CN109283495A - A kind of X-band radar ocean current inversion method based on cross-spectral analysis - Google Patents
A kind of X-band radar ocean current inversion method based on cross-spectral analysis Download PDFInfo
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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
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- 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
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Abstract
The present invention provides a kind of X-band radar ocean current inversion method based on cross-spectral analysis, does cross-spectral analysis respectively to two images adjacent in X-band radar image first, obtains coherence factor spectrum and phase spectrum；Then coherence factor spectrum and phase spectrum are averaged respectively, main wave wave number are determined according to the peak value that coherence factor is composed, and fuzzy using the direction that average phase eliminates main wave wave direction；Different wave direction is selected, model is established according to the phase velocity that dispersion relation obtains, and solve to obtain ocean current vector using least square method.The present invention is able to solve the problem of X-band radar observation sea flow field precision is lower in the prior art and cannot obtain vector flow field using a set of coherent X-band radar, and to meet, the businessization observation of nearshore marine environment, service ocean produces and the demands such as life.
Description
Technical field
The invention belongs to marine remote sensing technology fields, more particularly to a kind of X-band radar sea based on cross-spectral analysis
Flow inversion method.
Background technique
Sea flow field is important ocean dynamics parameter, it not only influence ocean engineering, ship navigation, sea farming and
The activities such as amusement, it is also close with the marine oil spill pollution and generation, the development of Oceanic disasters such as red tide that get worse in recent years etc.
Correlation, thus the observation of ocean current is of great significance.Current meter and acoustics doppler flow speed section plotter (ADCP) etc. are used extensively
In the observation of ocean current, but they can only be put or the ocean current of line variation, installation and it is difficult in maintenance, costly, especially exist
It may be available under complexity sea area concerned by people or extreme sea condition.Satellite remote sensing can obtain the ocean current of large area, still
Onboard GPS, which can only obtain geostrophic current, synthetic aperture radar, can only measure radial flow speed, and its time and space point
Resolution is poor, and the repeated accesses period of satellite is long, thus is not able to satisfy the Current Observations demand of offshore business.X-band radar tool
Have high time and spatial resolution, can round-the-clock, round-the-clock observation sea, be widely used in the observation of ocean current in recent years
In.
Mainly there are boat-carrying navigation X-band radar and coherent X-band radar to be all used for the Current Observations of offshore at present.Using non-
The algorithm of the navigation X-band radar image inverting ocean current of coherent is mainly based upon in three-dimensional Fu of Young et al. (1985) proposition
Leaf transformation algorithm[1-4], it is converted into ocean wave spectrum it require that composing radar image using the modulation transfer function of experience, and the tune
The factors such as modulation trnasfer function and radar system, sea situation, mounting condition are related, are difficult accurate determination, utilize different experimental datas
The form difference of the modulation transfer function obtained with emulation mode is very big[4,5].Coherent radar can recorde the intensity of sea return
And phase information, it can obtain the radial velocity on sea from the phase of echo according to Doppler effect, but the radial flow speed
It is related to ocean current, wave motion etc., it is not readily separated out ocean current, and two sets or more radar simultaneous observations is needed to obtain vector current
?[2].In addition, due to the limitation of radar system all there is time sampling aliasing, radar image with distance and direction in two kinds of radars
The problems such as decaying, these factors limit the accuracy of observation of ocean current.Therefore, a kind of simple and easy utilization X-band radar is invented
The method in inverting sea flow field, with solve in the prior art coherent and non-coherent X-band radar observation ocean current precision it is poor, with
And the problems such as merely with a set of coherent radar can not obtaining vector flow field, has become technology anxious to be resolved in the art and asks
Topic.
Bibliography:
[1]I.R.Young,W.Rosenthal,and F.Ziemer,"A three-dimensional analysis
of marine radar images for the determination ofocean wave directionality and
surface currents,"Journal ofGeophysical Research,vol.90,pp.1049-1059,1985.
[2]Trizna Dennis,Method and apparatus for coherent marine radar
Measurements of properties ofocean waves and currents, application number: US20100868912, beauty
State's patent, the applying date: 2010.8.26
[3] Wu Xiongbin etc., a kind of X-waveband wave observation radar ocean current inversion preprocess method, application number:
CN201310029849.7, China, the applying date: 2013.1.25
[4]J.C.Nieto-Borge,G.R.Rodriguez,K.Hessner,and P.I.Gonzalez,"
Inversion of Marine Radar Images for Surface Wave Analysis,"Journal of
Atmospheric and Oceanic Technology,vol.21,pp.1291-1300,2004.
[5] Zhongbiao Chen, Biao Zhang, Yijun He, Zhongfeng Qiu, Perrie William, A
New Modulation Transfer Function for Ocean Wave Spectra Retrieval from X-band
Marine Radar Imagery, Chinese Journal ofOceanology and Limnology.Vol.33No.5,
P.1132-1141,2015.
Summary of the invention
Goal of the invention: the present invention provides a kind of simple and easy method using X-band radar image inverting sea flow field,
Precision to solve X-band radar observation ocean current in the prior art is lower and can not be obtained using a set of coherent X-band radar
The problem of vector flow field.
Technical solution: the present invention provides a kind of X-band radar ocean current inversion method based on cross-spectral analysis, specifically includes
Following steps:
Step 1: choosing X-band radar image sequence I, cross-spectral analysis is done to adjacent two images respectively, obtains phase
Responsibility number
And phase
Φij(k, φ)=arg (Sij), i, j=1,2 ..., n (2)
Wherein Ii(x, y) is the intensity value of radar image, and x and y are the abscissa and ordinate at image midpoint, and i and j are figure
The sequence of picture, n be image quantity, k withFrequency domain coordinates are formed, K is wave number,For wave direction, SijIt is image Ii(x, y) and Ij
The power spectrum of (x, y), SiiFor IiThe power spectrum of (x, y) and its own, arg () expression take argument of a complex number.
Step 2: according to the coherence factor of step 1And phaseAll adjacent images are handed over
Spectrum analysis is pitched, average coherence coefficient is obtained
And average phase
Step 3: main wave wave number k is determined according to the peak value of the coherence factor in step 1m, and utilize the average phase in step 2
Position determines that direction of the true main wave wave number for eliminating 180 degree is fuzzy；The direction of the 180 degree obscures as phase average in equation 3
Two of responsibility number are about the symmetrical maximum value of far point.
Step 4: selecting main wave wave direction φmAll wave direction φ of neighbouring different directionsp, p is wave direction φmIt is neighbouring not
The number of equidirectional all wave direction, and establish such as drag；
Equation 5 is solved using least square method, obtains ocean current vectorValue；
Wherein, cradarFor wave directionThe phase velocity of direction wave,ctheoryFor the theory of phase velocity
Value, according to the scattered frequency relational theory of wave, obtainsWherein g is acceleration of gravity；H is water
It is deep,For ocean current vector, Δ t is the time interval of adjacent two images, and the time interval between all two images is all the same；For wave-number vector；Q=1,2,3 ..., p.
Further, determine that direction of the true main wave wave number for eliminating 180 degree is fuzzy in the step 3, selection is true
The method of main wave wave number are as follows: selection meetsPeak value wave numberFor true main wave wave number.
Further, the wave direction φ selected in the step 5p, wave direction φpMeet following requirements simultaneously:
1,φpCoherence factor γ (k, φp) > 0.6, wherein wave number k meets: 0.03≤k≤0.3rad/m；
2,|φp-φm| 30 ° of <,For main wave wave direction.
The utility model has the advantages that the invention is simple and feasible, be able to solve in the prior art X-band radar observation sea flow field precision compared with
It is low and the problem of vector flow field cannot be obtained using a set of coherent X-band radar, to meet the business of nearshore marine environment
The demands such as observation, the production of service ocean and life.
Detailed description of the invention
Fig. 1 is algorithm flow chart of the invention；
Fig. 2 is that the present invention utilizes the wave phase velocity of width X-band radar image acquisition compared with theoretical phase velocity.
Specific embodiment
The attached drawing for constituting a part of the invention is used to provide further understanding of the present invention, schematic reality of the invention
It applies example and its explanation is used to explain the present invention, do not constitute improper limitations of the present invention.
As shown in Figure 1, the present invention provides a kind of X-band radar ocean current inversion method based on cross-spectral analysis, it is specific to wrap
Include following steps:
Step 1: choosing X-band radar image sequence I, cross-spectral analysis is done to adjacent two images respectively, obtains phase
Responsibility number
And phase
Φij(k, φ)=arg (Sij), i, j=1,2 ..., n (2)
Wherein Ii(x, y) is the intensity value of radar image, and x and y are the abscissa and ordinate at image midpoint, and i and j are figure
The sequence of picture, n be image quantity, k withFrequency domain coordinates are formed, K is wave number,For wave direction, SijIt is image Ii(x, y) and Ij
The power spectrum of (x, y), SiiFor IiThe power spectrum of (x, y) and its own, arg () expression take argument of a complex number.
Step 2: according to the coherence factor of step 1And phaseAll adjacent images are handed over
Spectrum analysis is pitched, average coherence coefficient is obtained
And average phase
Step 3: main wave wave number k is determined according to the peak value of the coherence factor in step 1m, and utilize the average phase in step 2
Position determines that direction of the true main wave wave number for eliminating 180 degree is fuzzy；
Step 4: selecting main wave wave direction φmAll wave direction φ of neighbouring different directionsp, p is wave direction φmIt is neighbouring not
The number of equidirectional all wave direction, and establish such as drag；
Equation 5 is solved using least square method, obtains ocean current vectorValue；
Wherein, cradarFor wave directionThe phase velocity of direction wave,ctheoryFor the theory of phase velocity
Value, according to the scattered frequency relational theory of wave, obtainsWherein g is acceleration of gravity；H is water
It is deep,For ocean current vector, Δ t is the time interval of adjacent two images, and the time interval between all two images is all the same；For wave-number vector；Q=1,2,3 ..., p.
It should be noted that determine that direction of the true main wave wave number for eliminating 180 degree is fuzzy in the step 3, selection
The method of true main wave wave number are as follows: selection meetsPeak value wave numberFor true main wave wave
Number.
The wave direction φ selected in the step 5p, wave direction φpMeet following requirements simultaneously:
1,φpCoherence factor γ (k, φp) > 0.6, wherein wave number k meets: 0.03≤k≤0.3rad/m；
2,|φp-φm| 30 ° of <,For main wave wave direction.
As shown in Fig. 2, using the wave phase velocity of width X-band radar image acquisition compared with theoretical phase velocity, it can
To find out that the two has preferable consistency, so as to be fitted to obtain vector flow field using least square method.
Claims (3)
1. a kind of X-band radar ocean current inversion method based on cross-spectral analysis, which comprises the steps of:
Step 1: choosing X-band radar image sequence I, cross-spectral analysis is done to adjacent two images respectively, obtains phase responsibility
Number
And phase
Wherein Ii(x, y) is the intensity value of radar image, and x and y are the abscissa and ordinate at image midpoint, and i and j are image
Sequence, n be image quantity, k withFrequency domain coordinates are formed, K is wave number,For wave direction, SijIt is image Ii(x, y) and Ij(x, y)
Power spectrum, SiiFor IiThe power spectrum of (x, y) and its own, arg () expression take argument of a complex number；
Step 2: according to the coherence factor of step 1And phaseCross spectrum is done to all adjacent images
Analysis, obtains average coherence coefficient
And average phase
Step 3: main wave wave number k is determined according to the peak value of the coherence factor in step 1m, and it is true using the average phase in step 2
The direction that fixed true main wave wave number is used to eliminate 180 degree is fuzzy；
Step 4: selecting main wave wave direction φmAll wave direction φ of neighbouring different directionsp, p is wave direction φmNeighbouring not Tongfang
To all wave direction number, and establish such as drag；
Equation 5 is solved using least square method, obtains ocean current vectorValue；
Wherein, cradarFor wave directionThe phase velocity of direction wave,ctheoryFor the theoretical value of phase velocity, root
According to the scattered frequency relational theory of wave, obtainWherein g is acceleration of gravity；H is the depth of water,For
Ocean current vector, Δ t are the time interval of adjacent two images, and the time interval between all two images is all the same；For wave-number vector；Q=1,2,3 ..., p.
2. a kind of X-band radar ocean current inversion method based on cross-spectral analysis according to claim 1, feature exist
In the direction for determining that really main wave wave number is used to eliminate 180 degree in the step 3 obscures, the method for selecting true main wave wave number
Are as follows: selection meetsPeak value wave numberFor true main wave wave number.
3. a kind of X-band radar ocean current inversion method based on cross-spectral analysis according to claim 1, feature exist
In the wave direction φ selected in the step 5p, wave direction φpMeet following requirements simultaneously:
1,φpCoherence factor γ (k, φp) > 0.6, wherein wave number k meets: 0.03≤k≤0.3rad/m；
2,|φp-φm| 30 ° of <,For main wave wave direction.
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| CN111102120A (en) * | 2019-11-25 | 2020-05-05 | 国家海洋技术中心 | Method for testing power characteristics of wave energy power generation equipment |
| CN113050091A (en) * | 2021-03-08 | 2021-06-29 | 国家海洋技术中心 | Wind speed and direction joint inversion method and system for satellite-borne synthetic aperture radar |
| CN113064161A (en) * | 2021-03-30 | 2021-07-02 | 南京信息工程大学 | Sea wave spectrometer cross spectrum calculation method based on dual-sub pulse reconstruction |
| CN113176572A (en) * | 2021-04-27 | 2021-07-27 | 中山大学 | Sea surface wave spectrum inversion method and system based on circular scanning SAR |
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