CN111505646B - Ocean imaging radar altimeter calibration and inspection method with unified time-space spectrum - Google Patents

Ocean imaging radar altimeter calibration and inspection method with unified time-space spectrum Download PDF

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CN111505646B
CN111505646B CN202010342395.9A CN202010342395A CN111505646B CN 111505646 B CN111505646 B CN 111505646B CN 202010342395 A CN202010342395 A CN 202010342395A CN 111505646 B CN111505646 B CN 111505646B
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imaging radar
radar altimeter
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gnss
time
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CN111505646A (en
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杨磊
徐永生
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Institute of Oceanology of CAS
First Institute of Oceanography MNR
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Institute of Oceanology of CAS
First Institute of Oceanography MNR
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/95—Radar or analogous systems specially adapted for specific applications for meteorological use
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/25—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS
    • G01S19/258—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
    • G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/42—Determining position
    • G01S19/43—Determining position using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G01S7/4004—Means for monitoring or calibrating of parts of a radar system
    • G01S7/4026—Antenna boresight
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

The invention relates to a space-time spectrum unified marine imaging radar altimeter calibration and inspection method, and belongs to the technical field of marine altimeter calibration and inspection. The invention comprises the following steps: a GNSS buoy is arranged in an observation area of the imaging radar altimeter, buoy data calculation is carried out through a dynamic differential PPK technology, a proper time window length is selected by taking the observation time of the imaging radar altimeter as a center, and band-pass filtering, frequency spectrum calculation of energy density and wave number spectrum calculation of sea surface altitude energy density are carried out; deriving a unified equation of a frequency spectrum of a time domain and a wave number spectrum of a space domain; converting into a frequency spectrum of a time domain and integrating to obtain a fluctuation variance of the imaging radar altimeter and a field observed fluctuation variance; and calculating the cross-correlation coefficient of the unified energy density spectrum. According to the invention, the sea surface height time sequence in the time domain observed by the limited buoy is utilized to scale the two-dimensional sea surface height of the space domain observed by the imaging radar altimeter, so that the field scaling cost can be reduced.

Description

Ocean imaging radar altimeter calibration and inspection method with unified time-space spectrum
Technical Field
The invention relates to a space-time spectrum unified marine imaging radar altimeter calibration and inspection method, and belongs to the technical field of marine altimeter calibration and inspection.
Background
The imaging radar altimeter is the research focus field of the current domestic and foreign ocean remote sensing world, the satellite altimeter is not transmitted at present, and only the China and the United states develop airborne tests. The calibration and inspection technology mainly utilizes ground actual measurement data to calibrate load observation precision and data quality, and a large technical blank exists in the field of three-dimensional imaging altimeter calibration and inspection at present.
The known existing calibration technology mainly comprises point-to-point checking based on a tide station, a GNSS buoy and an active scaler, namely, a calibration result based on synchronous observation data is obtained every time a satellite passes through a calibration field. However, the imaging radar altimeter is different from the traditional satellite point altimeter in that the imaging radar altimeter can observe sea surface height with certain swath width, and is not limited to an along-track measuring line formed by satellite points, and three-dimensional sea surface height can be acquired by the observation mode, so that sea surface space fluctuation information with high resolution is acquired.
The known calibration verification techniques described above have not yet enabled spatial domain calibration verification of imaging radar altimeters. At present, the United states proposes a solution for the networking observation of the glide r controlled at fixed points, which is only in the conceptual description and simulation stage, and can realize the calibration check of the imaging radar altimeter, but has not been proved by experiments, and has larger uncertainty.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention provides a calibration and inspection method for the marine imaging radar altimeter with unified space-time spectrum, which can achieve the purpose by using a limited anchor system GNSS buoy, greatly reduce the cost and obtain a high-precision sea surface height time sequence.
The invention relates to a calibration and inspection method for a marine imaging radar altimeter with unified space-time spectrum, which comprises the following steps:
s1: a GNSS buoy is arranged in an imaging radar altimeter observation area and fixed through an anchor system;
s2: GNSS buoy data calculation is carried out through a dynamic differential PPK technology, and the dynamic differential PPK technology needs to arrange a GNSS reference station within 50km of a buoy in advance: in order to ensure the base station precision, the base station observation time is not less than 1 day;
s3: selecting a proper GNSS time window length by taking the observation time of the imaging radar altimeter as the center according to the sea condition change condition: to ensure the accuracy of the frequency spectrum, the time length of the selected GNSS sea surface height is usually not less than 30 minutes;
s4: band-pass filtering is carried out on the sea surface height time sequence of the selected GNSS buoy, and the influence of long-period tides and short-period noise is eliminated;
s5: performing frequency spectrum calculation of energy density on the GNSS, and setting a maximum period of sea surface fluctuation of which the unit step length is not less than twice;
s6: three-dimensional sea surface height data collected by an imaging radar altimeter around a GNSS buoy are extracted, bandpass filtering is carried out to eliminate noise influence of a long-wave ground level and a short wave, and a wave number spectrum of the filtered sea surface height energy density is calculated;
s7: the frequency spectrum observed by the GNSS buoy and the wave number spectrum observed by the imaging radar altimeter which belong to the time domain and the space domain can not be directly compared and analyzed;
s8: deducing a frequency spectrum of a time domain and a wave number spectrum unified equation of a space domain through a dispersion relation of ocean fluctuation and an energy density spectrum variance conservation formula;
s9: converting the wave number spectrum observed by the imaging radar altimeter into a frequency spectrum of a time domain through the last step;
s10: integrating on a frequency spectrum of a time domain to obtain a fluctuation variance of the imaging radar altimeter and a GNSS field observed fluctuation variance;
s11: and calculating the cross-correlation coefficient of the unified energy density spectrum of the imaging radar altimeter and the energy density spectrum observed on the GNSS site.
Preferably, in the step S2, the imaging radar altimeter is used for ensuring that high-frequency sea surface fluctuation data is acquired, the sampling frequency of the GNSS receiver of the GNSS reference station is set to be not lower than 1Hz, and the sampling frequency is properly increased to 5Hz under the high-dynamic sea condition; before the GNSS buoy is laid, antenna high-error calibration needs to be carried out indoors; the time of the offshore survey of the GNSS buoy required 1 hour each before and after the acquisition of data by the imaging radar altimeter.
Preferably, in the step S2, the method of the dynamic differential PPK technique includes the following steps:
s21: using the precise ephemeris and clock error file provided by the IGS to combine IGS stations around the reference station to calculate the coordinates of the reference station under the stable reference frame;
s22: taking the spatial correlation of positioning errors between a reference station and a mobile station into consideration, and adopting a post-processing differential positioning technology of carrier phase measurement to obtain the accurate three-dimensional coordinates of the mobile station, wherein the positioning method comprises the following steps:
Figure GDA0002513187490000021
wherein:
Figure GDA0002513187490000022
initiating a phase ambiguity for the rover; />
Figure GDA0002513187490000023
The phase integer number of cycles from the start epoch to the observation epoch for the rover; />
Figure GDA0002513187490000024
A fractional part of the rover phase observations; dρ is the residuals of each item of the same observation epoch.
Preferably, in the step S5, the value of the maximum period is obtained by trying to set different step sizes for test, and when the value of the energy density spectrum is about equal to 0, the corresponding period value is the maximum period.
Preferably, in the step S6, the data range of the three-dimensional sea surface height data should not be less than twice the maximum sea surface wave wavelength to identify the maximum wave number.
Preferably, in the step S8, the energy density spectrum variance conservation formula:
Figure GDA0002513187490000031
Figure GDA0002513187490000032
dispersion relation of ocean wave motion:
Figure GDA0002513187490000033
deriving a unified equation of a frequency spectrum in a time domain and a wave number spectrum in a space domain:
Figure GDA0002513187490000034
S(f)f＝2Q(k)k
wherein: sigma represents the integral variance; f and k represent frequency and wavenumber, respectively; d represents differentiating the parameters in brackets; ln is the logarithm of the base constant e; s and Q are expressed as energy density functions of f and k, respectively.
Preferably, in the step S10, the fluctuation variance of the imaging radar altimeter and the fluctuation variance observed by the GNSS field are the difference between the fluctuation variance and the fluctuation variance, which is the deviation variance of the three-dimensional sea surface height result measured by the imaging radar altimeter, and represents the difference of the overall fluctuation of the sea surface, and the smaller the index of the deviation variance is, the higher the accuracy of the imaging radar altimeter is.
Preferably, in the step S11, the index of the cross-correlation coefficient characterizes the correlation of the sea surface fluctuation energy distribution observed by the two, and the larger the value is, the higher the measurement accuracy of the imaging radar altimeter is.
The beneficial effects of the invention are as follows: the imaging radar altimeter calibration inspection based on the anchor system GNSS buoy can be realized through unification of the time domain frequency spectrum and the spatial domain wave number spectrum; the buoy is theoretically distributed, so that the aim of the invention can be fulfilled, thus greatly saving calibration and inspection cost and improving production efficiency.
Drawings
FIG. 1 is a block flow diagram of a calibration verification method of the present invention.
Fig. 2 (a) is a sea surface altitude frequency spectrum observed by the GNSS buoy 1 and a wave number spectrum observed by the imaging radar altimeter 1.
Fig. 2 (b) is an energy spectrum of a GNSS buoy 1 and an energy spectrum of an imaging radar altimeter 1 of the present invention which unify energy density spectra.
Fig. 3 (a) is a sea surface altitude frequency spectrum observed by the GNSS buoy 2 and a wave number spectrum observed by the imaging radar altimeter 2.
Fig. 3 (b) is an energy spectrum of the GNSS buoy 2 and an energy spectrum of the imaging radar altimeter 2 of the present invention unifying energy density spectra.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1:
as shown in figure 1, the calibration and inspection method for the marine imaging radar altimeter with unified time-space spectrum, provided by the invention, can be used for solving the problem of inapplicability of point-to-point calibration in the calibration of the imaging radar altimeter in the traditional calibration technology and realizing point-to-face calibration.
First of all, the theoretical assumption is made that for a uniform field of sea level elevation SSE induced by waves in the space-time domain, the following three statements are correct:
a if the time series of measured SSEs is long enough, the variance of the measured SSEs is the same at any location in the domain.
B if the area of the SSE to be measured is large enough, the variances of the SSEs measured at any time in the domain are the same.
C if conditions A and B are true, then the wave induced SSE is a spatially and temporally uniform field, and the variances of A and B are equal.
In the actual calibration process, the method for calibrating the space domain imaging radar altimeter data by using the GNSS buoy in the time domain is as follows:
s1: a GNSS buoy is arranged in an imaging radar altimeter observation area and fixed through an anchor system. In order to ensure that high-frequency sea surface fluctuation data are acquired, the sampling frequency of the GNSS receiver is usually not lower than 1Hz, and can be properly increased to 5Hz under the high-dynamic sea condition. The GNSS buoy requires antenna high error calibration indoors before deployment. The time of the offshore survey of the GNSS buoy required 1 hour each before and after the acquisition of data by the imaging radar altimeter.
S2: GNSS buoy data calculation is carried out through a dynamic differential PPK technology, the dynamic differential PPK technology needs to arrange a GNSS reference station within 50km of a buoy in advance, and in order to ensure the base station precision, the base station observation time is not less than 1 day.
The basic flow of PPK positioning is as follows: using the precise ephemeris and clock error file provided by the IGS to combine IGS stations around the reference station to calculate the coordinates of the reference station under the stable reference frame; taking the spatial correlation of positioning errors between a reference station and a mobile station into consideration, and obtaining the accurate three-dimensional coordinates of the mobile station by adopting a post-processing differential positioning technology of carrier phase measurement, wherein the positioning mode is as follows:
Figure GDA0002513187490000041
wherein:
Figure GDA0002513187490000042
initiating a phase ambiguity for the rover; />
Figure GDA0002513187490000043
The phase integer number of cycles from the start epoch to the observation epoch for the rover; />
Figure GDA0002513187490000044
A fractional part of the rover phase observations; dρ is each observation epochAnd (5) item residual errors.
S3: according to the sea condition change condition, selecting a proper GNSS time window length by taking the observation time of the imaging radar altimeter as the center, and in order to ensure the accuracy of a frequency spectrum, the time length of the selected GNSS sea surface height is usually not less than 30 minutes.
S4: and carrying out band-pass filtering on the selected sea surface height time sequence of the GNSS buoy to eliminate the influence of long-period tides and short-period noise.
S5: and (3) performing frequency spectrum calculation of energy density on the GNSS, and setting the maximum period of sea surface fluctuation of which the unit step size is not less than twice. The maximum period value can be obtained through trial by trying to set different step sizes, and when the value of the energy density spectrum is approximately equal to 0, the corresponding period value is the maximum period.
S6: three-dimensional sea surface height data collected by the imaging radar altimeter around the GNSS buoy are extracted, bandpass filtering is carried out to eliminate noise influence of a long-wave ground level and a short wave, and a wave number spectrum of the filtered sea surface height energy density is calculated. The data range should not be less than twice the wavelength of the maximum sea surface wave to identify the maximum wave number.
S7: the frequency spectrum observed by the GNSS buoy and the wave number spectrum observed by the imaging radar altimeter which belong to the time domain and the space domain are obtained, and the morphology of the energy spectrum cannot be directly compared and analyzed. The next step is needed for time-space unification.
S8: the uniform equation (such as equation 5) of the frequency spectrum in the time domain and the wave number spectrum in the space domain is deduced through the dispersion relation (such as equation 4) of ocean wave and the energy density spectrum variance conservation equation (such as equation 2 and equation 3):
Figure GDA0002513187490000051
/>
Figure GDA0002513187490000052
Figure GDA0002513187490000053
Figure GDA0002513187490000054
S(f)f＝2 Q(k)k (5)
wherein: sigma represents the integral variance, f and k represent frequency and wavenumber, respectively, d represents differentiation of the parameters in brackets, ln is the logarithm of the base constant e, and S and Q represent energy density functions f and k, respectively.
S9: the wave number spectrum observed by the imaging radar altimeter is converted into a frequency spectrum in the time domain through the last step.
S10: integrating over a frequency spectrum in a time domain to obtain a fluctuation variance of the imaging radar altimeter and a GNSS field observed fluctuation variance. The difference is the deviation variance of the three-dimensional sea surface height result measured by the imaging radar altimeter, and represents the difference of the overall fluctuation of the sea surface. The smaller this index represents the higher accuracy of the imaging radar altimeter.
S11: and calculating the cross-correlation coefficient of the unified energy density spectrum of the imaging radar altimeter and the energy density spectrum observed on the GNSS site. This index characterizes the correlation of the sea surface wave energy distribution observed by the two, and the larger the value is, the higher the measurement accuracy of the imaging radar altimeter is.
The beneficial effects of the invention are as follows: the imaging radar altimeter calibration inspection based on the anchor system GNSS buoy can be realized through unification of the time domain frequency spectrum and the spatial domain wave number spectrum; the buoy is theoretically distributed, so that the aim of the invention can be fulfilled, thus greatly saving calibration and inspection cost and improving production efficiency.
Example 2:
effects of the present invention will be explained below with reference to examples and drawings.
The current sea calibration technology of the radar altimeter is mainly suitable for the traditional satellite point observation altimeter, the technology is limited to time dimension calibration only through synchronous sea observation and point-to-point comparison of the satellite altimeter, and can not be applied to calibration inspection of three-dimensional space sea surface height of the imaging radar altimeter. In addition, an imaging radar altimeter calibration and inspection technology based on fixed-point glide networking is proposed abroad, 20 glide devices are required to be distributed within a range of 150 km, the main problems of the method are huge economic cost, the glide fixed-point observation technology is not completely mature, and the observation of the glide fixed-point observation technology can be interfered by stronger ocean currents.
Taking the imaging radar altimeter calibration test carried out in Shandong coast as an example.
Two GNSS buoys are arranged under the flying track of the airplane in coastal mountain areas: the GNSS buoy 1 and the GNSS buoy 2 are respectively provided with an imaging radar altimeter 1 and an imaging radar altimeter 2.
As shown in fig. 2 (a) and fig. 3 (a), the two graphs respectively show the sea surface altitude frequency spectrum observed by the two GNSS buoys and the wave number spectrum comparison graph observed by the airborne imaging altimeter, both graphs represent the non-uniform energy density spectrum, the X-axis unit is the spatial wave number or the time frequency, the dashed line represents the wave number spectrum of the space domain of the airborne imaging altimeter, and the solid line represents the frequency spectrum of the space domain observed by the GNSS buoys.
The invention collects the time domain frequency spectrum of sea surface height and the wave number spectrum of three-dimensional sea surface height collected by the imaging radar altimeter through the unified buoy, converts the wave number spectrum into the frequency spectrum, and performs calibration test of the imaging altimeter on the basis, and can obtain the sea surface height measurement error variance of the imaging radar altimeter of 8cm 2 The standard deviation is less than 3cm. As shown in fig. 2 (b) and 3 (b), both graphs represent the variance conservation spectrum unified by the present invention, the X-axis unit of which is unified to time frequency, wherein the dotted line represents the energy spectrum of the imaging radar altimeter, and the solid line represents the energy spectrum of the GNSS buoy.
From this, it can be seen that: the invention can realize calibration and inspection by using the limited GNSS buoy, greatly reduces the cost, has good operability and can greatly improve the efficiency.
The invention can be widely applied to the calibration and inspection occasion of the ocean altimeter, in particular to the offshore field calibration and inspection occasion of the ocean imaging radar altimeter of a new system.

Claims (8)

1. A space-time spectrum unified marine imaging radar altimeter calibration and inspection method is characterized by comprising the following steps:
s1: a GNSS buoy is arranged in an imaging radar altimeter observation area and fixed through an anchor system;
s2: GNSS buoy data calculation is carried out through a dynamic differential PPK technology, and the dynamic differential PPK technology needs to arrange a GNSS reference station within 50km of a buoy in advance: in order to ensure the base station precision, the base station observation time is not less than 1 day;
s3: selecting a proper GNSS time window length by taking the observation time of the imaging radar altimeter as the center according to the sea condition change condition: to ensure the accuracy of the frequency spectrum, the time length of the selected GNSS sea surface height is usually not less than 30 minutes;
s4: band-pass filtering is carried out on the sea surface height time sequence of the selected GNSS buoy, and the influence of long-period tides and short-period noise is eliminated;
s5: performing frequency spectrum calculation of energy density on the GNSS, and setting a maximum period of sea surface fluctuation of which the unit step length is not less than twice;
s6: three-dimensional sea surface height data collected by an imaging radar altimeter around a GNSS buoy are extracted, bandpass filtering is carried out to eliminate noise influence of a long-wave ground level and a short wave, and a wave number spectrum of the filtered sea surface height energy density is calculated;
s7: the frequency spectrum observed by the GNSS buoy and the wave number spectrum observed by the imaging radar altimeter which belong to the time domain and the space domain can not be directly compared and analyzed;
s8: deducing a frequency spectrum of a time domain and a wave number spectrum unified equation of a space domain through a dispersion relation of ocean fluctuation and an energy density spectrum variance conservation formula;
s9: converting the wave number spectrum observed by the imaging radar altimeter into a frequency spectrum of a time domain through the last step;
s10: integrating on a frequency spectrum of a time domain to obtain a fluctuation variance of the imaging radar altimeter and a GNSS field observed fluctuation variance;
s11: and calculating the cross-correlation coefficient of the unified energy density spectrum of the imaging radar altimeter and the energy density spectrum observed on the GNSS site.
2. The calibration and inspection method of the marine imaging radar altimeter with unified space-time spectrum according to claim 1, wherein in the step S2, the imaging radar altimeter ensures that the high-frequency sea surface fluctuation data is collected, the sampling frequency of the GNSS receiver of the GNSS reference station is set to be not lower than 1Hz, and the sampling frequency is properly increased to 5Hz under the high-dynamic sea condition; before the GNSS buoy is laid, antenna high-error calibration needs to be carried out indoors; the time of the offshore survey of the GNSS buoy required 1 hour each before and after the acquisition of data by the imaging radar altimeter.
3. The method for calibration and inspection of the marine imaging radar altimeter with uniform space-time spectrum according to claim 1, wherein in the step S2, the method of dynamic differential PPK technique comprises the following steps:
s21: using the precise ephemeris and clock error file provided by the IGS to combine IGS stations around the reference station to calculate the coordinates of the reference station under the stable reference frame;
s22: taking the spatial correlation of positioning errors between a reference station and a mobile station into consideration, and adopting a post-processing differential positioning technology of carrier phase measurement to obtain the accurate three-dimensional coordinates of the mobile station, wherein the positioning method comprises the following steps:
Figure FDA0002513187480000021
wherein:
Figure FDA0002513187480000022
initiating a phase ambiguity for the rover; />
Figure FDA0002513187480000023
The phase integer number of cycles from the start epoch to the observation epoch for the rover; />
Figure FDA0002513187480000024
A fractional part of the rover phase observations; dρ is the residuals of each item of the same observation epoch.
4. The calibration and inspection method for the marine imaging radar altimeter with unified space-time spectrum according to claim 1, wherein in the step S5, the value of the maximum period is obtained by trying to set different step sizes for test, and when the value of the energy density spectrum is about equal to 0, the corresponding period value is the maximum period.
5. The method according to claim 1, wherein in step S6, the three-dimensional sea level data has a data range not smaller than twice the maximum sea level fluctuation wavelength to identify the maximum wave number.
6. The method for calibration and inspection of the space-time spectrum unified marine imaging radar altimeter according to claim 3, wherein in the step S8, the energy density spectrum variance conservation formula:
Figure FDA0002513187480000025
Figure FDA0002513187480000026
dispersion relation of ocean wave motion:
Figure FDA0002513187480000027
deriving a unified equation of a frequency spectrum in a time domain and a wave number spectrum in a space domain:
Figure FDA0002513187480000028
S(f)f＝2Q(k)k
wherein: sigma represents the integral variance; f and k represent frequency and wavenumber, respectively; d represents differentiating the parameters in brackets; ln is the logarithm of the base constant e; s and Q are expressed as energy density functions of f and k, respectively.
7. The calibration and inspection method for the marine imaging radar altimeter with unified space-time spectrum according to claim 1, wherein in the step S10, the fluctuation variance of the imaging radar altimeter and the fluctuation variance observed by the GNSS field are the difference of the three-dimensional sea surface altitude result measured by the imaging radar altimeter, the difference of the overall fluctuation of the sea surface is represented, and the smaller the index of the difference is the higher the accuracy of the imaging radar altimeter.
8. The method according to claim 1, wherein in step S11, the index of the cross correlation coefficient characterizes the correlation of the sea wave energy distribution observed by the two, and the larger the value is, the higher the measurement accuracy of the imaging radar altimeter is.
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