A remote sensing water depth detection method, medium and system based on blue-green laser

Abstract

The invention provides a remote sensing water depth detection method, medium and system based on blue-green laser, which belongs to the field of water depth measurement technology, and includes: first, obtaining blue light and green light laser signals with known transmission power, and collecting water surface reflection and water bottom reflection data under different incident angles. Based on these data, a laser incident angle matrix is ​​established to calculate the water surface reflection coefficient and the water surface transmission coefficient. At the same time, an atmospheric transmission matrix is ​​established according to meteorological parameters to calculate the transmission loss of the laser signal in the atmosphere. Then, a water surface fluctuation model is established to separate the water surface reflection and water bottom reflection signals. Using the blue-green dual-wavelength signal intensity ratio matrix, combined with the optical characteristics of the water body, a water depth calculation equation group is established. Finally, according to the propagation time difference and equivalent propagation speed of the laser signal in the water, the water depth equation group is solved, and finally a water depth topographic map is obtained. The problem that the prior art cannot separate the water surface reflection signal and the water bottom reflection signal, which affects the measurement accuracy, is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of water depth measurement, and in particular, relates to a remote sensing water depth detection method, medium and system based on blue-green laser. Background Art

[0002] Underwater remote sensing is a technology that uses electromagnetic waves or sound waves to detect and measure underwater environments. Among them, water depth measurement technology based on laser remote sensing has received widespread attention and is mainly used in marine surveying, water conservancy projects, water environment monitoring and other fields. Compared with traditional acoustic depth measurement technology, laser remote sensing water depth detection has the advantages of high measurement accuracy, wide detection range and fast measurement speed. At present, the commonly used laser water depth measurement methods mainly include single-wavelength laser pulse method, green light laser method and blue-green dual-wavelength laser method. The single-wavelength laser pulse method uses the propagation time difference of the laser pulse in the water to calculate the water depth, but it is greatly affected by the transparency of the water body and the measurement accuracy is limited. The green light laser method uses the ability of green light to penetrate the water body for water depth detection. Compared with the single-wavelength method, it has certain improvements, but it is still limited by the optical properties of the water body. The blue-green dual-wavelength laser method can effectively suppress the influence of the optical properties of the water body by comparing the propagation characteristics of blue light and green light in water, thereby improving the accuracy and reliability of water depth measurement.

[0003] However, the existing blue-green dual-wavelength laser water depth measurement method has the problem of being unable to separate the water surface reflection signal and the bottom reflection signal, which affects the accuracy of water depth measurement. Summary of the invention

[0004] In view of this, the present invention provides a remote sensing water depth detection method, medium and system based on blue-green laser, which can solve the problem that the existing blue-green dual-wavelength laser water depth measurement method cannot separate the water surface reflection signal and the bottom reflection signal, thereby affecting the accuracy of water depth measurement.

[0005] The present invention is achieved in that:

[0006] A first aspect of the present invention provides a remote sensing water depth detection method based on blue-green laser, comprising the following steps:

[0007] S10, obtaining a blue laser signal and a green laser signal with known transmission power, and collecting water surface reflection echo data and water bottom reflection echo data at different incident angles;

[0008] S20, establishing a laser incident angle matrix, and calculating the water surface reflection coefficient and water surface transmission coefficient of the blue laser signal and the green laser signal at different incident angles;

[0009] S30, obtaining meteorological parameters of the detection area, establishing an atmospheric transmission matrix, and calculating the first-pass transmission loss of the blue laser signal and the green laser signal from the transmitting end to the water surface and the second-pass transmission loss from the water surface to the receiving end;

[0010] S40, establishing a water surface fluctuation model based on the laser incident angle matrix, and calculating the modulation function of the water surface fluctuation on the blue laser and green laser echo signals;

[0011] S50, according to the water surface reflection coefficient and the water surface transmission coefficient, combined with the modulation function, separating the water surface echo signal and the bottom echo signal after penetrating the water body, and establishing a blue-green dual-wavelength signal intensity ratio matrix;

[0012] S60, establishing a water optical property database, obtaining the extinction coefficient of the target water area, and calculating the downlink attenuation coefficient of the blue laser and the green laser from the water surface to the bottom and the uplink attenuation coefficient from the bottom to the water surface;

[0013] S70, establishing a water depth calculation equation group based on the blue-green dual-wavelength signal intensity ratio matrix and the downlink attenuation coefficient and the uplink attenuation coefficient;

[0014] S80, solving the water depth calculation equations according to the time difference between the emitted laser signal passing through the water surface and the bottom echo signal passing through the water surface and the equivalent propagation speed of the laser in the water, to obtain the water depth data of the target water area;

[0015] S90, performing grid interpolation processing on the water depth data to generate a high-precision water depth topographic map of the target water area.

[0016] By adopting the method of the present invention, the detection depth can reach 40-50 meters in relatively clear water bodies; in turbid water bodies, the detection depth will be significantly reduced to only 10-15 meters; the horizontal resolution can reach the centimeter level; and the vertical accuracy can reach the decimeter level.

[0017] Furthermore, the laser incident angle matrix in step S20 is specifically expressed as follows:

[0018] ;

[0019] In the formula, Indicates Line The incident angle of the column, in degrees, ranging from 0 to 90 degrees. Indicates the number of rows in the scan area; Indicates the number of columns in the scan area; In and The corresponding scanning areas are Row and The matrix actually represents the incident angle distribution of the laser scanning system in the entire detection area.

[0020] The calculation of reflection coefficient and transmission coefficient is specifically expressed as follows:

[0021] ;

[0022] ;

[0023] ;

[0024] ;

[0025] In the formula, and are the water surface reflectance coefficients for blue and green light, respectively; and are the water surface transmittance coefficients for blue and green light, respectively; and are the reflected signal intensities of blue light and green light, respectively; and are the emission powers of blue light and green light respectively; and are the reflection phases of blue and green light, respectively; and are the transmission phases of blue and green light, respectively; is the laser incident angle. and In and Represent blue light and green light respectively; Represents the incident angle, which is the same as the incident angle matrix correspond; and Indicates the incident angle The reflected signal strength under ; and are the emission powers of the blue and green lasers, respectively; and Indicates the incident angle The reflection phase under ; and Indicates the incident angle The transmission phase under .

[0026] The reflection coefficient matrix and transmission coefficient matrix are specifically expressed as follows:

[0027] ;

[0028] ;

[0029] ;

[0030] ;

[0031] In the formula, and Respectively represent blue light and green light in Line Reflection coefficient at column position; and Respectively represent blue light and green light in Line Transmission coefficient at column position; Indicates that blue light Line The reflection coefficient of the column position and the incident angle correspond; Indicates that green light is Line The reflection coefficient of the column position and the incident angle correspond; Indicates that blue light Line The transmission coefficient of the column position and the incident angle correspond; Indicates that green light is Line The transmission coefficient of the column position and the incident angle Corresponding to; the dimensions of these matrices Which is consistent with the incident angle matrix.

[0032] The atmospheric transmission loss calculation in step S30 is specifically expressed as follows:

[0033] ;

[0034] ;

[0035] ;

[0036] ;

[0037] This set of equations is based on the Beer-Lambert law and atmospheric optical transmission theory, describing the attenuation process of laser signals in the atmosphere. and are the first-pass transmission losses of blue light and green light respectively; and are the secondary transmission losses of blue light and green light respectively; and are the atmospheric attenuation coefficients of blue and green light, respectively; and are the atmospheric scattering coefficients for blue and green light, respectively; is the distance from the laser to the water surface; is the distance from the water surface to the receiver; is the laser emission angle.

[0038] like: , accurately describes the atmospheric transmission loss, distinguishes the first-pass and second-pass transmission characteristics, and takes into account the differential attenuation of different wavelengths; including:

[0039] Exponential decay term: , α represents the atmospheric attenuation coefficient; sec(θ) takes into account the effect of the propagation path inclination on attenuation; h is the propagation distance; it describes the exponential attenuation law of light intensity with distance;

[0040] Scattering compensation term: , β is the scattering coefficient; It represents the nonlinear relationship between the scattering effect and the distance, taking into account the enhancement effect of atmospheric scattering on the signal;

[0041] The remaining three equations are similar to this one.

[0042] The atmospheric transmission matrix is ​​specifically expressed as follows:

[0043] ;

[0044] ;

[0045] In the formula, and Represent the first-pass transmission losses of blue light and green light respectively; and Represent the secondary transmission losses of blue light and green light respectively; represents the atmospheric attenuation coefficient; represents the atmospheric scattering coefficient. represents the first-pass transmission matrix (from the transmitter to the water surface); represents the secondary transmission matrix (from the water surface to the receiving end); and Respectively represent The first-pass transmission loss of blue and green light at each location; and Respectively represent The blue and green light secondary transmission losses at each location; and Respectively represent Line The atmospheric attenuation coefficient and scattering coefficient at the column position.

[0046] The water surface fluctuation model in step S40 is specifically expressed as follows:

[0047] ;

[0048] ;

[0049] This set of equations is based on ocean spectrum theory and describes the modulation effect of water surface fluctuations on laser signals. In the formula, and are the water surface modulation functions for blue light and green light respectively; For the The amplitude of each wave component; For the The angular frequency of each wave component, describing its temporal variation; For the The wave number of the wave component, is the wave number term, describing the spatial distribution; and are the fluctuation attenuation coefficients of blue light and green light, respectively; for time; is the space coordinate.

[0050] The water surface wave modulation matrix is ​​specifically expressed as follows:

[0051] ;

[0052] In the formula, and Respectively represent blue light and green light in Line Modulation function of column position; Indicates the wave amplitude; Indicates the wave number. Indicates Line Blue light modulation function of column position; Indicates Line Green light modulation function of column position; Indicates Line Wave amplitude at column position; Indicates Line The wave number of the column position.

[0053] The signal strength calculation in step S50 is specifically expressed as follows:

[0054] ;

[0055] ;

[0056] ;

[0057] ;

[0058] ;

[0059] In the formula, and The water surface echo signal strengths are blue and green light respectively; and are the bottom echo signal intensities of blue light and green light respectively; and are the reflection coefficients of blue light and green light at the bottom of water respectively; It is the ratio of blue and green dual wavelength signal intensity.

[0060] The signal strength ratio matrix is ​​specifically expressed as follows:

[0061] ;

[0062] In the formula, Indicates Line The ratio of the blue-green dual-wavelength signal intensity at the column position reflects the water depth information and is an important parameter for water depth inversion.

[0063] The calculation of the attenuation coefficient in step S60 is specifically expressed as follows:

[0064] ;

[0065] ;

[0066] ;

[0067] ;

[0068] In the formula, and are the downlink attenuation coefficients of blue light and green light, respectively; and are the uplink attenuation coefficients of blue light and green light, respectively; and are the absorption coefficients of blue light and green light, respectively; and are the scattering coefficients of blue light and green light, respectively; and are the refraction angles of blue light and green light in water respectively; and They are the propagation angles of blue light and green light in water after being reflected from the bottom of the water. is the path correction term, which corrects the actual propagation path.

[0069] The attenuation coefficient matrix is ​​specifically expressed as follows:

[0070] ;

[0071] In the formula, and represent the downlink attenuation coefficients of blue light and green light, respectively; and Represent the uplink attenuation coefficients of blue light and green light respectively. Indicates Line The blue light downlink attenuation coefficient at the column position; Indicates Line Green light downlink attenuation coefficient at column position; Indicates Line The blue light uplink attenuation coefficient at the column position; Indicates Line Green light uplink attenuation coefficient at column position.

[0072] The water depth calculation equation group in step S70 is specifically expressed as follows:

[0073] ;

[0074] ;

[0075] In the formula, for water depth; is the speed of light in water; is the refractive index of water; For the time difference.

[0076] The first equation in this step is based on optical principles and describes the relationship between the blue-green dual wavelength signal intensity ratio and water depth. The equation can be divided into three main parts:

[0077] Transmittance value part: , which represents the ratio of blue light and green light transmission coefficients, reflects the difference in energy transmission efficiency when light of different wavelengths is transmitted through the water surface, and takes into account the effect of the incident angle on transmission;

[0078] Bottom reflectance value part: , which represents the ratio of the reflection coefficient of the bottom of the water to blue light and green light, reflects the difference in the reflection ability of the bottom of the water to light of different wavelengths, and is related to the characteristics of the bottom of the water material;

[0079] Exponential decay part: , represents the bidirectional attenuation process of light propagating in water, which includes two processes: downward propagation and upward reflection. The difference in attenuation coefficients reflects the selective absorption and scattering of light of different wavelengths by the water body. H is the water depth, which is the solution target.

[0080] The second equation is based on the time propagation principle of light and describes the relationship between the round trip time of the laser signal and the water depth. The equation contains:

[0081] Time difference: , which represents the time difference of the laser signal from the water surface to the bottom and back, can be directly measured by a high-precision timer;

[0082] Optical path term: , 2H represents the geometric distance of the light in the water. is the speed of light in water, reflecting the basic distance-time relationship;

[0083] Refraction Correction: , taking into account the effect of refraction on the optical path, it is derived based on Snell’s law, which is related to the angle of incidence and the refractive index of water.

[0084] The water depth calculation in step S80 is specifically expressed as follows:

[0085] ;

[0086] or ;

[0087] Among them, these two equations describe the same physical quantity (water depth H) from different principles: the first equation is based on the principle of light intensity ratio: by measuring the ratio of the intensity of blue and green dual-wavelength signals; using the differential attenuation of light of different wavelengths by water bodies; eliminating common influencing factors such as water surface fluctuations; suitable for precise measurement but requires more parameter calibration; the second equation is based on the principle of time ranging: by measuring the round-trip time of laser signals; using the speed of light propagation in water; considering the refraction effect for correction; the implementation is relatively direct but affected by the water surface state; the two equations describe the same physical quantity. Ideally, the two equations should get the same result. In practical applications, the two methods can be used in combination to verify and complement each other. Under different conditions, a more suitable equation can be selected or the average of the two can be calculated. The design of this dual depth measurement principle fully considers various situations that may be encountered in practical applications and improves the adaptability and reliability of the system.

[0088] That is, find the mean:

[0089] ;

[0090] The water depth data matrix is ​​specifically expressed as follows:

[0091] ;

[0092] In the formula, Indicates Line The water depth at the column location in meters.

[0093] The interpolation calculation in step S90 is specifically expressed as follows:

[0094] ;

[0095] ;

[0096] In the formula, Interpolation point The depth of water; For the The water depth at a known point; is the weight function; To interpolate the point to The distance to a known point; is the weight index, usually 2.

[0097] The gridded water depth terrain matrix is ​​specifically expressed as follows:

[0098] ;

[0099] In the formula, After interpolation, Line The water depth value at the column position, in meters; and Respectively represent the number of rows and columns after interpolation. Indicates Line The original water depth value at the column location; After interpolation, Line The water depth value at the column position; and Indicates the number of rows and columns of the interpolated grid, which is usually larger than the original and .

[0100] The method for obtaining the parameters involved in all the above calculations is:

[0101] 1. and It is obtained through experimental measurement, using a power meter to measure the reflected signal intensity at different incident angles;

[0102] 2. and Directly obtained through laser output power parameters;

[0103] 3. , , and Obtained by measuring with a phase measuring instrument;

[0104] 4. , , and Obtained through real-time measurement by atmospheric monitoring equipment;

[0105] 5. and Obtained by measuring with a laser rangefinder;

[0106] 6. , and Measured by wave monitoring equipment;

[0107] 7. and Obtained through water surface fluctuation experiments;

[0108] 8. and Obtained through bottom reflectivity measurement experiments;

[0109] 9. , , and Obtained through measurement of water quality optical parameter measuring instrument;

[0110] 10. , , and Obtained by calculation through the law of refraction;

[0111] 11. and Obtained through measurement of water quality parameter measuring instrument;

[0112] 12. Obtained through high-precision timer measurement.

[0113] Key relationship description:

[0114] 1. Relationship between reflection coefficient and transmission coefficient:

[0115] The magnitude of the transmission coefficient is related to the reflection coefficient, satisfying the energy conservation relationship;

[0116] ;

[0117] ;

[0118] 2. Relationship between incident angle and refraction angle:

[0119] Satisfies Snell's law: ;

[0120] in is the refractive index of air, is the refractive index of water; is the incident angle, is the refraction angle;

[0121] 3. Relationship between signal strength ratio and water depth:

[0122] The ratio of the blue-green dual-wavelength signal intensities decreases with increasing water depth. The rate of change of the ratio is related to the optical properties of the water body. A quantitative relationship between the ratio and water depth can be established through calibration.

[0123] A second aspect of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores program instructions, and when the program instructions are run in a computer, they are used to execute the above-mentioned remote sensing water depth detection method based on blue-green laser.

[0124] A third aspect of the present invention provides a blue-green laser-based remote sensing water depth detection system, which includes the above-mentioned computer-readable storage medium.

[0125] Compared with the prior art, the invention provides a method, medium and system for remote sensing water depth detection based on blue-green laser, which has the following beneficial effects:

[0126] 1) The effect of laser incident angle on echo signal is fully considered. A laser incident angle matrix is ​​established, which can realize comprehensive detection of complex waters without being limited to a single incident angle. This helps to improve the accuracy and reliability of water depth measurement.

[0127] 2) A detailed atmospheric transmission loss model was established, which can accurately compensate for the attenuation of the laser signal during atmospheric transmission, thereby improving the accuracy of the measurement results.

[0128] 3) A water surface fluctuation modulation model was established, which can effectively separate the water surface reflection signal and the bottom reflection signal and reduce the impact of water surface fluctuation on measurement accuracy.

[0129] 4) The complete optical characteristic parameters of the target water area are obtained, which can accurately calculate the uplink and downlink attenuation of blue light and green light in the water, providing more reliable basic data for water depth inversion.

[0130] In summary, the remote sensing water depth detection method based on blue-green laser proposed in the present invention can effectively solve the limitations of the existing blue-green dual-wavelength laser water depth measurement method by establishing a series of mathematical models for laser incident angle, atmospheric transmission, water surface fluctuation and water optical properties, and integrating high-precision measured parameters, significantly improve the accuracy and reliability of water depth detection, and solve the problem that the existing blue-green dual-wavelength laser water depth measurement method cannot separate the water surface reflection signal and the bottom reflection signal, thereby affecting the accuracy of water depth measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0131] Figure 1 A flow chart of the method provided by the present invention;

[0132] Figure 2 The laser transmission characteristics of shrimp at different incident angles are shown;

[0133] Figure 3 is the characteristic diagram of the absorption coefficient changing with depth;

[0134] Figure 4 It is the characteristic diagram of the variation of scattering coefficient parameters with depth;

[0135] Figure 5 This is the relationship between the blue-green laser signal intensity ratio and the water depth;

[0136] Figure 6 It is a high-precision bathymetric topographic map of the bay in the embodiment. DETAILED DESCRIPTION

[0137] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0138] like Figure 1 As shown, it is a flow chart of a remote sensing water depth detection method based on blue-green laser provided by the first aspect of the present invention. The method comprises the following steps:

[0139] S10, obtaining a blue laser signal and a green laser signal with known transmission power, and collecting water surface reflection echo data and water bottom reflection echo data at different incident angles;

[0140] S20, establishing a laser incident angle matrix, and calculating the water surface reflection coefficient and water surface transmission coefficient of the blue laser signal and the green laser signal at different incident angles;

[0141] S30, obtaining meteorological parameters of the detection area, establishing an atmospheric transmission matrix, and calculating the first-pass transmission loss of the blue laser signal and the green laser signal from the transmitting end to the water surface and the second-pass transmission loss from the water surface to the receiving end;

[0142] S40, establishing a water surface fluctuation model based on the laser incident angle matrix, and calculating the modulation function of the water surface fluctuation on the blue laser and green laser echo signals;

[0143] S50, according to the water surface reflection coefficient and the water surface transmission coefficient, combined with the modulation function, separate the water surface echo signal and the bottom echo signal after penetrating the water body, and establish a blue-green dual-wavelength signal intensity ratio matrix;

[0144] S60, establishing a water optical property database, obtaining the extinction coefficient of the target water area, and calculating the downlink attenuation coefficient of the blue laser and the green laser from the water surface to the bottom and the uplink attenuation coefficient from the bottom to the water surface;

[0145] S70, establishing a water depth calculation equation group based on the blue-green dual-wavelength signal intensity ratio matrix and the downlink attenuation coefficient and the uplink attenuation coefficient;

[0146] S80, solving a group of water depth calculation equations based on the time difference between the emitted laser signal passing through the water surface and the bottom echo signal passing through the water surface and the equivalent propagation speed of the laser in the water to obtain the water depth data of the target water area;

[0147] S90, performing grid interpolation processing on the water depth data to generate a high-precision water depth topographic map of the target water area.

[0148] The specific implementation methods of the above steps are described in detail below:

[0149] The specific implementation of step S10 is: first, obtain a blue laser signal and a green laser signal with known transmission power. This can be achieved by using a power meter to measure the output power of the laser. Then, collect water surface reflection echo data and water bottom reflection echo data at different incident angles. An adjustable angle laser scanning system can be used to scan laser signals at different angles in the entire detection area, and the photoelectric detector at the receiving end records the reflection echo signals of the water surface and the water bottom. In this way, the reflection information of the water surface and the water bottom at different incident angles can be obtained.

[0150] The specific implementation of step S20 is: first, establish a laser incident angle matrix This matrix represents the laser incident angle distribution in the entire detection area, and each element represents the incident angle at the position of row i and column j. This can be determined by the design parameters of the laser scanning system.

[0151] Then, the water surface reflection coefficient and water surface transmission coefficient of the blue laser signal and the green laser signal at different incident angles are calculated. According to optical theory, the water surface reflection coefficient and It can be expressed as the reflected signal strength and With transmit power and The ratio of multiplying by the reflection phase factor. Water surface transmission coefficient and It can be calculated by subtracting the square root of the reflection coefficient from 1 and multiplying it by the transmission phase factor. These parameters can be obtained through experimental measurements. Finally, the calculated reflection coefficient and transmission coefficient are organized into a matrix , , and These reflection and transmission coefficient matrices are in the form of One to one correspondence.

[0152] The specific implementation of step S30 is: first, obtain the meteorological parameters of the detection area, including the atmospheric attenuation coefficient , and the atmospheric scattering coefficient , These parameters can be measured in real time by atmospheric monitoring equipment.

[0153] Then, the atmospheric transmission matrix is ​​established and . Describes the first pass atmospheric transmission losses from the laser to the water surface, including blue light and green light The loss, as well as the corresponding attenuation coefficient and scattering coefficient. Describes the secondary atmospheric transmission loss from the water surface to the receiver, also including blue light and green light The losses, as well as the corresponding attenuation coefficient and scattering coefficient, can be calculated based on the distance from the laser to the water surface. , and the distance from the water surface to the receiving end , calculated in combination with atmospheric parameters.

[0154] The specific implementation of step S40 is: establish a water surface wave model. First, obtain the amplitude of the water surface waves through the wave monitoring device. , angular frequency and wave number Then, based on these parameters, the water surface modulation functions of blue light and green light are calculated. and These modulation functions describe the modulation effect of water surface fluctuations on laser echo signals, which include the amplitude, frequency and wavelength characteristics of the waves, as well as the different attenuation coefficients of blue and green light. and . These modulation functions are organized into matrices The form of incident angle matrix One to one correspondence.

[0155] The specific implementation of step S50 is: first, according to the parameters obtained in steps S20 and S40, the water surface echo signal strength is calculated. and , and the bottom echo signal strength and . Water surface echo signal strength and transmission power and , reflection coefficient and , atmospheric transmission loss , , and , and the water surface modulation function and The bottom echo signal strength is also related to the bottom reflection coefficient. and and the water surface transmittance and related.

[0156] Then, calculate the blue-green dual wavelength signal intensity ratio , which reflects the water depth information. These ratios are organized into a matrix The form of incident angle matrix This ratio matrix is ​​an important parameter for subsequent water depth inversion.

[0157] The specific implementation of step S60 is: first, according to the optical characteristic parameters of the water body, including the absorption coefficient , and scattering coefficient , , calculate the downlink attenuation coefficient of blue light and green light , and the uplink attenuation coefficient , These attenuation coefficients are key parameters for water depth inversion, and they are related to the absorption and scattering properties of water and the refraction angle of light in water.

[0158] Then, these attenuation coefficients are organized into a matrix The form of incident angle matrix This attenuation coefficient matrix will play an important role in the subsequent water depth calculation equation.

[0159] The specific implementation of step S70 is: first, establish the relationship equation between the blue-green dual wavelength signal intensity ratio and the water depth. According to optical theory, this ratio With water depth , water surface transmittance ratio , bottom reflectivity ratio , and the difference in uplink and downlink attenuation coefficients between blue and green light There is a log-linear relationship.

[0160] On the other hand, the round-trip propagation time difference of the laser from the water surface to the bottom is Also with water depth and the speed of light in water , refractive index and the angle of incidence Therefore, two water depth calculation equations can be established, one based on the signal strength ratio and the other based on the time difference. The water depth information of the target area can be obtained by solving these two equations simultaneously.

[0161] The specific implementation of step S80 is: according to the two water depth calculation equations established in step S70, various parameters that have been obtained are used to solve them. First, according to the blue-green dual wavelength signal intensity ratio , water surface transmission coefficient ratio, bottom reflectivity ratio and uplink and downlink attenuation coefficient difference to calculate the water depth On the other hand, according to the round-trip propagation time difference of laser in water , the speed of light in water , refractive index and the angle of incidence , the water depth can also be calculated The two calculation results should be consistent. Of course, the average of the two calculation results can also be used. Next, the calculated water depth values ​​are organized into a matrix In the form of The water depth at the i-th row and j-th column of the corresponding detection area.

[0162] The specific implementation method of step S90 is: the water depth data matrix obtained in step S80 Grid interpolation is performed to generate a high-precision water depth topographic map. First, the weighted distance interpolation method is used to calculate the water depth value of the known point. and the distance to the interpolation point , calculate the interpolation point The water depth . Weight function Can be taken as The normalized form of .

[0163] The water depth data obtained by interpolation calculation is sorted into a new water depth terrain matrix , where each element represents the water depth value at the position of the i-th row and the j-th column after interpolation. In this way, a high-precision water depth topographic map of the target water area is obtained.

[0164] A second aspect of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores program instructions, and when the program instructions are run in a computer, they are used to execute the above-mentioned remote sensing water depth detection method based on blue-green laser.

[0165] A third aspect of the present invention provides a blue-green laser-based remote sensing water depth detection system, which includes the above-mentioned computer-readable storage medium.

[0166] Specifically, the principle of the present invention is to make full use of the difference in the propagation characteristics of blue light and green light in water, and to comprehensively model and parameterize the complex underwater remote sensing environment by establishing mathematical models for different physical processes, thereby achieving accurate water depth inversion.

[0167] First, an adjustable angle laser scanning system is used to obtain the water surface and bottom reflection echo data at different incident angles. In this way, a laser incident angle matrix can be established to describe the incident angle distribution of the laser in the entire detection area. Then, according to optical theory, the water surface reflection coefficient and water surface transmission coefficient of blue and green light at different incident angles are calculated. These parameters can be obtained through experimental measurement and organized into the form of reflection coefficient matrix and transmission coefficient matrix.

[0168] Secondly, the meteorological parameters of the detection area are obtained, including the atmospheric attenuation coefficient and scattering coefficient. According to the distance from the laser to the water surface and the distance from the water surface to the receiving end, the atmospheric transmission matrix is ​​established to describe the first-pass and second-pass transmission losses of the laser signal in the atmosphere. These loss models can effectively compensate for the attenuation effect of the atmosphere on the laser signal.

[0169] In addition, the present invention also establishes a water surface fluctuation model to describe the modulation effect of water surface fluctuation on blue and green light echo signals. This model takes into account the amplitude, frequency and wavelength characteristics of water surface waves, as well as the different attenuation characteristics of the two wavelength lasers, which helps to accurately separate the water surface reflection signal and the bottom reflection signal.

[0170] Based on the various parameters obtained above, the present invention calculates the blue-green dual-wavelength signal intensity ratio matrix. This ratio matrix reflects the water depth information and is the key to subsequent water depth inversion. At the same time, the optical characteristic parameters of the target water area, including the absorption coefficient and the scattering coefficient, are also obtained to calculate the uplink and downlink attenuation coefficients of blue and green light in water.

[0171] Finally, the present invention establishes a water depth calculation equation group based on the signal intensity ratio and the round-trip propagation time difference of the laser in the water. By solving this equation group, the accurate water depth data of the target water area can be obtained. At the same time, the water depth data is gridded by using the weighted distance interpolation method to generate a high-precision water depth topographic map.

[0172] The following is an example of a specific application scenario of the present invention: detailed underwater topographic mapping is carried out in a bay. The bay has complex topography, with water depths ranging from 10 meters to 80 meters. At the same time, affected by factors such as tides and monsoons, the water surface fluctuates violently. In order to obtain a high-precision water depth topographic map of the bay, the researchers decided to use the remote sensing water depth detection method based on blue-green laser proposed in the present invention for measurement.

[0173] First, the researchers built a blue-green dual-wavelength laser scanning system. The system includes two laser emission modules, which output blue laser with a wavelength of 450nm and green laser with a wavelength of 532nm, and the output power of each is 200W. The laser scanning module can control the laser incident angle to continuously adjust between 0° and 85°. The receiving module uses two highly sensitive photodetectors to receive the reflected echo signals of blue light and green light respectively. At the same time, the system is also equipped with auxiliary sensors such as meteorological monitoring equipment, wave monitoring equipment, and water quality optical parameter measuring instruments.

[0174] Entering the measurement phase, the researchers first determined the scope of the detection area, which was divided into 50 rows and 50 columns, with a total of 2,500 grid cells. The horizontal resolution of each grid cell is 10m×10m. Then, the laser scanning module was started to scan each grid cell in turn in the angle range of 0° to 85° with a step size of 1°, recording the water surface reflection echo signal of blue and green light and the water bottom reflection echo signal. At the same time, the meteorological monitoring equipment monitored the atmospheric parameters of the detection area in real time, the wave monitoring equipment measured the characteristic parameters of the water surface waves, and the water quality optical parameter measuring instrument obtained the absorption and scattering coefficients of the target sea area.

[0175] Next, the researchers processed and analyzed the acquired data. First, they established a laser incident angle matrix. , each element Represents the incident angle of the grid cell in the i-th row and j-th column.

[0176] ;

[0177] Then, based on the experimental measurement data, the water surface reflection coefficient matrix of blue light and green light at different incident angles was calculated. , And the water surface transmission coefficient matrix , Taking the grid cell in row 1 and column 1 as an example, its blue light reflection coefficient is , green light reflection coefficient , blue light transmission coefficient , green light transmission coefficient .

[0178] Figure 2 The transmission characteristics of blue light and green light at different incident angles are described. The figure shows the change in transmission coefficient of blue light with a wavelength of 450nm and green light with a wavelength of 532nm in the range of 0° to 85°, reflecting the influence of the incident angle on the laser transmission efficiency.

[0179] Meteorological monitoring data show that the atmospheric attenuation coefficient in the bay detection area is km , km , the atmospheric scattering coefficient is km , km . Height of laser from water surface m, height from water surface to receiving end m. Based on this, the atmospheric transmission matrix can be established and , where the first row and first column element , , , , , .

[0180] Wave monitoring results show that there are three main wave components on the water surface of the bay, and their characteristic parameters are: m, rad / s, rad / m; m, rad / s, rad / m; m, rad / s, rad / m. Based on this, the water surface wave modulation matrix can be established , where the first row and first column element , , , .

[0181] The results of water quality optical parameter measurements show that the absorption coefficient of the bay water is m , m , the scattering coefficient is m , m Based on this, the downward attenuation coefficient and upward attenuation coefficient of blue light and green light in water can be calculated to form an attenuation coefficient matrix , where the first row and first column element m , m , m , m .

[0182] Figure 3 It shows the variation of the absorption coefficient of water quality optical parameters with water depth. Figure 4 The two figures show the variation of the scattering coefficient of water quality optical parameters with water depth. The two figures intuitively reflect the depth distribution law of water quality optical characteristics.

[0183] With the above parameters, researchers can calculate the blue-green dual-wavelength signal intensity ratio matrix according to the method proposed by the present invention. Taking the grid cell in row 1 and column 1 as an example, the signal intensity of blue light reflected from the water surface is W, green light water surface reflection signal strength W, blue light underwater reflection signal strength W, green light underwater reflection signal strength W. Then the blue-green dual-wavelength signal intensity ratio of the grid unit is:

[0184] ;

[0185] Figure 5 The figure shows the relationship between the blue-green laser signal intensity ratio and water depth. The figure shows the ratio change curves under three different incident angles (0°, 30°, and 60°), showing that as the water depth increases, the signal intensity ratio decays exponentially.

[0186] Arrange the ratio calculation results of all grid cells into a matrix , as shown in Table 1 below:

[0187] Table 1 Matrix Data Sheet

[0188] Row / Column 1 2 3 … 50 1 1.25 1.22 1.20 … 1.15 2 1.27 1.24 1.21 … 1.16 3 1.29 1.26 1.23 … 1.17 … … … … … … 50 1.35 1.32 1.29 … 1.22

[0189] According to step S70, the researchers established a water depth calculation equation group based on the blue-green dual-wavelength signal intensity ratio:

[0190] ;

[0191] ;

[0192] Among them, the bottom reflectivity ratio , the speed of light in water m / s, refractive index of water .

[0193] The matrix , And other known parameters into the above equations, we can solve the water depth of each grid cell For example, the water depth of the grid cell in row 1 and column 1 is 35.2 m. Arrange the water depth values ​​of all grid cells into a water depth matrix. , as shown in Table 2 below:

[0194] Table 2 Water depth matrix

[0195] Row / Column 1 2 3 … 50 1 35.2 36.1 37.0 … 41.5 2 34.8 35.7 36.6 … 41.0 3 34.4 35.3 36.2 … 40.5 … … … … … … 50 32.1 33.0 33.9 … 38.6

[0196] Finally, the researchers used the weighted distance interpolation method to calculate the water depth matrix. A high-precision bathymetric topographic map of the bay was generated. The map not only shows the topographical overview of the entire bay, but also the spatial resolution of the bathymetric data reaches 10m×10m, meeting the needs of fine underwater mapping.

[0197] Through the method proposed in this invention, researchers successfully obtained a high-precision bathymetric topographic map of the bay. Figure 6 The figure shows the water depth distribution of 50×50 grid cells in the measurement area. The color gradient and three-dimensional surface intuitively show the undulating changes in the bottom terrain of the bay.

[0198] Compared with the traditional single-wavelength laser water depth measurement, this method can effectively compensate for the influence of the atmosphere and water on the laser signal, make full use of the difference in the propagation characteristics of blue light and green light in water, and achieve more accurate and reliable water depth measurement. In particular, the modeling and compensation of water surface fluctuations make this method applicable to complex marine environments. In addition, this method uses laser scanning technology to comprehensively map the entire sea area, providing richer and more detailed water depth information, meeting the needs of marine mapping and other fields.

[0199] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A remote sensing water depth detection method based on blue-green laser, characterized in that: The following steps are involved: S10, obtaining a blue laser signal and a green laser signal with known transmission power, and collecting water surface reflection echo data and water bottom reflection echo data at different incident angles; S20, establishing a laser incident angle matrix, and calculating the water surface reflection coefficient and water surface transmission coefficient of the blue laser signal and the green laser signal at different incident angles; S30, obtaining meteorological parameters of the detection area, establishing an atmospheric transmission matrix, and calculating the first-pass transmission loss of the blue laser signal and the green laser signal from the transmitting end to the water surface and the second-pass transmission loss from the water surface to the receiving end; S40, establishing a water surface fluctuation model based on the laser incident angle matrix, and calculating the modulation function of the water surface fluctuation on the blue laser and green laser echo signals; S50, according to the water surface reflection coefficient and the water surface transmission coefficient, combined with the modulation function, separating the water surface echo signal and the bottom echo signal after penetrating the water body, and establishing a blue-green dual-wavelength signal intensity ratio matrix; S60, establishing a water optical property database, obtaining the extinction coefficient of the target water area, and calculating the downlink attenuation coefficient of the blue laser and the green laser from the water surface to the bottom and the uplink attenuation coefficient from the bottom to the water surface; S70, establishing a water depth calculation equation group based on the blue-green dual-wavelength signal intensity ratio matrix and the downlink attenuation coefficient and the uplink attenuation coefficient; S80, solving the water depth calculation equations according to the time difference between the emitted laser signal passing through the water surface and the bottom echo signal passing through the water surface and the equivalent propagation speed of the laser in the water, to obtain the water depth data of the target water area; S90, performing grid interpolation processing on the water depth data to generate a high-precision water depth topographic map of the target water area; Wherein, the meteorological parameters include atmospheric attenuation coefficient and atmospheric scattering coefficient; The laser incident angle matrix is ​​specifically expressed as follows: ; In the formula, Indicates Line The incident angle of the column, in degrees, ranging from 0 to 90 degrees; Indicates the number of rows in the scan area; Indicates the number of columns in the scan area; In and The corresponding scanning areas are Row and The angle of incidence of the column position; The calculation of reflection coefficient and transmission coefficient is specifically expressed as follows: ; ; ; ; In the formula, and are the water surface reflectance coefficients for blue and green light, respectively; and are the water surface transmittance coefficients for blue and green light, respectively; and are the reflected signal intensities of blue light and green light, respectively; and are the emission powers of blue light and green light respectively; and are the reflection phases of blue and green light, respectively; and are the transmission phases of blue and green light, respectively; is the laser incident angle; and In and Represent blue light and green light respectively; Represents the incident angle, which is the same as the incident angle matrix correspond; and Indicates the incident angle The reflected signal strength under ; and are the emission powers of the blue and green lasers, respectively; and Indicates the incident angle The reflection phase under ; and Indicates the incident angle The transmission phase under Among them, the calculation of atmospheric transmission loss is specifically expressed as follows: ; ; ; ; In the formula, and are the first-pass transmission losses of blue light and green light respectively; and are the secondary transmission losses of blue light and green light respectively; and are the atmospheric attenuation coefficients of blue and green light, respectively; and are the atmospheric scattering coefficients for blue and green light, respectively; is the distance from the laser to the water surface; is the distance from the water surface to the receiver; is the laser emission angle; Among them, the water surface fluctuation model is specifically expressed as follows: ; ; In the formula, and are the water surface modulation functions for blue light and green light respectively; For the The amplitude of each wave component; For the Angular frequency of each wave component; For the The wave number of each wave component; and are the fluctuation attenuation coefficients of blue light and green light, respectively; for time; is the spatial coordinate; The signal strength calculation is specifically expressed as follows: ; ; ; ; ; In the formula, and are the water surface echo signal intensities of blue light and green light respectively; and are the bottom echo signal intensities of blue light and green light respectively; and are the reflection coefficients of blue light and green light at the bottom of water, respectively; It is the ratio of blue and green dual wavelength signal intensity.

2. A method for remote sensing water depth detection based on blue-green laser according to claim 1, characterized in that: The attenuation coefficient calculation is specifically expressed as follows: ; ; ; ; In the formula, and are the downlink attenuation coefficients of blue light and green light, respectively; and are the uplink attenuation coefficients of blue light and green light, respectively; and are the absorption coefficients of blue light and green light, respectively; and are the scattering coefficients of blue light and green light, respectively; and are the refraction angles of blue light and green light in water respectively; and They are the propagation angles of blue light and green light in water after being reflected from the bottom of the water.

3. The method for remote sensing water depth detection based on blue-green laser according to claim 2 is characterized in that: The water depth calculation equations are specifically expressed as follows: ; ; In the formula, for water depth; is the speed of light in water; is the refractive index of water; For the time difference.

4. The method for remote sensing water depth detection based on blue-green laser according to claim 3 is characterized in that: The steps of solving the water depth calculation equations are specifically expressed as follows: ; or ; or ; The water depth data matrix is ​​specifically expressed as follows: ; In the formula, Indicates Line The water depth at the column location in meters.

5. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores program instructions, and when the program instructions are executed in a computer, they are used to execute the remote sensing water depth detection method based on blue-green laser according to any one of claims 1 to 4.

6. A remote sensing water depth detection system based on blue-green laser, characterized in that: Contains the computer-readable storage medium of claim 5.

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