阅读说明：本技术 一种基于强散射点的舰船目标定位方法及系统 (Ship target positioning method and system based on strong scattering points ) 是由 郑淙杰 王青松 于 2021-09-07 设计创作，主要内容包括：本发明公开了一种基于强散射点的舰船目标定位方法及系统,该方法包括：获取舰船SAR图像并基于像素点阈值进行判定,提取对应SAR图像内的强散射点；根据对应SAR图像内的强散射点对强散射点进行空间定位,得到舰船目标位置。该系统包括：提取模块和定位模块。本发明利用船舰目标的强散点特征来进行定位,成本低且实现过程简单。本发明作为一种基于强散射点的舰船目标定位方法及系统,可广泛应用于目标定位领域。(The invention discloses a ship target positioning method and system based on strong scattering points, wherein the method comprises the following steps: acquiring a ship SAR image, judging based on a pixel point threshold value, and extracting strong scattering points in the corresponding SAR image; and carrying out space positioning on the strong scattering points according to the strong scattering points in the corresponding SAR images to obtain the ship target position. The system comprises: the device comprises an extraction module and a positioning module. The invention utilizes the strong scatter point characteristic of the ship target to position, has low cost and simple realization process. The ship target positioning method and system based on the strong scattering points can be widely applied to the field of target positioning.)

1. A ship target positioning method based on strong scattering points is characterized by comprising the following steps:

acquiring a ship SAR image, judging based on a pixel point threshold value, and extracting strong scattering points in the corresponding SAR image; and carrying out space positioning on the strong scattering points according to the strong scattering points in the corresponding SAR images to obtain the ship target position.

2. The method according to claim 1, wherein before the step of obtaining the ship SAR image and determining based on a pixel threshold, extracting the strong scattering point in the corresponding SAR image, the method further comprises:

a spatial coordinate system is set.

3. The method according to claim 2, wherein the step of obtaining the ship SAR image, determining the ship SAR image based on a pixel threshold, and extracting the strong scattering point in the corresponding SAR image specifically comprises:

acquiring corresponding ship SAR images based on radars with different heights;

carrying out nonlinear transformation on each pixel point of the ship SAR image to obtain transformed pixel points;

amplitude value judgment is carried out on the transformed pixel points to obtain an amplitude value judgment result;

and according to the amplitude value judgment result, scanning peak points of which the azimuth direction and the distance direction are local maximum values, and extracting to obtain strong scattering points in the corresponding SAR image.

4. The method of claim 3, wherein the formula of the nonlinear transformation is as follows:

in the formula, a (x, y) represents each pixel point of the ship SAR image, and c (x, y) represents the converted pixel point.

5. The method according to claim 4, wherein the step of spatially locating the strong scattering points according to the strong scattering points in the corresponding SAR image to obtain the ship target position specifically comprises:

obtaining the distance of each radar reaching the strong scattering point according to the strong scattering point in the corresponding SAR image;

based on the coordinates of the two radars and the distance between the two radars and the strong scattering point, two distance equations are combined;

and (4) resolving the space position of the strong scattering point by combining a Doppler equation to obtain the position of the ship target.

6. The method of claim 5, wherein the distance equation is formulated as follows:

in the above formula, (u1, v1, w1) represents the three-dimensional coordinates of radar one, (x, y, z) represents the three-dimensional coordinates of the target, and R1 represents the distance of radar one to the strong scattering point.

7. The method of claim 6, wherein the formula of the Doppler equation is as follows:

in the above formula, f_DCIndicating the Doppler shift, V_SRepresenting the velocity vector of motion of radar one, V_TRepresenting the motion velocity vector, P, of the object_SIs the three-dimensional coordinate of Radar one (u1, v1, w1), P_TRepresenting the three-dimensional coordinates (x, y, z) of the object.

8. A ship target positioning system based on strong scattering points, comprising:

the extraction module is used for acquiring the ship SAR image, judging based on a pixel point threshold value and extracting strong scattering points in the corresponding SAR image;

and the positioning module is used for carrying out space positioning on the strong scattering points according to the strong scattering points in the corresponding SAR images to obtain the ship target position.

Technical Field

The invention relates to the field of target positioning, in particular to a ship target positioning method and system based on strong scattering points.

Background

Currently, a common ultrasonic positioning technology is a positioning technology using a reflective detection method. The ultrasonic positioning technology combines the time interval difference operation of transmitting ultrasonic waves to the corresponding echoes of the reference nodes and the interval between the reference nodes, and adopts a triangular positioning means to calculate the part of the target to be detected. The ultrasonic positioning technology can be transmitted at a non-visual interval, the positioning precision is high, the deviation is small, but the ultrasonic positioning technology also has the problems of limited positioning feasible range, high facility cost and the like.

Disclosure of Invention

In order to solve the technical problems, the invention aims to provide a ship target positioning method and system based on strong scattering points, which are used for positioning by utilizing the strong scattering point characteristics of a ship target, and have the advantages of low cost and simple implementation process.

The first technical scheme adopted by the invention is as follows: a ship target positioning method based on strong scattering points comprises the following steps:

acquiring a ship SAR image, judging based on a pixel point threshold value, and extracting strong scattering points in the corresponding SAR image;

and carrying out space positioning on the strong scattering points according to the strong scattering points in the corresponding SAR images to obtain the ship target position.

Further, before the step of acquiring the ship SAR image and determining based on a pixel point threshold value and extracting a strong scattering point in the corresponding SAR image, the method further includes:

a spatial coordinate system is set.

Further, the step of acquiring the ship SAR image, judging based on a pixel point threshold value, and extracting a strong scattering point in the corresponding SAR image specifically includes:

acquiring corresponding ship SAR images based on radars with different heights;

carrying out nonlinear transformation on each pixel point of the ship SAR image to obtain transformed pixel points;

amplitude value judgment is carried out on the transformed pixel points to obtain an amplitude value judgment result;

and according to the amplitude value judgment result, scanning peak points of which the azimuth direction and the distance direction are local maximum values, and extracting to obtain strong scattering points in the corresponding SAR image.

Further, the formula of the nonlinear transformation is expressed as follows:

in the formula, a (x, y) represents each pixel point of the ship SAR image, and c (x, y) represents the converted pixel point.

Further, the step of spatially locating the strong scattering point according to the strong scattering point in the corresponding SAR image to obtain a ship target position specifically includes:

obtaining the distance of each radar reaching the strong scattering point according to the strong scattering point in the corresponding SAR image;

based on the coordinates of the two radars and the distance between the two radars and the strong scattering point, two distance equations are combined;

and (4) resolving the space position of the strong scattering point by combining a Doppler equation to obtain the position of the ship target.

Further, the formula of the distance equation is expressed as follows:

in the above formula, (u1, v1, w1) represents the three-dimensional coordinates of radar one, (x, y, z) represents the three-dimensional coordinates of the target, and R1 represents the distance of radar one to the strong scattering point.

Further, the formula of the doppler equation is expressed as follows:

in the above formula, f_DCIndicating the Doppler shift, V_SRepresenting the velocity vector of motion of radar one, V_TRepresenting the motion velocity vector, P, of the object_SIs the three-dimensional coordinate of Radar one (u1, v1, w1), P_TRepresenting the three-dimensional coordinates (x, y, z) of the object.

The second technical scheme adopted by the invention is as follows: a strong scattering point based ship target positioning system comprising:

the extraction module is used for acquiring the ship SAR image, judging based on a pixel point threshold value and extracting strong scattering points in the corresponding SAR image;

and the positioning module is used for carrying out space positioning on the strong scattering points according to the strong scattering points in the corresponding SAR images to obtain the ship target position.

Further, still include:

and the setting module is used for setting a space coordinate system.

The method and the system have the beneficial effects that: according to the method, the SAR image of the ship target is used for extracting the strong scattering points, equations are established according to different images acquired by a radar, the simultaneous equations are solved, and the three-dimensional coordinate position of the strong scattering points is solved according to a distance equation and a Doppler equation, so that the positioning function is realized.

Drawings

FIG. 1 is a flow chart of steps of a ship target positioning method based on strong scattering points according to the present invention;

FIG. 2 is a block diagram of a ship target positioning system based on strong scattering points according to the present invention.

Detailed Description

The invention is described in further detail below with reference to the figures and the specific embodiments. The step numbers in the following embodiments are provided only for convenience of illustration, the order between the steps is not limited at all, and the execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

The invention utilizes the characteristic of strong scattering points of the ship target to carry out positioning. The strong scattering point of the ship target is a main characteristic point of the SAR image and appears as a brighter area in the SAR image. Synthetic Aperture Radar (Synthetic Aperture Radar) is an active microwave sensor, and has all-day and all-weather working capability. Particularly for a specific ship target, when the working frequency, the polarization mode and the observation angle of the radar are not changed, the scattering strength mainly depends on the structure and the material of the ship.

Referring to fig. 1, the invention provides a ship target positioning method based on strong scattering points, which comprises the following steps:

s1, acquiring a ship SAR image, judging based on a pixel point threshold value, and extracting strong scattering points in the corresponding SAR image;

and S2, carrying out space positioning on the strong scattering points according to the strong scattering points in the corresponding SAR images to obtain the ship target position.

Further as a preferred embodiment of the method, before the step of acquiring the ship SAR image, determining based on a pixel point threshold, and extracting a strong scattering point in the corresponding SAR image, the method further includes:

and S0, setting a space coordinate system.

Specifically, the XYZ coordinates may be selected to satisfy a right-handed screw criterion or a left-handed screw criterion, and one of the criteria may be selected.

Setting the coordinate starting point (0,0,0) establishes the XYZ plane, X-axis: the motion direction of the radar is taken as the positive direction of an X axis in the horizontal plane; y-axis: the direction of one side of the ship is taken as the positive direction of the Y axis in the horizontal plane; z-axis: perpendicular to the horizontal plane, the upward direction of the radar bottom is a square, and the X axis and the Y axis meet the left-hand spiral criterion.

Further, as a preferred embodiment of the method, the step of acquiring the ship SAR image, determining based on a pixel point threshold, and extracting a strong scattering point in the corresponding SAR image specifically includes:

acquiring corresponding ship SAR images based on radars with different heights;

carrying out nonlinear transformation on each pixel point of the ship SAR image to obtain transformed pixel points;

amplitude value judgment is carried out on the transformed pixel points to obtain an amplitude value judgment result;

and according to the amplitude value judgment result, scanning peak points of which the azimuth direction and the distance direction are local maximum values, and extracting to obtain strong scattering points in the corresponding SAR image.

Further as a preferred embodiment of the method, assuming that each pixel point of the image is a (x, y), first, a (x, y) is subjected to a nonlinear transformation process, so as to reduce the dynamic range of the original image and prevent the influence of the calculation of the azimuth direction and the distance direction caused by too high gray values of part of strong scattering points.

In the formula, a (x, y) represents each pixel point of the ship SAR image, and c (x, y) represents the converted pixel point.

In order to find out the target strong scattering point more conveniently, each pixel value range is limited to be 0-255, and the following operations are carried out: firstly, scanning in the azimuth direction and the distance direction to find out the point with the maximum scattering intensity and the point with the minimum scattering intensity, defining m as the point with the maximum scattering intensity by scanning in the azimuth direction and the distance direction, and defining n as the point with the minimum scattering intensity by scanning in the azimuth direction and the distance direction, namely:

m＝max c(x,y)

n＝min c(x,y)

secondly, the pixel value range is limited to 0-255, and the following transformation is performed:

further, as a preferred embodiment of the method, the step of spatially locating the strong scattering point according to the strong scattering point in the corresponding SAR image to obtain the ship target position specifically includes:

obtaining the distance of each radar reaching the strong scattering point according to the strong scattering point in the corresponding SAR image;

based on the coordinates of the two radars and the distance between the two radars and the strong scattering point, two distance equations are combined;

and (4) resolving the space position of the strong scattering point by combining a Doppler equation to obtain the position of the ship target.

Further as a preferred embodiment of the method, the three-dimensional coordinates of the target are set to (x, y, z), and the formula of the distance equation is expressed as follows:

in the above formula, (u1, v1, w1) represents the three-dimensional coordinates of radar one, (x, y, z) represents the three-dimensional coordinates of the target, and R1 represents the distance of radar one to the strong scattering point.

Specifically, two radars with different heights are used for imaging the strong scattering point, and each height corresponds to a distance equation:

in the above formula, (u2, v2, w2) represents the three-dimensional coordinates of radar two, and R2 represents the distance from radar two to a strong scattering point.

Further as a preferred embodiment of the method, the formula of the doppler equation is expressed as follows:

in the above formula, f_DCIndicating the Doppler shift, V_SRepresenting the velocity vector of motion of radar one, V_TRepresenting the motion velocity vector, P, of the object_SIs the three-dimensional coordinate of Radar one (u1, v1, w1), P_TRepresenting the three-dimensional coordinates (x, y, z) of the object.

By combining the above three equations, three unknowns x, y, z can be solved, i.e. the position (x, y, z) of the strong scattering point can be solved

As shown in fig. 2, a ship target locating system at a strong scattering point includes:

the extraction module is used for acquiring the ship SAR image, judging based on a pixel point threshold value and extracting strong scattering points in the corresponding SAR image;

and the positioning module is used for carrying out space positioning on the strong scattering points according to the strong scattering points in the corresponding SAR images to obtain the ship target position.

Further as a preferred embodiment of the present system, the present system further comprises:

and the setting module is used for setting a space coordinate system.

The contents in the above method embodiments are all applicable to the present system embodiment, the functions specifically implemented by the present system embodiment are the same as those in the above method embodiment, and the beneficial effects achieved by the present system embodiment are also the same as those achieved by the above method embodiment.

While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.