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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004
Table 1. Parameters of EYESCAN and SpheroCam panoramic cameras
Parameters
EYESCAN SpheroCam
Number of pixel in linear array (vertical format)
3600 or 10200 pixels per line
5300 pixels per line
Horizontal format (depends on the focal lens)
27489 pixels (35 mm lens)
39267 pixels (50 mm lens)
Pixel size 7 or 8 microns 8 microns
In our tests we used two line-based rotating panoramic cameras,
a prototype of EYESCAN M3, a joint development between
German Aerospace Center (DLR) and KST Dresden GmbH”.
The camera is engineered for rugged everyday field use as well
as for the measurement laboratory. The other panoramic camera
used here is the SpheroCam from the SpheronVR AG™ which
operates similar to EYESCAN.
2.1. EYESCAN M3
Figure 1 shows the sensor system and Table 1 shows format
parameters of the camera. The camera system contains three
parts: camera head, optical part, and high precision turntable
with a DC-gearsystem motor. The camera head is connected to
the PC with a bi-directional fiber link for data transmission and
camera control. The optical part of the system uses high
performance Rhodenstock lenses. With adjustment rings one
can use other lenses. The camera head is mounted on a high
precision turntable with a sinus-commutated DC-gearsystem
motor (Scheibe et al., 2001), internal motion control and direct
controlling by the PC. Rotation speed and scan angle are pre-
selectable and correspond to the shutter speed, image size and
focal length of the lens. For a more detailed description see
Schneider and Maas (2003).
2.2. SpheroCam
The structure of the SpheroCam (Figure 1) includes three parts,
the camera head, the optical part which is compatible with
NIKON-Ilenses, and a DC motor to rotate the Linear Array. The
SpheroCam is specially designed for use with a fish-eye lens,
with a near 180? vertical field of view. As it rotates about its
vertical axis, the SpheroCam then captures a complete spherical
image. It is designed to capture high quality images. Table !
contains the format parameters of SpheroCam. For more detail
on specifications of the camera see Amiri Parian and Gruen
(2003).
3. SENSOR MODEL
The sensor model as a mapping function is based on a
projective transformation in the form of bundle equations,
which maps the 3D object space information into the 2D image
space. The sensor model uses the following coordinate systems:
e Pixel coordinate system
e Linear Array coordinate system
e 3D auxiliary coordinate system
e 3D object coordinate system
Figure 2 shows the pixel coordinate (i, j) system. The original
image observations are saved in this system. Figure 3 shows the
other coordinate systems: Linear Array (0, y, z), auxiliary
(X', Y', Z') and object space (X, Y, Z) coordinate systems. The
* / ;
http://www.kst-dresden.de/
** rz
http WWW, spheron .com/
Figure 1. Digital terrestrial panoramic cameras. EYESCAN
(left) and SpheroCam (right).
effects of lens distortion and the shift of the principal point are
modeled in the Linear Array coordinate system. The rotation of
the Linear Array and mechanical errors of the rotating turntable
are modeled in the auxiliary coordinate system. The object
space coordinate system is used as a reference for determining
the exterior orientation parameters of the sensor.
To define the auxiliary coordinate system, an ideal panoramic
camera is considered. Here the origin of the auxiliary coordinate
system coincides with the projection center O. The rotation axis
passes through the projection center and coincides with Z'. X'
passes through the start position of the Linear Array before
rotation and Y' is defined to get a right-handed coordinate
system.
calumn(j)
row (i)
Figure 2. Pixel coordinate system (i, j).
The model, which directly relates pixel observations (i, j) to the
object points (X, Y, Z), for an ideal sensor becomes (Amiri
Parian and Gruen, 2003):
‘9 uy eue yr
y RAP A Ma | YE,
ge Le
With (1)
QU A :
Zml-1 0 OF y -(-—)A,
ol, 1 *
Where, 4 is horizontal pixel size and A, is vertical pixel size.
N is the number of pixel in linear array.
