CN117058532B - Method and system for inverting water depth and wave height based on sea wave and solar flare signals - Google Patents
Method and system for inverting water depth and wave height based on sea wave and solar flare signals Download PDFInfo
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Abstract
The invention provides a method and a system for inverting water depth and wave height based on sea wave and solar flare signals, wherein the method comprises the following steps: acquiring a multispectral image of a region to be detected; performing image preprocessing on the multispectral image to obtain relevant parameters of wave motion, calculating and processing by utilizing the relevant parameters of wave motion, and finally obtaining the high-resolution water depth of the whole image; acquiring the sea surface gradient of the area to be measured, and calculating the gradient standard deviation of the sea surface gradient; calculating the sea surface height standard deviation by combining the main wavelength and the gradient standard deviation; calculating a sea surface height autocorrelation function according to the sea surface height standard deviation; and processing the multispectral image of the sea surface height autocorrelation function, and calculating to obtain the wave height. The method and the device can acquire the water depth and the wave height by only utilizing the motion state of the sea wave on the optical image and flare forming information. Under the condition of no priori data, the water depth with high resolution and more accurate wave height data can be obtained.
Description
Technical Field
The invention belongs to the technical field of marine environment inversion, and particularly relates to a method and a system for inverting water depth and wave height based on sea wave and solar flare signals.
Background
The ocean is closely related to human production and life. The water depth and wave height are important ocean parameters, and have important influence on offshore navigation, marine fishery, coastal disaster early warning, offshore engineering and the like. The traditional shipborne sounding and buoy sounding have the defects of small coverage range and high acquisition cost. The passive optical remote sensing image is convenient to acquire, the analysis and interpretation work is simple, and the passive optical remote sensing image becomes an important means of ocean parameters gradually.
In consideration of the difficulty in acquiring various marine element data in dangerous or difficult-to-enter areas, the optical remote sensing image with higher spatial resolution can be utilized to obtain water depth and wave height data under the condition of no measured data. In areas lacking measured data, the methods of water depth optical remote sensing inversion are mainly divided into two types: one is based on the degree of attenuation of light in a body of water; the other is based on wave power parameters. The method has high requirements on water quality, which limits the application of the method in turbid water areas, and the method is independent of the quality and characteristics of the water, only focuses on the wave imaging quality on the image to acquire the wave motion parameters, and can be suitable for various water areas.
However, the inversion process for the water depth or wave height is complicated at present, so that the inversion time is long, and the water depth and wave height with high resolution cannot be obtained; meanwhile, the inversion between the water depth and the wave height does not have correlation, and two independent inversion programs exist for the water depth and the wave height, so that the research cost is improved. In addition, the current acquisition of water depth and wave height data is more dependent on field measured data, which limits the acquisition of the two types of data in the area without measured data. The solar flare imaging mechanism is the basis of wave height research, and the sea surface gradient is the key information for acquiring wave height. The solar light irradiates the sea surface with a specific slope inclination angle, is reflected by a mirror surface and enters a sensor, and forms solar flare on an optical image. Sea surface inclination, sensor and solar azimuth and altitude are all factors that affect solar flare formation. The formation of solar flares is independent of the specific states of the sea surface and the sensor, and contains rich sea state information. Therefore, the method and the system for inverting the water depth and the wave height based on the sea wave and solar flare signals are obtained.
Disclosure of Invention
The invention provides a method and a system for inverting water depth and wave height based on sea wave and solar flare signals, and aims to solve the problems that the existing inversion process of water depth or wave height is complex and the existing inversion process is not related to the existing inversion process.
In view of the above problems, the technical scheme provided by the invention is as follows:
in a first aspect, the present application provides a method for inverting water depth, wave height based on sea wave and solar flare signals, the method comprising:
acquiring a multispectral image of a region to be detected;
performing image preprocessing on the multispectral image to obtain wave motion related parameters, and calculating and processing by utilizing the wave motion related parameters to finally obtain the high-resolution water depth of the whole image, wherein the wave motion related parameters comprise main wave length, phase and wave velocity;
acquiring the sea surface gradient of the region to be detected, and calculating the gradient standard deviation of the sea surface gradient;
calculating the sea surface height standard deviation by combining the main wavelength and the gradient standard deviation;
calculating a sea surface height autocorrelation function according to the sea surface height standard deviation;
and processing the multispectral image of the sea surface height autocorrelation function, and calculating to obtain the wave height.
Further, the performing image preprocessing on the multispectral image to obtain related parameters of sea wave motion, and calculating by using the related parameters of sea wave motion to obtain water depth includes:
determining a sliding window of at least one n×n pixels for the multispectral image;
performing fast Fourier transform from an initial position based on a blue band image and a red band image of the multispectral image, and calculating a cross-correlation function of the blue band image and the red band image;
calculating the sea wave motion related parameters of the initial position;
calculating according to the related parameters of the sea wave motion to obtain the water depth;
giving at least four pixels in the center to the water depth at the position of the sliding window to obtain the water depth with high resolution;
and moving the sliding window to the next position by taking at least two pixels as sliding step length, and simultaneously continuing to execute the steps until the whole multispectral image is traversed, and finally obtaining the high-resolution water depth of the whole image.
Further, in the calculating the cross-correlation function between the blue band image and the red band image, the calculation formula is as follows:
wherein:representing a matrix of the blue band image after fast fourier transform;
representing a matrix of the red band image after fast fourier transform;
representing the conjugate matrix.
Further, in the calculating the parameter related to the sea wave motion of the initial position, a calculation formula is as follows:
wherein:representing the dominant wavelength;
representing sea wave in->Spatial frequency in the direction;
representing sea wave in->Spatial frequency in the direction;
wherein:representing phase;
wherein:the imaging time interval of the blue band image and the red band image is shown.
Further, the calculation is performed according to the related parameters of the sea wave motion, and the calculation formula is as follows in the water depth of the foundation:
wherein:representing the water depth;
representing wave velocity;
indicating the gravitational acceleration.
Further, in the calculating the sea surface height standard deviation by combining the main wavelength and the gradient standard deviation, the calculation formula is as follows:
wherein:represents the sea surface height standard deviation;
represents the standard deviation of the sea surface gradient data.
Further, in the calculating the sea surface height autocorrelation function according to the sea surface height standard deviation, the calculation formula is as follows:
wherein:representing a sea surface altitude autocorrelation function;
representation->Hysteresis variable in direction;
representation->Hysteresis variable in direction.
Further, the processing and calculating the multispectral image of the sea surface altitude autocorrelation function to obtain a wave height includes:
performing fast Fourier transform on the multispectral image with the sea surface height autocorrelation function again on the basis of N multiplied by N pixels to obtain a wave height frequency spectrum;
and calculating the wave height according to the wave height frequency spectrum.
Further, the calculation formula of the wave height mid-range according to the wave height frequency spectrum is as follows:
wherein:representing wave height;
representing the amplitude of the wave height spectrum;
representing the number of values for which the amplitude of the wave height spectrum is greater than 0.1.
In a second aspect, the present application provides a system for inverting water depth, wave height based on sea wave and solar flare signals, the system comprising:
the first acquisition module is configured to acquire a multispectral image of the region to be detected;
the image preprocessing module is configured to perform image preprocessing on the multispectral image to obtain wave motion related parameters, calculate and process the wave motion related parameters, and finally obtain the high-resolution water depth of the whole image, wherein the wave motion related parameters comprise main wave length;
a second acquisition module configured to acquire a sea surface gradient of the region to be measured and calculate a gradient standard deviation of the sea surface gradient;
a first calculation module configured to calculate a sea surface altitude standard deviation in combination with the main wavelength and the gradient standard deviation;
a second calculation module configured to calculate a sea surface altitude autocorrelation function from the sea surface altitude standard deviation;
and the processing module is configured to process the multispectral image of the sea surface altitude autocorrelation function and calculate the multispectral image to obtain the wave height.
Compared with the prior art, the beneficial effects of the technical scheme provided by the application at least comprise:
(1) The method and the device can acquire the water depth and the wave height by only utilizing the motion state of the sea wave on the optical image and flare forming information. Under the condition of no priori data, the water depth with high resolution and more accurate wave height data can be obtained.
(2) According to the method, the main wave length is used as the wave height inversion parameter to participate in the calculation of the surface height standard deviation, and the consistency of the water depth and the wave height inversion can be realized under the condition of no priori wave height data.
(3) The method combines the water depth and the wave height inversion process, and reduces the time and the complexity of a program caused by independent inversion of two data.
The foregoing description is only an overview of the present invention, and is intended to provide a better understanding of the technical means of the present invention, as it is embodied in the present specification, and is intended to provide a better understanding of the present invention with regard to the following specific examples.
Drawings
FIG. 1 is a flow chart of a method of inverting water depth and wave height based on sea wave and solar flare signals as disclosed in the present invention;
FIG. 2 is a schematic diagram of a technical route of the disclosed method for inverting water depth and wave height based on sea wave and solar flare signals;
FIG. 3 is a graph of the results of the shallow sea depth inversion disclosed in the present invention;
FIG. 4 is a scatter plot of shallow sea water depth assessment as disclosed herein;
FIG. 5 is a plot of shallow sea wave height evaluation scattergrams in accordance with the present disclosure;
fig. 6 is a schematic diagram of a system for inverting water depth and wave height based on sea wave and solar flare signals.
Reference numerals illustrate: 100. a first acquisition module; 200. an image preprocessing module; 300. a second acquisition module; 400. a first computing module; 500. a second computing module; 600. and a processing module.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, based on the embodiments of the invention, which are apparent to those of ordinary skill in the art without inventive faculty, are intended to be within the scope of the invention.
Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, based on the embodiments of the invention, which are apparent to those of ordinary skill in the art without inventive faculty, are intended to be within the scope of the invention.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
The method selects a certain island to carry out water depth inversion research, and takes a Sentinel-2 multispectral image as a research image. Taking other buoy sites as an example, the wave height inversion is performed in view of the fact that the wave height buoy data are not distributed in the water depth research area.
In fig. 2, FFT means fast fourier transform.
Example 1
Referring to fig. 1-2, the invention provides a technical scheme that: a method of inverting water depth and wave height based on sea wave and solar flare signals, the method comprising:
s1, acquiring multispectral images of a region to be detected.
S2, performing image preprocessing on the multispectral image to obtain wave motion related parameters, calculating and processing by utilizing the wave motion related parameters, and finally obtaining the high-resolution water depth of the whole image, wherein the wave motion related parameters comprise main wave length, phase and wave velocity.
S3, acquiring the sea surface gradient of the region to be detected, and calculating the gradient standard deviation of the sea surface gradient; the sea surface gradient comprises a solar zenith angle, a solar azimuth angle, a sensor azimuth angle and a sensor zenith angle.
And S4, calculating the sea surface height standard deviation by combining the main wavelength and the gradient standard deviation.
And S5, calculating a sea surface height autocorrelation function according to the sea surface height standard deviation.
S6, processing the multispectral image of the sea surface height autocorrelation function, and calculating to obtain wave height.
Specifically, the method and the device can acquire the water depth and the wave height by only utilizing the motion state of the sea wave on the optical image and flare forming information. Under the condition of no priori data, the water depth with high resolution and more accurate wave height data can be obtained.
In a preferred embodiment of the present application, the performing image preprocessing on the multispectral image to obtain a related parameter of ocean wave motion, and calculating by using the related parameter of ocean wave motion to obtain a water depth includes:
determining a sliding window of at least one n×n pixels for the multispectral image; where fast fourier transforms are used for more efficient calculations, then N needs to be an integer power of 2.
And performing fast Fourier transform from an initial position based on the blue band image and the red band image of the multispectral image, and calculating a cross-correlation function of the blue band image and the red band image.
And calculating the sea wave motion related parameters of the initial position.
Calculating according to the related parameters of the sea wave motion to obtain the water depth; the method comprises the steps of calculating by combining the data such as the wavelength, the phase and the like of the stay position of each sliding window.
Giving at least four pixels in the center to the water depth at the position of the sliding window to obtain the water depth with high resolution; wherein, at least four pixels can be arranged in two upper and two lower, namely, the arrangement of the 'field' shape.
And moving the sliding window to the next position by taking at least two pixels as sliding step length, and simultaneously continuing to execute the steps until the whole multispectral image is traversed, and finally obtaining the high-resolution water depth of the whole image.
In particular, the resolution of the water depth inversion can be improved by determining a sliding window for performing a fast fourier transform. And the resolution of the water depth result is the same as the sliding step length, so that the problem that the water depth result is overlapped is solved, the water depth with high resolution can be obtained, and the accuracy of the result can be ensured.
In a preferred embodiment of the present application, in the calculating the cross-correlation function between the blue band image and the red band image, the calculation formula is as follows:
wherein:representing a matrix of the blue band image after fast fourier transform;
representing the fast of red band imageA matrix after fourier transform;
representing the conjugate matrix.
In a preferred embodiment of the present application, in the calculating the parameter related to the ocean wave motion of the initial position, a calculation formula is as follows:
wherein:representing the dominant wavelength;
representing sea wave in->Spatial frequency in the direction;
representing sea wave in->Spatial frequency in the direction;
wherein:representing phase;
wherein:the imaging time interval of the blue band image and the red band image is shown.
In a preferred embodiment of the present application, the calculation is performed according to the parameters related to the ocean wave motion, so as to obtain a basic water depth, where the calculation formula is as follows:
wherein:representing the water depth;
representing wave velocity;
indicating the gravitational acceleration.
In a preferred embodiment of the present application, in the calculating the sea surface height standard deviation by combining the main wavelength and the gradient standard deviation, the calculation formula is as follows:
wherein:represents the sea surface height standard deviation;
represents the standard deviation of the sea surface gradient data.
In a preferred embodiment of the present application, in the calculating the sea surface altitude autocorrelation function according to the sea surface altitude standard deviation, a calculation formula is as follows:
wherein:representing a sea surface altitude autocorrelation function;
representation->Hysteresis variable in direction;
representation->Hysteresis variable in direction.
In a preferred embodiment of the present application, the processing and calculating the multispectral image of the sea surface altitude autocorrelation function to obtain a wave height includes:
performing fast Fourier transform on the multispectral image with the sea surface height autocorrelation function again on the basis of N multiplied by N pixels to obtain a wave height frequency spectrum; here, n×n is the same as n×n described above.
And calculating the wave height according to the wave height frequency spectrum.
In a preferred embodiment of the present application, the calculation formula of the wave height according to the wave height spectrum is as follows:
representing wave height;
representing wave height spectrumAmplitude of (2);
representing the number of values for which the amplitude of the wave height spectrum is greater than 0.1.
In particular, values with an amplitude below 0.1 should be directly screened out, since they contain insufficient information, or are noisy.
Next, referring to fig. 3 to 4, shallow sea water depth and wave height inversion results and accuracy are evaluated.
The method is used for carrying out the inversion of the global water depth and the wave height of the region to be detected, and the inversion result of the shallow sea water depth (less than or equal to 40 m) is shown in the figure 3. The size of the region to be measured is 2400m x 1600m, i.e. 240 x 160 picture elements. The assignment characteristic of the sliding window can lead to that the water depth value of the buffer area with the length of 7 pixels at the edge of the image can not be obtained, so that the used image with 240×160 pixels can finally obtain 226×146 water depth images with the spatial resolution of 20 m.
The inversion water depth gradually increases with increasing offshore distance. The coral reef exists in the sea area of the area, so that the underwater topography fluctuates greatly. The spatial resolution of the water depth result is improved, so that the underwater topography is displayed more carefully.
And uniformly selecting a certain number of ship-borne multi-beam actually measured water depth points in the water area of the area to be measured, comparing the water depth points with the water depth value of the position of the points obtained through the method, and quantitatively evaluating the water depth inversion precision. The water depth result precision is evaluated by using an average absolute error (Mean Absolute Error) and an average error (Mean Relative Error), and the average absolute error and average error are specifically expressed as follows:
wherein:indicate->Actually measured water depth values of the individual points;
indicate->Inversion water depth values of the individual points;
indicating the number of test points.
As can be seen from fig. 4, the average absolute error is 27.7% and the average relative error is 6.10m, and reliable accuracy can be achieved without any prior water depth data and with a large water depth interval span. The method has higher precision within 0-20 m, and the scatter diagram is similar to the trend of y=x. At a depth of 20m, scattered points are relatively scattered in the graph, and the precision is shallower than 20 m. The depth of the water depth inversion can reach 40m, the application range of the general optical water depth inversion method is 20m or less in shallow water, and larger errors can be caused by too deep water. The application can reach a certain precision even at a depth of 20 m.
As can be seen from fig. 5, the average absolute error is 0.18m, the average relative error is 16.33%, and a more reliable wave height inversion accuracy is obtained. Under the condition that sea state data such as wave height data and wind speed are unknown, the local main wave length obtained in the high-resolution water depth inversion process is used as a key parameter in the calculation of the sea surface height autocorrelation function, so that more accurate wave height can be obtained, and meanwhile, the consistency inversion of the water depth and the wave height can be realized.
Example two
Referring to fig. 6, the present invention further provides a technical solution: a system for inverting water depth and wave height based on sea wave and solar flare signals, the system comprising:
the first acquisition module is configured to acquire a multispectral image of the region to be detected;
the image preprocessing module is configured to perform image preprocessing on the multispectral image to obtain wave motion related parameters, calculate and process the wave motion related parameters, and finally obtain the high-resolution water depth of the whole image, wherein the wave motion related parameters comprise main wave length;
a second acquisition module configured to acquire a sea surface gradient of the region to be measured and calculate a gradient standard deviation of the sea surface gradient;
a first calculation module configured to calculate a sea surface altitude standard deviation in combination with the main wavelength and the gradient standard deviation;
a second calculation module configured to calculate a sea surface altitude autocorrelation function from the sea surface altitude standard deviation;
and the processing module is configured to process the multispectral image of the sea surface altitude autocorrelation function and calculate the multispectral image to obtain the wave height.
In the foregoing detailed description, various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the subject matter require more features than are expressly recited in each claim. Rather, as the following claims reflect, invention lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate preferred embodiment of this invention.
Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. The processor and the storage medium may reside as discrete components in a user terminal.
For a software implementation, the techniques described herein may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. These software codes may be stored in memory units and executed by processors. The memory unit may be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor via various means as is known in the art.
The foregoing description includes examples of one or more embodiments. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned embodiments, but one of ordinary skill in the art may recognize that many further combinations and permutations of various embodiments are possible. Accordingly, the embodiments described herein are intended to embrace all such alterations, modifications and variations that fall within the scope of the appended claims. Furthermore, as used in the specification or claims, the term "comprising" is intended to be inclusive in a manner similar to the term "comprising," as interpreted when employed as a transitional word in a claim. Furthermore, any use of the term "or" in the claims and specification is intended to mean "non-exclusive or".
Claims (7)
1. A method for inverting water depth and wave height based on sea wave and solar flare signals, the method comprising:
acquiring a multispectral image of a region to be detected;
performing image preprocessing on the multispectral image to obtain wave motion related parameters, and calculating and processing by utilizing the wave motion related parameters to finally obtain the high-resolution water depth of the whole image, wherein the wave motion related parameters comprise main wave length, phase and wave velocity;
the method specifically comprises the following steps:
determining a sliding window of at least one n×n pixels for the multispectral image;
performing fast Fourier transform from an initial position based on a blue band image and a red band image of the multispectral image, and calculating a cross-correlation function of the blue band image and the red band image;
calculating the sea wave motion related parameters of the initial position;
calculating according to the related parameters of the sea wave motion to obtain the water depth;
giving at least four pixels in the center to the water depth at the position of the sliding window to obtain the water depth with high resolution;
moving the sliding window to the next position by taking at least two pixels as sliding step length, and simultaneously continuing to execute the steps until the whole multispectral image is traversed, and finally obtaining the high-resolution water depth of the whole image;
acquiring the sea surface gradient of the region to be detected, and calculating the gradient standard deviation of the sea surface gradient;
calculating the sea surface height standard deviation by combining the main wavelength and the gradient standard deviation;
calculating a sea surface height autocorrelation function according to the sea surface height standard deviation;
processing the multispectral image of the sea surface height autocorrelation function, and calculating to obtain wave height;
the method specifically comprises the following steps:
performing fast Fourier transform on the multispectral image with the sea surface height autocorrelation function again on the basis of N multiplied by N pixels to obtain a wave height frequency spectrum;
calculating the wave height according to the wave height frequency spectrum; wherein, the calculation formula is as follows:
;
wherein:representing wave height;
representing the amplitude of the wave height spectrum;
representing the number of values for which the amplitude of the wave height spectrum is greater than 0.1.
2. The method for inverting water depth and wave height based on sea wave and solar flare signals according to claim 1, wherein in the calculating the cross-correlation function of the blue band image and the red band image, the calculation formula is as follows:
；
wherein:representing blue band images via fast Fourier transformA matrix of the following;
representing a matrix of the red band image after fast fourier transform;
representing the conjugate matrix.
3. The method for inverting water depth and wave height based on sea wave and solar flare signals according to claim 2, wherein in the calculating the sea wave motion related parameter of the initial position, a calculation formula is as follows in sequence:
;
wherein:representing the dominant wavelength;
representing sea wave in->Spatial frequency in the direction;
representing sea wave in->Spatial frequency in the direction;
;
wherein:representing phase;
;
wherein:the imaging time interval of the blue band image and the red band image is shown.
4. The method for inverting water depth and wave height based on sea wave and solar flare signals according to claim 3, wherein the calculation is performed according to the sea wave motion related parameters to obtain a basic water depth, and the calculation formula is as follows:
;
wherein:representing the water depth;
representing wave velocity;
indicating the gravitational acceleration.
5. The method for inverting water depth and wave height based on sea wave and solar flare signals according to claim 4, wherein in the calculation of the sea surface height standard deviation by combining the main wave length and the gradient standard deviation, the calculation formula is as follows:
;
wherein:represents the sea surface height standard deviation;
represents the standard deviation of the sea surface gradient data.
6. The method for inverting water depth and wave height based on sea wave and solar flare signals according to claim 5, wherein in the calculation of the sea surface height autocorrelation function according to the standard deviation of sea surface height, the calculation formula is as follows:
；
wherein:representing a sea surface altitude autocorrelation function;
representation->Hysteresis variable in direction;
representation->Hysteresis variable in direction.
7. A system for inverting water depth and wave height based on sea wave and solar flare signals, the system comprising:
the first acquisition module is configured to acquire a multispectral image of the region to be detected;
the image preprocessing module is configured to perform image preprocessing on the multispectral image to obtain wave motion related parameters, calculate and process the wave motion related parameters, and finally obtain the high-resolution water depth of the whole image, wherein the wave motion related parameters comprise main wave length;
the module specifically comprises:
determining a sliding window of at least one n×n pixels for the multispectral image;
performing fast Fourier transform from an initial position based on a blue band image and a red band image of the multispectral image, and calculating a cross-correlation function of the blue band image and the red band image;
calculating the sea wave motion related parameters of the initial position;
calculating according to the related parameters of the sea wave motion to obtain the water depth;
giving at least four pixels in the center to the water depth at the position of the sliding window to obtain the water depth with high resolution;
moving the sliding window to the next position by taking at least two pixels as sliding step length, and simultaneously continuing to execute the steps until the whole multispectral image is traversed, and finally obtaining the high-resolution water depth of the whole image;
a second acquisition module configured to acquire a sea surface gradient of the region to be measured and calculate a gradient standard deviation of the sea surface gradient;
a first calculation module configured to calculate a sea surface altitude standard deviation in combination with the main wavelength and the gradient standard deviation;
a second calculation module configured to calculate a sea surface altitude autocorrelation function from the sea surface altitude standard deviation;
the processing module is configured to process the multispectral image of the sea surface height autocorrelation function and calculate the multispectral image to obtain wave height;
the module specifically comprises:
performing fast Fourier transform on the multispectral image with the sea surface height autocorrelation function again on the basis of N multiplied by N pixels to obtain a wave height frequency spectrum;
calculating the wave height according to the wave height frequency spectrum; wherein, the calculation formula is as follows:
;
wherein:representing wave height;
representing the amplitude of the wave height spectrum;
representing the number of values for which the amplitude of the wave height spectrum is greater than 0.1.
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