KR20170088692A - Device and Method for Calculating Vehicle Speed by Image - Google Patents

Abstract

The present invention relates a device for calculating a vehicle speed using an image. The present invention provides the device for calculating a vehicle speed using an image, which includes a photographing unit which obtains a vehicle image by photographing a moving vehicle, an image processing unit which calculates the size change amount of the preset part of the vehicle image in the vehicle image by image-processing the minimum two images among the vehicle images, and a speed calculating unit which calculates the speed of the vehicle by converting the size change amount of the vehicle image into the moving distance of the vehicle. Accordingly, the present invention can calculate the vehicle speed without using a vehicle sensor which senses the speed of the vehicle.

Description

Technical Field [0001] The present invention relates to a device and a method for calculating a vehicle speed using an image,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to an apparatus and method for calculating a vehicle speed using an image, and more particularly, to a vehicle speed calculation apparatus and a method thereof for calculating a vehicle speed using an image of a vehicle.

Recently, vehicle identification systems such as public security and crime prevention systems and regulatory violation control systems have become commonplace by using CCTV cameras. The vehicle identification system captures the vehicle, reads the vehicle number from the captured image, and uses it for the appropriate purpose. For example, a regulatory violation control system such as a speeding system imposes penalties by reading license plates of oversized vehicles, and the public security and crime prevention system finds vehicles for crime.

Generally, the overspeed interception system captures a vehicle judged to be overspeed in a traveling vehicle. Whether or not the vehicle is overspeed is determined by using a vehicle detection sensor such as a pair of loops, a laser or the like. Accordingly, such a conventional overspeed intermittent system uses a vehicle detection sensor and a camera together, which complicates the structure and increases the cost. On the other hand, it is necessary to limit the travel speed of the vehicle traveling at a predetermined speed or higher by calculating the speed of the vehicle traveling in an area such as an alley, a child protection zone, and a school zone. However, there is a problem in that a conventional general system, that is, a method of using a sensor and a camera, is complicated in structure and requires expensive equipment, which limits installation.

On the other hand, it has been proposed to calculate the speed of the vehicle using the image of the taken vehicle without using a sensor for detecting the vehicle. That is, in an apparatus for collecting traffic information such as an average traffic speed, it has been proposed to calculate the speed of a vehicle traveling using an image. However, in this method, the speed of the vehicle can be calculated by using the end line of the vehicle in the image, but in this method, a structure including the 8-10 m high pile is required for image acquisition. Further, in such a conventional system, there is a problem that vehicle information such as the vehicle number can not be known in the photographed vehicle.

An object of the present invention is to provide a vehicle speed calculation apparatus and method for calculating a vehicle speed using an image without using a vehicle detection sensor for sensing the speed of the vehicle.

According to an embodiment of the present invention, there is provided an image processing apparatus comprising: a photographing unit photographing a moving vehicle to obtain a vehicle image; An image processing unit for image-processing at least two images of the vehicle image to calculate a magnitude variation of a predetermined portion of the vehicle image in the vehicle image; And a speed calculating unit for calculating a speed of the vehicle by converting the amount of change in the size of the image of the vehicle into the moving distance of the vehicle.

Preferably, the size variation of the vehicle is calculated using a reference indicator previously defined in the vehicle image. Wherein the reference indicator portion includes at least one of a width of the vehicle, a distance between the side mirrors of the vehicle, a distance between tires of the vehicle, a distance between the headlights of the vehicle and a size of the license plate, You can use one.

It is preferable that the amount of change in the size of the vehicle is determined using the pixel variation amount of the reference landmark. It is also preferable that the vehicle further includes a storage unit that stores a conversion travel distance table in which the amount of change in the size of the image of the vehicle is converted into the travel distance of the vehicle. It is preferable that the conversion travel distance table is configured of a reference number of pixels and an actual movement distance corresponding to a change amount of the number of pixels with respect to the reference number of pixels.

On the other hand, it is preferable that the photographing unit is installed on the road surface. On the other hand, it is preferable to further include an alarm unit for outputting an alarm when the calculated vehicle speed is equal to or higher than a predetermined speed.

According to another embodiment of the present invention, there is provided an image processing method comprising: an image acquiring step of photographing a moving vehicle to obtain at least two vehicle images; An image processing step of image-processing at least two images of the vehicle image to calculate a magnitude variation of a predetermined portion of the vehicle image in the vehicle image; And a speed calculating step of calculating a speed of the vehicle by converting the amount of change in the size of the image of the vehicle into the moving distance of the vehicle. And a subsequent processing step of performing predetermined follow-up if the speed of the vehicle calculated in the speed calculating step is equal to or higher than a predetermined speed. The subsequent processing step may be to generate an alarm if the calculated vehicle speed is above a predetermined speed.

Effects of the image-based vehicle speed calculation apparatus and method according to the present invention will be described as follows.

First, according to the present invention, there is an advantage that the speed of the vehicle can be calculated without using the vehicle detection sensor. In addition, there is an advantage that vehicle information such as vehicle number as well as vehicle speed can be acquired at the same time.

Second, according to the present invention, there is an advantage that a vehicle speed calculation device can be implemented with a simple installation and a low cost. In addition, since the present invention does not use a vehicle detection sensor, the camera unit can be embedded in a road, and a structure such as a pillar or the like can be advantageously used.

1 is a view schematically showing installation of a vehicle speed calculating device using an image according to the present invention;
2 is a view for explaining a principle of a vehicle speed calculating apparatus using an image and a method thereof according to the present invention;
3 is a block diagram schematically showing a configuration of an embodiment of an apparatus for calculating a vehicle speed using an image according to the present invention
4 is a flowchart showing an embodiment of a vehicle speed calculation method using an image according to the present invention.
Figs. 5 and 6 are diagrams showing photographs

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of an apparatus and method for calculating a vehicle speed using an image according to the present invention will be described with reference to the accompanying drawings. The embodiments described below are intended to facilitate understanding of the present invention, and the present invention is not limited to the embodiments described below.

First, with reference to FIG. 1 and FIG. 2, the principle of the vehicle speed calculation apparatus using the image and the method will be described.

1, the vehicle speed calculation device 1 according to the present invention is installed on the road 5 or the like on which the vehicle 3 travels. A photographing unit 10 such as a camera photographs the vehicle 3 at predetermined time intervals t1 and t2 and calculates the speed of the vehicle 3 using at least two images photographed.

In the present invention, a vehicle (3) running on the road is photographed using the photographing unit (10), and a change amount of a size of the vehicle image is calculated using at least two images of the photographed images, The traveling distance of the vehicle is calculated, and the traveling speed of the vehicle is calculated using the calculated traveling distance. More detailed description will be given below.

2 (a) shows an image A1 taken at a predetermined time t1, and FIG. 2 (b) shows an image A2 taken at a time t2 after a predetermined time elapses. As illustrated in Fig. 2, when the vehicle 3 approaches the photographing section 10, the image A2 at the time t2 is compared with the size B1 of the vehicle 3 from the image A1 at the time t1, The size B2 of the vehicle 3 becomes large. Conversely, when the vehicle 3 moves away from the photographing section 10, the size of the vehicle at the time point t2 becomes smaller than the size of the vehicle at the time t1.

In both cases, the size variation of the vehicle image has a certain correlation with the actual moving distance of the vehicle. (In FIG. 2, the size variation of the vehicle image is shown and explained based on the vehicle widths B1 and B2 for convenience. Therefore, by using this correlation and converting the size variation (? B = B2-B1) of the vehicle image into the actual moving distance s of the vehicle (hereinafter referred to as " The speed v of the vehicle can be calculated by dividing by the shooting interval t2-t1 of the image. That is, the vehicle speed v = s / | t1-t2 | = f (? B) / | t1-t2 |.

The meaning of the amount of change in the size of the vehicle image, the determination method, and the method of determining the translated distance will be described in more detail as follows.

The amount of change ΔB of the size of the vehicle image means the amount of change in the size of the vehicle in the captured image. Therefore, the amount of change in the size of the vehicle image may mean the amount of change in a predetermined portion of the vehicle in the captured image. In FIG. 2, the predetermined portion of the vehicle uses the widths B1 and B2 of the vehicle, but is not limited thereto. That is, a predetermined portion of the vehicle (hereinafter, referred to as "reference indicator portion " for convenience) may use two points in the vehicle image, and preferably uses an easy-to-analyze portion in image processing. For example, the reference indicator section can use at least one of the width of the vehicle, the distance between the side mirrors of the vehicle, the distance between the tires of the vehicle, the distance between the headlights of the vehicle, and the width of the vehicle's grille. Also, the width of the tire of the vehicle, the size of the license plate, the size of the license plate, and the like may be used.

However, it is convenient and accurate to use the license plate 7 of the vehicle as the reference surface portion. Because the types of vehicles vary, the shape of the vehicles also varies. However, compared to other parts of the vehicle, the number of the license plates of the vehicle is much smaller, and the feature of the image for calculating the size change contrasts with the background is clear. This is because the license plate of the vehicle is easier to perform image processing than other parts of the vehicle. Further, since the license plate of the vehicle is located at the center of the vehicle, since the images are located substantially at the center of the photographed images A1 and A2, the distortion of the image can be minimized or evened, and an accurate magnitude of variation can be obtained. It is also possible to use at least one of the right and left widths or the upper and lower widths of the size of the license plate.

Although the reference surface portion exemplified above is roughly two points on the horizontal axis of the vehicle, it is also possible to use two points on the longitudinal axis of the vehicle, for example, the height of the vehicle. Of course, it is also possible to mix the amount of change in the image size on the horizontal axis of the vehicle and the amount of change in the image size of the vertical axis of the vehicle. It is also desirable to solve the aberration problem due to the distortion caused by the characteristics of the lens of the camera that photographs the vehicle.

On the other hand, it is possible to use various methods to convert the amount of change in the size of the vehicle image into the actual moving distance of the vehicle. For example, the actual moving distance according to the size change of the reference indicator portion may be functioned. In addition, it is preferable that the actual moving distance according to the size of the reference indicator of the vehicle image acquired by the specific camera is measured, and a table in which the size variation of the image and the moving distance of the actual vehicle are prepared is prepared in advance. Of course, it is preferable to configure each of these tables according to the type of the camera that photographs the vehicle.

On the other hand, in order to calculate the size change amount of the reference indicator portion of the vehicle from the photographed image, an image processing algorithm for detecting the reference indicator portion from the acquired image is required. However, since a variety of techniques for detecting a predetermined portion of a vehicle using image processing are known in the art, for example, a overspeed control system, a detailed description thereof will be omitted.

When calculating the amount of change in the size of the reference indicator using the image processing in the captured image, it is possible to use the physical size of the reference indicator or the pixels of the image in the image. For example, when pixels are used, the width of the vehicle at time t1 is 360 pixels, and when the vehicle width at time t2 is 780 pixels, the size change amount is 420 pixels.

On the other hand, it is desirable to secure sufficient experimental data for obtaining the conversion variation distance of the reference landmark, for example, the conversion distance of the vehicle corresponding to the variation of the pixel size. This is because, depending on the features of the camera, such as the sensor, the lens, and the focal length, the camera has various differences in the image. Therefore, the conversion distance may vary depending on the characteristics of the camera. Therefore, in order to secure a more accurate conversion distance, it is desirable to calculate and verify the conversion distance according to the type of available camera. It is also preferable that the calculated and verified converted travel distance, that is, the actual travel distance (converted travel distance) with respect to the amount of change in the size of the vehicle is made into a predetermined table (hereinafter referred to as a "translated travel distance table" .

The translated shift distance table can be implemented in various ways. For example, the conversion shift distance corresponding to the image size change amount? B between the two image pickup points can be tabulated. In addition, the conversion shift distance for the image size may be tabulated at a plurality of end points corresponding to the images at one start point.

It is desirable that the minimum interval of the shooting time points t1 and t2 of the image has a sufficient temporal difference such that the velocity calculation minimizes the error range. For example, it is preferable to be several seconds rather than milliseconds.

On the other hand, in the above description, the front side of the vehicle is photographed in the direction in which the vehicle travels. However, it is also possible to use the image of the vehicle that photographs the rear side of the vehicle.

Referring to FIG. 3, a configuration of a preferred embodiment of a vehicle speed calculating apparatus using an image according to the present invention will be described below.

The vehicle speed calculating apparatus 1 using an image according to the present embodiment includes a photographing section 10 that photographs a moving vehicle to obtain a vehicle image. The photographing unit 10 is connected to an image processing unit 22 that processes at least two images of a vehicle image and calculates a change in the size of the vehicle image in the vehicle image. The image processing unit 22 is connected to a speedometer 24 that converts the size change of the image of the vehicle into the moving distance of the vehicle and calculates the speed of the vehicle. It is preferable that the vehicle speed calculating apparatus 1 using an image according to the present embodiment further comprises a storage unit 30 for storing a photographed image and a translated moving distance table. It is also preferable that the storage unit 30 is connected to the photographing unit 10, the image processing unit 22, and the speedometer 24. Further, the vehicle speed calculation device 1 preferably includes an input unit 40 and an output unit 50. In FIG. 3, the input unit 40 and the output unit 50 are connected to the speed meter unit 24, but the present invention is not limited thereto. For example, it may be connected to the image processing unit 22, and the image processing unit 22 and the speed measurement unit 24 may be connected to the control unit 20 by configuring one control unit 20 as well.

Each component will be described in detail as follows.

The photographing unit 10 can use a camera generally used in an overspeed intermittent system or the like. It is preferable that the photographing unit 10 obtains at least two images at different times at the same position in the same angle of view. That is, it is preferable that the photographing unit 10 is installed at a predetermined position on the road on which the vehicle travels, so that the photographing unit 10 can continuously photograph the traveling vehicle. Of course, the shooting time is recorded in each image.

The image processing unit 22 acquires the amount of change of the reference indicator of the vehicle from the image transmitted from the photographing unit 10 by image processing. As described above, in the image processing unit 22, the variation in the width of the reference indicator, for example, the license plate can be analyzed by image processing. In order to calculate the size change of the license plate of the vehicle, it is necessary to detect the license plate of the vehicle. Since the algorithm used in the overspeed intermittent system and the like can be used, detailed description thereof will be omitted. It is preferable that the image processing unit 22 accurately determines the amount of change in the reference indicator portion. Since the camera lens of the photographing unit 10, for example, is not a plane, if it is far from the center, a difference due to refraction may occur depending on the region. Therefore, it is preferable to correct the image or use an image obtained in a region with a small aberration. For example, the image at the time t1 uses an image taken at a predetermined pixel interval (for example, the center portion of the image) of the reference indicator at least in the captured image, and the image at the time t2 is also used for a predetermined pixel interval It is possible to use an image photographed at a central portion of the image. The image processing unit 22 preferably includes an algorithm for reading the vehicle number from the photographed image.

The speed meter section 24 will be described as follows. The speedometer section 24 converts the change amount of the reference indicator section analyzed by the image processing section 22 into the actual travel distance of the vehicle to calculate the converted travel distance. In the speedometer section 24, it is possible to calculate a moving distance of the vehicle in real time by making a function of the change amount of the reference landmark and the converted moving distance, or to calculate the moving distance of the vehicle using the converted moving distance table . It is preferable that the conversion travel distance table is prepared in advance by the experiment and stored and used in the storage unit 30 because the conversion travel distance varies depending on the type of the camera, installation location, and the like.

In the storage unit 30, it is desirable to store the actually photographed vehicle image, the translated shift distance table, the calculated vehicle speed, the read car number, and the like. In addition, it is preferable that the storage unit 30 stores the actual characteristic value information of each vehicle type.

Next, the input unit 40 and the output unit 50 will be described as follows. The input unit 40 and the output unit 50 provide an interface for the user to use the vehicle speed calculation device. For example, it is possible to provide an interface that enables the user to specify the reference indicator section so that the user-designated area can be used as the reference indicator section. Although not shown, it is preferable to further include an illumination device for assisting the photographing section 10. [

Although the photographing section 10, the image processing section 22, and the speed meter section 24 are shown and described differently in the above-described embodiment, the present invention is not limited thereto. The imaging section 10, the image processing section 22, and the speed meter section 24 may be integrally or separately configured. In particular, the image processing unit 22 and the speed measurement unit 24 may be integrally implemented in hardware or software, or may be implemented as one.

Meanwhile, the vehicle speed calculating apparatus according to the present invention can be used in a overspeed intermittent control system. In this case, the vehicle speed calculation apparatus 1 is connected to the integrated operation unit 70 by the communication network 60. [ The integrated operation unit 70 is installed in a police agency or the like, and is equipped with a predetermined database to perform integrated search and operation, a penalty notification function for a vehicle that violates regulations, and the like. That is, the vehicle speed calculation device 1 is installed at a specific site such as a road, and the integrated operation unit 70 is installed at a remote site. However, the present invention is not limited thereto. It is also possible to provide only the photographing section 10 of the vehicle speed calculating apparatus 1 on the road, and the image processing section 22 and the speedometer section 24 together in the integrated operation section 70 .

Meanwhile, the present invention does not require the use of a separate sensor such as a loop or a laser for detecting the speed of the vehicle or the vehicle. Therefore, in the present invention, the photographing unit 10 is buried in the road, and the photographing unit 10 may photograph the traveling vehicle on the road surface. With this structure, it is not necessary to use a support for installing the photographing unit 10, which is advantageous in that the structure is simple and installation is easy. Therefore, the vehicle speed calculation apparatus according to the present invention is relatively simple and relatively inexpensive, and can be installed in an area such as an alley, a child protection zone, and a school zone. Thus, according to the present invention, it is possible to calculate the speed of a vehicle traveling in an area such as an alleyway, a child protection zone, and a school zone, and to restrict the traveling at a speed exceeding a predetermined speed.

The alarm unit 52 calculates the velocity using the image and outputs the velocity to the vehicle And has a function for making a predetermined alarm or the like. For example, when the speed of the vehicle calculated in the control unit 24 is equal to or higher than the predetermined speed, it is possible to generate an alarm to decelerate the vehicle because it violates the specified speed. It is preferable that the alarm unit 52 performs various types of alarms, for example, an audiovisual method.

Referring to FIG. 4, a method of calculating a vehicle speed using an image according to the present invention will now be described.

First, at the photographing section, at least two vehicle images are obtained by photographing a moving vehicle (image acquiring step, S1). Next, the image processing unit performs image processing of at least two images of the captured vehicle images, and determines a size change amount of a predetermined portion of the vehicle image in the vehicle image (image processing step, S3). In the speedometer section, the amount of change in the size of the image of the vehicle is converted into the moving distance of the vehicle to calculate the speed of the vehicle (step S5). If the speed of the vehicle calculated in the speed calculating step is equal to or higher than the predetermined speed, a predetermined subsequent processing is performed (a subsequent processing step, S7). In the subsequent processing step, for example, . Alternatively, the Integrated Operations Department may notify the driver of the speeding-up penalty for the vehicle.

At this time, as described above, the predetermined portion of the vehicle image uses a reference indicator portion connecting two points of the vehicle, and the mood indicator portion may be the width of the vehicle, the size of the license plate of the vehicle, and the like. Further, it is preferable that the amount of change in the size of the image of the vehicle is used as the variation amount of the pixels in the reference indicator portion. It is also preferable that an actual moving distance (converted moving distance) corresponding to the amount of change of the pixel is made to be a table (converted moving distance table).

The translated shift distance table can be implemented in various ways. For example, the conversion shift distance corresponding to the image size change amount? B between the two image pickup points can be tabulated. In addition, the converted shift distance with respect to the image size may be tabulated at a plurality of end points corresponding to the image of one start point. That is, it is preferable to determine the number of reference pixels at the starting point, and to make a conversion movement distance table composed of the actual movement distance corresponding to the variation amount of the number of pixels with respect to the reference number of pixels. More specifically, it is preferable that the size of the license plate is defined as the number of reference pixels in an image at a predetermined start time, and the actual distance is tabulated as the difference between the number of pixels of the license plate and the number of reference pixels in various other images.

5 and 6, the following description will be made. The camera used was the sensor size 1 / 1.8 and the resolution (1280 X 1920). The width of the license plate of the vehicle was used as the reference index part. For example, as shown in FIG. 5, the number of pixels of the license plate is based on an image taken at a distance of 10 m from the camera. Then, the number of pixels of a number plate is processed by image processing within each 10-m image, and a table is created. For convenience, only the image at a distance of 4 m is shown in Fig.

As a result of the experiment, when the number of pixels of the number plate is 100 and the number of pixels of the number plate of the other image is 110 (that is, when the pixel number variation is 10) When the distance is 3.1m and 310, the actual moving distance is 3.3m, 410, the actual moving distance is 4.4m and 510, the actual moving distance is 5m. Of course, this relationship depends on the camera and the installation environment, so it can be created in advance through proper experimentation when installing the camera, and once the table is created, the table can be used continuously.

By making the conversion travel distance table in this way, it is possible to easily and accurately calculate the actual travel distance corresponding to the size change amount of the reference land portion. In the case of making the conversion travel distance table in this manner, at least two images are required when calculating the speed using the image. In the case of one image (image of t1), the number of pixels of the number plate is found to be 100, An appropriate image other than the t1 image can be selected as the image (image of t2). On the other hand, when creating the translated shift distance table, It is also possible to determine the size of the license plate as the number of reference pixels in the image of the viewpoint and to tabulate the actual distance as the difference between the number of pixels of the license plate and the number of reference pixels in the different images, It is also possible to create individual tables for the starting points of the dogs. In other words, each conversion distance table for the case where the number of reference pixels is 100, 200, or 300 may be created. With this configuration, since the number of pixels of the reference image is several, the distance can be converted by comparing two images more conveniently. The speed can also be calculated and averaged based on the number of different reference pixels.

The embodiments of the present invention described above can be implemented in a form that can be performed in an information processing apparatus such as a computer, and can be recorded in a medium readable by the information processing apparatus. A program command, a data file, a data structure, and the like may be included in the medium readable by the information processing apparatus, alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the present invention, or may be available to those of ordinary skill in the computer software arts. Examples of computer-readable media include magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine code generated by the compiler as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. That is, the present invention is not limited to the embodiments described above, and various modifications and variations are possible in light of the above description of the present invention.

10: photographing unit 20:
22: image processing unit 24:

Claims (11)

A photographing unit photographing a moving vehicle to obtain a vehicle image;
An image processing unit for image-processing at least two images of the vehicle image to calculate a magnitude variation of a predetermined portion of the vehicle image in the vehicle image;
And a speed calculation unit for calculating a speed of the vehicle by converting a variation amount of the image of the vehicle into a moving distance of the vehicle. The apparatus of claim 1, wherein the size variation of the vehicle is calculated using a reference index predefined in the vehicle image. 3. The vehicle driving force control apparatus according to claim 2, wherein the reference indicator section is configured to calculate the reference indicator section based on the width of the vehicle, the distance between the side mirrors of the vehicle, the distance between the tires of the vehicle, the distance between the headlights of the vehicle, And a character size of the license plate. 3. The apparatus according to claim 2, wherein the amount of change in the size of the vehicle is determined using a pixel variation amount of the reference landmark. The apparatus according to claim 1, further comprising a storage unit for storing a conversion travel distance table in which a size change amount of the image of the vehicle is converted into a travel distance of the vehicle. 6. The method according to claim 5, wherein the conversion travel distance table is configured with a reference number of pixels and an actual movement distance corresponding to a variation amount of the number of pixels with respect to the reference number of pixels. Device. The apparatus according to any one of claims 1 to 6, wherein the photographing unit is installed on a road surface. The vehicle speed calculating apparatus according to claim 8, further comprising an alarm section for outputting an alarm when the calculated vehicle speed is equal to or higher than a predetermined speed. An image acquiring step of acquiring at least two vehicle images by photographing a moving vehicle;
An image processing step of image-processing at least two images of the vehicle image to calculate a magnitude variation of a predetermined portion of the vehicle image in the vehicle image;
And calculating a speed of the vehicle by converting the amount of change in the size of the image of the vehicle into the moving distance of the vehicle. 10. The method of claim 9, further comprising a subsequent processing step of performing a predetermined subsequent task when the speed of the vehicle calculated in the speed calculating step is equal to or higher than a predetermined speed. 11. The method according to claim 10, wherein in the subsequent processing step, an alarm is generated when the calculated vehicle speed is equal to or greater than a predetermined speed.

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