JPS60143795A - Correction of oblique incident error in topography detection apparatus - Google Patents

Abstract

PURPOSE:To attain to reduce an oblique incident error, by integrating and averaging the intensity of a collected receiving reflective signal and detecting the max. position of the intensity value of a receiving reflective signal at every receiving of each receiving beam. CONSTITUTION:A sound wave is transmitted toward the objective sea bottom from a transmitter array 5 and the reflected sound wave arriving from the sea bottom is received by a receiver array 1. Receiving reflected signa intensity in the receiving beam is collected at every receiving beam and the receiving reflected signa intensity collected at every receiving beam is integrated and averaged at every transmitting wave and receiving beam by an integration and averaging circuit 20. The max. position of the receiving reflected signal is detected from the receiving reflected signal intensity value at every receiving beam by a max. position detection circuit 21 and the topography in the max. gain direction of each receiving beam is detected on the basis of the max. position. By this mechanism, a detection mistake caused by the whirling-up of earth and sand at the time of dredging or a school of fish is perfectly eliminated and an error caused by oblique incidence can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for correcting oblique incidence errors in a terrain detection device using sonar.

Typically, multibeam sonar uses a transmitter array or a transducer array to transmit sound waves toward a target.

A sonar device receives the reflected signals using a receiver array or a transducer array, synthesizes several multi-beams, and identifies the direction in which the sound waves arrive.

As shown in FIG. 1, a conventional submarine topography detection device using such a multi-beam sonar detects the reflected signals of the sound waves transmitted from a transmitter array 5 toward the target sea floor to a receiver array 1.
and the beam combiner 2 combines these received beams. Then, the received reflected 4W strength in each receiving beam is detected, and this is supplied to the seabed discrimination circuit 3 based on a threshold value, and the received reflected signal strength that is equal to or higher than the threshold value is extracted as a reflected signal from the seabed. , the seafloor topography f! detected based on this reflected signal. r: Displayed on the display 4.

By the way, as shown in FIG. 2, each of the receiving beams of the receiver array 1 consists of three receiving beams each having a different beam tilt with respect to the seabed 9, that is, a first receiving beam 6, It consists of a second receiving beam 7 and a third receiving beam 8, and the strength of each received reflected signal received within each of these three receiving beams is 33 in the vertical direction as shown in FIG.
can also be shown on a chart made by measuring the time 34 from the transmission of the wave to the arrival of the sound wave in the lateral direction. In the same figure, 1
0 is the first receiving beam, 11 is the second receiving beam, 12
represents the received reflected signal strength of the third received beam,
13 is a threshold value set for determining the seabed. The strength of each received reflected signal with this threshold 7 hold value of 13 or higher is taken as a reflected signal from the seabed as described above.

Based on this, the seabed topography as shown in Figure 4 was displayed. In the figure, 14 is the first receiving beam, 15
indicates the seabed position detected by the second receiving beam and 16 by the third receiving beam.

17 is a seafloor topography formed by connecting each seabed position 14 to 16, and 18 is a true seafloor topography.

In this way, the conventional device employs a means of detecting the seafloor topography based on each intensity value that is equal to or higher than the threshold value among the received reflected signal intensities in each receiving beam, and therefore, the method shown in FIG. As is clear from the above, the direction of arrival of the sound wave becomes uncertain by the width of the receiving beam, and the detection error increases as the oblique incidence angle with respect to the first to third receiving beams increases.

On the other hand, the present invention samples the received reflected signal strength for each receiving beam for each transmitted wave, calculates the integrated average or multiplicative average of the received reflected signal strength, and calculates the averaged value of each received reflected signal strength. By detecting the maximum position of the received reflected signal strength value for each receiving beam and detecting the topography in the direction of the maximum optical gain of each receiving beam from this maximum position, the oblique incidence error is reduced. This is the purpose.

An embodiment of the present invention will be described in detail below with reference to the drawings.

Fig. 5 is a block diagram of a peak/bottom topography @output device to which the method of the present invention is applied. In Fig. 5, 1 is a receiver array.

2 is a beam combining circuit that combines each receiving beam.

Reference numeral 20 denotes an averaging circuit for each receiving beam that cumulatively averages or storm-finds cumulatively averages the received reflected signal strength sampled for each receiving beam, and 21 indicates the averaged received reflected signal strength value for each received beam. Detection circuit for detecting the maximum position, 4
is a display consisting of a sweep type recorder or a cathode ray tube display, etc.;
5 is a transmitter array that transmits sound waves toward the target ocean floor.

To operate this, first, a sound wave is transmitted from the transmitter array 5 toward the target ocean floor.

The reflected sound waves returning from the ocean floor are received by the receiver array l. The received beams are combined by a beam combining circuit 2, and the intensity of the received reflected signal is sampled for each received beam. The received reflected signal strength for each sampled receiving beam is averaged by an integrating averaging circuit 2o provided for each receiving beam, and then
The maximum position of the average value is detected by the maximum position detection circuit 21 at the next stage. This signal is taken as the seabed reflection signal from the maximum gain direction of the receiving beam at the maximum position.

Determine the distance between the receiver array and the seabed in the maximum gain direction from the sound wave arrival time of this seabed reflected signal.

This is configured to be displayed on the display 4.

Therefore, the averaging circuit 20 is designed to stabilize the seabed reflection signal by removing the fluctuating reflected signals caused by the rolling up of earth and sand during dredging, schools of fish, etc., thereby eliminating detection errors caused by rolling up of earth and sand, schools of fish, etc. Furthermore, the maximum position detection circuit 21 has the effect of reducing oblique incidence errors.

Figure 6 is a diagram showing the directivity characteristics of one received beam combined by the beam combining circuit 2. In Figure 2, 1 is the receiver array, 9
is the seabed, and 30 is the receiving beam directional characteristic. In general, if the received beam width is narrow to some extent as shown in Figure 6, the strength of the reflected signal from the seabed within the beam width is considered to be uniform.

The intensity of the received reflected signal depends on the directional characteristic, and the intensity of the received reflected signal for one beat when the sound wave is incident from the direction Fll# is the maximum value of the directional characteristic. FIG. 7 is a diagram showing the received reflected signal strength 3J when received by the receiving beam 30 of FIG. 6, and in FIG. 9, 32 is the maximum position of the received reflected signal strength 31. Because of this.

By detecting the maximum position of the received reflected signal strength from the seabed within the receiving beam, the distance between the receiver array and the seabed in the maximum gain direction of the receiving beam, that is, the seafloor topography, can be determined.

In short, the present invention detects the topography in the maximum gain direction of each receiving beam as described above, so there is no uncertainty in the width of each receiving beam, which conventional devices had. (This is because the detection error due to oblique incidence can be reduced, and at the same time, the detection standard is based on the true seabed reflection signal intensity, which is higher than the reflection signal intensity from turbidity caused by sediment, etc.).

Detection errors caused by turbidity can also be reduced, and the system has the outstanding effect of accurately detecting and displaying seafloor topography.

Although the present invention has been described in connection with the case of a multi-beam beam as an embodiment, it goes without saying that it can be carried out in the same manner in a single beam beam.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional submarine topography detection device, Fig. 2 is a directional characteristic diagram of a receiving beam of the conventional device, and Fig. 3 shows the received reflected signal strength within each receiving beam shown in Fig. 2. FIG. 4 is a diagram showing a seabed topography detected by a conventional device, and FIG. 5 is a bottom topography detection device 1q to which the method of the present invention is applied. FIG. 6 is a diagram showing the directivity characteristics in the receiving beam according to the present invention, and FIG. 7 is a diagram showing the received reflected signal strength and its maximum position in the receiving beam shown in FIG. 6. 1...Receiver array, 2...Beam combining circuit, 4...
・Indicator, 5... Liquid feeder array, 9... Seabed, 2
0. Cumulative average acid for each received beam (・ is weighted product IF
Average circuit, 21・Maximum position detection circuit of seabed reflection signal, 3
0... Receiving beam directivity characteristics, 31 - Receiving (g reflected signal strength, 32 - Maximum position, 33 Signal strength, 34 Time until the sound wave arrives at the transmitter. Patent applicant: Japan Radio Co., Ltd.

Claims (1)

[Scope of Claims] In an apparatus for detecting seafloor topography by receiving transmitted sound waves separately and detecting the received reflected signal strength within each received wave beam, the received reflected signal within the received wave beam is The intensity of each received beam is sampled, and the received reflected signal strength of each sampled received beam is integrated and averaged for each transmitted beam and for each party beam. The maximum position of the received reflected signal strength is detected from the received reflected signal strength value. A method for correcting an oblique incidence error in a terrain detection device, characterized in that the oblique incidence error is reduced by detecting the terrain in the maximum gain direction of each received beam based on each of the maximum positions.