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essential drawback that the error accumulates 
with time by giro drift. The differential GPS 
(DGPS) with carrier phase observation allows 
the vehicle to get positions with a high accuracy 
of centimeter level, provided that the sky opens 
and the rover is within several ten kilometers 
of the base station. But, it is difficult to 
measure position continuously and reliably 
when the ground vehicle travels in the urban 
area. Also, the DGPS with pseudo-range 
observation can measure stable positions with 
accuracy of several meters if the sky opens to a 
certain extent. On the other hand, Japanese 
roads are narrow in addition that the traffic is 
very heavy. Therefore, the GPS receiver on the 
vehicle can not measure position or its 
measurement accuracy deteriorates because 
GPS signals are hidden by around building or 
facilities or passing heavy-duty trucks. 
Especially, it is impossible to measure positions 
for a distance of several kilometers when the 
vehicle runs parallel with a high-level road. 
To develop the robust position and attitude 
determination techniques coped with the 
special road circumstances in Japan is the most 
important problem for putting into practice a 
variety of Mobile Mapping applications. Asia 
Air Survey Co., Ltd. has developed the Hybrid 
Inertial Surveying System (HISS) which is 
integrated with INS, DGPS and odometer. This 
system can measure positions continuously 
with a accuracy of constant in tunnels or under 
elevated roads by changing into odometer 
hybrid mode automatically when GPS 
positioning do not work. 
2. STATUS AND PROBLEM OF ITS 
2.1 Upgrade Navigation Systems 
The cumulative shipments of the car navigation 
system in Japan came to three million units at 
the end of June 1998. It formed a big market of 
about 500 billions, and created new market in 
the transportation and information industry. 
Now it grows remarkably as the car 
multimedia terminal such as the “DVD NAV” 
which supplies various kind of multimedia 
contents, or the “Communication NAV” which 
supplies information services through 
automobile phone. Contrary to the progress of 
these conveniences technology, the performance 
of navigation has not been improved so much. 
The latest car navigation system determines a 
nearest location of road by the map-matching 
between DGPS positioning by FM multiplex 
broadcasting and the digital road map. But, 
there are frequent mismatches when car runs 
paralleled with overpass or passes through the 
complicated grade separation. To remove these 
problems, the 3D geometric road information 
including the height of road, the gradient, and 
the radius of curvature is required. 
2.2 Safety Driving Assistance 
In AHS, the steering control of vehicle is as 
follows. While the communications antenna 
mounted on the car receives the road alignment 
information from the LCX cables installed on 
the road, and the magnetic sensor perceives the 
magnetic nails on the road surface to maintain 
a balance on both sides. And the CCD camera 
recognizes the white lines on the road and 
complements the balance. Accordingly, in order 
to carry out these series of procedures, the road 
alignment information is indispensable and 
should be acquired certainly with sufficient 
accuracy. 
To pursue AHS successfully, it is essential to 
cooperate with functions between the vehicle 
system and the road system. But this subject of 
study has not been started yet. In the present 
circumstances, the investigation for practical 
use such as the reliability about automated 
driving, the social needs, and the social 
acceptability has not been executed. 
3. DEVELOPMENT OF MOBILE MAPPING 
Asia Air Survey Co., Ltd. has been developing 
the core technologies of MMS aiming at 3D 
data acquisition for the road management, the 
urban planning and the disaster prevention. 
This section describes the design concept, 
configuration, and functions of the MMS. 
3.1 Measurement Vehicle 
The external appearance of the measurement 
vehicle is shown in Picture 1. The AC 
alternating current generator with 100V, 50Ais 
mounted. When it does not work, the UPS can 
supply the power to electric instruments for 20 
minutes. The special platform, which is made of 
the flat duralumin, is shown in Picture 2. It 
was designed so that an INS and a pair of 
cameras are regarded as a rigid body. Also, this 
unit can absorb the minute vibration in all 
directions of the vertical and horizontal motion. 
Like this way, it eliminates any chance of 
camera movement during the survey.