JP2010230373A - Device, method and program for calculating vehicle speed - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine the speed of a vehicle with high accuracy from observation data of a radar. <P>SOLUTION: In this device 100 for calculating the vehicle speed, a vehicle detection unit 103 observes an area where a road is laid by a synthetic aperture radar (SAR), and detects the vehicle being present in the vicinity of the road from a radar image 201 obtained as the results of observation. A Doppler shift amount estimation unit 104 estimates a Doppler shift amount on the basis of on a distance between the position of the road 301 and the position of the vehicle in the radar image 201 detected by the vehicle detection unit 103. A speed calculation unit 105 converts the Doppler shift amount estimated by the Doppler shift amount estimation unit 104 into the speed of the vehicle detected by the vehicle detection unit 103. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a vehicle speed calculation device, a vehicle speed calculation method, and a vehicle speed calculation program. The present invention particularly relates to a vehicle monitoring technique based on a synthetic aperture radar (SAR) image and a road map.

  As a conventional technique, with respect to a SAR image observed on the sea, a ship whose image brightness is equal to or higher than a certain threshold is detected as a ship, and a Doppler shift is calculated from a deviation amount between the ship and its wake (wake). (For example, refer to Patent Document 1).

JP 2001-4398 A

  When the prior art is used to calculate the speed of the vehicle, the vehicle is simply detected based on the threshold value of the brightness. Therefore, an object other than the vehicle is detected as the vehicle, or the vehicle and the vehicle actually run. There was a possibility of calculating the Doppler shift from the amount of deviation from the road.

  An object of the present invention is to obtain the speed of a vehicle with high accuracy from radar observation data, for example.

A vehicle speed calculation device according to one aspect of the present invention includes:
A storage device that stores in advance observation data obtained by observing the ground surface on which the road is laid by a radar mounted on the flying object, and a processing device that performs data processing,
A vehicle detection unit for detecting a vehicle in the vicinity of the road from the observation data stored in the storage device by the processing device;
A Doppler shift amount estimation unit that calculates a distance between the position of the road and a position in the observation data of the vehicle detected by the vehicle detection unit by the processing device, and estimates a Doppler shift amount based on the calculated distance; ,
And a speed calculation unit that converts the Doppler shift amount estimated by the Doppler shift amount estimation unit into a vehicle speed detected by the vehicle detection unit by the processing device.

The storage device stores in advance a plurality of observation data obtained by observing the ground surface at different times by the radar as the observation data,
The vehicle speed calculation device further includes:
A difference extraction unit that extracts a difference between a plurality of observation data stored in the storage device by the processing device and stores difference data indicating the extracted difference in the storage device;
The vehicle detection unit detects a vehicle existing in the vicinity of the road from the difference data stored in the storage device by the difference extraction unit.

The vehicle speed calculation device further includes:
An observation data correction unit that orthorectifies a plurality of observation data stored in the storage device by the processing device;
The difference extraction unit extracts a difference between a plurality of observation data orthorectified by the observation data correction unit as the difference.

  The vehicle detection unit detects a vehicle within a distance corresponding to a Doppler shift amount generated for a vehicle at a predetermined speed from the position of the road as a vehicle existing in the vicinity of the road.

The storage device further stores in advance a speed V of the flying object, an altitude R of the flying object, and an off-nadir angle θ of the radar,
The Doppler shift amount estimation unit further includes an angle α formed by a straight line drawn in parallel with a traveling direction of the flying object from a position in the observation data of the vehicle detected by the vehicle detection unit and the road by the processing device. Calculate
The speed calculation unit is configured to estimate the Doppler shift estimated by the Doppler shift amount estimation unit using the speed V, the altitude R, the off-nadir angle θ, and the angle α calculated by the Doppler shift amount estimation unit. The quantity X is converted into a vehicle speed VT detected by the vehicle detection unit.

  The speed calculation unit calculates VT = − (X × V) / R / sin θ / sin α to obtain a vehicle speed VT detected by the vehicle detection unit.

The vehicle detection unit detects a plurality of vehicles existing in the vicinity of the road from the observation data stored in the storage device,
The speed calculation unit obtains a speed for each vehicle detected by the vehicle detection unit, stores speed data indicating the number of vehicles detected by the vehicle detection unit and each speed in the storage device,
The vehicle speed calculation device further includes:
The speed calculation unit includes a speed data analysis unit that analyzes the speed data stored in the storage device by the processing device.

A vehicle speed calculation method according to an aspect of the present invention includes:
The storage device stores the observation data obtained by observing the ground surface where the road is laid by the radar mounted on the aircraft,
The processing device detects a vehicle existing in the vicinity of the road from the observation data stored in the storage device,
The processing device calculates a distance between the position of the road and the position of the detected vehicle in the observation data;
The processing device estimates a Doppler shift amount based on the calculated distance,
The processing device converts the estimated Doppler shift amount into the detected vehicle speed.

A vehicle speed calculation program according to an aspect of the present invention includes:
Vehicle speed executed by a computer having a storage device for preliminarily storing observation data obtained by observing the ground surface on which a road is laid by a radar mounted on the flying object, and a processing device for performing data processing A calculation program,
From the observation data stored in the storage device, a vehicle detection process for detecting a vehicle in the vicinity of the road by the processing device;
A Doppler shift amount estimation process for calculating a distance between the position of the road and a position in the observation data of the vehicle detected by the vehicle detection process by the processing device, and estimating a Doppler shift amount based on the calculated distance; ,
The computer is caused to execute speed calculation processing in which the processing device converts the Doppler shift amount estimated by the Doppler shift amount estimation processing into the vehicle speed detected by the vehicle detection processing.

The storage device stores in advance a plurality of observation data obtained by observing the ground surface at different times by the radar as the observation data,
The vehicle speed calculation program further includes:
Extracting a difference between a plurality of observation data stored in the storage device by the processing device, causing the computer to execute a difference extraction process of storing difference data indicating the extracted difference in the storage device,
The vehicle detection process is characterized in that a vehicle existing in the vicinity of the road is detected from the difference data stored in the storage device by the difference extraction process.

The vehicle speed calculation program further includes:
Causing the computer to execute observation data correction processing for ortho-correcting a plurality of observation data stored in the storage device by the processing device;
The difference extraction process is characterized in that a difference between a plurality of observation data orthorectified by the observation data correction process is extracted as the difference.

  The vehicle detection process is characterized by detecting a vehicle within a distance corresponding to a Doppler shift amount generated for a vehicle at a predetermined speed from the position of the road as a vehicle existing in the vicinity of the road.

The storage device further stores in advance a speed V of the flying object, an altitude R of the flying object, and an off-nadir angle θ of the radar,
The Doppler shift amount estimation process further includes an angle α formed by a straight line drawn in parallel with the traveling direction of the flying object from the position in the observation data of the vehicle detected by the vehicle detection process and the road. Calculate
The speed calculation process includes the Doppler shift estimated by the Doppler shift amount estimation process using the speed V, the altitude R, the off-nadir angle θ, and the angle α calculated by the Doppler shift amount estimation process. The quantity X is converted into a vehicle speed VT detected by the vehicle detection process.

  In the speed calculation process, VT = − (X × V) / R / sin θ / sin α is calculated to obtain a vehicle speed VT detected by the vehicle detection process.

The vehicle detection process detects a plurality of vehicles existing in the vicinity of the road from the observation data stored in the storage device,
The speed calculation process obtains a speed for each vehicle detected by the vehicle detection process, stores speed data indicating the number of vehicles detected by the vehicle detection process and the respective speeds in the storage device,
The vehicle speed calculation program further includes:
The speed calculation processing causes the computer to execute speed data analysis processing for analyzing the speed data stored in the storage device by the processing device.

  According to one aspect of the present invention, in the vehicle speed calculation device, the vehicle detection unit detects a vehicle existing in the vicinity of the road from the radar observation data, and the Doppler shift amount estimation unit detects the position of the road. A Doppler shift amount is estimated based on a distance between the position of the vehicle in the observation data detected by the vehicle detection unit, and a speed calculation unit detects the Doppler shift amount estimated by the Doppler shift amount estimation unit. By converting into the vehicle speed detected by the unit, the vehicle speed can be obtained with high accuracy from the radar observation data.

1 is a block diagram showing a configuration of a vehicle speed calculation device according to Embodiment 1. FIG. 6 is a diagram illustrating an example of a radar image according to Embodiment 1. FIG. 6 is a diagram illustrating an example of a radar image according to Embodiment 1. FIG. 2 is a diagram illustrating an example of a hardware configuration of a vehicle speed calculation device according to Embodiment 1. FIG. 3 is a flowchart showing the operation of the vehicle speed calculation device according to the first embodiment. It is a figure which shows the content of the difference extraction process which concerns on Embodiment 1. FIG. FIG. 6 is a diagram showing the contents of Doppler shift amount estimation processing according to Embodiment 1; It is a figure which shows the content of the speed calculation process which concerns on Embodiment 2. FIG. It is a figure which shows the content of the speed calculation process which concerns on Embodiment 2. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing the configuration of the vehicle speed calculation device 100.

  In FIG. 1, the vehicle speed calculation device 100 includes an observation data correction unit 101, a difference extraction unit 102, a vehicle detection unit 103, a Doppler shift amount estimation unit 104, a speed calculation unit 105, and a speed data analysis unit 106. The vehicle speed calculation device 100 includes hardware such as a processing device 151, a storage device 152, an input device 153, and an output device 154.

  The operation of each part of the vehicle speed calculation device 100 will be described later.

  The processing device 151 performs data processing. The processing device 151 is used to perform calculation, processing, reading, writing, and the like of data and information in each unit of the vehicle speed calculation device 100.

  The storage device 152 stores data such as the radar image 201 and the map data 202. The storage device 152 is used for storing data and information in each part of the vehicle speed calculation device 100.

  The radar image 201 is an example of observation data obtained by observing the ground surface with a radar mounted on a flying object (artificial satellite, aircraft, etc.). In the present embodiment, an area where a road is laid is observed by a synthetic aperture radar (SAR) which is an example of a radar, and a radar image 201 is obtained as a result. When a synthetic aperture radar emits a radio wave from the sky toward the ground surface, the radio wave is reflected by the ground or a natural or artificial object on the ground and becomes a scattered wave. The radar image 201 can be obtained by measuring the scattering intensity of the scattered wave and imaging the result. Usually, in the radar image 201, for each pixel, the scattering intensity at the corresponding position on the ground is represented by luminance.

  The map data 202 is a record of a map of an area observed by the synthetic aperture radar, and is data indicating the position of a road laid in the area.

  The input device 153 receives data input. The input device 153 is used by each unit of the vehicle speed calculation device 100 to accept input of data and information from a user or the like.

  The output device 154 outputs data. The output device 154 is used by each unit of the vehicle speed calculation device 100 to output data and information to a user or the like.

  2 and 3 are diagrams illustrating an example of the radar image 201. FIG.

  When a moving object such as a vehicle is observed by a synthetic aperture radar, the object is imaged at a place away from a position where it should be. This is called Doppler shift. The degree of separation (ie, the amount of Doppler shift) is proportional to the speed of the object. In the example of FIGS. 2 and 3, the actual vehicle is traveling on the road 301, but the moving vehicle on the radar image 201 is displayed with a shift of the Doppler shift amount from the road 301. In the example of FIG. 2, the vehicle is moving in a direction perpendicular to the traveling direction of the flying object 300 (that is, the traveling direction of the synthetic aperture radar) and in a direction approaching the synthetic aperture radar. The images are shifted in the traveling direction. On the other hand, in the example of FIG. 3, since the vehicle is moving in a direction away from the synthetic aperture radar, the image is shifted in the direction opposite to the traveling direction of the synthetic aperture radar.

  Although the speed of the vehicle can be determined by measuring the distance between the road 301 and the vehicle, it is difficult to automatically recognize the road and the vehicle from one radar image 201. Therefore, in the present embodiment, vehicle extraction and speed measurement are automatically performed using two radar images 201 and map data 202.

  Therefore, in the present embodiment, the storage device 152 stores a plurality of radar images 201, and each radar image 201 is obtained by observing the same area at different times with a synthetic aperture radar. And Specifically, the storage device 152 travels on the road with the radar image 201 obtained by observation at a time (for example, daytime) when it is estimated that there are many or at least a certain number of vehicles traveling on the road. It is assumed that a radar image 201 obtained by observation at a time (for example, at night) when it is estimated that there are few or almost no vehicles is stored in advance.

  FIG. 4 is a diagram illustrating an example of a hardware configuration of the vehicle speed calculation apparatus 100.

  In FIG. 4, the vehicle speed calculation apparatus 100 is a computer, and includes an LCD 901 (Liquid / Crystal / Display), a keyboard 902 (K / B), a mouse 903, an FDD 904 (Flexible / Disk / Drive), and a CDD 905 (Compact / Disc / Drive). Drive) and a hardware device such as a printer 906 are provided. These hardware devices are connected by cables and signal lines. Instead of the LCD 901, a CRT (Cathode / Ray / Tube) or other display device may be used. Instead of the mouse 903, a touch panel, a touch pad, a trackball, a pen tablet, or other pointing devices may be used.

  The vehicle speed calculation apparatus 100 includes a CPU 911 (Central Processing Unit) that executes a program. The CPU 911 is an example of the processing device 151. The CPU 911 includes a ROM 913 (Read / Only / Memory), a RAM 914 (Random / Access / Memory), a communication board 915, an LCD 901, a keyboard 902, a mouse 903, an FDD 904, a CDD 905, a printer 906, and an HDD 920 (Hard / Disk) via a bus 912. Connected with Drive) to control these hardware devices. Instead of the HDD 920, a flash memory, an optical disk device, a memory card reader / writer, or other storage medium may be used.

  The RAM 914 is an example of a volatile memory. The ROM 913, the FDD 904, the CDD 905, and the HDD 920 are examples of nonvolatile memories. These are examples of the storage device 152. The communication board 915, the keyboard 902, the mouse 903, the FDD 904, and the CDD 905 are examples of the input device 153. The communication board 915, the LCD 901, and the printer 906 are examples of the output device 154.

  The communication board 915 is connected to a LAN (Local / Area / Network) or the like. The communication board 915 is not limited to a LAN, but is an IP-VPN (Internet, Protocol, Private, Network), a wide area LAN, an ATM (Asynchronous / Transfer / Mode) network, or a WAN (Wide / Area / Network) It does not matter if it is connected to. LAN, WAN, and the Internet are examples of networks.

  The HDD 920 stores an operating system 921 (OS), a window system 922, a program group 923, and a file group 924. The programs in the program group 923 are executed by the CPU 911, the operating system 921, and the window system 922. The program group 923 includes programs that execute the functions described as “˜units” in the description of the present embodiment. The program is read and executed by the CPU 911. The file group 924 includes data, information, and signal values described as “˜data”, “˜information”, “˜ID (identifier)”, “˜flag”, and “˜result” in the description of this embodiment. And variable values and parameters are included as items of “˜file”, “˜database”, and “˜table”. The “˜file”, “˜database”, and “˜table” are stored in a storage medium such as the RAM 914 or the HDD 920. Data, information, signal values, variable values, and parameters stored in a storage medium such as the RAM 914 and the HDD 920 are read out to the main memory and the cache memory by the CPU 911 via a read / write circuit, and extracted, searched, referenced, compared, and calculated. It is used for processing (operation) of the CPU 911 such as calculation, control, output, printing and display. During the processing of the CPU 911 such as extraction, search, reference, comparison, calculation, calculation, control, output, printing, and display, data, information, signal values, variable values, and parameters are temporarily stored in the main memory, cache memory, and buffer memory. Remembered.

  The arrows in the block diagrams and flowcharts used in the description of this embodiment mainly indicate input / output of data and signals. Data and signals are recorded in memory such as RAM 914, FDD904 flexible disk (FD), CDD905 compact disk (CD), HDD920 magnetic disk, optical disk, DVD (Digital Versatile Disc), or other recording media Is done. Data and signals are transmitted by a bus 912, a signal line, a cable, or other transmission media.

  In the description of the present embodiment, what is described as “to part” may be “to circuit”, “to device”, “to device”, and “to step”, “to process”, “to”. ~ Procedure "," ~ process ". That is, what is described as “˜unit” may be realized by firmware stored in the ROM 913. Alternatively, what is described as “˜unit” may be realized only by software, or only by hardware such as an element, a device, a board, and wiring. Alternatively, what is described as “to part” may be realized by a combination of software and hardware, or a combination of software, hardware and firmware. Firmware and software are stored as programs in a recording medium such as a flexible disk, a compact disk, a magnetic disk, an optical disk, and a DVD. The program is read by the CPU 911 and executed by the CPU 911. That is, the program causes the computer to function as “to part” described in the description of the present embodiment. Or a program makes a computer perform the procedure and method of "-part" described by description of this Embodiment.

  FIG. 5 is a flowchart showing the operation of the vehicle speed calculation apparatus 100 according to the present embodiment (vehicle speed calculation method according to the present embodiment, processing procedure of the vehicle speed calculation program according to the present embodiment).

  In step S101 of FIG. 5, the observation data correction unit 101 performs ortho correction on the plurality of radar images 201 stored in the storage device 152 by using the processing device 151 (each radar image using the elevation data of the observation target area). The distortion due to the foreshortening at 201 is corrected). As described above, one of the radar images 201 is an image at a moment when vehicle monitoring is desired (daytime, etc., when there is a lot of traffic), and the other image is a time zone where traffic is low, such as at night on weekdays. It is an image observed at. Here, the former is SAR data 203a and the latter is SAR data 203b. The observation data correction unit 101 performs ortho correction on the SAR data 203 a, b and generates a SAR ortho image 204 a, b by the processing device 151. Then, the observation data correction unit 101 stores these SAR ortho images 204 a and b in the storage device 152 as the radar image 201. Here, the SAR data 203a, b and the SAR ortho image 204a, b are described as imaged data. However, even if the SAR data 203a, b is not imaged data, the ortho-corrected 2 is used. It is possible to obtain SAR ortho images 204a and 204b as a single radar image 201. Further, as described above, since the radar image 201 is an example of observation data, the processing from step S102 onward may be performed using observation data that has not been imaged.

  Thus, in this Embodiment, the SAR observation image of two different periods is orthorectified, The both difference extraction mentioned later and the comparison with a road map are implement | achieved.

  In step S <b> 102, the difference extraction unit 102 causes the processing device 151 to extract differences between the plurality of radar images 201 stored in the storage device 152. Here, as illustrated in FIG. 6, the difference extraction unit 102 uses the processing device 151 to extract the difference between the SAR orthoimages 204a and 204b stored in the storage device 152 by the observation data correction unit 101 in step S101. Then, the difference extraction unit 102 stores the difference data 205 indicating the extracted difference in the storage device 152.

  In step S <b> 103, the vehicle detection unit 103 detects, from the radar image 201 stored in the storage device 152, a vehicle that exists in the vicinity of a specific road by the processing device 151. Here, the vehicle detection unit 103 uses the processing device 151 to detect a vehicle existing in the vicinity of the road 301 described on the map of the map data 202 from the difference data 205 stored in the storage device 152 by the difference extraction unit 102 in step S102. To detect. The difference data 205 is obtained by obtaining a difference between two orthorectified radar images 201. That is, the difference data 205 is an ortho-corrected difference image. Therefore, the difference data 205 and the map data 202 can be superimposed. The vehicle detection unit 103 is an image obtained by superimposing the difference data 205 and the map data 202 and has a size of a vehicle (for example, a length in the longitudinal direction of 2 m to 20 m) and a bright spot close to the road 301 (A pixel or a pixel group having a certain luminance or higher) is determined as a vehicle. At this time, the vehicle detection unit 103 regards a bright spot within a certain distance from the position of the road 301 as a bright spot close to the road 301. Alternatively, the vehicle detection unit 103 determines the road 301 from a predetermined speed (for example, a constant speed such as 150 km / hour, a speed limit of the road 301 indicated by the map, a speed limit + a constant overspeed such as 10 km / hour). Assuming that no vehicle travels at a high speed, a bright spot within a distance corresponding to a Doppler shift amount generated for a vehicle traveling at the speed from the position of the road 301 is regarded as a bright spot close to the road 301 (ie, Only vehicles that travel below a predetermined speed are subject to detection).

  Thus, in this Embodiment, the detection accuracy of a vehicle is improved by considering the bright spot of the magnitude | size of about several m-several tens of m near the road 301 on a map as a vehicle.

  In step S104, the Doppler shift amount estimation unit 104 calculates the distance between the position of the specific road and the position in the radar image 201 of the vehicle detected by the vehicle detection unit 103 by the processing device 151, and based on the calculated distance. To estimate the Doppler shift amount. Here, as shown in FIG. 7, the Doppler shift amount estimation unit 104 calculates the distance between the position of the road 301 in the map data 202 and the vehicle position detected by the vehicle detection unit 103 in Step S <b> 103 as the Doppler shift amount. I reckon. The speed calculation unit 105 automatically converts the Doppler shift amount estimated by the Doppler shift amount estimation unit 104 into the vehicle speed detected by the vehicle detection unit 103 by the processing device 151.

  As described above, in the radar image 201, since the moving object has a characteristic of being imaged at a position shifted from the original position in proportion to the speed, in the present embodiment, the moving object is extracted by the determination method described above. The moving speed of the vehicle can be measured by measuring the distance between the bright spot (vehicle) and the road 301 and converting the distance to the speed.

  In step S103, when the vehicle detection unit 103 detects a plurality of vehicles existing in the vicinity of the road 301, the process of step S104 is performed for each detected vehicle. In step S104, the speed calculation unit 105 obtains the speed for each vehicle detected by the vehicle detection unit 103 in step S103 by the processing device 151, and speed data indicating the number of vehicles detected by the vehicle detection unit 103 and the respective speeds. 206 is stored in the storage device 152. The speed data 206 may indicate the traveling direction of each vehicle along with the speed of each vehicle.

  In step S <b> 105, the speed data analysis unit 106 analyzes the speed data 206 stored in the storage device 152 by the speed calculation unit 105 using the processing device 151. For example, the speed data analysis unit 106 calculates the average speed of the vehicle by the processing device 151 by adding up the speeds of all the vehicles and dividing the total value by the number of vehicles. The calculated average speed data can be used when determining measures for traffic control, such as road planning and road maintenance. In addition, for example, the speed data analysis unit 106 may calculate the average speed of the vehicle by the processing device 151 for each traveling direction of the vehicle by the same calculation method as described above. The calculated average speed data can be divided into an upstream direction and a downward direction and used when determining measures for traffic volume control.

Embodiment 2. FIG.
In the present embodiment, differences from the first embodiment will be mainly described.

  The configuration of vehicle speed calculation apparatus 100 according to the present embodiment is the same as that of the first embodiment shown in FIG.

  The radar image 201 is usually added with attribute data such as the velocity V and altitude R of the flying object 300 at the time of observation and the off-nadir angle θ of the synthetic aperture radar. In the present embodiment, it is assumed that the storage device 152 stores attribute data such as the velocity V, the altitude R, and the off-nadir angle θ together with the radar image 201.

  Hereinafter, the operation of the vehicle speed calculation apparatus 100 according to the present embodiment will be described with reference to FIG.

  In the present embodiment, the processes in steps S101 to S103 and S105 in FIG. 5 are the same as those in the first embodiment.

  In step S104, the Doppler shift amount estimation unit 104 performs Doppler shift on the distance between the position of the road 301 in the map data 202 and the vehicle position detected by the vehicle detection unit 103 in step S103, as in the first embodiment. It is regarded as an amount (referred to as Doppler shift amount X). In the present embodiment, the Doppler shift amount estimation unit 104 further includes an angle α formed by a road 301 and a straight line drawn parallel to the traveling direction of the synthetic aperture radar from the vehicle position detected by the vehicle detection unit 103 in step S103. Is calculated by the processing device 151. The speed calculation unit 105 uses the speed V, the altitude R, the off-nadir angle θ, and the angle α calculated by the Doppler shift amount estimation unit 104 stored in the storage device 152 to estimate the Doppler estimated by the Doppler shift amount estimation unit 104. The shift amount X is converted into the vehicle speed VT detected by the vehicle detection unit 103.

  Details of the speed VT calculation process performed by the speed calculation unit 105 will be described below with reference to FIGS.

  In FIG. 8, as described above, the velocity of the air vehicle 300 on which the synthetic aperture radar is mounted is V. It is also assumed that the vehicle is at a distance R from the synthetic aperture radar and is traveling on the ground surface at a speed VT. VT is a vector in which the direction away from the synthetic aperture radar is positive. At this time, the velocity VR obtained by projecting the vector VT in the beam irradiation direction (that is, the range direction) of the synthetic aperture radar is obtained.

First, let VA be the component projected in the azimuth direction. VA is a vector in which the same direction as the traveling direction of the synthetic aperture radar is positive and the reverse direction is negative.
VA = VT × cos α
Here, as described above, α is an angle formed by the traveling direction of the synthetic aperture radar and the moving direction of the vehicle.

Next, a direction VC orthogonal to VA and parallel to the ground surface is called a cross track direction, and a velocity VC projected in the cross track direction is obtained.
VC = VT × sin α

Finally, a component obtained by projecting VC in the range direction is VR. VR is a vector in which the direction away from the synthetic aperture radar is positive and the direction approaching the synthetic aperture radar is negative.
VR = VC × sin θ = VT × sin α × sin θ
Here, as described above, θ is an off-nadir angle.

  Here, VA is also obtained for reference, but since it is not used for calculating the speed VT, the calculation of VA may be omitted.

  In the radar image 201, the vehicle appears in the direction opposite to the traveling direction (azimuth direction) of the synthetic aperture radar in proportion to VR. As described above, this is a Doppler shift.

In FIG. 9, as described above, the displacement of the vehicle on the radar image 201 due to the Doppler shift (that is, the amount of Doppler shift) is set to X (the unit is, for example, a meter and is expressed by a distance). When the vehicle moves away from the synthetic aperture radar, the vehicle is imaged in a direction opposite to the traveling direction of the synthetic aperture radar. Conversely, when the vehicle approaches the synthetic aperture radar, the vehicle is imaged in the same direction as the direction of travel of the synthetic aperture radar. Therefore, X is defined as a positive direction for the traveling direction of the synthetic aperture radar (that is, the azimuth direction) and a negative direction for the reverse direction.
X = − (R / V) × VR

For example, when the synthetic aperture radar is a PALSAR (Phased, Array, type, L-band, Synthetic, Aperture, Radar) onboard satellite DAICHI (ALOS: Advanced, Land, Observing, Satellite), R≈1000 km, V≈ Since 7 km / sec and θ≈45 degrees, the vehicle temporarily moves in a direction perpendicular to the satellite traveling direction at VT = 40 km / hour (≈11 m / sec) and away (VA = 0, VC = 40 km / hour). If
VR = VC × sin (45 degrees) ≈7.8 m / sec
X≈− (1000 km / (7 km / sec)) × 7.8 m / sec≈−1.1 km
It becomes. That is, the vehicle is imaged at a position shifted by 1.1 km. Similarly, if VT = 100 km / hour (≈27.7 m / sec), X≈−2.8 km. Since one pixel of the radar image 201 is about 10 m, in this case, the vehicle is imaged at a position shifted by 280 pixels.

  Hereinafter, a procedure for obtaining the vehicle speed from the Doppler shift of the vehicle on the radar image 201 will be described.

As a premise, the following processing is performed by the Doppler shift amount estimation unit 104.
(1) Read how many pixels the vehicle is away from the road 301. Here, m pixels are assumed.
(2) A Doppler shift amount (distance) X is obtained.
X = + m × Δ (when separated in the same direction as the synthetic aperture radar traveling direction)
X = −m × Δ (when separated from the traveling direction of the synthetic aperture radar)
Here, Δ is the distance per pixel.

In addition, the following processing is performed by the speed calculation unit 105.
(3) VR is obtained from X = − (R / V) × VR.
VR = − (X × V) / R
Here, although the altitude of the flying object 300 is regarded as R, the distance from the flying object 300 to the vehicle needs to be R in order to perform more accurate calculation. In this case, R can be calculated by knowing how many pixels the radar image 201 has from the side closer to the synthetic aperture radar (left in FIG. 9) (as described above, the radar image 201 that is normally distributed). Is stored with additional information for calculating the distance from the radar image 201 to the synthetic aperture radar). Alternatively, if the altitude of the flying object 300 and the off-nadir angle are known, it can be calculated geometrically (as described above, the off-nadir angle is also usually given as additional information of the radar image 201). The traveling speed V of the synthetic aperture radar is also known because it is obtained as additional information of the radar image 201.
(4) The cross track speed VC is calculated from the VR and the off-nadir angle θ.
VC = VR / sin θ
(5) An angle α between the traveling direction of the road 301 and the synthetic aperture radar is obtained (if the road 301 is given as vector information, α can be obtained from the direction of the road 301 in the radar image 201 as it is. If it is given as raster data, α can be obtained by the same method using techniques such as edge detection and Hough transform in order to detect the line of the road 301).
(6) Obtain VT from VC and α.
VT = VC / sin α = VR / sin θ / sin α
It is assumed that VR = 0 (that is, VC = 0 and the vehicle is stationary or moving in parallel with the synthetic aperture radar).

  Thus, in the present embodiment, the speed calculation unit 105 calculates VT = − (X × V) / R / sin θ / sin α, and the processing device 151 calculates the vehicle speed VT detected by the vehicle detection unit 103. Ask for.

  As mentioned above, although embodiment of this invention was described, you may implement combining 2 or more embodiment among these. Alternatively, one of these embodiments may be partially implemented. Or you may implement combining two or more embodiment among these partially.

  DESCRIPTION OF SYMBOLS 100 Vehicle speed calculation apparatus, 101 Observation data correction part, 102 Difference extraction part, 103 Vehicle detection part, 104 Doppler shift amount estimation part, 105 Speed calculation part, 106 Speed data analysis part, 151 Processing apparatus, 152 Storage device, 153 Input Device, 154 output device, 201 radar image, 202 map data, 203a, b SAR data, 204a, b SAR ortho image, 205 difference data, 206 speed data, 300 flying object, 301 road, 901 LCD, 902 keyboard, 903 mouse , 904 FDD, 905 CDD, 906 printer, 911 CPU, 912 bus, 913 ROM, 914 RAM, 915 communication board, 920 HDD, 921 operating system, 922 window system, 923 program Beam group, 924 files.

Claims (15)

A storage device that stores in advance observation data obtained by observing the ground surface on which the road is laid by a radar mounted on the flying object, and a processing device that performs data processing,
A vehicle detection unit for detecting a vehicle in the vicinity of the road from the observation data stored in the storage device by the processing device;
A Doppler shift amount estimation unit that calculates a distance between the position of the road and a position in the observation data of the vehicle detected by the vehicle detection unit by the processing device, and estimates a Doppler shift amount based on the calculated distance; ,
A vehicle speed calculation device comprising: a speed calculation unit that converts the Doppler shift amount estimated by the Doppler shift amount estimation unit into a vehicle speed detected by the vehicle detection unit by the processing device. The storage device stores in advance a plurality of observation data obtained by observing the ground surface at different times by the radar as the observation data,
The vehicle speed calculation device further includes:
A difference extraction unit that extracts a difference between a plurality of observation data stored in the storage device by the processing device and stores difference data indicating the extracted difference in the storage device;
The vehicle speed calculation device according to claim 1, wherein the vehicle detection unit detects a vehicle existing in the vicinity of the road from the difference data stored in the storage device by the difference extraction unit. The vehicle speed calculation device further includes:
An observation data correction unit that orthorectifies a plurality of observation data stored in the storage device by the processing device;
The vehicle speed calculation device according to claim 2, wherein the difference extraction unit extracts a difference between a plurality of observation data orthorectified by the observation data correction unit as the difference.   The vehicle detection unit detects a vehicle within a distance corresponding to a Doppler shift amount generated for a vehicle at a predetermined speed from the position of the road as a vehicle existing in the vicinity of the road. 4. The vehicle speed calculation device according to any one of items 1 to 3. The storage device further stores in advance a speed V of the flying object, an altitude R of the flying object, and an off-nadir angle θ of the radar,
The Doppler shift amount estimation unit further includes an angle α formed by a straight line drawn in parallel with a traveling direction of the flying object from a position in the observation data of the vehicle detected by the vehicle detection unit and the road by the processing device. Calculate
The speed calculation unit is configured to estimate the Doppler shift estimated by the Doppler shift amount estimation unit using the speed V, the altitude R, the off-nadir angle θ, and the angle α calculated by the Doppler shift amount estimation unit. The vehicle speed calculation device according to any one of claims 1 to 4, wherein the amount X is converted into a vehicle speed VT detected by the vehicle detection unit.   The vehicle according to claim 5, wherein the speed calculation unit calculates VT = − (X × V) / R / sin θ / sin α to obtain a vehicle speed VT detected by the vehicle detection unit. Speed calculator. The vehicle detection unit detects a plurality of vehicles existing in the vicinity of the road from the observation data stored in the storage device,
The speed calculation unit obtains a speed for each vehicle detected by the vehicle detection unit, stores speed data indicating the number of vehicles detected by the vehicle detection unit and each speed in the storage device,
The vehicle speed calculation device further includes:
The vehicle speed calculation device according to any one of claims 1 to 6, further comprising a speed data analysis unit that analyzes the speed data stored in the storage device by the speed calculation unit. The storage device stores the observation data obtained by observing the ground surface where the road is laid by the radar mounted on the aircraft,
The processing device detects a vehicle existing in the vicinity of the road from the observation data stored in the storage device,
The processing device calculates a distance between the position of the road and the position of the detected vehicle in the observation data;
The processing device estimates a Doppler shift amount based on the calculated distance,
The vehicle speed calculation method, wherein the processing device converts the estimated Doppler shift amount into the detected vehicle speed. Vehicle speed executed by a computer having a storage device for preliminarily storing observation data obtained by observing the ground surface on which a road is laid by a radar mounted on the flying object, and a processing device for performing data processing A calculation program,
From the observation data stored in the storage device, a vehicle detection process for detecting a vehicle in the vicinity of the road by the processing device;
A Doppler shift amount estimation process for calculating a distance between the position of the road and a position in the observation data of the vehicle detected by the vehicle detection process by the processing device, and estimating a Doppler shift amount based on the calculated distance; ,
A vehicle speed calculation program that causes a computer to execute a speed calculation process in which the processing device converts the Doppler shift amount estimated by the Doppler shift amount estimation process into the vehicle speed detected by the vehicle detection process. The storage device stores in advance a plurality of observation data obtained by observing the ground surface at different times by the radar as the observation data,
The vehicle speed calculation program further includes:
Extracting a difference between a plurality of observation data stored in the storage device by the processing device, causing the computer to execute a difference extraction process of storing difference data indicating the extracted difference in the storage device,
The vehicle speed calculation program according to claim 9, wherein the vehicle detection process detects a vehicle existing in the vicinity of the road from the difference data stored in the storage device by the difference extraction process. The vehicle speed calculation program further includes:
Causing the computer to execute observation data correction processing for ortho-correcting a plurality of observation data stored in the storage device by the processing device;
The vehicle speed calculation program according to claim 10, wherein the difference extraction process extracts, as the difference, a difference between a plurality of observation data orthorectified by the observation data correction process.   The vehicle detection process detects a vehicle within a distance corresponding to a Doppler shift amount generated for a vehicle at a predetermined speed from the position of the road as a vehicle existing in the vicinity of the road. The vehicle speed calculation program in any one of from 11. The storage device further stores in advance a speed V of the flying object, an altitude R of the flying object, and an off-nadir angle θ of the radar,
The Doppler shift amount estimation process further includes an angle α formed by a straight line drawn in parallel with the traveling direction of the flying object from the position in the observation data of the vehicle detected by the vehicle detection process and the road. Calculate
The speed calculation process includes the Doppler shift estimated by the Doppler shift amount estimation process using the speed V, the altitude R, the off-nadir angle θ, and the angle α calculated by the Doppler shift amount estimation process. The vehicle speed calculation program according to any one of claims 9 to 12, wherein the amount X is converted into a vehicle speed VT detected by the vehicle detection process.   14. The vehicle according to claim 13, wherein the speed calculation process calculates VT = − (X × V) / R / sin θ / sin α to obtain a vehicle speed VT detected by the vehicle detection process. Speed calculation program. The vehicle detection process detects a plurality of vehicles existing in the vicinity of the road from the observation data stored in the storage device,
The speed calculation process obtains a speed for each vehicle detected by the vehicle detection process, stores speed data indicating the number of vehicles detected by the vehicle detection process and the respective speeds in the storage device,
The vehicle speed calculation program further includes:
The vehicle speed calculation program according to any one of claims 9 to 14, wherein the speed calculation processing causes the computer to execute speed data analysis processing for analyzing speed data stored in the storage device by the processing device. .

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