CN105163065B - A kind of traffic speed-measuring method based on video camera front-end processing - Google Patents
A kind of traffic speed-measuring method based on video camera front-end processing Download PDFInfo
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Abstract
The invention discloses a kind of traffic speed-measuring methods based on video camera front-end processing, which comprises the following steps: (1) installs video camera, demarcate to video camera, to obtain camera parameters；(2) scene coordinate reconstruction is carried out to the raw video image of video camera shooting, grounding point detection is carried out to vehicle in rebuilding figure and grounding point tracks, then calculates operating range and travel speed；Alternatively, carrying out grounding point detection and grounding point tracking to vehicle in original video frame, by the grounding point coordinate transformation of multiframe at scene actual coordinate, the operating range and travel speed of vehicle are then calculated.The present invention can realize that high precision velocity detects at low cost, have very high practical value.
Description
Technical field
The present invention relates to a kind of vehicle speed measuring methods, specifically, being to be related to a kind of friendship based on video camera front-end processing
Logical speed-measuring method.
Background technique
In order to guarantee road driving safety, the heat that travel speed detection is field of traffic is carried out to the vehicle travelled on road
One of point application, it had both been related to the management of road traffic, statistics, the confirmation of responsibility after also involving accident.
It mainly includes detections of radar, Coil Detector and video that the existing vehicle in traveling, which carries out the technology of velocity measuring,
Detect several ways.Although wherein detections of radar and Coil Detector precision and high stability, due to its hardware facility or
The higher cost of construction often can be only installed at the emphasis such as main crossroads and high speed bayonet position.
And video frequency speed-measuring is since camera may be used as illegal evidence obtaining simultaneously, is detection mode the most economical and the most practical.Depending on
The method that frequency tests the speed can substantially be divided into virtual coil detection and three-dimensional scaling detects two kinds according to its principle difference.Dummy line
The major defect of circle detection method is: first, the time difference can only determine that vehicle passes through virtual coil according to the frame number of video
The time of flag bit can not precise measurement, systematic error not can avoid, and error can increase as speed improves；Second, root
The method for determining vehicle location according to the position of the labels such as license plate in the picture also brings along error, the different vehicle of license plate height
When license plate is in image same position, the physical location of vehicle can differ several meters even more than ten meters.And three-dimensional scaling detection side
The major defect of method is then: first, the point that manually selects need known three-dimensional coordinate it is therein certain is one-dimensional, answered actually testing the speed
This mode interacted manually is difficult to functionization in；Second, calibration reference point needs six s' or more of known three-dimensional coordinate
Point, the difficulty obtained in practical application are larger.
Based on above-mentioned status, it is necessary to a kind of speed-measuring method for being easy to apply, can automatically detect grounding point is developed, with full
Needs in sufficient real work.
Summary of the invention
The purpose of the present invention is to provide a kind of traffic speed-measuring methods based on video camera front-end processing, solve the prior art
The problem of, while not improving cost, the difficulty of vehicle speed measuring is reduced, improves accuracy.
To achieve the goals above, The technical solution adopted by the invention is as follows:
A kind of traffic speed-measuring method based on video camera front-end processing, comprising the following steps:
(1) hypothesis camera optical axis is pitch angle t, camera shooting relative to the vertical angle of X-Y plane in three-dimensional world coordinate
Machine field angle is θ, from the water to camera optical axis on X-Y plane projection line in the counterclockwise direction of the Y-axis in three-dimensional system of coordinate
Flat angle is angle of rotation p；Video camera, input four are installed in such a way that pitch angle t is more than or equal to θ/2, angle of rotation p is greater than 70 °
The image coordinate of a calibration point demarcates video camera using double end point standardizations or single end point standardization, to obtain
Camera parameters；
(2) scene coordinate reconstruction is carried out to the raw video image of video camera shooting, vehicle is connect in reconstruction figure
Place detection and grounding point tracking, then calculate operating range and travel speed；Alternatively, being carried out in original video frame to vehicle
Grounding point detection and grounding point track, and by the grounding point coordinate transformation of multiframe at scene actual coordinate, then calculate the row of vehicle
Sail distance and travel speed.
In addition, can first pass through flash lamp in the scene of insufficient light and carry out light filling twice, then according to two frame light fillings
Image positions vehicle ground point, and calculates vehicle driving distance and speed；Alternatively, by the characteristic point on car light to vehicle
Carry out tracking and positioning, and using estimation car light height value, calculate the travel speed of vehicle；Alternatively, first vehicle farther out when
It carries out speed to vehicle to estimate, when the velocity amplitude estimated is more than the speed limit of current scene, trigger flashing lamp is to driving into
The vehicle in best shooting area carries out light filling twice and shoots, and according to two frame light filling pictures, positions to vehicle ground point, then counts
Calculate the operating range and speed of vehicle.
Preferably, in the step (2), the grounding point coordinate transformation of multiframe is passed through into following equation at scene actual coordinate
It completes:
Preferably, light filling interval time 0.5 second twice.
Preferably, the travel speed of the vehicle is calculated by following equation:
Preferably, the operating range of vehicle and travel speed are calculated by OMAPL138 chip completes.
Compared with prior art, the invention has the following advantages:
The present invention carries out reasonable set by the mounting means to video camera, reduces first from the operating angle of video camera
Imaging error, including the deformation of position error, jitter error, license plate etc., are established reliably for the accuracy of vehicle speed detection
Basis.Then, the calibrating template mated formation by six or nine graticules by road and manually demarcates video camera, by simple
Method determine the working environment of video camera；Finally, passing through grounding point detection and tracking and scene actual coordinate conversion phase
Mutually cooperation, the travel speed of vehicle is obtained using OMAPL138 chip, is realized low cost and is obtained high-precision car speed
Detection has very high practical value and market prospects.
Detailed description of the invention
Fig. 1 is the camera imaging model in the present invention.
Fig. 2 is the calibrating template of double end point standardizations in the present invention.
Fig. 3 is the calibrating template of single end point standardization in the present invention.
Fig. 4 is the error that two kinds of standardizations calculate pitch angle under different angle of rotation environment in the present invention.
Fig. 5 is two kinds of standardizations pitch angle as caused by different calibrated error grades in ill phenomenon environment in the present invention
Calculate error.
Fig. 6 is the relation schematic diagram tracked between point height and projector distance in the present invention.
Specific embodiment
Present invention will be further explained below with reference to the attached drawings and examples, and embodiments of the present invention include but is not limited to
The following example.
Embodiment
As shown in Figure 1, a kind of traffic speed-measuring method based on video camera front-end processing disclosed by the invention, main to utilize
OMAPL138 chip realizes algorithm process.The chip is pair of the C6748 Floating-point DSP kernel that TI company releases and ARM9 kernel
Core high speed processor, collection image, network, are stored in one at voice, and cost performance is high.Frequency is up to the C6748 kernel of 456MHz
The fixed point ability to work of floating-point ability to work and higher performance is provided；ARM9 has the flexibility of height, and developer can be with
On it using operating systems such as Linux, convenient for its application addition man-machine interface, network function, touch screen etc..
OMAPL138 chip under different service conditions total power consumption be 440mW, standby mode power consumption be 15mW, memory and
Peripheral resources very abundant, can satisfy the design requirement of high-precision video frequency speed-measuring system, and facilitate carry out in future system
Extension and upgrading.
Before actually testing the speed, installation video camera is first had to, the mounting means of video camera largely affects speed
Spend the accuracy of detection.The mounting height of video camera not only needs to consider range rate error, position error, it is also contemplated that construction is difficult
Degree, field range in the case where guaranteeing the visual field, increase pitch angle and in order to reduce jitter error as far as possible, in the present embodiment,
Pitch angle t is set greater than equal to θ/2.Angle of rotation determines that video camera belongs to side dress or formal dress, and angle of rotation is close when formal dress
90 °, increase visual angle when side fills and reduce the deformation of license plate, should also be incited somebody to action as close as possible to 90 ° of directions, therefore in the present embodiment
It is set greater than 70 °.As for rotation angle, then installed according to close to 0 °.
After video camera installs, calibration is carried out to video camera first and coordinate is converted.As shown in Figure 1, using pitching
Several parameters such as angle t, angle of rotation p, rotation angle s, focal length f and camera height h define the plane of delineation and practical three-dimensional world
The relationship of coordinate.Pitch angle t is vertical angle of the camera optical axis relative to X-Y plane in three-dimensional world coordinate；Angle of rotation p is
From the horizontal sextant angle to camera optical axis on X-Y plane projection line in the counterclockwise direction of the Y-axis in three-dimensional system of coordinate；Rotation angle
S refers to video camera along the rotation angle of its optical axis；Focal length refers to from the plane of delineation along optical axis to video camera center of lens
Distance；Camera height refers to the vertical height from camera lens center to X-Y plane.
Assuming that Q=(XQ,YQ,ZQ) be in three-dimensional world coordinate a bit, its corresponding points in two dimensional image coordinate is q
=(xq,yq).One Direct mapping function phi from the point in three-dimensional world coordinate to image coordinate can be given by following formula
Out:
Wherein, spin matrix R and translation matrix T is used to characterize the external parameter of video camera, and 3 × 3 upper triangular matrix K
For characterizing the inner parameter of video camera, they have following form:
Wherein, XCAM=h sin p cot t, YCAM=h cos p cot t, ZCAM=h.And f is focal length, a=fu/fvFor
Aspect ratio (usually 1),For obliquity factor (being typically set to 0), (u0,v0) it is the origin that optical axis intersects with the plane of delineation
(being typically set to (0,0)).By above formula, can derive:
And
If Q point is located at X-Y plane, ZQEqual to zero, XQAnd YQIt can be by (xq,yq) it is calculated:
The core content that camera parameters are camera calibrations is calculated by calibration point, for the meter of video camera external parameter
It calculates, the algorithm that the present embodiment uses includes double end point standardizations and single two kinds of standardization of end point.
As illustrated in fig. 2, it is assumed that in calibrating templateWithIn parallel,WithIn parallel, five can be listed below
Equation:
Because ABCD is all the point on road surface, i.e. formula (4) and (5) are substituted into aforesaid equation, can solved each by Z=0
Camera parameters are as follows:
Wherein, αPQ=xq-xp,βPQ=yq-yp,χPQ=xpyq-xqyp；(xA,yA),(xB,yB),(xC,yC),(xD,yD) point
Image coordinate that Wei be 4 points of ABCD.
For the calibrating template of single end point standardization as shown in figure 3, according to this calibrating template, the equation group listed is as follows:
According to this group of equation, it is as follows to solve camera parameters:
Wherein αPQ=xq-xp, βPQ=yq-yp,χPQ=xpyq-xqyp。
Herein
Wherein,
UQ=xq sin s+yq cos s,VQ=xq cos s-yq sin s
F=F/tan t (15)
Wherein, if f < 0, f=-f, and s=s+ π are enabled.
Wherein, if h < 0, h=-h and p=p+ π is enabled.
Double end point standardizations calculating are relatively easy, but when integral multiple of the angle of rotation close to 90 °, have ill phenomenon
Occur, i.e. one in two end points is close to infinity, so that it is special to the error of calibration point to calculate resulting camera parameters
Insensitive, this method is only applicable to camera side dress environment.And single end point method selects in two end points from image origin
Closer one, the generation of ill phenomenon is effectively evaded, camera side dress, formal dress can have been well adapted to.This reality
Example is applied according to the configuring condition of video camera in specific implementation environment, selects corresponding scaling method automatically.
Shown in Fig. 4 is when adding Gaussian noise of the variance for a pixel to calibration point, and two kinds of scaling methods are in difference
The error between pitch angle and practical pitch angle calculated under angle of rotation environment.Shown in fig. 5 is the (p in ill phenomenon environment
=89 °) two kinds of scaling methods calculate the error of pitch angle under different calibration point grade of errors.Particularly, in calibration point tolerance
When for a pixel, pitching angle error is about 0.10 °, and thus bring range rate error is about 2%.Set focal length of camera with
The ratio of CCD single pixel size is 800 pixels, and the focal length of camera in real road measurement is generally higher than this value, i.e. image
Resolution ratio is higher, can be smaller by calibration point quantization error bring range rate error, in the error range of video frequency speed-measuring national standard
Within.
Camera calibration at least need to only input two pairs of roadmarking fixed points, i.e., the position of four points, the party in the present embodiment
Method can easily be extended to the multipair roadmarking of input, and the essence of calibration is improved by straight line fitting and least square method
Degree.
After completing camera calibration and obtaining camera parameters, video camera is taken according to formula (4) and formula (5)
Raw video image carries out scene coordinate reconstruction, and rebuilding, which becomes X-Y plane, rebuilds figure.Rebuild figure in, all height be 0 object
Its image coordinate of body is consistent with actual coordinate, the grounding point that we can use vehicle tracks vehicle in reconstruction figure,
Positioning and is tested the speed at ranging.Moving object detection and the algorithm of tracking include background modeling, and foreground extraction carries out light to characteristic point
The algorithm comparison of stream tracking or template matching tracking etc., this respect is mature, is not emphasis of the invention, herein no longer in detail
Narration.It is worth noting that in the present embodiment locating and tracking can be carried out to vehicle in original video frame, then to positioning
Coordinate is coordinately transformed, to calculate the mode of Vehicle Speed；Scene coordinate first can also be carried out to original video frame
It rebuilds, vehicle location tracking is carried out in rebuilding figure, then directly calculate travel speed.
Under certain conditions, such as in the case that night does not have light filling, the grounding point of vehicle is often invisible, we are general
The point of point or license plate position that car light position can only be used is as a reference point to carry out tracking of testing the speed.The height of vehicle speed measuring trace point
The influence to rate accuracy is spent, with reference to model of place shown in fig. 6.The height of known video camera A is hcam, observe high on vehicle
Degree is hBPoint, BkAnd Bk+1It respectively tests the speed in two field pictures the position of point of observation.CkAnd Ck+1Respectively BkAnd Bk+1Along camera shooting
Projection of the machine optical axis on ground, CkAnd Ck+1The distance between dpWe are known as projector distance, DkAnd Dk+1Respectively BkAnd Bk+1?
The upright projection on ground, we term it actual range d for the distance between theya.It can be calculated according to the geometrical relationship in figure
Out:
When we assume that the height of B point be zero carry out displacement and calculate when, calculating the displacement of resulting B point is really C point
Displacement, that is, projector distance.So this when of range rate error are as follows:
Actual vehicle travel speed are as follows:
Herein, vpResulting projection speed is calculated to rebuild tracking characteristics point in figure in scene coordinate.
By above-mentioned formula it is recognised that when carrying out positioning-speed-measuring to vehicle speed measuring trace point in reconstruction image:
(1) test the speed trace point height it is higher, range rate error is bigger；
(2) camera height is higher, and by testing the speed, trace point height bring error is smaller；
(3) in camera height and under testing the speed and tracking situation known to point height, error is measurable, can compensate for.
The present invention can realize high-precision velocity measuring, automatic detection vehicle when testing the speed by the above method at low cost
And position the grounding point of vehicle, according to position of the coordinate transformation vehicle in practical three-dimensional system of coordinate of grounding point in the picture
It sets, its travel speed is then calculated according to alternate position spike of the vehicle in different video frame, there are very high market prospects and practical
Value.
Above-described embodiment is merely a preferred embodiment of the present invention, and it is not intended to limit the protection scope of the present invention, as long as using
Design principle of the invention, and the non-creative variation worked and made is carried out on this basis, it should belong to of the invention
Within protection scope.
Claims (4)
1. a kind of traffic speed-measuring method based on video camera front-end processing, which comprises the following steps:
(1) hypothesis camera optical axis is pitch angle t, video camera view relative to the vertical angle of X-Y plane in three-dimensional world coordinate
Rink corner is θ, and the level from the Y-axis in three-dimensional system of coordinate in the counterclockwise direction to camera optical axis on X-Y plane projection line is pressed from both sides
Angle is angle of rotation p；Video camera is installed in such a way that pitch angle t is more than or equal to θ/2, angle of rotation p is greater than 70 °, inputs four marks
The image coordinate of fixed point demarcates video camera using double end point standardizations or single end point standardization, to obtain camera shooting
Machine parameter；
(2) scene coordinate reconstruction is carried out to the raw video image of video camera shooting, grounding point is carried out to vehicle in rebuilding figure
Detection and grounding point tracking, then calculate operating range and travel speed；Alternatively, being grounded in original video frame to vehicle
Point detection and grounding point tracking, by the grounding point coordinate transformation of multiframe at scene actual coordinate, then calculate the traveling of vehicle away from
From and travel speed；Wherein,
In the scene of insufficient light, first passes through flash lamp and carry out light filling twice, then vehicle is connect according to two frame light filling images
Place is positioned, and calculates vehicle driving distance and speed；
Alternatively, carrying out tracking and positioning to vehicle by the characteristic point on car light, and utilize estimation in the scene of insufficient light
Car light height value calculates the travel speed of vehicle；
Alternatively, in the scene of insufficient light, first vehicle farther out when speed carried out to vehicle estimate, when the velocity amplitude estimated is super
When crossing the speed limit of current scene, trigger flashing lamp carries out light filling twice to the vehicle for driving into best shooting area and shoots, root
According to two frame light filling pictures, vehicle ground point is positioned, then calculates the operating range and speed of vehicle；
The grounding point coordinate transformation of multiframe is completed at scene actual coordinate by following equation:
Wherein, s refers to video camera along the rotation angle of its optical axis；F refers to from the plane of delineation along optical axis to video camera eyeglass
The distance at center；H refers to the vertical height from camera lens center to X-Y plane；Q=(XQ,YQ,ZQ) it is that three-dimensional world is sat
In mark a bit, its corresponding points in two dimensional image coordinate is q=(xq,yq)。
2. a kind of traffic speed-measuring method based on video camera front-end processing according to claim 1, which is characterized in that twice
Light filling interval time 0.5 second.
3. a kind of traffic speed-measuring method based on video camera front-end processing according to claim 2, which is characterized in that described
The travel speed of vehicle is calculated by following equation:
Wherein, vaFor the travel speed of vehicle；vpResulting projection speed is calculated to rebuild tracking characteristics point in figure in scene coordinate
Degree；hcamFor the height of video camera A；hBFor the height of certain point B on vehicle.
4. a kind of traffic speed-measuring method based on video camera front-end processing according to claim 3, which is characterized in that vehicle
Operating range and travel speed by OMAPL138 chip calculate complete.
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| CN106781536A (en) * | 2016-11-21 | 2017-05-31 | 四川大学 | A kind of vehicle speed measuring method based on video detection |
| AT519679A1 (en) * | 2017-02-27 | 2018-09-15 | Zactrack Gmbh | Method for calibrating a rotating and pivoting stage equipment |
| CN106991414A (en) * | 2017-05-17 | 2017-07-28 | 司法部司法鉴定科学技术研究所 | A kind of method that state of motion of vehicle is obtained based on video image |
| CN107492123B (en) * | 2017-07-07 | 2020-01-14 | 长安大学 | Road monitoring camera self-calibration method using road surface information |
| CN110310492B (en) * | 2019-06-25 | 2020-09-04 | 重庆紫光华山智安科技有限公司 | Speed measuring method and device for mobile vehicle |
| CN110632339A (en) * | 2019-10-09 | 2019-12-31 | 天津天地伟业信息系统集成有限公司 | Water flow testing method of video flow velocity tester |
| CN111612849A (en) * | 2020-05-12 | 2020-09-01 | 深圳市哈工大交通电子技术有限公司 | Camera calibration method and system based on mobile vehicle |
| CN111899525A (en) * | 2020-08-18 | 2020-11-06 | 重庆紫光华山智安科技有限公司 | Distance measuring method, distance measuring device, electronic device, and storage medium |
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| US8213685B2 (en) * | 2007-01-05 | 2012-07-03 | American Traffic Solutions, Inc. | Video speed detection system |
| US8385658B2 (en) * | 2007-07-27 | 2013-02-26 | Sportvision, Inc. | Detecting an object in an image using multiple templates |
| CN102254318B (en) * | 2011-04-08 | 2013-01-09 | 上海交通大学 | Method for measuring speed through vehicle road traffic videos based on image perspective projection transformation |
| CN102722886B (en) * | 2012-05-21 | 2015-12-09 | 浙江捷尚视觉科技股份有限公司 | A kind of video frequency speed-measuring method based on three-dimensional scaling and Feature Points Matching |
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