Dual-frequency high-frequency ground wave radar radial current fusion method

Abstract

The application discloses a dual-frequency high-frequency ground wave radar radial current fusion method, which comprises the following steps: obtaining two different radial current fields obtained by respectively irradiating two different frequency radar electromagnetic waves to the sea; spatially registering the two different radial current fields to the same spatial resolution; fusing the two spatially registered radial current fields based on a time-space linear fitting method; and performing spatial interpolation on the fused radial current field based on an inverse distance weighting method to obtain a final radial current field. Therefore, the application fully utilizes the uniformity and slow change of the sea current in time and space, simultaneously introduces time and space multi-dimensional information, and fuses to obtain an accurate ocean radial current field.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radio ocean remote sensing and digital signal technology, in particular to a dual-frequency high-frequency ground wave radar radial current fusion method. BACKGROUND

[0002] High-frequency ground wave radar has unique advantages in the inversion of ocean surface flow field. Its inversion results have wide coverage, high resolution, strong real-time performance, and relatively reliable accuracy. The radar detection area is divided into independent grid points according to a certain spatial resolution. By using ocean echoes (radar electromagnetic waves irradiated on sea waves to produce echoes), the flow velocity and direction corresponding to each grid point are inverted. The point set composed of the flow data of all effective grid points is the surface flow field inverted by the radar.

[0003] High-frequency ground wave radar can extract the radial component of the superimposed ocean current on the first-order wave (the projection of the real ocean current along the radar beam direction) by using the Doppler effect of the first-order wave (the first-order wave is a wave with a wavelength equal to half the wavelength of the radar electromagnetic wave, and propagates along the radar beam direction). The first-order wave is not widely and uniformly distributed in the radar detection range, and its distribution is closely related to the wave spectrum distribution of the detection sea area. For a commonly used single-frequency high-frequency ground wave radar, once a specific main frequency is set, the first-order wave frequency that resonates with it is also determined. However, in many cases, the first-order wave corresponding to the radar main frequency is not saturated in the detection range, and its development is insufficient, resulting in weak radar echoes. In this case, there are fewer effective first-order waves that can be used for current inversion, resulting in many empty areas in the inverted flow field. (That is, in the radar detection range, there are places where the first-order wave exists, and the radial current in this area can be inverted; but in some places, there is no or does not meet the conditions, and the radial current in this area cannot be inverted.) In extreme cases, there may be a large number of singular values or false alarms. Although post-processing quality control techniques can eliminate these singular values as much as possible, this will further reduce the data available for inversion, thereby reducing the area of the actual inverted flow field. Secondly, single-frequency radar is also affected by ionospheric interference, radio frequency interference or other electromagnetic interference. These interferences will seriously weaken the quality of ocean echoes at some moments, and thus reduce the overall quality of the inverted flow field. In summary, single-frequency high-frequency ground wave radar is limited by the distribution of wave spectrum and electromagnetic interference when inverting the radial flow field, and it is difficult to continuously provide high-quality inversion results.

[0004] Since the dual-frequency HFW radar can greatly alleviate the problems brought by the single-frequency HFW radar. The dual-frequency HFW radar can radiate two different frequencies of high-frequency electromagnetic waves to its detection range at the same time, and correspondingly, two different frequency first-order ocean waves will resonate with the radar electromagnetic waves, and then the two different radial flow fields can be finally inverted from the radar echo. Because the spatial distribution of the first-order ocean waves of different frequencies is inconsistent, which causes the spatial distribution of the two different radial flow fields to be inconsistent. But the real flow field in the radar detection range is uniquely determined, and theoretically the radial flow field should also be unique. Therefore, the radial flow fields obtained by different frequencies are actually complementary and corrected to each other. Although the radial flow fields corresponding to different frequencies have slight differences in water depth, but this difference can be ignored in engineering application (much smaller than the radar detection error). The key challenge is how to effectively fuse the radial flow fields of the two different frequencies to make the final flow field more complete and accurate, which is a core problem in the dual-frequency ocean current detection technology. SUMMARY

[0005] The application provides a dual-frequency HFW radar radial ocean current fusion method, which fully utilizes the uniformity and slow change of ocean currents in time and space, and introduces time and spatial multi-dimensional information at the same time to obtain an accurate ocean radial flow field.

[0006] In a first aspect, a dual-frequency HFW radar radial ocean current fusion method is provided, comprising the following steps:

[0007] Obtaining two different radial flow fields inverted by respectively irradiating two different frequency radar electromagnetic waves to the ocean;

[0008] Spatially registering the two different radial flow fields to the same spatial resolution;

[0009] Based on the spatiotemporal linear fitting method, the two radial flow fields after spatial registration are fused;

[0010] Based on the inverse distance weighted method, the fused radial flow field is spatially interpolated to obtain the final radial flow field.

[0011] In some embodiments, the step of spatially registering the two different radial flow fields to the same spatial resolution comprises the following steps:

[0012] Obtaining the spatial resolution corresponding to the two different radial flow fields respectively, wherein the two spatial resolutions are defined as a first spatial resolution and a second spatial resolution, and the first spatial resolution is higher than the second spatial resolution;

[0013] Re-determine the resolution grid division of the radar electromagnetic wave detection range corresponding to the second spatial resolution based on the first spatial resolution, and re-assign the distance element and angle element corresponding to each grid point in the grid;

[0014] If one of the grid points to be registered finds a grid point with position coincidence in the radial flow field under the second spatial resolution, the distance element and angle element corresponding to the found grid point are assigned as the distance element and angle element of the grid point to be registered;

[0015] If one of the grid points to be registered does not find a grid point with position coincidence in the radial flow field under the second spatial resolution, interpolation calculation and assignment of the grid point to be registered are required.

[0016] In some embodiments, the step of performing interpolation calculation and assignment on the grid point to be registered specifically includes the following steps:

[0017] If a target rectangle that satisfies the preset surrounding condition and surrounds the grid point to be registered is found in the radial flow field under the second spatial resolution, the grid point to be registered is calculated by two-dimensional linear interpolation method based on the target rectangle;

[0018] If a target rectangle that satisfies the preset surrounding condition and surrounds the grid point to be registered is not found in the radial flow field under the second spatial resolution, and if the grid point to be registered is found to be located on the line connecting two grid points that satisfy the preset distance condition, the grid point to be registered is calculated by one-dimensional linear interpolation method based on the two found grid points;

[0019] If a target rectangle that satisfies the preset surrounding condition and surrounds the grid point to be registered is not found in the radial flow field under the second spatial resolution, and if the grid point to be registered is not found to be located on the line connecting two grid points that satisfy the preset distance condition, a reference point dependent on the grid point to be registered is found, and if the distance between the found reference point and the grid point to be registered is less than a distance threshold, the distance element and angle element corresponding to the reference point are assigned as the distance element and angle element of the grid point to be registered.

[0020] In some embodiments, the grid point to be registered is calculated by two-dimensional linear interpolation method based on the target rectangle The calculation formula is as follows:

[0021]

[0022] Wherein, , ;

[0023] In the formula, is the distance element and angle element of the grid point to be registered; respectively are four grid points of the target rectangle respectively; respectively are radial flows corresponding to the two grid points respectively; is a distance resolution in the second spatial resolution; is an angle resolution in the second spatial resolution.

[0024] In some embodiments, the step of interpolating the to-be-registered grid point based on the one-dimensional linear interpolation method and according to the two found grid points specifically comprises the following steps:

[0025] According to the to-be-registered grid point , the two found grid points are respectively, and the radial flows corresponding to the two grid points are , respectively. The to-be-registered grid point is interpolated

[0026] If , then

[0027]

[0028] If , then

[0029]

[0030] In the formula, is a distance resolution in the second spatial resolution; is an angle resolution in the second spatial resolution.

[0031] In some embodiments, the step of spatiotemporal fusion of the two radial flow fields after spatial registration based on the spatiotemporal linear fitting method specifically comprises the following steps:

[0032] For a to-be-fused grid point in the two radial flow fields after spatial registration, the to-be-fused grid point is converted into longitude and latitude, and two sets of grid point radial flow data in matrix form are obtained, which respectively represent the to-be-fused grid point in a preset local range centered on the to-be-fused grid point and varying with time in the two radial flow fields after the conversion into longitude and latitude.

[0033] Joint two sets of the grid point radial flow data to obtain joint data, and remove singular grid point radial flow data in the joint data based on a three-sigma rule;

[0034] The joint data from which the singular grid point radial flow data is removed is substituted into a radial flow function containing grid points in the form of longitude and latitude, and a to-be-estimated parameter corresponding to the to-be-fused grid point in the radial flow function is obtained by least square method, and singular value judgment is performed on the to-be-estimated parameter based on a three-sigma rule;

[0035] If the to-be-fused grid point corresponds to a singular value of the to-be-estimated parameter, it is determined that the to-be-fused grid point fails to be fused;

[0036] If the to-be-fused grid point corresponds to no singular value of the to-be-estimated parameter, the to-be-estimated parameter is substituted into the radial flow function to obtain the radial flow of the to-be-fused grid point after fusion at the current time point.

[0037] In some embodiments, the step of substituting the joint data excluding the singular grid point radial flow data into the radial flow function including the grid points represented in the form of latitude and longitude to obtain the to-be-estimated parameter corresponding to the to-be-fused grid point in the radial flow function by least square method specifically includes the following steps:

[0038] The expression of the radial flow function is as follows:

[0039] (Formula I);

[0040] The other columns except the last column in the matrix form of the joint data are denoted as matrix A, and the last column is denoted as matrix B;

[0041] Let (Formula II);

[0042] In the formula, a, b, c, and e are to-be-estimated parameters; and T is a transpose;

[0043] The matrix A is increased by one column, and the added column is assigned a preset value;

[0044] Then, the joint of Formula I, Formula II, the matrix A after assignment, and the matrix B are obtained:

[0045] (Formula III);

[0046] The least square solution of y obtained by solving Formula III by least square method is as follows:

[0047] (Formula IV);

[0048] And the to-be-estimated parameters a, b, c, and e in the radial flow function are obtained.

[0049] In some embodiments, the step of singular value judgment on the to-be-estimated parameters based on the three-sigma method specifically includes the following steps:

[0050] For the to-be-estimated parameters solved by the least square solution of y, all the to-be-estimated parameters corresponding to different time points and different positions in a preset local range are counted to obtain the to-be-estimated parameters a, b, and c obeying normal distribution, and the singular value judgment is performed on the to-be-estimated parameters a, b, and c obeying normal distribution based on the three-sigma method.

[0051] In some embodiments, the step of performing spatial interpolation on the spatio-temporally fused radial flow field based on the inverse distance weighting method to obtain a final radial flow field comprises the following steps:

[0052] Obtaining a failed-to-fuse grid point in the spatio-temporally fused radial flow field, finding all grid point sets within a preset distance around the failed-to-fuse grid point, calculating the distance between each grid point set and the failed-to-fuse grid point, and obtaining the radial flow of the failed-to-fuse grid point based on the inverse distance weighting method according to the calculated distance and the radial flow of each grid point set in the radial flow field.

[0053] In some embodiments, the step of obtaining the radial flow of the failed-to-fuse grid point based on the inverse distance weighting method according to the calculated distance and the radial flow of each grid point set in the radial flow field comprises the following steps:

[0054] According to the calculated distance and the radial flow of each grid point set in the radial flow field to obtain the radial flow of the failed-to-fuse grid point The calculation formula is as follows:

[0055]

[0056] In the formula, .

[0057] Compared with the prior art, the present application has the following advantages: the present application discards the traditional double-frequency radial sea current weighted average fusion method, because the weight calculation of this method is complex and unreliable. By fully utilizing the uniformity and slow variation of sea currents in time and space, time and spatial multi-dimensional information is introduced at the same time. This makes the fusion process rely on more reference points, so that the fusion result is more accurate, and an accurate marine radial flow field is obtained. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 is a flowchart of an embodiment of a double-frequency high-frequency ground wave radar radial sea current fusion method of the present application;

[0059] Figure 2 is a schematic diagram of the wave radiation angle range of the ground wave radar of the present application;

[0060] Figure 3 is a structural schematic diagram of a double-frequency high-frequency ground wave radar radial sea current fusion system of the present application. DETAILED DESCRIPTION

[0061] Reference will now be made in detail to specific embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Although the present invention will be described in conjunction with specific embodiments, it will be understood that the present invention is not intended to be limited to those embodiments. On the contrary, it is intended to cover variations, modifications, and equivalents within the spirit and scope of the present invention as defined by the appended claims. It should be noted that the method steps described herein can be implemented by any functional block or functional arrangement, and any functional block or functional arrangement can be implemented as a physical entity or a logical entity, or a combination of the two.

[0062] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0063] Note: The following example is only a specific example and is not intended to limit the embodiments of the present invention to the following specific steps, values, conditions, data, sequence, etc. Those skilled in the art can apply the concepts of the present invention to construct more embodiments not described in this specification by reading this specification.

[0064] See also Figure 1 The embodiment of the present invention provides a dual-frequency high-frequency ground wave radar radial current fusion method, comprising the following steps:

[0065] S100, obtaining two different radial flow fields obtained by respectively irradiating two radar electromagnetic waves of different frequencies onto the ocean;

[0066] The inversion calculation method for the radial flow field of single-frequency high-frequency ground-wave radar is relatively mature and will not be described in detail in this invention. Generally speaking, the inversion of the radial flow field of traditional single-frequency radar consists of three steps: initial radial ocean current calculation (initial field), quality control, interpolation, and smoothing. In this invention, there is no need to perform separate quality control, interpolation, and smoothing for different frequencies; only the initial field needs to be calculated. The initial field here refers to the radial flow field calculated solely from ocean echoes without any post-processing. The initial field generally has a relatively discrete data grid distribution, a large number of singular values, and large errors.

[0067] The radio wave radiation angle range (i.e. detection area) of the high-frequency ground wave radar will be determined according to a certain distance resolution (denoted as ) is divided into distance elements one by one (the distance resolution is , B is the sweep bandwidth, C is the speed of light). At the same time, according to a certain angular resolution (the angular resolution depends on the beam width of the radar antenna array, denoted as ), the entire radiation angle is divided into angle elements. A certain distance element and angle element uniquely determine a specific position grid point, which is recorded as When the first-order ocean echo comes from an angle element The arrival angle of the echo is considered to be the angle of the grid point Different grid points constitute the entire radiation range of the radar wave, as shown in FIG. 2.

[0068] The radar station R transmits at two different frequencies, frequency 1 being 8 MHz (low frequency) and frequency 2 being 13.5 MHz (high frequency). The detection distance corresponding to frequency 1 is 200 km, and the detection distance corresponding to frequency 2 is 100 km. The frequency band width of frequency 1 is 30 KHz, and the frequency band width of frequency 2 is 60 KHz. The detection angles of frequency 1 and frequency 2 are consistent, both being 60° (clockwise) offset from the normal direction of the radar as a reference. Frequency 1 and frequency 2 share the same receiving antenna array, and the angle resolutions corresponding to the two frequencies are completely consistent, both being 1.5°.

[0069] According to the traditional high-frequency ground wave radar radial current inversion method, the initial fields of the radial flow field under the conditions of frequency 1 and frequency 2 are calculated. It is noted that the initial field does not need to be post-processed, and is only the original radial flow field calculated by the sea echo.

[0070] According to the calculation formula of the distance resolution, the distance resolution of the radial flow field corresponding to frequency 1 is 5 km, and the distance resolution of the radial flow field corresponding to frequency 2 is 2.5 km, and the angle resolutions of the two are consistent.

[0071] Therefore, the radial flow field of frequency 1 needs to be interpolated to make the distance resolution "interpolated to" 2.5 km, so as to realize the spatial registration with frequency 2.

[0072] S200, spatially registering two different radial flow fields to the same spatial resolution;

[0073] S300, fusing the two radial flow fields after spatial registration based on a time-space linear fitting method;

[0074] S400, spatially interpolating the fused radial flow field based on an inverse distance weighting method to obtain a final radial flow field.

[0075] Specifically, in the embodiment, the application discards the traditional fusion method of double-frequency radial sea current weighted average, because the weight calculation of this method is complex and unreliable. By fully utilizing the uniformity and slow change of the sea current in time and space, time and space multi-dimensional information are introduced at the same time. This makes the fusion process rely on more reference points, so that the fusion result is more accurate, and an accurate ocean radial flow field is obtained.

[0076] Preferably, in another embodiment of the application, the S200, spatially registering two different radial flow fields to the same spatial resolution step specifically comprises the following steps:

[0077] S210, obtaining spatial resolutions corresponding to two different radial flow fields, wherein the two spatial resolutions are defined as a first spatial resolution and a second spatial resolution, and the first spatial resolution is higher than the second spatial resolution;

[0078] S220: Re-grid the radar electromagnetic wave detection range corresponding to the second spatial resolution based on the first spatial resolution, and re-assign the distance element and angle element corresponding to each grid point in the grid.

[0079] S230, if one of the to-be-registered grid points in the grid finds a grid point with an overlapping position in the radial flow field at the second spatial resolution, assigning the distance element and angle element corresponding to the found grid point as the distance element and angle element of the to-be-registered grid point;

[0080] S240: If one of the to-be-registered grid points in the grid does not find a grid point with an overlapping position in the radial flow field at the second spatial resolution, it is necessary to perform interpolation calculation and assignment on the to-be-registered grid point.

[0081] Specifically, in this embodiment, for a dual-frequency high-frequency ground wave radar, the waveform parameters and antenna arrays corresponding to different frequencies are not necessarily completely consistent in theory. Typically, when the sweep bandwidths and antenna arrays corresponding to different frequencies differ significantly, the range and angular resolutions of the radial flow fields corresponding to the two frequencies will differ. To facilitate the final flow field fusion, the two radial flow fields must first be spatially registered to achieve a consistent spatial resolution (range and angular resolution).

[0082] It should be noted that if two different frequencies share the same sweep bandwidth and antenna array, in this case, the spatial coordinate systems of the two radial flow fields are completely consistent, that is, no spatial registration is required.

[0083] This paper uses a combination of linear interpolation and neighbor interpolation for spatial registration, aiming to align a lower spatial resolution radial flow field to a higher resolution. Using the higher-resolution flow field grid as the reference coordinate system, interpolation is performed point by point based on the results of the lower-resolution radial flow field.

[0084] For frequency 1, the detection range (the range defined by the detection angle and the detection range) is re-gridified with a range resolution of 2.5 km and an angle resolution of 1.5°. Each grid point on the grid is re-assigned in ascending order of distance and angle.

[0085] If one of the to-be-registered grid points in the grid can find a point of coincidence in the radial flow field at the frequency 1 original resolution (distance resolution is 5km), it can be directly copied.

[0086] If one of the to-be-registered grid points in the grid cannot find a point of coincidence in the radial flow field at the frequency 1 original resolution (distance resolution is 5km), it needs to be interpolated.

[0087] Preferably, in another embodiment of the present application, the S240, the interpolation calculation assignment step for the to-be-registered grid point specifically comprises the following steps:

[0088] Case 1, if a target rectangle that meets the preset surrounding condition surrounding the to-be-registered grid point is found in the radial flow field at the second spatial resolution, the to-be-registered grid point is interpolated based on a two-dimensional linear interpolation method and according to the target rectangle;

[0089] The step of interpolating the to-be-registered grid point based on the two-dimensional linear interpolation method and according to the target rectangle specifically comprises the following steps:

[0090] The interpolation calculation in the angle element direction is as follows:

[0091]

[0092] The interpolation in the distance element direction is as follows:

[0093]

[0094] In the formula, is the distance element and the angle element of the to-be-registered grid point; are four grid points of the target rectangle respectively; are radial flows corresponding to the four grid points of the target rectangle respectively.

[0095] The preset surrounding condition is: .

[0096] In the formula, is the distance resolution in the second spatial resolution (original resolution); is the angle resolution in the second spatial resolution (original resolution).

[0097] If the to-be-registered grid point finds a smallest "target rectangle" surrounding the point in the radial flow field at the frequency 1 original resolution, and the four grid points of the target rectangle meet the conditions that the maximum distance is not more than 3 original distance resolutions (15km) and the maximum angle deviation is not more than 3 original angle resolutions (4.5°), the two-dimensional linear interpolation method is used to interpolate the to-be-registered grid point.

[0098] For example, if the grid point distance element and angle element to be registered are (12.5, 3), the coordinates of the rectangular vertices surrounding the grid point to be registered in the radial flow field at the original resolution are (10, 1.5), (10, 4.5), (15, 1.5), and (15, 4.5), and the values of the four grid points of the target rectangle corresponding to the radial current are 1, 1.5, 2, and 3, respectively. The interpolation calculation method is as follows:

[0099] First, interpolation is performed in the angle direction:

[0100]

[0101]

[0102] Then, interpolation is performed in the distance element direction:

[0103]

[0104] At this point, the interpolation of the grid point to be registered under condition 1 is completed.

[0105] Condition 2: If a target rectangle satisfying the preset surrounding condition is not found to surround the grid point to be registered in the radial flow field at the second spatial resolution, and if two grid points satisfying the preset distance condition are found to be located on the line connecting the grid point to be registered, then the grid point to be registered is calculated based on one-dimensional linear interpolation and according to the two grid points found.

[0106] The step of calculating the grid point to be registered based on one-dimensional linear interpolation and according to the two grid points found, specifically includes the following steps:

[0107] According to the grid point to be registered , the two grid points found are , and the radial flow corresponding to the two grid points, respectively, the grid point to be registered is interpolated as follows:

[0108] If , then

[0109]

[0110] If , then

[0111]

[0112] In the formula, is the distance resolution in the second spatial resolution; is the angle resolution in the second spatial resolution.

[0113] Therefore, if condition 1 is not met, but the to-be-registered grid point is on the line connecting two grid points of the radial flow field at the original resolution of frequency 1, and the distance between the two grid points does not exceed the distance resolution (5 km) or the angle resolution (1.5°) at the original resolution, one-dimensional linear interpolation can be performed based on the two grid points.

[0114] Condition 3: If the target rectangle that meets the preset surrounding condition surrounding the to-be-registered grid point is not found in the radial flow field at the second spatial resolution, and the to-be-registered grid point is not found on the line connecting two grid points that meet the preset distance condition, then the reference point relied on by the to-be-registered grid point is found. If the distance between the reference point relied on and the to-be-registered grid point is less than the distance threshold, then the distance element and the angle element corresponding to the reference point relied on are assigned as the distance element and the angle element of the to-be-registered grid point.

[0115] Therefore, conditions 1 and 2 are not met, but the nearest reference point relied on can be found. If the distance between the to-be-registered grid point and the reference point relied on is less than the distance threshold , then the value of the reference point relied on is directly copied. The distance threshold can be 1 km.

[0116] Condition 4: When conditions 1, 2, and 3 are not met, no interpolation is performed.

[0117] The above assignment process is performed for each to-be-registered grid point of the re-subdivided grid, and the spatial registration of the two radial flow fields at different spatial resolutions is completed.

[0118] Preferably, in another embodiment of the present application, the S300, based on the spatiotemporal linear fitting method, performs a spatiotemporal fusion step on the two radial flow fields after spatial registration, specifically including the following steps:

[0119] For the same to-be-fused grid point in the two radial flow fields after spatial registration, the to-be-fused grid point is converted into longitude and latitude, and two sets of grid point radial flow data in matrix form are obtained, which are the to-be-fused grid point in a preset local range centered on the to-be-fused grid point and change over time in the two radial flow fields.

[0120] The joint data is obtained by combining the two sets of grid point radial flow data, and the singular grid point radial flow data in the joint data is removed based on the three-sigma method.

[0121] The joint data from which the singular grid point radial flow data is removed is substituted into the radial flow function containing the grid points in the form of longitude and latitude, and the corresponding estimated parameters of the to-be-fused grid point in the radial flow function are obtained by least squares method, and the singular value judgment is performed on the estimated parameters based on the three-sigma method.

[0122] If the to-be-fused eligible point corresponds to the to-be-estimated parameter with a singular value, it is determined that the to-be-fused eligible point fusion fails;

[0123] If the to-be-fused eligible point corresponds to the to-be-estimated parameter without a singular value, the to-be-estimated parameter is substituted into the radial flow function to obtain the radial flow of the to-be-fused eligible point after fusion at the current time.

[0124] Specifically, in the embodiment, the ocean current not only has stationarity and slow variation in time and space distribution, but also presents a certain periodicity. For example, a typical semidiurnal tide or diurnal tide, and the ocean current derived from a single point is often a trigonometric function changing with time in the time dimension. Therefore, many two-dimensional or three-dimensional functions can be used to fit the flow field. For example, a two-dimensional Fourier series can be used to fit the entire radial flow field, and the ocean current generated by this fitting method is very smooth and well considers the spatial variation details of the ocean current. The only difficulty is that the order of the two-dimensional Fourier series is difficult to determine, although a relatively fixed order can be determined through a large number of experiments. However, the ocean current changes greatly in different regions and at different times, and the characteristics are different. Therefore, it is often difficult to achieve good results with a fixed order. Therefore, the above method still has some difficulties in actual engineering application.

[0125] However, the change of a complex curve or surface in a small space-time range can be regarded as linear. In the real world, it is “curved” on a macro level and “straight” on a micro level. When we “differentiate” the change of the flow field in time and space, it is linear. Based on this, it is assumed that, for any grid point , the latitude and longitude thereof are converted to (the value of according to the station coordinates and the corresponding of the grid cell, that is, the latitude and longitude can be calculated), and the expression of the radial flow of the grid point at time t (the radial flow function of the grid point with linear change in time and space in the form of latitude and longitude) is as follows:

[0126] (Formula 1)

[0127] where a, b, c, and e are to-be-estimated parameters.

[0128] The high-frequency ground wave radar generates result data according to a certain fixed frequency. Therefore, the value of time t can also be represented by a field sequence (for example, 0, 1, 2, 3, 4, 5, …).

[0129] When a, b, c, and e are determined, (1) formula is substituted into the current time , and the latitude and longitude of the to-be-estimated point , that is, the radial flow of the to-be-fused eligible point after fusion at the current time can be calculated.

[0130] For dual-frequency radar, the same local small range, because of the uniqueness of the radial current, can be assumed that the radial current detected by two frequencies obeys the same Expression. Therefore, after spatial registration, without regard to frequency, the two radial flow fields can be treated indifferently.

[0131] For a certain grid point of the spatially registered radial flow field, according to its position , a certain pre-set local range centered on it is determined. The local range can be determined according to the distance element and the angle element offset to determine the radius threshold, or the spatial distance can be used to determine the radius threshold, denoted as .

[0132] The invention assumes that the radial current of a certain to-be-fused grid point in the local range is also linearly changed in a short time. Therefore, there is also a threshold in time to describe how long it is linearly changed. The value is generally an integer between 0 and 5. Based on this , by analogy. The above indicates the time (field) sequence, respectively, the current field, the previous field, the previous two fields…

[0133] Therefore, for frequency 1, the radial flow data of the grid points in the local range are as follows:

[0134]

[0135] For frequency 2, the effective point set in the local range is as follows:

[0136]

[0137] The point sets of the above frequency 1 and frequency 2 are jointly written in matrix form, and a result point is a row, for example: is a row.

[0138] The first 3 columns of the matrix are denoted as A, and the last column is denoted as B.

[0139] Let (Equation II), T is the transpose.

[0140] Add a column to the matrix A, and assign all values in the column (fourth column) to 1.

[0141] Then according to equation (1), in the ideal case, there is:

[0142] (Equation III);

[0143] Under actual measurement conditions, obviously the above equation only exists for the least squares solution. The least squares solution of y is:

[0144] (Formula Four)

[0145] So far, the estimation of a, b, c, and e is completed. The spatio-temporal coordinate value of the fusion-qualified point is brought in

[0146] The fusion estimation of the radial current of the fusion-qualified point in the dual-frequency fusion mode is completed.

[0147] Specifically, after the spatial registration of the above-mentioned frequency 1 and frequency 2 is completed, the radial flow fields of the two different frequencies can be regarded as a whole, that is, the two are "overlapped" in space. The resolution of this overlapping area is 2.5 km, the angle resolution is 1.5°, the detection distance is 200 km, and the radiation angle is 60° (positive for clockwise) based on the normal direction of the radar.

[0148] Each point on the grid in this area is fitted one by one in the order of distance element from small to large and angle element from small to large. The fitting process of each point is the dual-frequency radial current fusion process.

[0149] For example, when the fusion-qualified point P with a distance element and an angle element of (10, 20) and a longitude and latitude of (112°E, 22°N) is selected for fitting, the local range is determined according to the offset of the distance element and the angle element to determine the radius threshold . Taking =1, the local range is a 3*3 nine-square area with P as the center and the offset of the distance element and the angle element being 1. It is assumed that the local range with P as the center is also linearly changed within time period. In this embodiment, =5, indicating that the radial current in the local range with P as the center is linearly changed within the consecutive 6 fields of data.

[0150] Based on this, the current field t=0, the last field t=1, the last two fields t=2, and so on.

[0151] Therefore, the joint data of the fusion-qualified point P is as follows:

[0152]

[0153] The joint data of P is written in the form of a matrix, denoted as Q. The first three columns of Q are denoted as matrix A, and A is increased by one column, and the column (fourth column) is all assigned as 1. The last column of Q is denoted as column vector B. Let , T is the transpose.

[0154] Each row of Q represents a data point, and its meaning is (time subscript, longitude, latitude, radial flow rate). All the radial flow rate values in the joint data are selected, and the standard deviation and the average value For each radial flow rate value A three-sigma criterion is used to determine if a value is singular. That is

[0155]

[0156] Then The point is considered singular and is removed from B.

[0157] Correspondingly, the first row of matrix A is removed.

[0158] Further, it is solved that:

[0159] .

[0160] Preferably, in another embodiment of the present application, the singular value judgment step of the estimated parameters based on the three-sigma criterion specifically includes the following steps:

[0161] For the estimated parameters solved by the least square solution of y, all the estimated parameters corresponding to different time points and different positions in the preset local range are counted to obtain the estimated parameters a, b, and c obeying normal distribution, and the three-sigma criterion is used to judge the singular values of the estimated parameters a, b, and c obeying normal distribution.

[0162] Specifically, in the present embodiment, through a large number of statistics of the parameters a, b, and c corresponding to different time points and different local ranges, it can be found that the a, b, and c as a whole obey normal distribution, so that the newly calculated a, b, and c can be singularized by the three-sigma criterion. When any one of the newly calculated a, b, and c does not satisfy the three-sigma criterion, it is determined that the current fitting fails, and the radial flow corresponding to the a, b, and c is set to an invalid value.

[0163] When the ground wave radar performs sea state inversion calculation, a dynamic matrix space with 3 columns and a maximum of 50000 rows is opened, which is denoted as C. Each row of C respectively stores the values of a, b, and c calculated by each fitting. When the number of rows of C reaches 50000, the first row is removed, and the newly calculated a, b, and c are inserted into the last row.

[0164] The mean and standard deviation of the a, b, and c statistical distribution are calculated at a fixed frequency using each column of C. When three fields of data are continuously calculated during sea state inversion, the mean and standard deviation of the a, b, and c distribution are recalculated using C. The newly calculated a, b, and c are singularized by the three-sigma criterion.

[0165] ​For example, the distribution mean of a calculated by C is 0.05, and the standard deviation is 0.1. Then, for a certain fitting process, when the value of a is calculated as 0.5, it is determined that the current fitting fails because Whether the newly calculated values of b and c are singular is determined in the same way as a.

[0166] Note that the mean and standard deviation of the statistical distribution of a, b, and c need to be set with initial values when the sea state inversion is started. The mean of the initial values is set to 0, and the standard deviation is set to 0.1.

[0167] When a, b, and c are determined to be non-singular, the spatiotemporal coordinates of P can be brought in The fused radial flow rate is calculated.

[0168] The above steps are performed for each grid point in the region, and the fusion of all points is completed.

[0169] Preferably, in another embodiment of the present application, the S400, based on the inverse distance weighting method, performs spatial interpolation on the spatiotemporally fused radial flow field to obtain the final radial flow field step, specifically comprising the following steps:

[0170] Obtain the fusion-failed to-be-fused grid point in the spatiotemporally fused radial flow field, find all grid point sets within a predetermined distance around the to-be-fused grid point, calculate the distance between the to-be-fused grid point and each grid point set, and obtain the radial flow of the fusion-failed to-be-fused grid point based on the inverse distance weighting method according to the calculated distance and the radial flow of each grid point set in the radial flow field.

[0171] Preferably, in another embodiment of the present application, the step of obtaining the radial flow of the fusion-failed to-be-fused grid point based on the inverse distance weighting method according to the calculated distance and the radial flow of each grid point set in the radial flow field specifically comprises the following steps:

[0172] According to the calculated distance and the radial flow of each grid point set in the radial flow field , the radial flow of the fusion-failed to-be-fused grid point is obtained The calculation formula is as follows:

[0173]

[0174] In the formula, .

[0175] Specifically, in this embodiment, point P is the grid point to be fused where fusion failed. The distance element and angle element are (30, 40), and the longitude and latitude are (114.23°E, 22.15°N). All data points within 5km of point P are found as reference point sets. The distance between these point sets and point P is calculated as , the radial velocity of the point set is expressed as .

[0176] When there is and

[0177] When , the interpolated flow velocity is:

[0178]

[0179] See also Figure 3 As shown, an embodiment of the present invention further provides a dual-frequency high-frequency ground wave radar radial current fusion system, comprising:

[0180] The radial flow field acquisition module is used to obtain two different radial flow fields obtained by inverting two different frequency radar electromagnetic waves onto the ocean;

[0181] a registration module, in communication with the radial flow field acquisition module, for spatially registering two different radial flow fields to the same spatial resolution;

[0182] a fusion module, communicatively connected to the registration module, for performing spatiotemporal fusion of the two radial flow fields after spatial registration based on a spatiotemporal linear fitting method; and

[0183] The spatial interpolation module is in communication with the fusion module and is used to perform spatial interpolation on the radial flow field after time-space fusion based on the inverse distance weighted method to obtain the final radial flow field.

[0184] The present invention abandons the traditional dual-frequency radial current weighted averaging fusion method, because the weight calculation of this method is complex and unreliable. Instead, the present invention fully utilizes the uniformity and slow variation of ocean currents in time and space, and simultaneously introduces multidimensional information in time and space. This allows the fitting process to rely on more reference points, thereby making the fitting results more accurate. At the same time, the present invention automatically determines the rationality of the estimated coefficients during the fitting process, eliminates singular values, and eliminates the tedious post-processing process based on quality control.

[0185] Specifically, this embodiment corresponds one-to-one to the above method embodiment, and the functions of each module have been described in detail in the corresponding method embodiment, so they will not be repeated here.

[0186] Based on the same inventive concept, the embodiment of the present application further provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement all method steps or part of method steps of the above method.

[0187] The present application can implement all or part of the above method, and can also be completed by a computer program instructing related hardware. The computer program can be stored in a computer readable storage medium, and the computer program can implement the steps of the above method embodiments when executed by a processor. The computer program includes computer program code, which can be in the form of source code, object code, executable files or some intermediate forms. The computer readable medium can include any entity or device capable of carrying computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content of the computer readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction, for example, in some jurisdictions, according to legislation and patent practice, the computer readable medium does not include electrical carrier signals and telecommunication signals.

[0188] Based on the same inventive concept, the embodiment of the present application further provides an electronic device, which includes a memory and a processor, and the memory stores a computer program running on the processor. When the processor executes the computer program, all method steps or part of method steps of the above method are implemented.

[0189] The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor, etc. The processor is the control center of the computer device, and connects all parts of the computer device through various interfaces and lines.

[0190] The memory can be used to store computer programs and / or modules, and the processor realizes various functions of the computer device by running or executing the computer programs and / or modules stored in the memory, and calling data stored in the memory. The memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system and at least one application program required by a function (for example, a sound playing function, an image playing function, etc.); and the data storage area can store data created according to use of the mobile phone (for example, audio data, video data, etc.). In addition, the memory can include a high-speed random access memory, and can also include a non-volatile memory, for example, a hard disk, a memory, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, at least one disk storage device, a flash memory device, or other volatile solid-state memory devices.

[0191] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, a server or a computer program product. Therefore, the present application can adopt a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can adopt a form of a computer program product implemented on one or more computer usable storage media (including but not limited to disk storage and optical storage, etc.) containing computer usable program codes.

[0192] The present application is described with reference to flowcharts and / or block diagrams of methods, devices (systems), servers and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams can be realized by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device that implements the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 an apparatus that carries out the functions specified in one or more flows and / or blocks.

[0193] These computer program instructions can also be stored in a computer readable memory capable of guiding a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer readable memory produce a product including instruction apparatus, which realizes the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 an apparatus that carries out the functions specified in one or more flows and / or blocks.

[0194] These computer program instructions can also be loaded into a computer or other programmable data processing devices, so that a series of operational steps are performed on the computer or other programmable devices to generate computer-implemented processes, thus the instructions executed on the computer or other programmable devices provide processes for implementing the functions specified in the flowchart Figure 1 one or more flows and / or blocks Figure 1 one or more blocks or steps of the functions specified in the flowchart

[0195] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application belong to the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

Claims

1. A dual-frequency high-frequency surface wave radar radial current fusion method, characterized in that: The following steps are involved: Obtain two different radial flow fields by irradiating two radar electromagnetic waves of different frequencies onto the ocean respectively; spatially registering the two different radial flow fields to the same spatial resolution; Based on a spatiotemporal linear fitting method, the two radial flow fields are fused after spatial registration; Based on the inverse distance weighted method, the fused radial flow field is spatially interpolated to obtain the final radial flow field; The step of performing spatiotemporal fusion on the two radial flow fields after spatial registration based on the spatiotemporal linear fitting method specifically includes the following steps: For the same grid point to be fused in the two radial flow fields after spatial registration, convert the grid point to be fused into longitude and latitude, and obtain two sets of grid point radial flow data represented in matrix form, which show that the grid point to be fused, after being converted into longitude and latitude, changes with time within a preset local range centered on the grid point to be fused in the two radial flow fields; Combining the two sets of grid radial flow data to obtain combined data, and removing singular grid radial flow data in the combined data based on a triple standard deviation method; Substituting the combined data with the singular grid point radial flow data removed into a radial flow function containing grid points represented in the form of longitude and latitude, solving the problem by the least squares method to obtain the estimated parameters corresponding to the grid points to be fused in the radial flow function, and performing singular value judgment on the estimated parameters based on the triple standard deviation method; If the parameter to be estimated corresponding to the grid point to be fused has a singular value, it is determined that the fusion of the grid point to be fused has failed; If the parameters to be estimated corresponding to the grid points to be fused have no singular values, the parameters to be estimated are substituted into the radial flow function to obtain the radial flow after the grid points to be fused at the current time point.

2. The dual-frequency high-frequency surface wave radar radial current fusion method according to claim 1, characterized in that: The step of spatially registering the two different radial flow fields to the same spatial resolution specifically includes the following steps: Obtaining spatial resolutions corresponding to two different radial flow fields, wherein the two spatial resolutions are defined as a first spatial resolution and a second spatial resolution, and the first spatial resolution is higher than the second spatial resolution; Re-gridding the radar electromagnetic wave detection range corresponding to the second spatial resolution based on the first spatial resolution, and re-assigning the distance element and angle element corresponding to each grid point in the grid; If one of the to-be-registered grid points in the grid finds a grid point with an overlapping position in the radial flow field at the second spatial resolution, assigning the distance element and angle element corresponding to the found grid point as the distance element and angle element of the to-be-registered grid point; If one of the to-be-registered grid points in the grid does not find a grid point with a coincident position in the radial flow field at the second spatial resolution, it is necessary to perform interpolation calculation and assignment on the to-be-registered grid point.

3. The dual-frequency high-frequency surface wave radar radial current fusion method according to claim 2, characterized in that: The step of performing interpolation calculation and assignment of values ​​for the registration grid points specifically includes the following steps: If a target rectangle that meets the preset enclosing condition and surrounds the grid points to be registered is found in the radial flow field at the second spatial resolution, interpolation calculation is performed on the grid points to be registered based on the target rectangle based on a two-dimensional linear interpolation method; If a target rectangle that meets the preset enclosing condition and surrounds the grid point to be registered is not found in the radial flow field at the second spatial resolution, and the grid point to be registered is found to be located on a line connecting two grid points that meet the preset distance condition, then interpolation calculation is performed on the grid point to be registered based on the two found grid points based on a one-dimensional linear interpolation method; If a target rectangle that meets the preset enclosing conditions and surrounds the grid point to be registered is not found in the radial flow field at the second spatial resolution, and the grid point to be registered is not found to be located on the line connecting two grid points that meet the preset distance conditions, then a dependent reference point of the grid point to be registered is searched. If the distance between the found dependent reference point and the grid point to be registered is less than the distance threshold, the distance element and angle element corresponding to the dependent reference point are assigned to the distance element and angle element of the grid point to be registered.

4. The dual-frequency high-frequency surface wave radar radial current fusion method according to claim 3, characterized in that: The two-dimensional linear interpolation method is used to interpolate the grid points to be registered according to the target rectangle. The calculation formula is as follows: in, , ; Where, are the distance element and angle element of the grid points to be registered; are the four grid points of the target rectangle; are the radial flows corresponding to the four grid points of the target rectangle respectively; is the distance resolution in the second spatial resolution; is the angular resolution in the second spatial resolution.

5. The dual-frequency high-frequency surface wave radar radial current fusion method according to claim 3, characterized in that: The step of performing interpolation calculation on the grid points to be registered based on the two found grid points based on the one-dimensional linear interpolation method specifically includes the following steps: According to the grid points to be registered The two grid points found are , and the radial flows corresponding to the two grid points , interpolate the registration grid points The calculation is as follows: like ,but like ,but Where, is the distance resolution in the second spatial resolution; is the angular resolution in the second spatial resolution.

6. The dual-frequency high-frequency surface wave radar radial current fusion method according to claim 1, characterized in that: The step of substituting the combined data from which the singular grid radial flow data is removed into a radial flow function including grid points represented in the form of longitude and latitude, and solving the problem by the least square method to obtain the estimated parameters corresponding to the grid points to be fused in the radial flow function, specifically comprises the following steps: The expression of the radial stream function is as follows: (Equation 1); The other columns except the last column of the combined data represented in matrix form are recorded as matrix A, and the last column is recorded as matrix B; make (Formula 2); Where a, b, c, e are the parameters to be estimated; T is the transpose; lon and lat is the latitude and longitude; t is the time; Add a column to matrix A and assign the added column to the preset value; Then, combining Equation 1, Equation 2, the assigned matrix A and matrix B, we get: (Formula 3); Solving Equation 3 using the least squares method, we get the least squares solution of y as follows: (Formula 4); And the parameters a, b, c, and e to be estimated in the radial stream function are obtained.

7. The dual-frequency high-frequency surface wave radar radial current fusion method according to claim 6, characterized in that: The step of performing singular value determination on the parameter to be estimated based on the triple standard deviation method specifically includes the following steps: For the parameters to be estimated obtained by the least squares solution of y, all the parameters to be estimated corresponding to different time points and different positions in the preset local range are statistically analyzed to obtain the parameters to be estimated a, b, c that obey the normal distribution, and the singular values ​​of the parameters to be estimated a, b, c that obey the normal distribution are judged based on the triple standard deviation method.

8. The dual-frequency high-frequency surface wave radar radial current fusion method according to claim 1, characterized in that: The step of performing spatial interpolation on the radial flow field after time-space fusion based on the inverse distance weighted method to obtain the final radial flow field specifically includes the following steps: Obtain the grid points to be fused that failed to be fused in the radial flow field after spatiotemporal fusion, search for all grid point sets within a preset distance around the grid points to be fused, calculate the distances between the grid point sets and the grid points to be fused, and obtain the radial flows of the grid points to be fused that failed to be fused based on the inverse distance weighted method according to the calculated distances and the radial flows of the grid point sets in the radial flow field.

9. The dual-frequency high-frequency surface wave radar radial current fusion method according to claim 8, characterized in that: The step of obtaining the radial flow of the grid points to be fused that failed to be fused based on the calculated distance and the radial flow of the grid point set in the radial flow field, and based on the inverse distance weighted method, specifically includes the following steps: The calculated distance , and the grid point set is respectively the radial flow in the radial flow field , we get the radial flow of the grid points to be fused where fusion fails The calculation formula is as follows: Where, .

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