Picture 1 
Measurement Vehicle 
Picture 2 Special Platform 
A block diagram of the components mounted 
into the measurement vehicle is illustrated in 
Figure 1, which consists of the HISS and 
Position and Image Input System essentially. 
H I s 
S 
D G P S 
Receiver 
^R8232C ; 
PPS 
I N S 
(TA7421) 
Position and Image Input System 
camera trigger 
MIL-STD-1668 
pulae 
yn © 
Range Sonaora Odometer 
”> 
Industrial PC 
(Pentium200) 
fi 
Digital Camera 
Digital Camera 
Digital VTR 
Controller 
Video Camera 
Vdeo Camera 
J Car Navigation 
“lyatem 
Figure 1 Block Diagram 
3.2 Hybrid Inertial Surveying System 
The HISS integrates a medium accuracy 
strapdown INS, a DGPS receiver with pseudo 
range observation, a odometer and four range 
sensors. The INS (TA7421) was improved the 
Attitude and Heading Reference System 
(AHRS) embedded with a Monolithic Ring 
Laser Gyro and three accelerometers into land 
surveying. This system operates on DC 24V 
and weighs 9 kg. The MIL-STD-1553B bus is 
used to interface to the Position and Image 
Input System. The navigation data, inertial 
sensor data, GPS data and estimates and 
covariances of Kalman Filter for post 
processing are output to the Position and Image 
Input System at a data rate of 50 Hz. A DGPS 
unit (DX ANTENNA) comprises a Ashtech G12 
GPS receiver, a portable phone to receive 
differential correction data from base station. 
Position, velocity and event marker are 
transmitted to the INS through RS232C at a 
data rate of 10Hz. The GPS Pulse per Second 
(PPS) signal for time synchronization is also 
output. The encoder of odometer outputs 500 
pulse per revolution with the TTL signal to the 
INS and the Position and Image Input System. 
Figure 2 illustrates an explanation drawing for 
the hybrid inertial surveying. 
Figure 2 Hybrid Inertial Surveying 
The INS calculates attitude, velocity and 
position successively by integrating angular 
velocities and accelerations. But the errors of 
inertial sensors are also integrated, 
consequently they diverge with the time. To 
control the increase of error, it is necessary to 
correct the error of gyros, accelerometers, 
attitudes, velocities and positions at the same 
time by combining with the other sensors to 
detect position or velocity. In the HISS, there 
are two navigation modes, INS/DGPS mode 
and INS/Odometer mode. When the DGPS 
signals are available, the position and velocity 
of DGPS are used as the measurement values 
in the Kalman filter to estimate inertial errors 
and instrument biases or drifts. In other words, 
the measurements are differences between