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Florin Savopol 
2 CONCEPT OF THE DIGITAL MULTI CAMERA SYSTEM 
The existing classical, film-based, aerial photogrammetric cameras exhibit very high metric performances. The 
existing, commercially available frame CCD cameras can not compete with the resolution of a 9 by 9 inch 
photogrammetric camera. There is a trend in the industry for an increased resolution but it will take probably some time 
before it will be possible to directly replace the film with a large CCD sensor. 
For the present situation, we propose to build a system using multiple CCD cameras as more economical solution. 
21 General design 
Some Multiple Cameras Systems were built in the past for remote sensing applications (King, D., 1995). In all of these 
systems, multiple cameras were used to produce multispectral images for the same object or area of the earth surface. 
.Each camera was equipped with a different filter and all the cameras were pointing towards the same area - the optical 
axes of all cameras being parallel. 
In the present project, each camera has a different orientation in order to obtain a maximum coverage of the terrain 
surface. There is only a minimum overlap between the individual images captured by each of the cameras. The optical 
axes of the cameras form a divergent bundle and the cameras are fixed using a rigid, sturdy metal mount. 
If we consider a system using 4 identical cameras, the total ground surface covered by the 4 images (i.e., the total 
"footprint) is shown in Figure 1 (C). For a better understanding, Figure 1 also shows the "footprint" of a single vertical 
camera (A) and the "footprint" of a single tilted camera (B). 
  
  
  
  
  
  
EL 
C 
Figure 1: The "Footprint" of a single vertical camera (A), of a tilted camera (B) and of a 4 camera system (C). 
In a multiple camera airborne system, the cameras must be synchronized with high precision in order to take advantage 
of the "multiple camera" configuration. A poor synchronization will not only generate some gaps in the terrain coverage 
but also will increase the need for ground control points (GCP) because each image will have to been oriented, as in a 
more classical photogrammetry survey. Figure 2 illustrates the generic configuration for such a 4-cameras system. The 
number of cameras was chosen as 4 because there are some frame grabber cards on the market offering up to 4 input 
connectors and enabling the simultaneous capture of up to 4 synchronized video signals. 
22 Calibration and first experimentation 
We tested a first configuration of our system with 4 CCD video cameras using the RSS-170 standard (the North 
American video standard). The analog video output signal was digitized using a Genesis-LC frame grabber card, build 
by Matrox Inc., Montreal. This card accepts 4 analog inputs and has the capacity to capture 4 black and white RSS-170 
standard signals. The mount used for this configuration is shown in Figure 3. 
Any camera used for a photogrammetric work needs to be calibrated. All of the cameras used for the present research 
Work were calibrated using the facilities of the Department for Geomatics at Laval University. This “Calibration and 
Test Site" has 133 spherical targets distributed in 3D over a space cube of about 4 by 3 by 4 meters. The method used is 
the self-calibration technique (Kenefick and al., 1972). The calibration of a digital imaging system should always be 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part Bl. Amsterdam 2000. 267