where A is an value of kth element of lateral histogram, and n is
shift of zone relative to the etalon.
Output pitch increment value selection
To select Aq value we take into account:
e number of zones with the same value of AQ;
® contrast in each zone:
* correlation function value in each zone.
The value Aq is selected, for which there was a greatest number
of coincidences on zones. With other conditions being equal
preference is made to zones with the greatest contrast, and the
value of function of correlation is used as some threshold
restriction. The number of coincidences is at the same time
characteristic of reliability of a value produced by the block.
Current pitch angle value calculation
The pitch angle increment value (Ao) that was selected on the
previous step is added to some value that was accumulated and
that is current pitch angle value. In case when for n consecutive
Ag = 0, we set the accumulator value to 0.
Road situation analysis
Task of this procedure is the prevention of situations, when
some moving object, or it’s part, get into an analyzable
fragment of the image. For this purpose the output data of the
block of obstacle detection and tracking are used.
Determination of new position for zones on course angle
The position of zones on curse angle and angle of elevation is
determined. Position on course is determined according to
above mentioned method. Zone positions on an angle of
elevation are displaced so that to compensate vehicle pitch
deviation, i.e. zones are displaced by the angle equivalent to the
pitch angle deviation, taken with opposite sign.
Calculating of lateral histograms of etalon images and
calculation of contrast in every zone
In case when some zones do not satisfy to restrictions on
contrast, the choice of a new position of zones is made.
3. DEFINITION OF PITCH ANGLE OSCILLATIONS, BY
RESULTS OF ROAD MARKING LINES DETECTION.
Pitch angle calculations using road marking lines in a near zone
is based on determination of marking lines point of convergence
position on stereo images. Since cameras of a stereopair are
adjusted then all parallel lines on images will converge in one
point, i.e. marking lines on images represent a bunch of straight
lines. Here, coordinates of points of convergence of parallel
lines on right and left images will coincide. Thus, to calculate
point of convergence coordinates any pair of the detected
marking lines could be used (for example, left on the left image
and left on the right image). Depending on what lines were
detected, point of convergence coordinates are determined by
one or another way.
After detection of fragments of road marking lines in the area of
interest of the image these fragments are represented as
segments of straight lines in focal planes of the left and right
TV-cameras. This segments have the top and bottom
boundaries, which can coincide with the appropriate boundaries
of areas of interest (solid road marking lines), or to not coincide
with them (dash road marking lines). Therefore outcome of
primary measurements are the coordinates of boundaries of
these segments of lines in focal planes of TV-cameras of
stereopair in a co-ordinates (Z - horizontal axis, Y - vertical
axis) which origins coincide with principal points on focal
planes of cameras:
(Z11> V11) and (213, V13) — top boundary coordinates on the left
camera;
(Z14, y14) and (zi; V12) — top boundary coordinates on the right
camera;
(Z21, V21) and (223, V23) — bottom boundary coordinates on the left
camera;
(Zo4, y24) and (z», y»;) — bottom boundary coordinates on the
right camera.
The points having such coordinates, can lay on boundaries of
areas of interest or be inside these areas.
As a result of one act of measurements any of above mentioned
pairs coordinates can appear (line is detected) or to not appear
(line is not detected).
The tangents of angles between a vertical axis (Y) and these
segments of straight lines (directed from below upwards) can be
defined by the obvious formulas:
fj, 3 - tangents of angles of declination of the left and right lines
on the left image,
ls, 1 - tangents of angles of declination of the left and right lines
on the right image,
and also the coordinates of points of convergence of straight
lines, on which lay these segments (3, zy). At lack of errors in
direct measurements and the parallelisms of optical axes of
cameras coordinate of points of convergence, obtained on any
pair segments of straight lines should coincide (since point on
convergence is the indefinitely remote point).
The analysis of results of direct measurements obtained on
experimental registration in various conditions, shows, that only
bottom boundaries of straight lines segments in a near zone are
measured with adequate accuracy. The angles of declination a
often are determined with the large errors, which has especially
strong effect on errors of calculating of vertical coordinate of a
point of convergence y, if this point is determined by simple
geometrical construction. The experience of experimental
registration processing has shown, that this factor (as well as all
connected with the vertical channel) very strongly influences
process of road marking lines tracking, both in vertical, and in
horizontal planes, greatly increasing required sizes of areas of
interest.
Therefore, to increase an accuracy of measurement of pitch
angle 0 and roll angle Y of stereosystem relative to a Near
Zone plane the method of dynamic correction of direct
measurements was developed.
Direct measurements are understood as measurements, which
can be obtained on one image frame of a stereosystem by
geometrical constructions on two images formed in stereopair
without use of outcomes of dynamic data processing.
The offered method consists in that the primary measurements
are grouped so that to express the obtained generalized
parameters through constants and slowly varying parameters,
and to use as / and 4 values outcomes of a filtration (average) of
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