MULTI SENSOR AIRBORNE SYSTEMS: THE POTENTIAL FOR IN SITU SENSOR CALIBRATION

Airborne LiDAR systems are integrated with a positioning and orientation system including GPS (Global Positioning System) and INS (Inertial Navigation System) to measure the exterior orientation of the sensors. LiDAR systems are frequently integrated with digital cameras in recent years. The digital camera imagery is directly oriented by using the platform navigation solution of the integrated GPS and IMU system. The direct sensor orientation approach, used for georeferencing of imaging sensors, is more sensitive to calibration errors, and therefore, the calibration of individual sensors and the relation between sensors (system calibration) is critical for accurate georeferencing. In addition, the physical parameters during the flight mission may differ from assumed calibration parameters, causing errors in object space for any products derived from the imagery; the calibration of digital cameras as well as laser sensor is usually performed in laboratory conditions. The displacement vectors between GPS, INS and imaging sensors, such as digital camera and LiDAR should be determined as well as their attitude relationship. The boresight misalignment, the determination of the displacement vector and attitude relationship between sensors is critical and requires a test field with distributed control points of high accuracy where adequate data can be collected for the parameter determination. Finding such a test field nearby or within project area, however, is not always possible. On the other hand, the multi sensor environment could provide redundant object space information that potentially could be exploited for certain calibration and QA/QC processes. This paper aims to share our experiences obtained by in situ calibrating a digital camera using LiDAR data. The multi sensor syste