, 0.076 m for Y and 0.050 m for Z. 
The boresight angles were also estimated using the POSCal 
utility of the Applanix POSEO software version 4.1. The 
POSCal computation is based on least squares adjustment and 
the required inputs are the image coordinates, control points and 
GPS/IMU-derived projection centers and orientations. The 90° 
rotation between the x axes of the camera and IMU had to be 
also defined for the computation. The determined boresight 
angles were 0.16867° for roll, 1.27303° for pitch and 0.40910° 
for yaw. 
The GPS/IMU-derived attitudes and positions were improved 
by the BLUH and Applanix POSCal boresight misalignment. 
Based on the improved GPS/IMU derived attitudes and 
positions, the object coordinates of measured tie points and 
check points were computed by combined intersection (direct 
sensor orientation). The 25 control points derived from the 
LiDAR point cloud were used as check points. The a 0 of the 
direct georeferencing and root means square errors at check 
points can be seen in Table 2. 
Approach 
Of) 
[ft 
m] 
RMS at Control 
Points [m] 
X 
Y 
Z 
1 
Direct georeferencing using 
BLUH boresight misalignment 
52.2 
1.1 
4 
0. 
79 
5. 
35 
2 
Direct georeferencing using 
Applanix boresight misalignment 
46.0 
1.1 
8 
0. 
70 
5. 
57 
Table 2. Direct georeferencing results in UTM 
The effect of the orientation discrepancies can be seen as y 
parallaxes. The y parallax in the model is important for stereo 
model setup. The comparison of the model y parallaxes from 
direct sensor orientation based on BLUH and Applanix 
boresight angles, and GPS supported bundle block adjustment 
can be seen in Figure 7. The similar results obtained for both 
direct sensor orientations clearly indicate an unacceptable 
quality for stereo models. 
Figure 7. Comparison of the y parallaxes 
To further check the quality of the sensor calibration and 
boresight misalignment, orthoimages were generated using GPS 
supported bundle block adjustment results and GPS/IMU 
derived attitudes and positions improved by BLUH boresight 
misalignment. The effect of orientation discrepancies to the 
orthoimages can be seen comparing the LiDAR intensity 
images and the generated orthoimages in Figure 8. The in-situ 
camera and boresight calibration were determined based on the 
data collected on May 25, 2005. The performance of the in-situ