JP2007156897A - Speed-measuring apparatus, method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a speed-measuring apparatus, method, and program capable of extracting a moving object from an aerial photographic image in measuring speed of a moving object by using the aerial photographic image. <P>SOLUTION: In acquiring the aerial photographic image in which a vehicle moving along a white line on the road exists in a central part of a picture by using a camera mounted on an airplane to measure speed of the vehicle on the basis of the acquired aerial photographic image, a white line detection part 11 extracts a line with specific width, selects a white line on the basis of an angle with respect to a horizontal direction of the picture, links white lines on the same straight line, and groups them. A vehicle area position detection part 12 extracts an area surrounded by the grouped white lines as a vehicle area and detects a position of the vehicle in the vehicle area. A white line selection and dotted line data acquisition part 13 acquires data of dotted lines which are adjacent to the vehicle and divide the white lines. A speed calculating part 2 calculates the speed of the vehicle on the basis of the position of the white lines and the data of the dotted lines. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a speed measuring device that measures the speed of a moving object using an aerial image in which a moving object that moves along a fixed object of a specific width that is periodically arranged exists in the center portion of the screen. , Methods and programs.

Conventionally, when measuring the speed of a moving object (for example, a vehicle) using an aerial image, a method for extracting a moving object in an aerial image in which the background moves is based on a background difference (for example, see Patent Document 1). , A technique based on a motion vector (for example, see Patent Document 2) or a technique based on stereo vision (for example, see Patent Document 3).
JP 2003-303397 A JP 2001-357492 A Japanese Patent Laid-Open No. 11-211738

  In the method based on the background difference, the difference between two aerial images at different times is calculated, and when the background is stationary, only the area of the moving object is extracted. Movement is also included in the difference result. In addition, in the method based on the motion vector, when the background is stationary, the motion vector distribution is generated only in the area of the moving object. However, if the background is moved, the motion vector is also generated in the background. It is necessary to investigate the difference in vector distribution and to divide the background area and the moving object area. Furthermore, in the method based on stereo vision, three-dimensional information is extracted from the aerial images of the two cameras based on the correspondence between the object positions in the aerial images, and as a result, the height of the ground (background) and the moving object Due to the difference, the area of the moving object in the aerial image is extracted. However, when the shooting position is very far from the ground or the moving object, it may be difficult to find the difference in height between the ground and the moving object. In addition, it is necessary to synchronize the shooting time using two cameras, which increases the cost of the apparatus. Therefore, it is difficult to accurately extract a moving object from an aerial image by any of the conventional method based on background difference, the method based on a motion vector, and the method based on a stereo image.

  An object of the present invention is to provide a speed measurement device, method, and program capable of accurately extracting a moving object from an aerial image when measuring the speed of the moving object using an aerial image.

The speed measuring device according to the present invention is:
A moving object that moves along an immovable object having a specific width arranged periodically is a speed measuring device that measures the speed of the moving object using an aerial image, which exists in the center portion of the screen,
First extraction means for extracting the line of the specific width using a line extraction filter;
The line segments of the specific width are rearranged according to the angle of the lines of the specific width with respect to the horizontal direction of the screen, the angle range of the line segments of the specific width is set from the median value of the angles, and the angle range A selection means for selecting the line segment to be stored as the candidate for the immovable target;
A grouping means for connecting and grouping the immovable objects arranged on the same straight line using a morphological operation;
Second extraction means for extracting a region sandwiched between the grouped immovable objects as a movement target region;
Detecting means for detecting a position of the moving object in the moving object region;
An acquisition means for acquiring dotted data adjacent to the moving object and dividing the immovable object;
And calculating means for calculating the speed of the moving object based on the position of the moving object and the dotted line data.

The speed measurement method according to the present invention includes:
A moving object that moves along an immovable object having a specific width that is periodically arranged is present in the center portion of the screen, and is a speed measuring method that measures the speed of the moving object using an aerial image,
A first extraction step of extracting the line having the specific width using a line extraction filter;
The line segments of the specific width are rearranged according to the angle of the lines of the specific width with respect to the horizontal direction of the screen, the angle range of the line segments of the specific width is set from the median value of the angles, and the angle range A selection step of selecting the line segments to be included as candidates for the immovable target;
A grouping step of grouping the immovable objects arranged on the same straight line together by using a morphological operation;
A second extraction step of extracting a region sandwiched between the grouped immovable objects as a movement target region;
A detecting step for detecting a position of the moving object in the moving object region;
An acquisition step of acquiring data of a dotted line adjacent to the moving object and dividing the immovable object;
And a calculation step of calculating a speed of the moving object based on the position of the moving object and the dotted line data.

The speed measurement program according to the present invention includes:
A moving object that moves along an immovable object having a specific width arranged periodically, is a speed measurement program that measures the speed of the moving object using an aerial image, which exists in the center portion of the screen,
A first extraction step of extracting the line having the specific width using a line extraction filter;
The line segments of the specific width are rearranged according to the angle of the lines of the specific width with respect to the horizontal direction of the screen, the angle range of the line segments of the specific width is set from the median value of the angles, and the angle range A selection step of selecting the line segments to be included as candidates for the immovable target;
A grouping step of grouping the immovable objects arranged on the same straight line together by using a morphological operation;
A second extraction step of extracting a region sandwiched between the grouped immovable objects as a movement target region;
A detecting step for detecting a position of the moving object in the moving object region;
An acquisition step of acquiring data of a dotted line adjacent to the moving object and dividing the immovable object;
And a calculation step of calculating a speed of the moving object based on the position of the moving object and the dotted line data.

  According to the present invention, when measuring the speed of the moving object using the aerial image, the moving object moving along the fixed object of a specific width arranged periodically is present in the center portion of the screen. Lines with a specific width are extracted using a line extraction filter, and the line segments with a specific width are rearranged according to the angle of the line with the specific width with respect to the horizontal direction of the screen. Set an angle range, select line segments that fall within the angle range as candidates for immovable objects, use morphological operations to connect and group the immovable objects that are aligned on the same straight line, and sandwich them between the grouped immovable objects. The extracted area is extracted as a movement target area, the position of the movement target in the movement target area is detected, the dotted line data that is adjacent to the movement target and divides the non-moving target is obtained, and the position of the stationary target and the dotted line Move based on data To calculate the speed of the elephant.

  Therefore, when measuring the speed of a moving object using an aerial image without the inconvenience of extraction of the moving object in the method based on background difference, the method of motion vector, and the method based on stereo vision, It can be accurately extracted from the captured image.

  Preferably, the first extraction means outputs a candidate point of the line by using a convolution operation of an image and a partial derivative of a Gaussian function, and connects the candidate points based on a proximity relationship, and A line is formed, and the grouping means translates in accordance with the concentric rectangular displacement for each line segment, and superimposes all the figures drawn by the line segment, leaving a length that is equal to or greater than a threshold value.

  Preferably, the second extraction means sets a portion having a change in density in a region sandwiched between the immovable objects as a candidate for the movement target region, and a candidate near the central portion of the screen among the candidates. The movement target area is used, and the detection unit detects the position of the movement target by collating the movement target area with a template.

  Preferably, the acquisition means selects a dotted line that partitions the stationary objects among the stationary objects adjacent to the movement target area, outputs the dotted lines as the dotted line data, and the calculation means includes: The dimension on the aerial image regarding the amount of movement of the moving object is obtained from the position of the moving object, and the dimension on the aerial image regarding the amount of movement of the immovable object and the period of the immovable object from the dotted line data. The dimension on the aerial image is obtained, the dimension on the aerial image regarding the movement amount of the moving object, the dimension on the aerial image regarding the movement amount of the stationary object, and the aerial image regarding the period of the stationary object. The speed of the moving object is calculated using the above dimensions.

DESCRIPTION OF EMBODIMENTS Embodiments of a speed measuring device, method, and program according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing an embodiment of a speed measuring device according to the present invention. This speed measurement device uses a camera mounted on an aircraft to acquire an aerial image in which a vehicle moving along a white line on a road exists in the center of the screen, and based on the acquired aerial image, It measures speed, and includes a feature extraction unit 1 and a speed calculation unit 2.

  The feature extraction unit 1 exists for each frame (in FIG. 1, only the (k−1) -th frame and the k-th frame are shown). As will be described later, the feature extraction unit 1 represents a representative point of the tracking vehicle and a white line adjacent to the tracking vehicle. (Dotted line) Data is extracted, and includes a white line detection unit 11, a vehicle region position detection unit 12, and a white line selection and dotted line data acquisition unit 13.

  FIG. 2 is a flowchart of the operation of the embodiment of the speed measuring device according to the present invention. This flowchart shows the processing operation performed for each still image. First, the white line detection unit 11 extracts a line having a specific width by using a line extraction filter. In the line extraction filter, a candidate point of a line is output by using a convolution operation between an image and a partial derivative of a Gaussian function, and the candidate points are connected based on the proximity relation to form the line. Since these are output as a data string of connected candidate points, they are approximated to a line segment in the subsequent calculation.

  Next, the white line detection unit 11 performs line segment selection based on the angle. A relatively long line segment in the image has many road white lines. Sort the long line segments by the angle with respect to the horizontal direction of the screen, and set the angle range of the road white line from the median angle. Line segments that fall within the set angle are selected as white line candidates.

  Next, white lines are grouped using a morphological operation, and road white line regions are extracted. Specifically, as shown in FIG. 3, a Minkowski sum operation, which is a kind of morphological operation, is used. First, each line segment is translated in accordance with a concentric rectangular displacement (FIG. 3A) to obtain a figure drawn by the line segment. All the drawn figures are overlapped, leaving the one whose length is more than the threshold value. As a result, the areas drawn by the dotted lines arranged in a straight line are connected to each other to surround one long straight line (FIG. 3B). This area is extracted as a road white line area.

  Next, the vehicle region position detection unit 12 extracts a portion sandwiched between the white line regions as a lane region, and extracts a portion having a density change from the lane region as a vehicle region. In FIG. 4, when the rectangular area is A and the white line areas are B1 to B6, (A∩B1) ∪ (A∩B2) ∪ (A∩B3) ∪ (A∩B4) ∪ (A∩B5) ∪ A region X that is (A∩B6) (therefore, the region X corresponds to the regions B1 to B4 in the region A) is obtained, and the region Y that is the convex hull of the region X (therefore, the region Y is a rectangular region) (Corresponding to a parallelogram road area in A), and the area Y minus the area X is extracted as a lane area (the lane area is therefore a white line area B1 from the parallelogram road area). ~ B6 is excluded).

  When the lane region is extracted, as shown in FIG. 5, the absolute value of the difference from the average value is obtained in the lane region and binarized. After that, dilation with a circle that is one of the morphological operations is performed, and then convex closure is performed.Selection by length is performed in order to eliminate a horizontally long region, and a portion having a change in density is regarded as a candidate vehicle region. To do. Of the candidates, the one close to the center of the image is set as the vehicle area.

  Next, the vehicle region position detection unit 12 performs vehicle position tracking processing. As shown in FIG. 6, the vehicle position tracking process includes a template matching process set in the previous image, a vehicle position detection process, and a template setting used in the next image.

  When the vehicle position tracking process is performed, a template is set in a region (vehicle position) where the density change is large in the vehicle region, and the vehicle position is tracked by inter-frame matching. Search for the vehicle position in the second and subsequent frames (the tracking may fail just by taking over the previous frame comparison result, and the vehicle position is repositioned for each frame) from the area where the vicinity of the verification position and the vehicle area overlap. . If there is no overlap, an area close to the center of the screen is selected, and the vehicle position is determined in the same procedure.

  FIG. 7 is a flowchart of the vehicle position detection processing operation. In this case, a target region is set, and a median filter process is performed to remove a severe density change (noise) and obtain a median value. Thereafter, the maximum value and the minimum value with respect to the median value are obtained using the maximum value filter and the minimum value filter, and the difference between the maximum value and the minimum value within the filter size is obtained. A position where the difference between the maximum value and the minimum value is remarkably large and includes both the low density area and the high density area is selected as the template center position. In the speed calculation described later, this position is handled as the vehicle position.

  Next, the white line selection and dotted line data acquisition unit 13 acquires neighboring white line data (white line selection / dot line data extraction process). In this case, among the white lines adjacent to the vehicle area, a dotted line-shaped one that divides the lanes is selected, and dotted line data is output. The dotted line data is a section length data string delimited by line segment end points for each line. For information from the screen edge, as shown in FIG. 8, the length from the start point to the first point is inserted first.

  Next, a traveling speed calculation process is performed in the speed calculator 2. The traveling speed is calculated from two frames based on the vehicle position coordinates and the white line data, and the traveling speed calculation processing includes, as shown in FIG. 9, the evaluation function sample acquisition of the period, the estimation of the white line period, and the evaluation of the movement amount. It consists of function sample acquisition, white line movement estimation, and travel speed calculation.

  The vehicle movement amount (image size) is obtained from the vehicle position based on the template matching shown in FIG. By using the calculation method using the movement correlation described later, the movement amount (image size) of the white line (background) and the reference length (cycle) of the white line are obtained from the dotted line data of the white line. The vehicle speed between frames is calculated based on the vehicle movement amount, the white line movement amount, and the white line reference length.

  The average speed V between N frames is

によって求められる。このときの車両の移動量は、期間の最初の位置及び最後の位置で計算可能であり、１／Ｎに平均化される。なお、

を画像上の白線の移動速度とし、

を、画像上の車両（代表点）の移動速度とし、

を、画像上の車両（代表点）の位置（期間の最初ｎ＝０）とし、

を、画像上の車両（代表点）の位置（期間の最後ｎ＝Ｎ）とする。

Sought by. The moving amount of the vehicle at this time can be calculated at the first position and the last position of the period, and is averaged to 1 / N. In addition,

Is the moving speed of the white line on the image,

Is the moving speed of the vehicle (representative point) on the image,

Is the position of the vehicle (representative point) on the image (first n = 0 in the period)

Is the position of the vehicle (representative point) on the image (n = N at the end of the period).

  Further, when reading from an image, information (reference length) for converting the dimension on the image into the actual dimension is required. When there are 2 to 3 lanes on one side of the highway, the white line separating the lanes is a dotted line, and the period of the white line and the gap is estimated.

  Here, the simplification of the movement amount / reference length calculation will be described. The dotted line data of the white line itself has a correlation with the movement pattern for the period, and there is a correlation with the movement pattern for the movement amount between frames. According to the present embodiment, as shown in FIG. 10, with respect to the line segment end point, the sum of the distances between the nearest points with respect to the fixed distance row of the movement distance row is evaluated, and the movement amount at which the evaluation value is minimized (minimum). It is obtained as a dotted line cycle (interframe movement amount).

  In addition, the distance to the nearest point is converted into a function, and the point pair combination trial is omitted. Furthermore, the evaluation is based on the sum of the distances of the nearest neighbor points corresponding to the number of white line end points, and the amount of calculation is lower than that of calculating the movement correlation.

  Next, the distance sum function of the period (reference length) will be described. The function f (x) in FIG. 10 is the sum of the distances, and the influence of the error is reduced with respect to missing / disconnected part of the line segment. From the same effect, use of overlapping the results of a plurality of white lines (between frames, parallel lines, etc.) is also conceivable. In addition, a minimum value occurs in the period, and the period (reference length) estimation can be performed not only for a single period but also for a double period.

  Next, the distance sum function of the movement amount will be described. Between frames, the total distance is minimized when the amount of movement is returned. For example, with respect to the movement amount v at the left end portion of the image, the function value at the point where the position is almost restored is minimized. On the other hand, in a situation where a new white line appears in the screen in the subsequent frame, the function value is minimized when the sum of the movement amount v and the appearing white line length is returned.

  According to the present embodiment, by specifying a road area by extracting a white line, an area candidate having a density distribution different from the road surface is extracted, and a vehicle area is extracted by integrating adjacent area candidates. When measuring the speed of a moving object using an aerial image without the inconvenience of moving object extraction in the method based on motion, the method of motion vector and the method based on stereo vision, Can be extracted. In addition, regarding the background density change due to the time variation of the illumination, since the road surface density of each lane is examined at each time, the influence of the background density change is not exerted.

The present invention is not limited to the above-described embodiment, and many changes and modifications can be made.
For example, in the above embodiment, the case where the vehicle moves along the white line on the road has been described. However, the immovable object may be other than the white line, and the moving object may be other than the vehicle. it can.

It is a figure showing an embodiment of a speed measuring device by the present invention. It is a flowchart of operation | movement of embodiment of the speed measuring device by this invention. It is a figure for demonstrating grouping of a white line. It is a figure for demonstrating extraction of a lane area. It is a flowchart of extraction operation of a vehicle area. It is a flowchart of the tracking processing operation | movement of a vehicle position. 4 is a flowchart of a vehicle position detection processing operation. It is a figure for demonstrating acquisition of neighboring white line data. It is a flowchart of driving speed calculation processing operation. It is a figure for demonstrating simplification of movement amount and reference | standard length calculation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Feature extraction part 2 Speed calculation part 11 White line detection part 12 Vehicle area position detection part 13 White line selection and dotted line data acquisition part

Claims (9)

A moving object that moves along an immovable object having a specific width arranged periodically is a speed measuring device that measures the speed of the moving object using an aerial image, which exists in the center portion of the screen,
First extraction means for extracting the line of the specific width using a line extraction filter;
The line segments of the specific width are rearranged according to the angle of the lines of the specific width with respect to the horizontal direction of the screen, the angle range of the line segments of the specific width is set from the median value of the angles, and the angle range A selection means for selecting the line segment to be stored as the candidate for the immovable target;
A grouping means for connecting and grouping the immovable objects arranged on the same straight line using a morphological operation;
Second extraction means for extracting a region sandwiched between the grouped immovable objects as a movement target region;
Detecting means for detecting a position of the moving object in the moving object region;
An acquisition means for acquiring dotted data adjacent to the moving object and dividing the immovable object;
A speed measuring apparatus comprising: a calculating means for calculating a speed of the moving object based on the position of the moving object and the dotted line data.   The first extraction means outputs a candidate point of the line by using a convolution operation of an image and a partial derivative of a Gaussian function, and connects the candidate points based on a proximity relation to form the line. The speed measuring device according to claim 1, wherein:   The grouping means translates in accordance with the displacement of a concentric rectangle for each line segment, superimposes all the figures drawn by the line segment, and leaves a length equal to or greater than a threshold value. Item 2. The speed measuring device according to Item 1.   The second extraction means sets a portion having a density change in a region sandwiched between the immovable objects as a candidate for the movement target region, and a candidate near the central portion of the screen among the candidates is the movement target region. The speed measuring device according to claim 1, wherein:   The speed measuring apparatus according to claim 1, wherein the detecting unit detects the position of the moving target by performing template matching on the moving target area.   The said acquisition means selects the dotted line which divides between the said stationary objects among the said stationary objects adjacent to the said movement object area | region, These these dotted lines are output as the data of the said dotted line. Speed measuring device.   The calculation means obtains the dimension on the aerial image regarding the movement amount of the movement target from the position of the movement target, and the dimension on the aerial image regarding the movement amount of the stationary object from the dotted line data and The dimension on the aerial image regarding the period of the stationary object is obtained, the dimension on the aerial image regarding the amount of movement of the moving object, the dimension on the aerial image regarding the amount of movement of the stationary object, and the period of the stationary object. The speed measuring apparatus according to claim 1, wherein the speed of the moving object is calculated using a dimension on the aerial image regarding the moving object. A moving object that moves along an immovable object having a specific width that is periodically arranged is present in the center portion of the screen, and is a speed measuring method that measures the speed of the moving object using an aerial image,
A first extraction step of extracting the line having the specific width using a line extraction filter;
The line segments of the specific width are rearranged according to the angle of the lines of the specific width with respect to the horizontal direction of the screen, the angle range of the line segments of the specific width is set from the median value of the angles, and the angle range A selection step of selecting the line segments to be included as candidates for the immovable target;
A grouping step of grouping the immovable objects arranged on the same straight line together by using a morphological operation;
A second extraction step of extracting a region sandwiched between the grouped immovable objects as a movement target region;
A detecting step for detecting a position of the moving object in the moving object region;
An acquisition step of acquiring data of a dotted line adjacent to the moving object and dividing the immovable object;
A speed measurement method comprising: a calculation step of calculating a speed of the moving object based on the position of the moving object and the dotted line data. A moving object that moves along an immovable object having a specific width arranged periodically, is a speed measurement program that measures the speed of the moving object using an aerial image, which exists in the center portion of the screen,
A first extraction step of extracting the line having the specific width using a line extraction filter;
The line segments of the specific width are rearranged according to the angle of the lines of the specific width with respect to the horizontal direction of the screen, the angle range of the line segments of the specific width is set from the median value of the angles, and the angle range A selection step of selecting the line segments to be included as candidates for the immovable target;
A grouping step of grouping the immovable objects arranged on the same straight line together by using a morphological operation;
A second extraction step of extracting a region sandwiched between the grouped immovable objects as a movement target region;
A detecting step for detecting a position of the moving object in the moving object region;
An acquisition step of acquiring data of a dotted line adjacent to the moving object and dividing the immovable object;
A speed measurement program comprising: a calculation step of calculating a speed of the moving object based on the position of the moving object and the dotted line data.

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