Full text: XVIIIth Congress (Part B5)

  
An example of running locus measurement is shown 
in Figure 5. The specified turning radius (15m) and 
measuring results are shown in this Figure. The 
measured locus of 5 times running are overlaid in the 
figure. The measured values represent the locus of right 
front edge of the vehicle. 
As for the measuring result of running locus, we 
could obtain the measured values within 0.5m from the 
specified radius in general for any turning radius. The 
measuring results were generally satisfactory excepting 
that discontinuity took place in the locus for about 10 cm 
when the system switched over the image for 
correlation. 
(2) Comparison of the results taken at different 
observation altitude 
In this study, the same pattern of test run was 
observed from two different altitude of 100m and 150m. 
We could obtain almost similar results both from 100m 
and 150m altitude photographing because this extent of 
difference could be offset by the adjustment of zoom 
lens of video camera. So ,it may be better to select the 
high observation altitude so as to minimize the 
displacement of image. 
(3) Influence of mid-way stop at turning 
The car was stopped (for 2 seconds) at the mid-way 
of leftward turn in this experiment. We confirmed 
whether the deviation took place during the stop, and 
  
* Measurement reference line 
Turning radius 15m 
  
  
  
  
Figure 5 Example of running locus measurement result 
(Observation altitude 100m, Turning radius 15m ) 
382 
found that no significant deviation occurred to the locus. 
We could also obtain the graph to show the change of 
running speed including those of mid-way stop. As a 
result, we could confirm that mid-way stop does not give 
any significant influence on the measurement in case of 
our measuring system. 
From the above, we confirmed that appropriate 
results are obtained in general in the measurement of 
running locus. Partly, there were cases where matching 
was impossible because the road surface and vehicle 
could not be distinguished each other just like in the 
cases of speed measurement, therefore, we are 
planning to add pre-processing to photographing 
condition to make it robust. 
6. Application for the Identification of Car Type 
We attempted to identify the car type utilizing the 
measuring results of running speed. If it is possible to 
classify the running cars into the rough two groups of 
normal size car and large sized car, it will be quite 
effective in saving energy in the current traffic 
investigations. 
In this experiment, we calculated length of cars 
passing through the test section using the following 
formula, and discussed the possibility to identify the 
type of car by the difference of length. 
T 
L=2> Nenn WI. 
n=1 
Where, L: Car length; 
W: Length of measuring section 
v: Measured Speed of car (each 1/60 second) 
t: Unit time of measurement (1/60 second) 
T: Time when the car passed the section 
n: Number of video field 
When this method was applied to the video image 
used for the measurement of running speed, the 
measuring error of maximum 2.5m was observed in 
case of normal size white car and maximum 1.5 in case 
of large sized car. In case of the car with black body, the 
measuring error close to 4.5m was observed at 
maximum. It is barely possible to distinguish normal 
size white passenger car from large sized car as there is 
a difference of 3m or more in the length between the 
normal size and large sized cars, but the judgment is 
quite unstable. The main cause of these errors would be 
the accumulation of error involved in measuring the 
speed at the unit of 1/60 and measuring error of passing 
time of the section. The reason why the error is larger in 
case of black car body is attributable to the fact that car 
body cannot be distinguished from road surface of 
asphalt at the automatic tracing by image matching. 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996 
  
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