Seabed sediment real-time analysis method based on multi-beam sonar

Abstract

The invention discloses a seabed sediment real-time analysis method based on multi-beam sonar. The method comprises the steps of collecting seabed scattering intensity calibration data and navigation data, constructing a seabed scattering data matrix, extracting a seabed scattering intensity coefficient, evaluating a scattering fitting curve and a model curve, and outputting a sediment analysis result. Compared with a traditional seabed sediment analysis method, the seabed scattering intensity calibration method is established, the fitting problem of a seabed scattering model is solved, the sediment type is obtained in real time, seabed exploration operation and engineering construction can be guided, and seabed exploration efficiency and operation safety are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of seabed detection, and in particular relates to a real-time analysis method of seabed sediment based on multi-beam sonar. Background Art

[0002] The seabed sediment is the material that makes up the seabed surface. According to the particle size, it can be divided into three categories: mud, sand and gravel. The seabed sediment is the boundary between the ocean water body and the seabed. As the carrier of marine resources and the operating interface of marine engineering, the analysis of the sediment is an important part of resource and engineering evaluation, and it is of great significance to the exploration of marine resources and the construction of marine engineering. There are two methods for seabed sediment analysis: one is sampling measurement, and the other is remote sensing measurement. Sampling measurement is to collect sediment samples from the seabed using equipment such as samplers, transport the sediment samples to the laboratory, and conduct sediment analysis in the laboratory. The advantage of this measurement method is that the analysis accuracy is high, and the disadvantage is that the efficiency is low; remote sensing measurement is to use acoustic or optical technology to transmit acoustic or optical pulses to the seabed, collect the scattered echoes of the seabed sediment, and obtain the characteristics of the sediment by analyzing the scattered echoes. The advantage of this measurement method is that the efficiency is high, and the disadvantage is that the accuracy is low. The two measurement methods complement each other and are indispensable means to fully understand the seabed sediments. With the increasing exploration of marine resources and engineering construction, the need for large-scale seabed sediment analysis has become increasingly urgent. The high efficiency advantage of seabed sediment remote sensing measurement is an effective way to meet this demand.

[0003] Acoustic and optical technologies are effective means of detecting the seabed. Acoustic technology can test full-sea depth detection. The wavelength of sound waves is long and the resolution is low, but its attenuation in the ocean is small and the measurement range is large. Optical technology is mainly used for high-precision measurement in shallow water. Its wavelength is short and the resolution is high, but the attenuation of light waves in the ocean is large and the measurement range is small. Acoustic measurement technology is one of the most widely used means of ocean exploration, among which multi-beam sonar is the main means of conducting seabed measurements. Multi-beam sonar can collect seabed scattered echoes of multiple beams, and convert them into water depth based on the travel time of the echoes and the sound velocity profile to obtain the seabed topography; based on the scattering intensity of the echoes, interpret the physical properties of the seabed and conduct seabed bottom analysis. At present, the bottom analysis based on the multi-beam echo scattering intensity is all data post-processing, that is, after real-time data collection, data analysis and processing are performed. This method has a lag in obtaining bottom characteristics. The exploration of marine resources and the construction of submarine engineering projects are increasingly dependent on the seabed sediments. The need for real-time analysis of the seabed sediments is becoming increasingly urgent. It is necessary to solve the problems of calibration of the seabed scattering intensity and fitting of the seabed scattering model to obtain the sediment characteristics, which is conducive to guiding exploration operations and engineering construction, and improving exploration efficiency and operation safety. Summary of the invention

[0004] The purpose of the present invention is to provide a real-time analysis method of seabed sediment based on multi-beam sonar in view of the deficiencies of the prior art.

[0005] The present invention is realized by the following technical scheme: a method for real-time analysis of seabed sediment based on multi-beam sonar, the method comprising the following steps:

[0006] (1) Calibrate the seabed scattering intensity of the multi-beam sonar to obtain navigation data of the target area;

[0007] (2) extracting measurement data and sonar operating parameters from navigation data to obtain seafloor scattering data based on time;

[0008] (3) Based on the parameter relationship of the beam, the seabed target intensity is calculated, including the scattering coefficient per unit area and the beam irradiation area, and the scattering coefficient per unit area is decomposed into a function of the inherent scattering coefficient of the seabed and the beam incident angle;

[0009] (4) Establishing a curve of unit area scattering coefficient and beam incident angle; fitting it with the scattering model curve and the roughness contribution curve respectively to obtain the correlation coefficient;

[0010] (5) Based on the two correlation coefficients obtained in step (4) and the set threshold comparison relationship, analyze the seabed sediment type.

[0011] Furthermore, the specific process of calibrating the seabed scattering intensity of the multi-beam sonar is as follows:

[0012] (1.1) Select a flat sea area, set up a "well"-shaped survey line, use multi-beam sonar to measure along the survey line, and collect seabed scattering intensity data along the route;

[0013] (1.2) Extract the repeated seafloor scattering intensity data of horizontal and vertical survey lines;

[0014] (1.3) Based on the difference in seabed scattering intensity data between the horizontal survey line and the vertical survey line extracted in step (1.2), the seabed scattering intensity correction number corresponding to different beam angles is obtained, and the multi-beam sonar parameters are calibrated.

[0015] Furthermore, in step (1.2), the seabed scattering intensity of a certain repeated ping of the horizontal survey line and the seabed scattering intensity of the central beam of the vertical survey line are extracted. The seabed scattering intensity of a certain ping of the horizontal survey line should correspond to the same beam footprint area as the seabed scattering intensity of the central beam of the vertical survey line.

[0016] Furthermore, the measurement data includes ping, beam, time, longitude, latitude, depth, and scattering intensity coefficient. Beam incident angle Sonar operating parameters include time Time, transmit gain TG, receive gain RG, pulse width τ, transmit beam width θx and receive beam width θy; based on the water depth of the measured data, calculate the seabed slope Slope parallel to the course alongtrack , Slope of vertical heading acrosstrack ; Based on the beam angle of the multi-beam sonar, calculate the area A of each beam footprint; based on the time Time, match the data of each beam to construct the seabed scattering data matrix.

[0017] Furthermore, the beam incidence angle is calculated as follows:

[0018] The beam incidence angle is calculated based on the seafloor interface formed by the corresponding water depth of each beam obtained by the continuous transmission of n pings, that is, [Depth alongtrack ,Depth acrosstrack ] is used as the reference plane and calculated according to the beam emission angle, where Depth alongtrack ,Depth acrosstrack They are the water depth values ​​of each beam along the heading and vertical heading respectively.

[0019] Furthermore, the beam footprint area A is calculated as follows:

[0020] hour

[0021] hour

[0022] Among them, θ x θ y are the transmitting beam width and the receiving beam width respectively, c is the speed of sound in water, and τ is the beam pulse width.

[0023] Furthermore, based on the parameter transfer process of the beam, the scattering coefficient per unit area is calculated, and based on the LAMBERT law, it is decomposed into a function of the inherent scattering coefficient of the seabed and the beam incident angle. Based on the inherent scattering coefficient of the seabed and the beam incident angle control, real-time seabed analysis is performed:

[0024]

[0025]

[0026] in, is the scattering coefficient per unit area, in dB / m 2 , BS is the inherent scattering coefficient of the seabed, is the beam incident angle, SL is the sonar emission energy, EL is the sonar received echo, A is the seabed area where the beam is projected, R is the beam sound line length, α is the sound attenuation coefficient, is the correction factor for the seabed scattering intensity.

[0027] Furthermore, the scattering model curve as follows:

[0028]

[0029] in, is the beam incident angle, and BS model The values ​​are assigned according to the empirical values ​​of the three types of bottom soils, namely mud: -20dB / m 2 ;Sand:-30dB / m 2 ; Gravel: -40dB / m 2 .

[0030] Furthermore, based on the water depth data of the collected beam, the roughness curve n is solved by using the water depth and plane position, taking the beam footprint area as the calculation unit:

[0031]

[0032] Among them, BS is the intrinsic scattering coefficient of the seabed, is the beam incidence angle, and A is the area of ​​the beam footprint.

[0033] Furthermore, the results of the low-quality analysis of the seafloor are as follows:

[0034] 1) If the roughness scattering contribution correlation coefficient g ≥ 0.5, and the scattering model is consistent with the BS of gravel model If the correlation coefficient k of the model curve is ≥ 0.5, the output substrate type is gravel;

[0035] 2) If the roughness scattering contribution correlation coefficient g < 0.5, and the scattering model is consistent with the sand BS model If the correlation coefficient k of the model curve is ≥ 0.5, the output bottom type is sand;

[0036] 3) If the roughness scattering contribution correlation coefficient g < 0.5, and the scattering model is consistent with the BS of the mud model If the correlation coefficient k of the model curve is ≥ 0.5, the output bottom type is mud;

[0037] 4) If it is not the case above, the output substrate type is mixed substrate.

[0038] The beneficial effects of the present invention are as follows: the present invention establishes a calibration method for seabed scattering intensity, solves the problem of fitting the seabed scattering model, obtains the bottom type in real time, is highly efficient, is suitable for use with multi-beam sonar, can conduct real-time seabed bottom analysis, can serve seabed resource exploration and marine engineering construction, is conducive to guiding seabed exploration operations and engineering construction, and improves seabed exploration efficiency and operation safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 It is the work flow chart of the method of the present invention;

[0041] Figure 2 is the scattering contribution curve;

[0042] Figure 3 for Curve and Curvilinear correlation graph. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] like Figure 1 As shown, the present invention provides a method for real-time analysis of seabed sediment based on multi-beam sonar, the method comprising the following steps:

[0045] Step 1.1: Collect seafloor scattering intensity calibration data and navigation data

[0046] 1.1.1 Calibration of the seafloor scattering intensity of multibeam sonar

[0047] 1) Plan a set of "well"-shaped survey lines consisting of 4 survey lines, each with a length of 10 km, so that the coverage of the survey lines on one side is completely overlapped. Select a sea area with flat terrain, use multi-beam sonar to measure along the survey line, and collect the seabed scattering intensity data of the route;

[0048] 2) Extract the repeated seafloor scattering intensity data of horizontal and vertical survey lines;

[0049] 3)3) Based on 2), screen the seabed scattering intensity of a certain repeated ping of the horizontal survey line and the seabed scattering intensity of the central beam of the vertical survey line. The seabed scattering intensity of a certain ping of the horizontal survey line should correspond to the same beam footprint area as the seabed scattering intensity of the central beam of the vertical survey line;

[0050] 4) The seabed scattering intensity of each beam on the horizontal survey line is expressed as The seafloor scattering intensity of the central beam of the vertical survey line is expressed as (BS ver ,ping), then

[0051] 5) Construct different beam angles The corresponding seafloor scattering intensity correction is

[0052] 1.1.2 Collecting multi-beam sonar navigation data

[0053] 1) Design the navigation survey line and configure the multi-beam sonar working parameters;

[0054] 2) Conducting navigation surveys in target areas where real-time seafloor sediment analysis is planned;

[0055] Step 1.2: Construct the seafloor scattering data matrix

[0056] 1.2.1 Extracting navigation measurement data and multibeam sonar configuration parameters

[0057] 1) Extract measurement data, including ping, beam, time, longitude, latitude, water depth, and scattering intensity coefficient Angle of incidence

[0058] 2) Extracting sonar operating parameters, including time Time, transmitting gain TG, receiving gain RG, pulse width τ, transmitting beam width θx and receiving beam width θy;

[0059] 1.2.2 Constructing the seafloor scattering data matrix

[0060] 1) Depth based on measured data alongtrack ,Depth acrosstrack ], calculate the seabed slope Slope parallel to the course alongtrack , Slope of vertical heading acrosstrack ;

[0061] 2) Based on the beam angle of the multibeam sonar, calculate the area A of each beam footprint;

[0062] 3) Based on the time Time, match the data of each beam, including ping, beam, longitude long, latitude lat, water depth Depth, and scattering intensity coefficient Angle of incidence Transmitting beam width θx and receiving beam width θy; seabed slope Slope parallel to the heading alongtrack , the slope of the vertical heading Slope acrosstrack , beam footprint area A.

[0063] Step 1.3: Extraction of seafloor scattering intensity coefficient

[0064] 1.3.1 Beam-based parameter transfer

[0065] The sonar transmits energy SL, which is reflected by the seabed after the propagation loss TL on the outbound and return trips, and becomes the target intensity BTS. The sonar receives the echo EL, and the beam incidence angle is The seabed area where the beam is projected is A, α is the sound attenuation coefficient, and R is the length of the beam sound line.

[0066] EL=SL-2TL+BTS

[0067]

[0068] in, is the seafloor scattering coefficient per unit area, The decibel form of the seafloor scattering coefficient per unit area, with the unit of dB / m 2 .

[0069]

[0070] in, It can be decomposed into a function of the inherent scattering intensity BS of the seabed and the beam incident angle. The unit of BS is dB / m 2 .

[0071]

[0072]

[0073] 1.3.2 Seafloor scattering parameter decomposition

[0074] The intensity of the seabed target is determined by the following parameters: scattering coefficient per unit area Beam irradiation area in, Based on the LAMBERT law, it can be decomposed into a function of the inherent scattering coefficient BS of the seabed and the beam incident angle. Real-time bottom analysis is based on the control of the inherent scattering coefficient BS and the beam incident angle.

[0075] Step 1.4: Scattering fitting curve and model curve evaluation

[0076] 1.4.1 Constructing scattering curves

[0077] After the parameter correction in step 1.3, the scattering coefficient is established With the incident angle The beam incident angle is calculated based on the seabed interface formed by the corresponding water depth of each beam obtained by the continuous transmission of n pings. alongtrack ,Depth acrosstrack ] is used as the reference plane and calculated according to the beam emission angle, where Depth alongtrack ,Depth acrosstrackThey are the water depth values ​​of each beam along the heading and vertical heading respectively.

[0078] 1.4.2 Constructing the model curve

[0079] After the parameter correction in step 1.3, based on the formula:

[0080]

[0081] B.S. model The values ​​are assigned according to the empirical values ​​of the three types of bottom soils, namely mud: -20dB / m 2 ;Sand:-30dB / m 2 ; Gravel: -40dB / m 2 . Establish the scattering coefficient The curve with incident angle is the model curve.

[0082] 1.4.4 Extracting the scattering contribution index

[0083] Based on the formula:

[0084]

[0085] Roughness contribution index curve

[0086] The area A of the beam footprint is determined by the transmit beam width, receive beam width, beam angle, and beam ray length.

[0087] hour

[0088] hour

[0089] Among them, θ x θ y are the transmitting beam width and the receiving beam width respectively, c is the speed of sound in water, and τ is the beam pulse width.

[0090] Step 1.5: Sediment analysis

[0091] 1.5.1 Evaluation of the correlation of scattering model curves

[0092] like Figure 3 As shown, the least squares fitting Curve and The correlation coefficient k can be obtained by pinging and beaming the plane. Based on the incident angle of each beam, the beam footprint is used as the plane unit to form Surface and Surface layer, find the correlation coefficient k.

[0093] 1.5.2 Evaluation of the correlation of scattering contribution curves

[0094] like Figure 2 As shown, based on the water depth data of the collected beam, the beam footprint area is used as the calculation unit, the water depth and plane position are used to solve the roughness curve, and the least squares method is used to fit the roughness curve. And the roughness contribution curve n, obtain the correlation coefficient g.

[0095] You can also use ping and beam to construct a plane. Based on the water depth data of the collected beam, the beam footprint is used as the plane unit to form a roughness layer. Based on the layer, the scattering contribution correlation is analyzed to solve the roughness g.

[0096] 1.5.3 Sediment analysis

[0097] 1) If the roughness scattering contribution correlation coefficient g ≥ 0.5, and the scattering model is consistent with the BS of gravel model If the correlation coefficient k of the model curve is > 0.5, the output substrate type is gravel;

[0098] 2) If the roughness scattering contribution correlation coefficient g < 0.5, and the scattering model is consistent with the sand BS model If the correlation coefficient k of the model curve is greater than 0.5, the output bottom type is sand;

[0099] 3) If the roughness scattering contribution correlation coefficient g < 0.5, and the scattering model is consistent with the BS of the mud model If the correlation coefficient k of the model curve is > 0.5, the output bottom type is mud;

[0100] 4) If it is not the case above, the output substrate type is mixed substrate.

[0101] The above embodiments are used to illustrate the present invention rather than to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for real-time analysis of seabed sediments based on multi-beam sonar, characterized in that: The method comprises the following steps: (1) Calibrate the seabed scattering intensity of the multi-beam sonar to obtain navigation data of the target area; (2) extracting measurement data and sonar operating parameters from navigation data to obtain seafloor scattering data based on time; (3) Based on the parameter relationship of the beam, the seabed target intensity is calculated, including the scattering coefficient per unit area and the beam irradiation area, and the scattering coefficient per unit area is decomposed into a function of the inherent scattering coefficient of the seabed and the beam incident angle; (4) Establishing a curve of unit area scattering coefficient and beam incident angle; fitting it with the scattering model curve and the roughness contribution curve respectively to obtain the correlation coefficient; (5) Based on the two correlation coefficients obtained in step (4) and the set threshold comparison relationship, analyze the seabed sediment type.

2. The method for real-time analysis of seabed sediment based on multi-beam sonar according to claim 1, characterized in that: The specific process of calibrating the seabed scattering intensity of multi-beam sonar is as follows: (1.1) Select a flat sea area, set up a "well"-shaped survey line, use multi-beam sonar to measure along the survey line, and collect seabed scattering intensity data along the route; (1.2) Extract the repeated seafloor scattering intensity data of horizontal and vertical survey lines; (1.3) Based on the difference in seabed scattering intensity data between the horizontal survey line and the vertical survey line extracted in step (1.2), the seabed scattering intensity correction number corresponding to different beam angles is obtained, and the multi-beam sonar parameters are calibrated.

3. The method for real-time analysis of seabed sediment based on multi-beam sonar according to claim 2, characterized in that: In step (1.2), the seabed scattering intensity of a certain repeated ping of the horizontal survey line and the seabed scattering intensity of the central beam of the vertical survey line are extracted. The seabed scattering intensity of a certain ping of the horizontal survey line should correspond to the same beam footprint area as the seabed scattering intensity of the central beam of the vertical survey line.

4. The method for real-time analysis of seabed sediment based on multi-beam sonar according to claim 1, characterized in that: The measurement data includes ping, beam, time, longitude, latitude, water depth, and scattering intensity coefficient. Beam incident angle Sonar operating parameters include time Time, transmit gain TG, receive gain RG, pulse width τ, transmit beam width θx and receive beam width θy; based on the water depth of the measured data, calculate the seabed slope Slope parallel to the course alongtrack , Slope of vertical heading acrosstrack ; Based on the beam angle of the multi-beam sonar, calculate the area A of each beam footprint; based on the time Time, match the data of each beam to construct the seabed scattering data matrix.

5. The method for real-time analysis of seabed sediment based on multi-beam sonar according to claim 4, characterized in that: The beam incidence angle is calculated as follows: The beam incidence angle is calculated based on the seafloor interface formed by the corresponding water depth of each beam obtained by the continuous transmission of n pings, that is, [Depth alongtrack ,Depth acrosstrack ] is used as the reference plane and calculated according to the beam emission angle, where Depth alongtrack , Depth acrosstrack They are the water depth values ​​of each beam along the heading and vertical heading respectively.

6. The method for real-time analysis of seabed sediment based on multi-beam sonar according to claim 4, characterized in that: The beam footprint area A is calculated as follows: hour hour Among them, θ x θ y are the transmitting beam width and the receiving beam width respectively, c is the speed of sound in water, and τ is the beam pulse width.

7. The method for real-time analysis of seabed sediment based on multi-beam sonar according to claim 1, characterized in that: Based on the parameter transfer process of the beam, the scattering coefficient per unit area is calculated, and based on the LAMBERT law, it is decomposed into a function of the inherent scattering coefficient of the seabed and the beam incident angle. Based on the inherent scattering coefficient of the seabed and the beam incident angle control, real-time seabed analysis is performed: in, is the scattering coefficient per unit area, in dB / m2, BS is the inherent scattering coefficient of the seabed, is the beam incident angle, SL is the sonar emission energy, EL is the sonar received echo, A is the seabed area where the beam is projected, R is the beam sound line length, α is the sound attenuation coefficient, is the correction factor for the seabed scattering intensity.

8. The method for real-time analysis of seabed sediment based on multi-beam sonar according to claim 1, characterized in that: Scattering model curve as follows: in, is the beam incident angle, and BS model The values ​​are assigned according to the empirical values ​​of the three types of bottom soils, namely mud: -20dB / m 2 ;Sand:-30dB / m 2 ; Gravel: -40dB / m 2 .

9. The method for real-time analysis of seabed sediment based on multi-beam sonar according to claim 1, characterized in that: Based on the water depth data of the collected beam, the roughness curve n is solved by taking the beam footprint area as the calculation unit and using the water depth and plane position: Among them, BS is the intrinsic scattering coefficient of the seabed, is the beam incidence angle, and A is the area of ​​the beam footprint.

10. The method for real-time analysis of seabed sediment based on multi-beam sonar according to claim 8, characterized in that: The results of the low-quality analysis of the seafloor are as follows: 1) If the roughness scattering contribution correlation coefficient g ≥ 0.5, and the scattering model is consistent with the BS of gravel model If the correlation coefficient k of the model curve is > 0.5, the output substrate type is gravel; 2) If the roughness scattering contribution correlation coefficient g < 0.5, and the scattering model is consistent with the sand BS model If the correlation coefficient k of the model curve is greater than 0.5, the output bottom type is sand; 3) If the roughness scattering contribution correlation coefficient g < 0.5, and the scattering model is consistent with the BS of the mud model If the correlation coefficient k of the model curve is ≥ 0.5, the output bottom type is mud; 4) If it is not the case above, the output substrate type is mixed substrate.

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