Post-mission misalignment angle calibration for airborne laser scanners

An Airborne Laser Scanning (ALS) system operates by locating returned laser pulses independently from all others. Locating the returned laser pulses requires knowing precisely for each laser pulse, the aircraft position (e.g. GPS), the attitude of the aircraft (e.g. IMU), the scanner angle when the laser pulse left the sensor, and the slant range to the terrain surface for that pulse. One of the most critical errors in ALS systems is the angular misalignment between the scanner and the IMU, which is called the misalignment or boresight error. This error must be addressed before an ALS system can accurately produce data. The purpose of this thesis was to develop and test a method of estimating the small misalignment angles between the laser scanner and the combined GPS/IMU solution for position and attitude. This method is semi-automated, requires no ground control and does not re-sample the ALS data in order to match the overlapping strips of data. A computer program called Misalignment Estimator was developed to estimate the misalignment angles using a least squares adjustment. The method was tested using a data set located at the Oshawa airport and provided by Optech. The misalignment angles were estimated to be -0.0178 degrees, -0.0829 degrees and 0.0320 degrees, for roll, pitch and heading respectively. The estimation of the misalignment angles was considered to be successful. Further research into automated point matching is recommended.