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MULTI SENSOR AIRBORNE SYSTEMS: THE POTENTIAL FOR IN SITU SENSOR 
CALIBRATION 
N. Yastikli 3 *, C. Toth b , D. Brzezinska c 
a YTU, Department of Geodetic and Photogrammetric Engineering, 34349, Istanbul, Turkey - ynaci@yildiz.edu.tr 
b Center for Mapping , Ohio State University, Columbus Ohio, 43212 USA - toth@cfm.ohio-state.edu 
c Department of Civil and Environmental Engineering and Geodetic Science, Ohio State University, Columbus Ohio, 
43210, USA - grejner-brzezinska.l@osu.edu 
KEY WORDS: LiDAR, Digital Camera, GPS, IMU, Sensor, Orientation, Calibration. 
ABSTRACT: 
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 system 
included the small format Redlake MS 4100 RGB/CIR digital camera and the Obtech 3100 ALSM, supported by the Applanix 
georeferencing system (Novatel GPS and LN200 IMU). The investigation focused on determination of in-situ determined camera 
and boresight calibration parameters based on using only the LiDAR data acquired in the project. The performance of the 
determined in-situ camera calibration parameters and boresight misalignment were analyzed by comparing the results of measuring 
points in stereo models formed using bundle block adjustment and direct sensor orientation, respectively for multi sensor system. 
The performance of multi sensor orientation was also tested using independent LiDAR-specific target points which were originally 
used for testing of the LiDAR data accuracy. In addition, the effect of orientation discrepancies as a model deformation was also 
checked by computing y-parallaxes and generated orthoimage. 
1. INTRODUCTION 
The laser scanning is a mature technology, with the integration 
of the fields in optics, opto-mechanics and electronics. Airborne 
LiDAR systems are fully accepted in surveying and mapping 
community since mid-1990’s, which supply us the X,Y,Z 
coordinates of the locations of a footprint of a laser beam in 3D 
space with high accuracy as well as intensity data . The 
positioning and orientation system including GPS (Global 
Positioning System) and INS (Inertial Navigation System) is 
integrated with the Airborne LiDAR systems. The accuracy of 
the X, Y, Z coordinates of the laser footprints on the target 
surface depend on the sensor orientation parameters from GPS 
and IMU and range measurements from airborne LiDAR. 
In recent years, digital cameras are frequently integrated with 
Airborne LiDAR system to allow for visual coverage and to 
improve the mapping performance of the multi sensor system. 
The orientation of images acquired by digital camera in 
integrated system is performed by the platform navigation 
solution from GPS and IMU system. 
In photogrammetry, the determination of image orientation, 
solved indirectly by block adjustment. In multi sensor airborne 
system, such as LiDAR, digital camera, GPS and IMU, the 
direct determination of the exterior orientation parameters of 
imaging sensors is performed by the combined use of IMU and 
GPS. For accurate determination of object points based on 
GPS/IMU oriented imagery, the system calibration is of vital 
importance, and includes the determination of the boresight 
misalignment, the interior camera orientation, and the GPS 
antenna offset. The system calibration procedure includes the 
calibration of individual sensors and the calibration between 
sensors. The calibration between sensors is comprised of the 
GPS antenna offset (lever arm), and the determination of an 
offset vector and attitude difference between the IMU body 
frame and the imaging sensor. The accurate calibration of 
multi-sensor airborne systems, including digital camera, LiDAR, 
* Corresponding author