As a result, the measurement of the height of accuracy 
about 1/200 is possible for a perpendicular movement. 
However, accuracy is very bad when leaning by hand. The 
cause of this is thought to be that for the acceleration to 
work horizontally in time when the device is lifted from the 
level stand, putting, and when had the device by the hand, 
and to calculate accelerations other than the direction of 
the gravity axis as combined power. 
3-2. Horizontal basic experiment 
To do the experiment by which the height (error) calculated 
when horizontally moving was confirmed, by movement 
time regularity, distance was changed and it moved on the 
almost horizontal passage of the third floor of the fourth 
Chiba Institute of Technology building (Figure 4). Each 
distance of the horizontal distance 10m, 15m, 20m, 25m, 
30m, and 35m was measured at 30 seconds. 
Measurement was performed on the sampling frequency 
of 50Hz. Figure 5 shows the result 
  
  
Figure 4 Experiment place 
  
Error by horizontal acceleration 
  
  
  
  
E20 
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5 10 © : 
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3 05 | Ts 
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0 10 20 30 40 
Horizontal movement distance (m) 
Figure 5 Experiment result 
280 
An experiment result shows that the large error has come 
out of a quicker motion. As a result, the influence of the 
horizontal acceleration is understood. How this horizontal 
acceleration is processed because the horizontal 
acceleration greatly influences in the measurement which 
uses the combined power of three axes becomes a 
problem. 
4. APPLICATION TO FIELD EXPERIMENT 
4-1. Ideal model 
The influence of the horizontal acceleration is considered. 
The horizontal acceleration is included in the combined 
power of three accelerometers as shown in Figure 6. To 
examine the influence of the horizontal acceleration, the 
following models were examined theoretically. 
Combined power of acceleration a, b, and c 
Acceleration c 
  
    
   
Acceleration b 
Acceleration a 
Acceleration of 
combined power 
Gravity acceleration 
- 
Vertical acceleration 
  
Horizontal acceleration 
Figure 6 Influence of horizontal acceleration 
«The conditions of a model» 
It goes straight on a horizontal plane, and it is accelerated 
to 40km/h (11m/s) at 8 seconds. It runs 40km/h for 85 
seconds, and it stops at 5 seconds. The gravity 
acceleration is assumed to be 9.8m/s°. On the basis of this, 
it verifies by actual motion (Figure 7~10). 
4-2. Comparison with Ideal model 
It experimented by considering application in an actual 
geographical feature from the result of a perpendicular 
basic experiment and a horizontal basic experiment, and 
carrying measurement device in a car. 
Horizontal 
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