Issues and Method for InFlight and OnOrbit Calibration

Issues and Method for In-Flight and On-Orbit Calibration (only geometry) Karsten Jacobsen Institute of Photogrammetry and Geo. Information University of Hannover jacobsen@ipi. uni-hannover. de Universität Hannover Institut für Photogrammetrie und

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 Universität Hannover Institut für Photogrammetrie und

Inner Orientation t‘ t CCD-line sensors photographic camera – fiducial marks Inner orientation only for 1 CCDline digital array camera – principal point F(line, sample) Universität Hannover Institut für Photogrammetrie und

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“ averaged image company 2 coordinate residuals (66 images, 1484 image points) Universität Hannover image company 1 Institut für Photogrammetrie und

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 Universität Hannover Institut für Photogrammetrie und

Additional parameters Jacobsen (program system BLUH) 1 angular affinity 6 mathematic 11 radial sym. Universität Hannover 2 3 affinity 7 mathematic 5 mathematic justification 8 tangential distortion 12 4 9 10 radial symmetric distortion mixture between physical and mathematical justification – parameters less correlated like with Ebner set if image points randomly distributed Institut für Photogrammetrie und

radial symmetric additional parameters Often used: Dr = K 1* r 3 + K 2* r 5 + K 3* r 7 disadvantage: highly correlated, K 2 and K 3 effective only in corner Program system BLUH: Dr = P 9* (r 3 – A*r) + P 10*r*sin(r*A/(2 p) + P 11*r*sin(r*A/(4 p) 9 10 11 - -0. 36 0. 24 - -0. 32 correlation matrix Universität Hannover same data set: correlation K 1 – K 2 = 0. 94 only K 1 P 9 – P 11 Institut für Photogrammetrie und

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 1. 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 ß OEEPE test block “direct sensor orientation”, image scale 1 : 5000, 1 : 10 000 Universität Hannover Institut für Photogrammetrie und

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) hg 1 – DZ 1 hg 2 – DZ 2 control points Universität Hannover GPS DATA FOR DATA SET 1 GPS DATA FOR DATA SET 2 CHANGE OF FOCAL LENGTH GPS-SHIFT ABSOLUT GPS-SHIFT STANDARD DEVIATION X Y Z SX SY SZ. 010 -. 113 -. 278. 008. 004 -. 069. 124 -. 460. 014. 015. 006. 039 = CORR. FOR F -> 153. 383 -. 094 Institut für Photogrammetrie und

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 CCDarray camera Rollei Q 16 typical strong radial symmetric distortion of off-the-shelf optics Universität Hannover Institut für Photogrammetrie und

Digital aerial array cameras “systematic image” errors of the Therm. Scan 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 Universität Hannover Institut für Photogrammetrie und

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 Universität Hannover Institut für Photogrammetrie und

CCD-line cameras IRS-1 C 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 Universität Hannover Institut für Photogrammetrie und

“level 1 A” space images Quick. Bird SPOT ASTER “systematic image errors” of the orientation of level 1 A space images - no calibration, dominated by exterior orientation - in general sub-pixel accuracy possible Universität Hannover Institut für Photogrammetrie und

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 Universität Hannover Institut für Photogrammetrie und