Calibration and orientation of airborne image and laser scanner data using GPS and INS

Abstract: GPS and INS measurements provide positions and attitudesthat can be used for direct orientation of airborne sensors.This research improves the final results by performingsimultaneous adjustments of GPS, INS and image or laser scannerdata. The first part of this thesis deals with in-airinitialisation of INS attitude using GPS and INS velocitydifference. This is an improvement over initialisation on theground. Even better results can probably be obtained ifaccelerometer biases are modelled and horizontal accelerationsmade larger.The second part of this thesis deals with GPS/INSorientation of aerial images. Theoretical investigations havebeen made to find the expected accuracy of stereo models andorthophotos oriented by GPS/INS. Direct orientation will becompared to block triangulation. Triangulation can to greaterextent model systematic errors in image and GPS-coordinates.Further, the precision in attitude after triangulation isbetter than that found in present INS performance. On the otherhand, direct orientation can provide more effective dataprocessing, since there is no need for finding or measuring tiepoints or ground control points. In strip triangulation, thenumber of ground control points can be reduced, since INSattitude measurements control error propagation through thestrip. Even if consecutive images are strongly correlated indirect orientation, it is advisable to make a relativeorientation to minimise stereo model deformations.The third part of this thesis deals with matching laserscanner data. Both elevation and intensity data are used formatching and the differences between overlapping strips aremodelled as exterior orientation errors. Special attention ispaid to determining misalignment between the INS and the laserscanner coordinate systems. We recommend flying in fourdifferent directions over an area with elevation and/orintensity gradients. In this way, misalignment can be foundwithout any ground control. This method can also be used withother imaging sensors,e.g.an aerial camera.Keywords:Airborne, Camera, Laser scanner, GPS, INS,Adjustment, Matching.