CIPA 2003 XIX"' International Symposium, 30 September - 04 October, 2003, Antalya, Turkey 
carrying out a calibration procedure after mounting the 
camera. This calibration routine is described in detail 
below. As soon as the scan position is registered in the 
project coordinate system the image information can be 
completely utilized. 
The mounting calibration information specifies the 6 
degrees of freedom of the camera's coordinate system 
with respect to the scanner's coordinate system, i.e., 3 
rotational parameters and 3 translation parameters. 
Within RiSCAN PRO the mounting calibration is 
stored as a 4 x 4 matrix for convenience of definition 
and of application. The mounting calibration matrix 
transforms from the scanner coordinate system into the 
camera system in case the rotational part of the scanner 
is at the position of phi equal to 0 deg. The additional 
rotation at an other angle is modelled by the COP 
matrix (camera’s orientation and position matrix) 
stored with every image of Type 1 reflecting the phi 
angle. 
The three translation parameters are well defined and 
are determined for a specific camera model and lens 
after final calibration at the manufacturer's premises. 
Mounting and de-mounting the camera do not change 
these three parameters. The three parameters describe 
simply the coordinates of the center of the scanner's 
coordinate system at phi equal 0 deg within the 
camera's coordinate system. 
4 Calibration tasks 
4.1 Laser sensor calibration 
The laser sensor itself has not to be calibrated by the 
user. As the sensor accurately measures all geometrical 
information, i.e., range and the angles, no calibration 
tasks with respect to the laser data have to be carried 
out. 
4.2 Calibration of internal camera 
parameters 
For a camera with a wide-angle lens calibration of the 
camera is done by taking images of a flat regular 
structure with well-defined dimensions, for example a 
flat black-and-white image of a check pattern. A series 
of images are taken covering in total the complete 
field-of-view of the camera. 
For a camera with a telephoto lens the method with the 
check pattern becomes impractical. In order to get an 
image in focus the distance of the camera to the check 
pattern has to be quite large. In this case it is possible 
to base the camera calibration on identifying tie points 
in the calibration images which are arbitrarily 
distributed in 3D with known 3D coordinates. Again, 
by taking a series of images covering in total the 
complete field-of-view with a nore or less uniform 
distribution, the parameters can be determined 
accurately. 
4.3 Mounting calibration 
The three rotational parameters of the mounting 
calibration have to be optimised after each mounting of 
the camera. This can be done directly after mounting 
the camera and taking both scan data and an image 
sequence, but can also be done off-line after taking all 
data of the data acquisition campaign. This calibration 
task is based on identifying at least two tie points in the 
images taken at one scan position with well-known 3D 
coordinates in the scanner's own coordinate system 
(SOCS). 
As the mounting calibration has to be carried out after 
each mounting of the camera RiSCAN PRO manages a 
large number of mounting calibrations within a single 
project, although most projects can be handled with a 
single mounting calibration. 
5 Example project 
Data have been acquired with a RIEGL LMS-Z360 3D 
Imaging Sensor combined with a Nikon D100 camera 
with a Nikkor 14 mm lens. The key features of the 
instrument are summarized in Table 1. 
3D Imaging Laser Sensor RIEGL LMS-Z360 
Measuring range 
2m up to 200m 
Range measurement 
accuracy 
12 mm 
Laser 
0.9pm/Class 1 (eye safe)/3 mrad 
beam divergence 
Measurement rate 
8000 -24000 points/s 
Scanner performance 
Scan range 
Up to 90 deg x up to 360 deg 
Minimum scan step width 
0.004 deg 
Angular resolution 
0.0025 deg 
Physical data 
Main dimensions (Lx0) 
490 mm x 210 mm 
Weight 
approx. 13 kg 
Power supply 
12-28 V DC, 4 A @15 V DC 
Temperature range 
Operation: -10°C to +50°C, 
Storage: -20°C to +60°C 
High-resolution camera system 
Camera type 
Nikon D100 
Resolution 
3008 x 2000 pixel, pixel size 7.8 pm 
Lens 
Nikkor 20 mm 
Table 1: Key parameters of the data acquisition system used in the 
example. For a more detailed description of the laser measurement 
system see www.riegl.com and (ULLRICH 2001). 
The object is the arena in Verona, Italy (compare 
Figure5). Data have been acquired from only four 
positions. Data acquisition has been done in 
cooperation with Instiuto Universitario di Architettura 
di Venezia, Prof. F. Guerra. At every scan position at 
least 9 images have been taken with fixed focus and 
fixed aperture. For merging the data numerous retro- 
reflecting targets have been posed in the scene