Underwater Target Depth and Distance Positioning Method Based on Azimuth History Diagram with Adjacent Stripes

Abstract

The present invention discloses an underwater target depth and distance positioning method based on the accompanying stripes of the azimuth history diagram. Read a main stripe and two accompanying stripes on the left and right of the azimuth history diagram to obtain the azimuth angles of these three stripes; read the height of the observation device from the bottom of the water and the depth from the water surface; establish a vertical two-dimensional regional rectangular coordinate system according to the observation device; in the two-dimensional regional rectangular coordinate system, the observation device processes the azimuth angles, height, and depth of the two accompanying stripes according to the geometric relationship among the real target, the target surface reflection mirror image, and the target bottom reflection mirror image in the azimuth history diagram to obtain the depth and distance of the real target underwater. The present invention quickly performs target depth positioning and distance estimation through the accompanying stripes of the azimuth history diagram, with simple calculation, no need for a complex sound propagation model, fast calculation speed, low carbon, can always automatically track the target, and further determine whether it is an underwater or water surface target according to the change of its depth during the tracking process.

Description

Technical Field

[0001] The present invention relates to a method for estimating the position of an underwater target in the ocean, and particularly to a method for underwater target depth positioning and distance estimation based on the adjoint stripes of the bearing history diagram. Background Art

[0002] For the existing methods for target depth and distance positioning, the common one is matched field processing. This method uses the acoustic signals collected by a vertical hydrophone array, divides the grid in the vertical profile at a certain azimuth angle, then places the sound source in all these grids respectively for acoustic propagation simulation, calculates the acoustic field characteristics reaching the hydrophone array respectively, and matches them one by one with the actual collected acoustic field at that place. The situation with the best matching degree corresponds to the depth and horizontal position where the sound source is most likely to be actually located. The existing methods have large computational amounts and high requirements for the hydrographic environment. Summary of the Invention

[0003] In order to solve the problems existing in the background art and to solve the problems of large computational amount and slow calculation speed commonly existing in the traditional target depth and distance positioning methods, the present invention proposes a method for target depth using the adjoint stripes on the bearing history diagram, which can accurately and quickly obtain the position and depth of the underwater target.

[0004] The method of the present invention has a small computational amount, fast calculation speed, supports multi-target cluster analysis at the same time, and can further determine whether the target is a surface ship or a submarine according to the change of its depth during the tracking process.

[0005] The technical solution adopted by the present invention is as follows:

[0006] On the bearing history diagram, sometimes a pair of adjoint stripes will appear on both sides of the target respectively, and their intensities are weaker than the target stripe. The essence of the formation of these two adjoint stripes is the multipath effect of acoustic propagation in the ocean environment, that is, the multi-waveguides caused by the ocean surface, seabed, and stratified ocean. Traditionally, these two adjoint stripes are generally treated as noise and removed.

[0007] The present invention discovers that under certain assumed preconditions, these adjoint stripes can be used to directly calculate and obtain the depth of the target and the horizontal distance of the target relative to the array based on the principle of geometric optics, improving the speed and efficiency, and at the same time being able to obtain good accuracy.

[0008] In the solution of the present invention, the left and right adjoint stripes correspond to the surface reflection and bottom reflection (the middle main stripe corresponds to the direct signal), and data processing is carried out accordingly to obtain an accurate underwater target depth estimation result.

[0009] Specifically, by using an observation device to move underwater with a ship to conduct real-time detection of real targets, an azimuth history map is obtained, and then the real-time azimuth history map is processed according to the following method steps:

[0010] 1) Read a main stripe and two accompanying stripes on the azimuth history map at a certain moment to obtain the azimuth angle θ2 of the main stripe and the azimuth angles θ1 and θ3 of the two accompanying stripes;

[0011] 2) Read the height h of the observation device from the bottom of the water and the depth d from the water surface;

[0012] 3) Establish a vertical two-dimensional regional rectangular coordinate system based on the observation device;

[0013] 4) In the two-dimensional regional rectangular coordinate system, the observation device processes according to the relationship among the real target, the target table reflection mirror image, and the target bottom reflection mirror image in the azimuth history map, using the azimuth angles θ1 and θ3 of the two accompanying stripes, the height h, and the depth d to obtain the depth of the real target underwater.

[0014] In the method of the present invention, the depth of the underwater target can be obtained by using the azimuth angles θ1 and θ3 of the two accompanying stripes and the azimuth angle θ2 of the main stripe.

[0015] The observation device described above uses an optical fiber array. One end of the optical fiber array is tied to the tail of the ship.

[0016] In step 3) above, taking the vertical section where the observation device is located as the coordinate plane, with the center (0, 0) position of the observation device as the origin, the vertical direction as the positive x-axis, and the tail extension direction of the observation device as the positive y-axis, a two-dimensional regional rectangular coordinate system is established.

[0017] In step 4) above, it is processed and obtained according to the following formula:

[0018]

[0019]

[0020] Among them, D is the depth of the real target underwater, and L is the straight-line distance between the real target and the center of the observation device.

[0021] After step 4), every once in a while, the variance of the depth of the real target is statistically obtained according to the depth of the real target at each moment, and then it is judged:

[0022] If the depth D of the real target itself is greater than 0 meters and the variance is greater than the preset threshold var crtc , then the real target is an underwater target and is calibrated as a dangerous target.

[0023] The present invention ingeniously utilizes the relationship among the target, the reflection mirror image of the target table, and the reflection mirror image of the target bottom. By obtaining the angles of two accompanying fringes on the azimuth history diagram and the azimuth angle of the target itself, the depth and distance of the target are directly calculated, achieving fast and effective positioning estimation. The beneficial effects of the present invention are as follows:

[0024] 1) The present invention quickly performs target depth positioning and distance estimation through the accompanying fringes of the azimuth history diagram, with simple calculations and no need for a complex sound propagation model.

[0025] 2) The present invention has a fast calculation speed and is low-carbon, and can support multi-target cluster analysis on ordinary computers.

[0026] 3) The present invention can always automatically track the target and further determine whether it is an underwater or above-water target according to the change of its depth during the tracking process. Description of the Drawings

[0027] Figure 1 is a schematic diagram of the accompanying fringes of the azimuth history.

[0028] Figure 2 is a schematic diagram of the relative positions of the array and the target. Detailed Embodiments

[0029] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0030] The embodiments of the present invention and their implementation processes are as follows:

[0031] The conditions of the embodiment are set as a shallow sea (water depth not exceeding 200 meters), the sound speed is vertically uniform or approximately uniform, and the seabed is flat.

[0032] One end of the optical fiber array is tied to the tail of the ship, and the optical fiber array is used to move underwater with the ship to perform real-time detection on the real target to obtain the azimuth history diagram, and then process it according to the following method steps based on the real-time azimuth history diagram:

[0033] 1) As Figure 1 shown, read a main fringe and two left and right accompanying fringes on the azimuth history diagram at a certain moment to obtain the azimuth angle θ2 of the main fringe and the azimuth angles θ1 and θ3 of the two accompanying fringes;

[0034] 2) Read the height h of the optical fiber array from the seabed and the depth d from the water surface;

[0035] 3) Establish a vertical two-dimensional regional rectangular coordinate system based on the optical fiber array;

[0036] In step 3), a two-dimensional rectangular coordinate system can be established with the vertical section where the fiber optic array is located as the coordinate plane, the center (0, 0) of the fiber optic array as the origin, the vertical direction as the positive x-axis, and the extending direction of the tail of the fiber optic array as the positive y-axis. The extending direction of the fiber optic array is basically arranged horizontally.

[0037] 4) As Figure 2 shown, in the two-dimensional rectangular coordinate system, the fiber optic array processes the azimuth angles θ1 and θ3, height h, and depth d of two accompanying stripes according to the relationship among the real target, the target table reflection mirror image, and the target bottom reflection mirror image in the azimuth history diagram to obtain the depth of the real target underwater.

[0038] Using the major relationship that the real target, the target table reflection mirror image, and the target bottom reflection mirror image are located on a straight line, specifically, for the real target, the target table reflection mirror image, or the target bottom reflection mirror image, a connection line is established with the center of the fiber optic array. A conical surface is established with the connection line as the generatrix and the extending direction of the fiber optic array as the central axis. The depth of the real target underwater is obtained by processing the relationship that the bottom surfaces of the conical surfaces corresponding to the real target, the target table reflection mirror image, or the target bottom reflection mirror image are in the same plane.

[0039] The azimuth angle θ2 of the main stripe is characterized as the azimuth angle of the real target, and the azimuth angles θ1 and θ3 of the two accompanying stripes are characterized as the azimuth angle of the table reflection and the azimuth angle of the bottom reflection.

[0040] In step 4), it is processed and obtained according to the following formula

[0041]

[0042]

[0043] where D is the target depth and L is the straight-line distance of the target relative to the array center.

[0044] 5) Every 5 - 10 minutes, the variance of the depth of the real target is statistically obtained according to the depth of the real target at each moment, and then it is judged:

[0045] If the depth D of the real target itself is greater than 0 and the variance is greater than the preset threshold var crtc (such as 0 m), then the real target is an underwater target and is calibrated as a dangerous target.

[0046] The specific implementation further verifies that the possibility of this target being an underwater target is relatively high.

[0047] Specific implementation case:

[0048] The parameters at three time points in a certain test are read, and the specific values are shown in the following table.

[0049] Table 1. Parameter values at three time points in a certain experiment and the calculated target depth and distance

[0050]

[0051] After calculation based on the parameters at three time points (09:13, 09:23, and 09:33), the obtained target depths are 100.0 m, 100.0 m, and 80.0 m respectively, and their variance is 133.333 m. Both the depth and the depth variance are significantly greater than 0, thus further verifying that the target is an underwater target.

[0052] As a comparison, the traditional matched field method was also implemented. In this specific case, it takes about 5 seconds for the matched field algorithm to complete one acoustic propagation, and the total calculation duration is several times that of 5 seconds (the specific duration is determined by the number of search grids divided, and the more grids, the longer the total duration). While on the same PC, the present invention only takes 60 milliseconds, showing obvious advantages.

[0053] Summary description: The present invention quickly estimates the target depth and distance through the azimuth history diagram accompanied by stripes. Compared with the traditional method, the present invention does not need to call a complex acoustic model, has simple calculation, high speed, energy-saving and low-carbon, can always automatically track the target, and further determines whether it is an underwater target according to the change of its depth during the tracking process.

Claims

1. An underwater target depth and distance positioning method based on the azimuth history diagram accompanied by stripes, characterized in that: The real target is detected in real time by using the observation equipment moving underwater with the ship to obtain the azimuth history diagram, and then the real-time azimuth history diagram is processed according to the following method steps: 1) Read a main stripe and two accompanying stripes on the azimuth history diagram to obtain the azimuth angles θ1 and θ3 of the two accompanying stripes; 2) Read the height h of the observation equipment from the bottom of the water and the depth d from the water surface; 3) Establish a vertical two-dimensional regional rectangular coordinate system according to the observation equipment; 4) Under the two-dimensional regional rectangular coordinate system, the observation equipment processes the depth of the real target underwater by using the relationship among the real target, the target surface reflection mirror image, and the target bottom reflection mirror image in the azimuth history diagram, and using the azimuth angles θ1 and θ3 of the two accompanying stripes, the height h, and the depth d.

2. The underwater target depth and distance positioning method based on the azimuth history diagram accompanied by stripes according to claim 1, wherein: The observation equipment adopts an optical fiber array.

3. The underwater target depth and distance positioning method based on the azimuth history diagram accompanied by stripes according to claim 1, wherein: After the step 4), the variance of the depth of the real target is statistically obtained according to the depth of the real target at each moment at intervals of a period of time, and then it is judged: If the depth D of the true target itself is greater than 0 meters and the variance is greater than the preset threshold var crtc , then the true target is an underwater target and is labeled as a dangerous target.

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