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designed as desired, but its drawback is that the camera itself 
will also be captured in the picture. The lens type, in contrast, 
can capture a completely omnidirectional image without 
capturing the camera, but its drawback is that design is quite 
difficult. In our system, we have adopted a fish-eye lens that can 
support the capturing of tall buildings without capturing the 
camera itself. It must also be pointed out, however, that spatial 
resolution in an omnidirectional camera is low since a wide-area 
image must be projected onto a finite pickup device at one time. 
There are two approaches to solving this problem: a hardware 
approach such as using a high-definition camera, and a software 
approach such as processing multiple images to raise resolution. 
We have adopted the former approach, using high-definition 
cameras in our mobile mapping system. 
2. MOBILE MAPPING SYSTEM 
2.1 Configuration of the mobile mapping system 
The configuration of this system is shown in Fig. 1 and an 
external view of our mobile mapping system is shown in Fig. 2. 
The system can be broadly divided into an “Imaging Section” 
that captures and stores omnidirectional images and a 
“Positioning Section” that collects positional information when 
capturing images. 
The Imaging Section consists of omnidirectional cameras, a 
computer for recording captured images, and a shutter controller 
for controlling each camera’s shutter. The cameras are placed 
on the roof of the vehicle to prevent the vehicle from being 
captured in the images. 
The Positioning Section consists of a GPS antenna, a 
Differential Global Positioning System (D-GPS) device, a 
vehicle-speed sensor, a gyro sensor, a GPS interpolation device, 
and a computer for recording positional information. The 
Imaging Section and Positioning Section are synchronized by a 
GPS-based time server. 
This system can accurately acquire the data required for 
reconstructing building models while moving. 
  
Roof of vehicle 
? Positioning section 
GPS antenna i : Omnidirectional camera 
^ / Imaging section N 
Omnidirectional camera 
  
  
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Image recording PC 
      
     
  
  
  
  
| Shutter controller 
  
  
  
Vehicle interior 
  
  
Figure 1. Mobile mapping system composition 
  
Figure 2. External view of our mobile mapping system 
2.2 Omnidirectional cameras adopted for the system 
In an urban area, a mobile mapping system must be able to 
capture tall buildings. This condition can be met by an 
omnidirectional camera that can capture a 360° scene at one 
time. As mentioned above, there are two major types of 
omnidirectional cameras: a mirror-projection type and a lens 
type. Because the camera is captured in the image and forms an 
obstruction in the former type, we have adopted an 
omnidirectional camera that employs a fish-eye lens for which 
the camera will not be picked up. This type of camera, however, 
while being able to capture an expansive 360° area, suffers from 
low spatial resolution. As a countermeasure to this problem, we 
decided to use a digital camera having a 6-million-pixel CCD. 
Using a camera with high spatial resolution makes it possible to 
reconstruct high-quality texture and high-accuracy building 
models. 
On the other hand, it takes about two seconds to capture one 
image with the type of camera adopted in our system, making 
for a low shooting rate. For this reason, the interval between the 
shooting positions for each image is large, and variation occurs 
in texture quality and model accuracy according to the distance 
from the shooting position and target building. To avoid this 
problem, we mount two omnidirectional cameras in our system 
and incorporate a shutter controller so as to control the shutter 
interval for each camera and facilitate flexible control of the 
shooting interval. This, in turn, makes it possible to adjust the 
baseline distance in omnidirectional stereo according to the 
distance to the target building and to therefore eliminate the 
variation in accuracy and texture quality among the buildings to 
be reconstructed. 
Table 1 lists main specifications of our omnidirectional camera 
and Fig. 3 shows an actual example of an omnidirectional image 
taken with our mobile mapping system. The omnidirectional 
images captured by this system are of high quality and can 
accommodate tall buildings. 
On the basis of these features, the omnidirectional cameras 
adopted for our system are considered to be an effective means 
of acquiring data in an urban area. 
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