Graphics Reference
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position of front vehicles and pixel coordinates can be obtained from the geometric
relationship ,that is,
(
)
(
)
2
fz
tan
ʱ
+
h
cos
ʱ
z
tan
ʱ
+
h
cos
ʱ ʱ
sin
z
=
+
(4)
y
y
The following method is used to establish the relationship between the position of
front vehicles and pixel coordinates.
First, the camera is fixed in front and rear of the rearview mirror in the vehicle, and
some calibration boards are put at some places with known spatial distance in front of
the vehicle in a reasonable flat and wide space, as shown in figure 8; then record im-
age information; and finally, get the pixel ordinate at the lower edge of the calibration
board and fit the curve about the relationship between pixel ordinate and spatial dis-
tance. This fitted curve can be regarded as the mapping relationship of pixel ordinate
and spatial distance.
In this essay, the camera sensor is installed on a passenger car, and the calibration
boards are placed in front of the camera sensor, propose corresponding function mod-
el, fit curve by using the least squares method and repeatedly amend it. Eventually,
the fitting result is,
1.845
ln( )
z
=
0.026
xe
0.995
x
+
1.708
(5)
53.58
x
43.47
(
)
xay
100
, a is the height of pixel point.
The fitting curve, as shown in figure 9, describes the mapping relationship between the
spatial distance and the ordinate of pixel, and the corresponding spatial distance of pixel
can be obtained from the curve; therefore, this can be used to locate the front vehicle.
where
Fig. 9. Fitting Curve of Pixel Ordinate and Distance
Fig. 10. Simulation Scenarios of PreScan
 
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