JPH0257877B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a side scan sonar having means for correcting disturbances in records related to the position and oscillation of a towed body equipped with a transducer. Side-scan sonar typically processes sound waves received on both sides of the towed vehicle and records images of the waves reflected from the ocean floor. Normally, each side has a sonic signal A/D.
Then, calculate the distance from the towed object to the target by multiplying the time from the wave transmission to each time in the wave reception record by the sound speed (this is called the oblique distance). Then, each wave transmission time is set as one axis, A two-dimensional image is constructed using the strength of each transmitted wave's reflected waves returning from the ocean floor as another axis. However, if an image is created using the above-mentioned oblique distance to determine the distance from the towed object to the target object, there will be a distance deviation (hereinafter also referred to as accuracy) from the actual seafloor topography, so geometrically Slant distance correction (slope distance correction is where the distance from the towed object to the seabed is used to replace the horizontal distance from the towed object to the target). When detecting with side scan sonar, the general rule is to maintain a constant course and speed, but if the direction or speed needs to be changed for unavoidable reasons (see Figure 1), the above corrections should be made. In addition, corrections must be made that take into account the wake (hereinafter referred to as track correction). Track correction requires track data for the period of exploration. In addition, when processing, if there are N side data, 2N calculations are required to correct the position of the towed body [(X, Y) coordinates], and on the other hand, in the scan line direction (towing direction) 2N calculations are also required to correct the search line perpendicular to .
Therefore, it takes a certain amount of calculation time to construct an image that approximates the topography of the actual ocean floor, and the storage capacity of the device must also be large to some extent. In order to solve the above-mentioned drawbacks, the present invention provides a side scan sonar that displays an image close to the actual seafloor topography by reducing the scale of data processing by performing track correction only when necessary. It is something. The present invention mounts a positioning and azimuth sensor on the towing body of a conventional sidescan sonar, estimates the search surface of the acoustic beam of the sidescan sonar based on the results, and if it is not perpendicular to the towing direction, the The amount of deviation is detected and the display signal is corrected. These corrected signals are displayed on the image display, but in order to speed up the correction process, the control unit corrects the towed body position and scan line direction for the data used to determine the necessity of track correction. . As described above, this device is composed of a towing body equipped with an azimuth sensor, a positioning sensor, and a transducer, a display device, and a control section. Next, embodiments of the present invention will be described with reference to the drawings. FIG. 2 shows its configuration block diagram. The side scan sonar is equipped with a transducer 2 on a towed body 1, and sends recorded sound wave signals to a control unit 3, while a means for measuring the position and direction of the towed body, that is, a positioning sensor 5 and a positioning sensor 5. There is a sensor 6. It is used when inputting data on the position and orientation of the towed object to the control unit and making corrections. The data processed by the control unit is output as an image on the display unit 4. An example of a case where the track is not on a fixed course is shown in track map No. 1a. Let F be the starting point and the ending point of the track to be processed. Rectangle ABCD is the area to be processed, and an enlarged view is shown in FIG. 1B. Ia in Figure 1b
= Id = bF = Fc = side range of side scan sonar, T1 and T2 are the positions of the towed body at time 1 and time 2 in the image, t1 and t2 are T1 and T2, respectively
This is the projection at IF. S1 and S2 are each T
Scan lines at 1 and T2. θ ₁ and θ ₂ are the angles between S1 and S2 passing through t ₁ and t ₂ and the straight line perpendicular to IF, respectively. In the case of a fixed course, the wake overlaps with the IF, so the position of the towed object is on the straight IF,
The scan line is also in the same direction. On the contrary,
In the case of non-regular heading, the positions T1 and T of the towed body are first corrected, and then the azimuth is corrected by determining the inclinations of S1 and S2 (direction perpendicular to the direction of travel). Figure 1
Since θ _i (i=1 or 2) in the case of fixed needle is zero in b, θ _i is also the angle between the scan line when the needle is not fixed and the scan line when the needle is fixed. Details of the control unit 3 in FIG. 2 are shown in FIG. 3. The signal data 11 is an analog signal obtained through exploration, converted by an A/D converter 14, and stored in a RAM 16 via an interface of an input board 15. The track data 12 is data such as time and ship position, and is stored in the RAM via the input board 15.
16 to be memorized. Judgment criterion parameter 13 is 2
Set two parameters. One reference parameter is the difference between the towed body position before and after the correction, and this is Δr. T ₁ t ₁ or T ₂ t ₂ in FIG. 1b is the deviation of the target object after and before the towing object position correction, in other words, it is a quantity related to the correction of the origin of the scan line. Another reference parameter is Δθ, which is a quantity related to the azimuth of the scan line, where Δθ=ΔS/R, and the arc ΔS is the error allowed in the distance R (range width) from the towed object. The parameters for these two criteria are given empirically by the user.
These amounts are determined by the user depending on the accuracy required by the user. Δr and Δθ pass through the input board,
Store in RAM16. 21 is a microcomputer, basically CPU17, RAM16, ROM1
It is composed of 8. ROM18 has CPU17
A program has been written to control the
According to this program, the CPU 17 takes in the required data from the input board 15, does not exchange data with the RAM 16, performs arithmetic processing, and outputs the data as necessary. The board 19 outputs the image display 2
Display as 0. FIG. 4 shows a flowchart of the program in ROM 18. Signal data {(xi, yi, zi)}
({ } indicates a set). xi and yi are coordinates in real space before track correction, and zi is brightness (intensity of sound wave). Here, the coordinates are I as the origin [therefore, (xo, yo)
= (0,0)], and set IF to the x-axis and ad to the y-axis.
In the same coordinate system, the track data is 1(Xi, Yi)}N. Calculation of σr in Figure 4 32 Standard deviation of the position of the towing body in the track from I to F with respect to the case of fixed heading

[Formula] Here, Yi is the Y coordinate at time i, N is the number of pieces of track data, and thus the quantity Dr seen statistically through IF is compared with Δr at 33. If σr>Δr, it is necessary to correct the towed object timing, and the tracking data Yi value is used to correct the timing before correction. Next, in calculation 35 of σθ

[Formula] θi is the angle between the skin line and the axis perpendicular to IF. θi is θi
= tan ^-1 (-Xi+1-Xi-1)/Yi+1-Yi-1 time i
+1 Determine from the track position at time i -1. 36, the statistically observed quantity σθ passing through the IF is compared with Δθ. If σθ>Δθ
37, xi=xicosθi+yisinθi, yi=xisinθ+yicosθi
Let {(Xi, yi, zi)} of each scan be {(xi′,
yi′zi)}. (However, the xi′ value is fixed in each scan.) In this way, the signal data {(xi, yi, zi)} is track corrected and converted to {(xi′, yi′, zi)}, and these data Assign the set to each pixel on the image display. Assuming that the image display device consists of LXM pixels, and the data of pixel j is {xj, ηi, ζi) x, the coordinates of the image in the y direction are xi, ηj, and the brightness is ζj, to find the value of ζj Convert the real space coordinates of {(xi′, yi′, zi)} to the coordinates on the image display, and convert the coordinates of {(i, i,
zi)}), then set the value of (xj, ηj, ζj) to {(
i, i, zi)} by interpolation and extrapolation. Until the track correction is displayed as an image, even if the
If there is data, the correction of the towed body position is 2×
2×2 calculations are required. Furthermore, θ of direction correction
It takes N times to calculate the value and 2×2×n times to correct the direction. To obtain the pixel value in image display, L x M x 2 x n calculations are required (interpolation, extrapolation)
It is. As explained above, by evaluating the necessity of such large-scale calculations in advance, unnecessary calculations can be eliminated.

[Brief explanation of the drawing]

FIG. 1a shows an example of a wake, and a rectangle ABCD is an area that requires trajectory correction. Figure 1b is a rectangle
An enlarged view of abcd, Figure 2 is a block diagram showing the configuration,
Fig. 3 is a configuration diagram of the control section in Fig. 2, and Fig. 4 is a block diagram of the control section in Fig. 3.
This is a flowchart of a program written to the ROM 16 of. DESCRIPTION OF SYMBOLS 1... Towing body, 2... Transducer/receiver, 3... Control unit, 4...
Display unit, 5...positioning sensor, 6...direction sensor.

Claims (1)

[Claims] 1. A device that is installed approximately parallel to the direction of travel of a towed vehicle towed by a ship or aircraft or a navigation vehicle that operates independently, and arranged to transmit and receive sound waves in a fan-shaped beam in a direction approximately perpendicular to the direction of travel of the towed vehicle. A side scan sonar comprising a transducer, a control unit that controls the emission of sound waves from the receiver, and an image display that records the received signal from the transducer under the control of the control unit, or means for measuring the position and orientation of the transducer or towed body for each of a plurality of scans, and the orientation or position of the scan line displayed on a display unit based on the position or orientation of the towed body obtained by the measuring means. a means for correcting the position or direction of the scan line using the position or direction of the towed object; and a correction means when the deviation is smaller than a preset value. and means for prohibiting interpolation calculations for correction and display.