CN111505646A - Space-time spectrum unified marine imaging radar altimeter calibration and inspection method - Google Patents

Space-time spectrum unified marine imaging radar altimeter calibration and inspection method Download PDF

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CN111505646A
CN111505646A CN202010342395.9A CN202010342395A CN111505646A CN 111505646 A CN111505646 A CN 111505646A CN 202010342395 A CN202010342395 A CN 202010342395A CN 111505646 A CN111505646 A CN 111505646A
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imaging radar
radar altimeter
gnss
time
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CN111505646B (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 an imaging radar altimeter, buoy data calculation is carried out through a dynamic difference 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 the frequency spectrum of the time domain and the wave number spectrum of the space domain; converting the frequency spectrum into a time domain frequency spectrum and integrating to obtain the fluctuation variance of the imaging radar altimeter and the fluctuation variance observed on site; and calculating the cross-correlation coefficient of the unified energy density spectrum. The invention utilizes the sea surface height time sequence in the time domain observed by the limited buoy to calibrate the two-dimensional sea surface height of the space domain observed by the imaging radar altimeter, thereby reducing the on-site calibration cost.

Description

Space-time spectrum unified marine imaging radar altimeter calibration and inspection method
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 ocean remote sensing world at home and abroad at present, no satellite altimeter of the type transmits and operates at present, and airborne tests are developed only in China and America. The calibration inspection technology mainly utilizes ground measured data to calibrate the load observation precision and the data quality, and a larger technical blank exists in the field of calibration inspection of the three-dimensional imaging altimeter at present.
The known calibration technology is mainly based on point-to-point checking of a tide station, a GNSS buoy and an active calibrator, that is, a calibration result based on synchronous observation data is obtained each time a satellite passes through a calibration field. However, the imaging radar altimeter and the traditional off-satellite point altimeter are different in that the imaging radar altimeter can observe the sea level with a certain swath width, and is not limited to an along-track measuring line formed by off-satellite points, and the three-dimensional sea level height can be acquired through the observation mode, so that high-resolution sea level space fluctuation information can be acquired.
The known calibration verification technology cannot realize the spatial domain calibration verification of the imaging radar altimeter. At present, a solution proposed in the united states is fixed-point control glider networking observation, which is only in the conceptual description and simulation stage, and has a calibration test capable of realizing an imaging radar altimeter, but has not been proved by experiments, and has larger uncertainty.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a space-time spectrum unified marine imaging radar altimeter calibration inspection method, which can realize the purpose by using a limited anchor system GNSS buoy, greatly reduce the cost and acquire a high-precision sea level altitude time sequence.
The invention relates to a calibration inspection method of a marine imaging radar altimeter with unified space-time spectrum, which comprises the following steps:
s1: a GNSS buoy is arranged in an observation area of the imaging radar altimeter and is fixed through an anchor system;
s2: the GNSS buoy data are resolved by a dynamic difference PPK technology, and the dynamic difference PPK technology needs to arrange a GNSS reference station within a range of 50km away from the buoy in advance: in order to ensure the precision of the base station, the observation time of the base station is not less than 1 day;
s3: according to the sea state change condition, selecting a proper GNSS time window length by taking the observation time of the imaging radar altimeter as a center: in order to ensure the precision of the frequency spectrum, the time length of the selected GNSS sea surface height is usually not less than 30 minutes;
s4: performing band-pass filtering on the selected sea surface height time sequence of the GNSS buoy to eliminate the influence of long-period tide and short-period noise;
s5: performing frequency spectrum calculation of energy density on the GNSS, and setting the maximum period of sea surface fluctuation with unit step length not less than twice;
s6: extracting three-dimensional sea surface height data acquired by an imaging radar altimeter around a GNSS buoy, carrying out band-pass filtering to eliminate noise influence of a ground level surface of a long wave and a short wave, and calculating a wave number spectrum of the filtered sea surface height energy density;
s7: the frequency spectrum observed by the GNSS buoy and the wave number spectrum observed by the imaging radar altimeter are obtained, the two spectrums belong to time and space domains, and the form of the energy spectrum cannot be directly compared and analyzed;
s8: deducing a frequency spectrum unified equation 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 a wave number spectrum observed by the imaging radar altimeter into a time domain frequency spectrum through the previous step;
s10: integrating on a frequency spectrum of a time domain to obtain fluctuation variance of an imaging radar altimeter and fluctuation variance observed on a GNSS site;
s11: and calculating the cross-correlation coefficient of the unified imaging radar altimeter energy density spectrum and the energy density spectrum observed on the GNSS site.
Preferably, in step S2, the imaging radar is designed to ensure that the high-frequency sea surface fluctuation data is collected, and the sampling frequency of the GNSS receiver of the GNSS reference station is set to not lower than 1Hz, which is appropriately increased to 5Hz under the high dynamic sea condition; before the GNSS buoy is arranged, high-error calibration of an antenna needs to be carried out indoors; the time for the GNSS buoy to take the marine survey needs to be 1 hour each before and after the imaging radar altimeter collects the data.
Preferably, in step S2, the method of the dynamic differential PPK technique includes the following steps:
s21: the coordinates of the reference station under a stable reference frame are calculated by using a precise ephemeris and a clock error file provided by the IGS and combining with IGS stations around the reference station;
s22: the space correlation of the positioning error between the reference station and the mobile station is considered, the post-processing differential positioning technology of carrier phase measurement is adopted to obtain the accurate three-dimensional coordinates of the mobile station, and the positioning method comprises the following steps:
Figure BDA0002469001640000021
in the formula:
Figure BDA0002469001640000022
starting phase ambiguities for the rover;
Figure BDA0002469001640000023
the number of whole cycles of phase from the rover start epoch to the observation epoch;
Figure BDA0002469001640000024
is the fractional part of the rover phase observation; and d rho is residual errors 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 an experiment, and when the value of the energy density spectrum is approximately equal to 0, the corresponding period value is the maximum period.
Preferably, in step S6, the data range of the three-dimensional sea height data should not be less than twice the maximum sea wave length to identify the maximum wave number.
Preferably, in step S8, the energy density spectrum variance conservation formula is:
Figure BDA0002469001640000031
Figure BDA0002469001640000032
dispersion relation of ocean wave:
Figure RE-GDA0002513187490000033
deriving a unified equation of the frequency spectrum of the time domain and the wave number spectrum of the space domain:
Figure BDA0002469001640000034
S(f)f＝2Q(k)k
in the formula: σ represents the integral variance; f and k represent frequency and wave number, respectively; d represents the differential to the parameter in parentheses; ln is a logarithm based on a constant e; s and Q are expressed as energy density functions of f and k, respectively.
Preferably, in step S10, the fluctuation variance of the imaging radar altimeter and the fluctuation variance observed in the GNSS field are different, that is, the deviation variance of the result of the imaging radar altimeter measuring the three-dimensional sea level height represents the difference of the total fluctuation of the sea level, and a smaller index of the deviation variance indicates a higher precision of the imaging radar altimeter.
Preferably, in the step S11, the indicator of the cross-correlation coefficient represents the correlation between the two observed sea surface fluctuation energy distributions, and a larger value thereof indicates a higher measurement accuracy of the imaging radar altimeter.
The invention has the beneficial effects that: by unifying the time domain frequency spectrum and the space domain wave number spectrum, the calibration inspection of the imaging radar altimeter based on the anchor system GNSS buoy can be realized; theoretically, the purpose of the invention can be realized by arranging a buoy, thereby greatly saving the calibration and inspection cost and improving the production efficiency.
Drawings
FIG. 1 is a block flow diagram of the calibration verification method of the present invention.
Fig. 2(a) is a sea surface height frequency spectrum observed by the GNSS buoy 1 and a wave number spectrum observed by the imaging radar altimeter 1.
Fig. 2(b) is the energy spectrum of the GNSS buoy 1 and the energy spectrum of the imaging radar altimeter 1 of the unified energy density spectrum of the present invention.
Fig. 3(a) is a sea surface height frequency spectrum observed by the GNSS buoy 2 and a wave number spectrum observed by the imaging radar altimeter 2.
Fig. 3(b) is a GNSS buoy 2 energy spectrum and an imaging radar altimeter 2 energy spectrum of the unified energy density spectrum of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1:
as shown in FIG. 1, the marine imaging radar altimeter calibration and inspection method with unified space-time spectrum, provided by the invention, can realize point-to-surface calibration for the purpose of calibration and inspection of the imaging radar altimeter and make up the problem of inapplicability of point-to-point calibration in the conventional calibration technology in the calibration of the imaging radar altimeter.
First, a theoretical assumption is made that, for a homogeneous field of wave-induced sea level elevation SSE in the space-time domain, the following three statements are correct:
a if the time series of measured SSE is long enough, the variance of the measured SSE is the same at any location within the domain.
B if the area of the SSE to be measured is large enough, the variance of the SSE measured at any time in the domain is the same.
C if conditions a and B are true, the wave-induced SSE is a uniform field in space and time, and the variance of a and B is equal.
In the actual calibration process, the method for calibrating the data of the space domain imaging radar altimeter by using the GNSS buoy in the time domain comprises the following steps:
s1: and arranging a GNSS buoy in an observation area of the imaging radar altimeter, and fixing the GNSS buoy through an anchoring system. In order to ensure the collection of high-frequency sea surface fluctuation data, the sampling frequency of the GNSS receiver is set to be not lower than 1Hz, and can be properly increased to 5Hz under the high dynamic sea condition. The GNSS buoy needs to be calibrated for high antenna error indoors before being deployed. The marine survey time of the GNSS buoy needs to be 1 hour before and after the imaging radar altimeter collects data.
S2: the GNSS buoy data are resolved by a dynamic difference PPK technology, a GNSS reference station needs to be arranged in advance within a range of 50km away from the buoy by the dynamic difference PPK technology, and in order to guarantee the accuracy of the base station, the observation time of the base station is not less than 1 day.
Wherein, the basic flow of PPK positioning is as follows: calculating the coordinates of the reference station under the stable reference frame by using a precise ephemeris and a clock error file provided by the IGS and combining with IGS stations around the reference station; the space relativity of positioning errors between a reference station and a mobile station is considered, the post-processing differential positioning technology of carrier phase measurement is adopted to obtain the accurate three-dimensional coordinates of the mobile station, and the positioning mode is as follows:
Figure BDA0002469001640000041
in the formula:
Figure BDA0002469001640000042
starting phase ambiguities for the rover;
Figure BDA0002469001640000043
the number of whole cycles of phase from the rover start epoch to the observation epoch;
Figure BDA0002469001640000044
is the fractional part of the rover phase observation; and d rho is residual errors of the same observation epoch.
S3: according to the sea state change condition, the appropriate GNSS time window length is selected by taking the observation time of the imaging radar altimeter as the center, and in order to ensure the precision of the frequency spectrum, the selected GNSS sea height time length is usually not less than 30 minutes.
S4: and performing band-pass filtering on the selected sea surface height time sequence of the GNSS buoy to eliminate the influence of long-period tide and short-period noise.
S5: and performing frequency spectrum calculation of energy density on the GNSS, and setting the maximum period of sea surface fluctuation with unit step length not less than twice. The value of the maximum period can be obtained by trying to set different step lengths for testing, and when the numerical value of the energy density spectrum is approximately equal to 0, the corresponding period value is the maximum period.
S6: and extracting three-dimensional sea surface height data acquired by the imaging radar altimeter around the GNSS buoy, carrying out band-pass filtering to eliminate the noise influence of the ground level surface of the long wave and the short wave, and calculating the wave number spectrum of the filtered sea surface height energy density. Its data range should not be less than twice the maximum sea wave wavelength 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 are obtained, and the two spectrums belong to time and space domains, so that the form of the energy spectrum cannot be directly compared and analyzed. Space-time unification needs to be performed using the next step.
S8: the frequency spectrum of the time domain and the wave number spectrum of the space domain are derived by the dispersion relation of the ocean wave (as shown in formula 4) and the energy density spectrum variance conservation formula (as shown in formula 2 and formula 3) (as shown in formula 5):
Figure BDA0002469001640000051
Figure RE-GDA0002513187490000053
Figure BDA0002469001640000054
S(f)f＝2Q(k)k (5)
in the formula: σ denotes the integral variance, f and k denote frequency and wave number, respectively, d denotes the differential to the parameter in parentheses, ln is a logarithm based on a constant e, and S and Q denote energy density functions of f and k, respectively.
S9: and converting the wave number spectrum observed by the imaging radar altimeter into a time domain frequency spectrum through the last step.
S10: and integrating on a frequency spectrum of a time domain to obtain fluctuation variance of the imaging radar altimeter and fluctuation variance observed on the GNSS site. The difference between the two is the deviation variance of the three-dimensional sea surface height result measured by the imaging radar altimeter, and the difference of the fluctuation of the sea surface total body is represented. Smaller this index indicates higher accuracy of the imaging radar altimeter.
S11: and calculating the cross-correlation coefficient of the unified imaging radar altimeter energy density spectrum and the energy density spectrum observed on the GNSS site. The index represents the correlation of the sea surface fluctuation energy distribution observed by the two indexes, and the larger the value of the index is, the higher the measurement accuracy of the imaging radar altimeter is.
The invention has the beneficial effects that: by unifying the time domain frequency spectrum and the space domain wave number spectrum, the calibration inspection of the imaging radar altimeter based on the anchor system GNSS buoy can be realized; theoretically, the purpose of the invention can be realized by arranging a buoy, thereby greatly saving the calibration and inspection cost and improving the production efficiency.
Example 2:
the effects of the present invention will be explained below with reference to examples and drawings.
The invention relates to a method for calibrating sea height of an imaging radar altimeter, which is mainly suitable for a traditional satellite point observation altimeter, only by point-to-point comparison of synchronous sea observation and a satellite altimeter, belongs to calibration limited in a time dimension, and cannot be applied to calibration inspection of three-dimensional space sea height of the imaging radar altimeter. In addition, a calibration inspection technology of an imaging radar altimeter based on fixed-point glider networking is provided abroad, 20 glider devices are required to be arranged within the range of 150 kilometers, the method has the main problems of high economic cost, the fixed-point glider observation technology is not completely mature, and the observation of the method can be interfered by strong ocean currents.
Take the example of the imaging radar altimeter calibration test conducted in Shandong coastal areas.
Two GNSS buoys are arranged under the flight track of the airplane in Shandong coastal areas: the imaging radar altimeter 1 and the imaging radar altimeter 2 are respectively mounted on the GNSS buoy 1 and the GNSS buoy 2.
As shown in fig. 2(a) and fig. 3(a), two graphs respectively show a comparison graph of a sea surface height frequency spectrum observed by two GNSS buoys and a wave number spectrum observed by an airborne imaging altimeter, wherein both graphs represent non-uniform energy density spectrums, the X-axis unit of which is a space wave number or a time frequency, a dotted line represents a wave number spectrum of a space domain of the airborne imaging altimeter, and a solid line represents a frequency spectrum of the space domain observed by the GNSS buoy.
The method acquires a time domain frequency spectrum of sea surface height and a wave number spectrum of three-dimensional sea surface height acquired by an imaging radar altimeter through a unified buoy, converts the wave number spectrum into the frequency spectrum, performs calibration inspection on the imaging altimeter on the basis, and can obtain the sea surface height measurement error variance of the imaging radar altimeter of 8cm2And the standard deviation is less than 3 cm. As shown in FIGS. 2(b) and 3(b), both graphs show the conservation of variance spectra after being unified by the present invention, with the X-axis units being unifiedTo the time frequency, where the dashed line represents the energy spectrum of the imaging radar altimeter and the solid line represents the energy spectrum of the GNSS buoy.
Thus, it can be seen that: the invention can realize the calibration and inspection by using the limited GNSS buoy, the cost is greatly reduced, the GNSS buoy has good operability, and the efficiency can be greatly improved.
The invention can be widely applied to the calibration and inspection occasions of the ocean altimeter, in particular to the offshore field calibration and inspection occasions of the ocean imaging radar altimeter of a new system.

Claims (8)

1. A calibration inspection method for a marine imaging radar altimeter with unified space-time spectrum is characterized by comprising the following steps:
s1: a GNSS buoy is arranged in an observation area of the imaging radar altimeter and is fixed through an anchor system;
s2: the GNSS buoy data are resolved by a dynamic differential PPK technology, and the dynamic differential PPK technology needs to arrange a GNSS reference station within a range of 50km away from a buoy in advance: in order to ensure the precision of the base station, the observation time of the base station is not less than 1 day;
s3: according to the sea state change condition, selecting a proper GNSS time window length by taking the observation time of the imaging radar altimeter as the center: in order to ensure the precision of the frequency spectrum, the time length of the selected GNSS sea surface height is usually not less than 30 minutes;
s4: performing band-pass filtering on the selected sea surface height time sequence of the GNSS buoy to eliminate the influence of long-period tide and short-period noise;
s5: performing frequency spectrum calculation of energy density on the GNSS, and setting the maximum period of sea surface fluctuation with unit step length not less than twice;
s6: extracting three-dimensional sea surface height data acquired by an imaging radar altimeter around a GNSS buoy, carrying out band-pass filtering to eliminate noise influence of a ground level surface of a long wave and a short wave, and calculating a wave number spectrum of the filtered sea surface height energy density;
s7: obtaining a frequency spectrum observed by the GNSS buoy and a wave number spectrum observed by the imaging radar altimeter, wherein the frequency spectrum and the wave number spectrum belong to time and space domains, and the form of an energy spectrum cannot be directly compared and analyzed;
s8: deriving a frequency spectrum unified equation 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 a wave number spectrum observed by the imaging radar altimeter into a time domain frequency spectrum through the previous step;
s10: integrating on a frequency spectrum of a time domain to obtain fluctuation variance of an imaging radar altimeter and fluctuation variance observed on a GNSS site;
s11: and calculating the cross-correlation coefficient of the unified imaging radar altimeter energy density spectrum and the energy density spectrum observed on the GNSS site.
2. The space-time spectrum unified marine imaging radar altimeter calibration test method according to claim 1, wherein in step S2, the imaging radar altimeter is designed to ensure the collection of high-frequency sea surface fluctuation data, the sampling frequency of the GNSS receiver of the GNSS reference station is set to not less than 1Hz, and is properly increased to 5Hz under high dynamic sea conditions; before the GNSS buoy is arranged, high-error calibration of an antenna needs to be carried out indoors; the marine survey time of the GNSS buoy needs to be 1 hour before and after the imaging radar altimeter collects data.
3. The space-time spectrum unified marine imaging radar altimeter calibration test method according to claim 1, wherein in the step S2, the dynamic differential PPK technique is implemented by the following steps:
s21: calculating the coordinates of the reference station under the stable reference frame by using a precise ephemeris and a clock error file provided by the IGS and combining with IGS stations around the reference station;
s22: the space correlation of the positioning error between the reference station and the flowing station is considered, the post-processing differential positioning technology of carrier phase measurement is adopted to obtain the accurate three-dimensional coordinates of the flowing station, and the positioning method comprises the following steps:
Figure FDA0002469001630000021
in the formula:
Figure FDA0002469001630000022
starting phase ambiguities for the rover;
Figure FDA0002469001630000023
the whole cycle number of the phase from the initial epoch to the observation epoch of the rover station;
Figure FDA0002469001630000024
is the fractional part of the rover phase observation; and d rho is residual errors of the same observation epoch.
4. The method for calibrating and checking a space-time spectrum unified marine imaging radar altimeter according to claim 1, wherein in step S5, the value of the maximum period is obtained by trying to set different step sizes for experiments, and when the value of the energy density spectrum is approximately equal to 0, the corresponding period value is the maximum period.
5. The space-time spectrum unified marine imaging radar altimeter calibration test method according to claim 1, wherein in step S6, the data range of the three-dimensional sea level height data should not be less than twice the maximum sea level fluctuation wavelength to identify the maximum wave number.
6. The space-time spectrum unified marine imaging radar altimeter calibration test method according to claim 3, wherein in the step S8, the energy density spectrum variance conservation formula:
Figure FDA0002469001630000025
Figure FDA0002469001630000026
dispersion relation of ocean wave:
Figure DEST_PATH_FDA0002513187480000027
deriving a unified equation of the frequency spectrum of the time domain and the wave number spectrum of the space domain:
Figure FDA0002469001630000028
S(f)f＝2Q(k)k
in the formula: σ represents the integral variance; f and k represent frequency and wave number, respectively; d represents the differential to the parameter in parentheses; ln is a logarithm based on a constant e; s and Q are expressed as energy density functions of f and k, respectively.
7. The method for calibrating and checking a marine imaging radar altimeter with unified space-time spectrum according to claim 1, wherein in step S10, the fluctuation variance of the imaging radar altimeter and the fluctuation variance observed in the GNSS site are different, that is, the deviation variance of the result of measuring the three-dimensional sea level height by the imaging radar altimeter, and the difference representing the total fluctuation of the sea level represents that the smaller the index of the deviation variance is, the higher the accuracy of the imaging radar altimeter is.
8. The method for calibrating and checking a space-time spectrum unified marine imaging radar altimeter according to claim 1, wherein in step S11, the index of the cross-correlation coefficient represents the correlation between the sea wave energy distributions observed by the two, and a larger value indicates a higher measurement accuracy of the imaging radar altimeter.
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CN112731453A (en) * 2020-12-21 2021-04-30 自然资源部第一海洋研究所 Vertical reference detection method for tide station by utilizing GNSS buoy
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