Issues and Method for In-Flight and On-Orbit Calibration (only geometry)

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Issues and Method for In-Flight and On-Orbit
Calibration (only geometry)
Karsten Jacobsen Institute of Photogrammetry and
GeoInformation University of Hannover jacobsen_at_ipi
.uni-hannover.de
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Camera Calibration
Reconstruction of the bundle of rays from the
projection center to the object based on measured
image positions Inner orientation of
sensor Exterior orientation location of
projection center attitude information System
calibration inner orientation relation to
positional sensors
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Inner Orientation
t
photographic camera fiducial marks
t
CCD-line sensors Inner orientation only for 1
CCD-line
digital array camera principal point F(line,
sample)
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Deformation of the bundle of rays - systematic
image errors
deformed bundle of rays
deformation of bundle of rays causing systematic
image errors effect in images systematic
image errors OEEPE test block direct sensor
orientation
image
averaged image company 2
company 1 coordinate residuals
(66 images, 1484 image points)
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Self calibration by additional parameters
Set of additional unknowns for fitting systematic
errors Additional parameters from Gotthard /
Ebner optimal if image points located in Gruber
points only mathematic interpretation
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Additional parameters Jacobsen (program system
BLUH)
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5
1
2
3
angular affinity affinity
mathematic justification
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9
10
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mathematic tangential distortion
radial symmetric distortion
mixture between physical and mathematical
justification parameters less correlated like
with Ebner set if image points randomly
distributed
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radial sym. mathematic
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radial symmetric additional parameters
Often used Dr K1 r3 K2 r5 K3 r7
disadvantage highly correlated, K2 and K3
effective only in corner Program system BLUH
Dr P9 (r3 Ar)
P10rsin(rA/(2p) P11rsin(rA/(4p) 9
10 11 9 - -0.36 0.24 10
- -0.32
same data set correlation K1 K2 0.94
correlation matrix
only K1 P9 P11
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in-flight calibration of photographic aerial
cameras

• Bundle adjustment with self-calibration by
  additional parameters
• based on the over-determination of the bundle
  adjustment control point information

• Standard block configuration only parallel
  flight lines affinity parameters depending upon
  control points, other just by over-determination

• 2. Crossing flight lines also affinity
  parameters just by over-determination
• OEEPE test block direct sensor orientation,
• image scale 1 5000, 1 10 000

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determination of focal length and principal point
under standard conditions of aerial images
determination of focal length not possible
strong correlation Zo focal length Z of
projection centers required possible by GPS,
but problems with GPS datum shift, no separation
of GPS datum and focal length - 2 different
flying height levels required (like in OEEPE test
block)
hg1 DZ1 hg2 DZ2 control points

GPS-SHIFT STANDARD DEVIATION

X Y Z SX SY SZ
GPS DATA FOR DATA SET 1 .010 -.113
-.278 .008 .008 .004 GPS DATA FOR DATA
SET 2 -.069 .124 -.460 .014
.015 .006 CHANGE OF FOCAL LENGTH .039
CORR. FOR F -gt 153.383 GPS-SHIFT ABSOLUT
-.094
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Digital aerial array cameras
No problems with film deformation, CCD-array
usually perfect flat, main problem caused by
optics affinity of CCD (will never change)
systematic image errors of synthetic ZI-DMC
images (flight over test area) small affinity
deformation, has been confirmed by following
laboratory calibration - original distortion of 4
single optics always respected
systematic image errors of CCD-array camera
Rollei Q16 typical strong radial symmetric
distortion of off-the-shelf optics
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Digital aerial array cameras
systematic image errors of the ThermScan camera
tangential distortion
wide angle optics normal angle
optics largest vector 1.7 pixels If optics
are exchanged, focal length and principal points
have to be calibrated again focus has to be
fixed, after change of focus and going back, not
same inner orientation calibration of zoom-lenses
not possible, inner optical system has no
sufficient stability, may change after shaking
the camera
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line scan cameras
HRSC CCD-line camera linearity of CCD-line by
laboratory calibration can also be calibrated
under flight conditions, higher number of control
points or crossing flight lines required real
problem boresight
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CCD-line cameras
IRS-1C Pan-camera 3 combined CCD-lines
available configuration for calibration
determined geometry most
CCD-line cameras used in space equipped with a
combination of shorter CCD-lines, calibration
under flight conditions required, with
combination of images taken from different orbits
reduction of required number of control points
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level 1A space images
QuickBird SPOT
ASTER

• systematic image errors of the orientation of
  level 1A space images
• no calibration, dominated by exterior
  orientation
• in general sub-pixel accuracy possible

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conclusion
Perspective aerial cameras can and should be
calibrated under flight conditions by bundle
block adjustment with self-calibration by
additional parameters optimal set of parameters
should be used, statistical analysis of
parameters required Stability of film-camera
calibration limited, only parts stable over
time focal length and principal point can only be
determined by 2 different flying heights
GPS-projection center coordinates Digital
CCD-array cameras mainly influenced by optical
distortion CCD-line cameras used in space usually
do use a combination of shorter CCD-lines, has to
be calibrated under flight conditions