The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
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GPS, IMU, etc, is of high importance, since sensor orientation 
is very sensitive to changes in sensor geometry because of the 
extrapolation from the camera projection center to the ground. 
The camera calibration process involves the geometric 
calibration, resolution determination and radiometric calibration 
of camera. The laboratory calibration is a standard method for 
analog airborne frame cameras and the interior camera 
geometry, i.e. focal length, principle point location and lens 
distortion parameters are estimated. In-situ calibration, also 
called self-calibration originates from close range applications 
and requires a large number of signalized control points in 3D 
terrestrial calibration fields. The airborne in-situ calibration also 
requires a calibration field with signalized control points of 
high accuracy. The focal length, principle point location and 
lens distortion parameters are estimated during the calibration 
process from the measurements reflecting actual conditions. 
The ASPRS and the EUROSDR continue their research on 
digital camera calibration and validation (Stensaas, 2005, 
Cramer, 2005). The lab calibration method is still used for 
geometric calibration of large format digital cameras such as ZI 
Imaging DMC and Leica ADS40 together with in-situ 
calibration (Dorstel et al., 2003, Tempelmann, et al., 2003). For 
medium format digital cameras such as the Applanix/Emerge 
DSS geometric calibration is done by terrestrial and airborne 
calibration (Mostafa, 2004). The terrestrial in-situ calibration 
method is used for geometric calibration of the Vexcel 
Ultracam D large format digital camera (Kropfl, et al, 2004). The 
U.S. Geological Survey (USGS) began its certification efforts 
with digital aerial cameras in January 2006 (Stensaas, 2006). 
Current investigations at USGS focus on geometric and spatial 
characterization and calibration, although research on 
radiometric characterization and calibration of airborne sensors 
also continues with the recently established digital camera 
calibration lab at the USGS Center for Earth Resources 
Observation and Science (EROS). To perform in-situ camera 
calibration, a calibration range was established also at USGS 
EROS with 150 surveyed panels and one CORS station 
(http://calval.cr.usgs.gov). 
The offset between the GPS antenna and the IMU or imaging 
sensor can be precisely measured by conventional survey 
methods. The boresight misalignment is determined by a 
comparison of the GPS/IMU derived image orientation with the 
results of a bundle block adjustment over a calibration field 
containing control points. Finding such a calibration field 
nearby or within project area, however, is not always possible. 
This research was motivated by the circumstances of a LiDAR 
mapping project, where a small format digital camera was 
installed next to the LiDAR system in the last minute before the 
airborne surveys started. There were no measurements and no 
dedicated data acquisition performed to support boresight 
calibration of the camera except for an earlier lab camera 
calibration. Furthermore, there was no target range or any area 
with signalized controls in the project area. Therefore, this 
investigation aimed to determine the system calibration 
parameters for that multi sensor airborne system using only the 
LiDAR data acquired in the project. The multi sensor airborne 
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). Experiments with the data set and the results obtained 
are analyzed and discussed to assess the performance of system 
calibration for the Redlake MS 4100 camera. 
2. PROJECT AREA AND DATA ACQISITION 
The data set from the project B4 Airborne Laser Swath 
Mapping (ALSM) survey of the San Andreas Fault (SAF) 
System of Central and Southern California, including the 
Banning Segment of the SAF and the San Jacinto Fault system 
was used (Toth et al., 2007). The project B4, codenamed to 
reference to the “before” status of a widely anticipated major 
earthquake, the Big One, is a National Science Foundation 
(NSF) sponsored project, led by scientists from The Ohio State 
University (OSU) and the U.S. Geological Surveys (USGS), to 
create an accurate surface model (DEM) along the San Andreas 
and San Jacinto Faults in southern California. Besides the 
USGS, the OSU-led team included NCALM (National Center 
for Airborne Laser Mapping) from the University of Florida, 
UNAVCO (a non-profit, membership-governed consortium, 
supporting Earth science) and Optech International. 
The airborne surveys took place May 15-25, 2005 with a 
Cessna 310 aircraft which was hired and Optech International 
provided the ALTM 3100 system. The state-of-the-art Optech 
3100 system was configured for 70 kHz, resulting in an about 2 
pts/m 2 LiDAR data. An experimental Redlake MS 4100 digital 
camera was installed next to the Optech 3100 system, providing 
imagery of 1K by 2K resolution in four bands. The images were 
captured at 1 Hz, synchronized to the 1PPS GPS signal. The 
project area, encompassing about 1,000 km of fault line, was 
segmented into smaller sections during flight planning, 
including the San Andreas and San Jacinto Fault lines. 
3. GEOMETRIC CALIBRATION 
An experimental digital camera used in this project was the 
Redlake MS 4100 RGB/CIR digital camera, which has four 
CCD sensors each with 1920 x 1075 pixels and pixel size of 7.4 
pm x 7.4 pm. The laboratory camera calibration was performed 
in RGB mode and a focal length was estimated for 25.966 mm 
in the calibration report. The calibration values were used as 
initial calibration parameters for the in situ calibration of the 
Redlake MS 4100 camera. The camera was configured for CIR 
image capture for the airborne surveys. The CIR imagery has 
1892 x 1060 pixels, different from the RGB images. The 
approximate image size is 8 mm in the flight direction and 14.2 
mm across the flight direction. 
A reference block was selected from a typical flight on May 25, 
2005 with 21 images, where several man-made structures were 
available (Figure 1). 25 control points were used to perform an 
airborne in-situ calibration of the Redlake MS 4100 digital 
camera which were extracted from the LiDAR point cloud and 
intensity data (Figure 2). 
Figure 1. The 3D view of geo-registered LiDAR point clouds