CN103869299B - Based on the polarimetric synthetic aperture radar calibrating method of natural exposed soil - Google Patents

Abstract

The invention discloses a kind of polarimetric synthetic aperture radar calibrating method based on natural exposed soil, first the present invention carries out estimating to the crosstalk of POLSAR radar image and cross polarization channel imbalance parameter and eliminates; Then, to POLSAR radar image carry out distance to orientation to piecemeal; Finally, with the low conveyor screw composition of true soil for optimization aim builds majorized function, and utilize same distance to have the feature of identical unknown number to block, solve same polarization channel imbalance.The present invention utilizes the conveyor screw weak scattering characteristic of nature exposed soil, the transmitting existed in POLSAR radar system, reception distortion matrix are calibrated, observed reading devious is calibrated again as true scattering matrix, can be radar and provide powerful guarantee in application aspect such as survey of territorial resources, disaster emergency responses.

Description

Based on the polarimetric synthetic aperture radar calibrating method of natural exposed soil

Technical field

The invention belongs to SAR image processing technology field, particularly a kind of polarimetric synthetic aperture radar (PolarimetricSyntheticApertureRadar, POLSAR) calibrating method based on natural exposed soil.

Background technology

As a kind of Advanced Synthetic Aperture Radar technology, POLSAR(polarimetric synthetic aperture radar) obtain Terrain Scattering matrix by transmitting, reception level and vertical polarization electromagnetic wave, land observation is carried out under round-the-clock, round-the-clock condition, make up the deficiency of other remote sensings, effectively auxiliary land resources Classification Count, physical parameter such as acquisition vegetation biomass and surface humidity etc.The information of POLSAR observation is often subject to systems radiate, receives the impact of distortion matrix, makes observed reading and actual value generation deviation.Distortion process can be divided into three parts usually: crosstalk (Crosstalk), cross polarization channel imbalance (Cross-polarizationChannelImbalance), same polarization channel imbalance (Co-polarizationChannelImbalance).

Existing polarimetric calibration method utilizes reciprocity and the scattering symmetry of natural feature on a map, corrects under the condition not needing reference target to crosstalk, cross polarization channel imbalance; For same polarization channel imbalance, existing calibrating method all needs to lay at least one active or passive corrner reflector in scene and calibrates, and is often difficult to carry out corner reflector laying in some rugged countries, mountain region (as China is western), unmanned desert area.External machine-borne polarization synthetic-aperture radar hardware system is reliable and stable, and when not carrying out the calibration of same polarization channel imbalance, image range error is often less than 0.5dB, phase error is less than 5 degree, can meet the most basic land accuracy of observation requirement; China's electronic hardware systematic error is often higher, and the data of not carrying out polarimetric calibration are difficult to meet remote sensing primary demand, and this seriously constrains China POLSAR systematic difference scope.

Summary of the invention

For the deficiency that prior art exists, the present invention proposes a kind of polarimetric synthetic aperture radar calibrating method based on natural exposed soil estimating same polarization channel imbalance, the method utilizes the low conveyor screw scattering properties of nature exposed soil, by mathematics and EM scatter model, and a kind of majorized function is proposed, by the POLSAR observed reading that natural exposed soil is corresponding, estimate same polarization channel imbalance.

For solving the problems of the technologies described above, the present invention adopts following technical scheme:

Based on the polarimetric synthetic aperture radar calibrating method of natural exposed soil, comprise step:

Step 1, with exposed soil in Synthetic Aperture Radar images for observed object, estimates and eliminates crosstalk and the cross polarization channel imbalance of polarimetric synthetic aperture radar image;

Step 2, the acquisition of covariance matrix observed reading, this step comprises sub-step further:

2.1 by polarimetric synthetic aperture radar image in orientation to be divided into P block orientation to block, in distance to being divided into N block distance to block, that is, each distance is to the corresponding P block orientation of block to block;

2.2 for each distance to block, adjust the distance respectively to each orientation that block is corresponding and be averaging processing to the polarization covariance matrix of exposed soil pixel in block, obtain the average polarization covariance matrix of each orientation to block, using P average polarization covariance matrix of acquisition as distance to the observed reading of block;

Step 3, estimate same polarization channel imbalance, this step comprises sub-step further:

3.1 with soil conveyor screw composition for optimization aim builds majorized function wherein, p=k ^-1=a+jb, a and b are real part and the imaginary part of p, and j is imaginary symbols, and k is same polarization channel imbalance to be solved; Im operates for asking imaginary part; C ₁₂for the element that the 1st row the 2nd in average covariance matrices C arranges, C ₂₃for the element that the 2nd row the 3rd in average covariance matrices C arranges;

3.2 according to the observed reading of distance to block, adopts Newton solution by iterative method majorized function to obtain the estimated value of a and b, thus obtain the same polarization channel imbalance estimated value of each distance to block;

Step 4, carries out the matching of intensity and phase place to the same polarization channel imbalance estimated value of block to each distance, obtain closely end to same polarization channel imbalance corresponding to remote each pixel, eliminate distortion factor.

Above-mentioned steps 1 comprises sub-step further:

1.1 windows opening size n × n respectively in polarimetric synthetic aperture radar image centered by each pixel, adopt grey scale pixel value in window to build polarization coherence matrix corresponding to window, n value is artificial default;

1.2 with exposed soil pixel in Synthetic Aperture Radar images for observed object, adopt Qugen scaling method to eliminate crosstalk and the cross polarization channel imbalance of the polarization coherence matrix built.

Above-mentioned sub-step 3.2 comprises further:

A) system of linear equations BM=L is built, wherein, $B=\left[\begin{array}{cc}\frac{{\∂f}_{\mathrm{UZHEX}}^1}{{\∂a}_x}& \frac{{\∂f}_{\mathrm{UZHEX}}^1}{{\∂b}_x}\\ \·& \·\\ \·& \·\\ \·& \·\\ \frac{{\∂f}_{\mathrm{UZHEX}}^P}{{\∂a}_x}& \frac{{\∂f}_{\mathrm{UZHEX}}^P}{{\∂b}_x}\end{array}\right];M=\left[\begin{array}{c}{\mathrm{\Δa}}_x\\ {\mathrm{\Δb}}_x\end{array}\right],{\mathrm{\Δa}}_x$ With Δ b _yfor corrected value to be solved; $L=\left[\begin{array}{c}{-f}_{\mathrm{UZHEX}}^1\\ \·\\ \·\\ \·\\ {-f}_{\mathrm{UZHEX}}^P\end{array}\right];$ represent that distance is to m orientation of block to the majorized function of block, m=1,2 ..., P;

B) iteration initial value p is set _x=a _x+ jb _x, bring iteration initial value and distance into system of linear equations BM=L to the P group observations of block, solve Δ a _xwith Δ b _y;

C) Δ a is adopted _xwith Δ b _yundated parameter a _x=a _x+ Δ a _x, b _y=b _y+ Δ b _y, with the parameter a after upgrading _xand b _yfor parameter current, the corrected value Δ a adopting this to solve _x, Δ b _yand parameter current a _x, b _ycalculating solves residual error || BM-L|| ₂, and compare and solve residual error || BM-L|| ₂with predetermined threshold value size, if the residual error of solving || BM-L|| ₂be less than predetermined threshold value, parameter current a _x, b _ybe solving result, finishing iteration; Otherwise, perform step d);

D) by parameter current a _x, b _yand distance is to the P group observations substitution system of linear equations BM=L of block, continues to solve corrected value Δ a _xwith Δ b _y, then, perform step c).

In sub-step 3.2, the iteration initial value p that many groups are different can be set _x=a _x+ jb _x, the step a) ~ d described in employing) and obtain solving result corresponding to many group iteration initialization respectively, will residual error be solved || BM-L|| ₂minimum solving result is as last solution.

Compared to the prior art, the present invention has following features:

1, the conveyor screw weak scattering characteristic of nature exposed soil is utilized, the transmitting existed in POLSAR radar system, reception distortion matrix are calibrated, observed reading devious is calibrated again as true scattering matrix, can be radar and provide powerful guarantee in application aspect such as survey of territorial resources, disaster emergency responses.

2, based on image block, normalization soil conveyor screw ingredient f is proposed _uZHEX, and by making conveyor screw ingredient f in POLSAR image _uZHEXmeet f _uZHEX=0 solves same polarization channel imbalance k, effectively can avoid the solution trivials such as k=± ∞, and same polarization channel imbalance is estimated in the regional stability that can be dominant at exposed soil.

3, without the need to artificially laying scaler in scene, high-precision radar data calibration can be carried out to the area such as Complex Mountain, unmanned desert under round-the-clock, round-the-clock condition, effectively can improve the POLSAR image precision in depopulated zone, expansion POLSAR radar image range of application, reduce the financial cost of POLSAR radar image calibration, have broad application prospects and economic worth.

Accompanying drawing explanation

Fig. 1 is the idiographic flow schematic diagram of the inventive method;

Fig. 2 is the schematic flow sheet adopting Newton solution by iterative method same polarization channel imbalance.

Embodiment

For estimating the same polarization channel imbalance of POLSAR observation information, first the specific embodiment of the invention adopts classical Kui Geng (Qugen) scaling method carry out estimating to the crosstalk of POLSAR radar image and cross polarization channel imbalance parameter and eliminate.Then, build majorized function with the low conveyor screw composition of true soil for optimization aim, carry out same polarization channel imbalance and solve.Because same polarization channel imbalance is plural number, two different covariance matrixes are at least needed to solve as observed reading.In embodiment, to POLSAR radar image carry out distance to orientation to piecemeal, utilize same distance to have the feature of identical unknown number to block, solve same polarization channel imbalance.

Technical solution of the present invention is further illustrated below in conjunction with the drawings and specific embodiments.

Technical solution of the present invention can adopt computer technology to realize automatic operational scheme, and as shown in Figure 1, idiographic flow of the present invention comprises step:

Step 1, estimates and eliminates crosstalk and the cross polarization channel imbalance of POLSAR radar image.

Centered by each point to be restored, open the window of a size n × n respectively, carry out multiple look processing by all pixels in window and estimate polarization coherence matrix, point to be restored refers to each pixel in POLSAR radar image here.During concrete enforcement, those skilled in the art can according to concrete image preset window size n value.

This step comprises following sub-step further:

Step 1.1 builds polarization coherence matrix.

Generally speaking, POLSAR observation information comprises 4 channel datas of reflection Terrain Scattering mechanism, i.e. original polarization scattering matrix S2.Original polarization scattering matrix S2 is converted, in n × n size windows, builds polarization coherence matrix C _observer:

$S2=\left[\begin{array}{cc}{\mathrm{HH}}_i& {\mathrm{HV}}_i\\ {\mathrm{VH}}_i& {\mathrm{VV}}_i\end{array}\right]\→C_{\mathrm{observer}}=\underset{i=1}{\overset{n\×n}{\mathrm{\Σ}}}(l_i\·l_i^{*T})---\left(1\right)$

In formula (1), HH _i, HV _i, VH _i, VV _ibe respectively image that POLSAR radar HH passage observes, i-th grey scale pixel value in the respective window of image that image that image that radar HV passage observes, radar VH passage observe, radar VV passage observe, i=1,2 ..., n × n.

Complex vector l _ifor:

l _i＝[HH _i,VH _i,HV _i,VV _i] ^T（2）

In formula (2), T representing matrix transposition, * represents conjugate operation.

Step 1.2 utilizes Qugen scaling method, and in POLSAR radar image, exposed soil is estimated as observed object and eliminated crosstalk and cross polarization channel imbalance.

Utilize Qugen scaling method to the polarization coherence matrix C built _observereliminate crosstalk and cross aisle imbalance.

Suppose observing matrix C _observerfor:

$C_{\mathrm{observer}}=\left[\begin{array}{cccc}{C}_{o11}& C_{o12}& C_{o13}& C_{o14}\\ C_{o21}& C_{o22}& C_{o23}& C_{o24}\\ C_{o31}& C_{o32}& C_{o33}& C_{o34}\\ C_{o41}& C_{o42}& C_{o43}& C_{o44}\end{array}\right]---\left(3\right)$

Solve plural crosstalk factor u, v, w, z and plural cross aisle unbalance factor α:

u＝(C _o44C _o21-C _o41C _o24)/(C _o11C _o44-|C _o14| ²)

v＝(C _o11C _o24-C _o21C _o14)/(C _o11C _o44-|C _o14| ²)

z＝(C _o44C _o31-C _o41C _o34)/(C _o11C _o44-|C _o14| ²)（4）

w＝(C _o11C _o34-C _o31C _o14)/(C _o11C _o44-|C _o14| ²)

$\mathrm{\α}=\frac{\left|\mathrm{\β\γ}\right|-1+\sqrt{{\left(\right|\mathrm{\β\γ}|-1)}^2+4{\left|\mathrm{\γ}\right|}^2}}{2\left|\mathrm{\γ}\right|}\·\exp (j\·\mathrm{Arg}\left(\mathrm{\β}\right))$

In formula (4), $\mathrm{\β}=\frac{C_{o22}-u{C}_{o12}-v{C}_{o42}}{C_{o32}-z{C}_{o12}-w{C}_{o42}},\mathrm{\γ}=\frac{C_{o33}-z{C}_{o21}-v{C}_{o42}}{C_{o33}-z^{*}{C}_{o31}-w^{*}{C}_{o34}},$ Arg is that plural number asks phase operation, and j represents imaginary symbols.

According to plural crosstalk Summing Factor plural number cross aisle unbalance factor definition matrix distortion matrix X, Q and permutation matrix A:

$X=\left[\begin{array}{cccc}1& w& v& \mathrm{vw}\\ u& 1& \mathrm{uv}& v\\ z& \mathrm{wz}& 1& w\\ \mathrm{uz}& z& u& 1\end{array}\right],Q=\left[\begin{array}{cccc}\mathrm{\α}& 0& 0& 0\\ 0& \mathrm{\α}& 0& 0\\ 0& 0& 1& 0\\ 0& 0& 0& 1\end{array}\right],A=\begin{array}{c}\left[\begin{array}{ccc}1& 0& 0\\ 0& 1/\sqrt{2}& 0\\ 0& 1/\sqrt{2}& 0\\ 0& 0& 1\end{array}\right]\end{array}---\left(5\right)$

Because the data eliminating cross polarization channel imbalance meet VH ≡ HV, definable polarization covariance matrix C ₃:

C ₃＝A ^*(XQ) ^-1C _observer(Q ^*X ^*) ^-1A（6）

In formula (6), subscript * represents conjugate transpose.

About covariance matrix C ₃calculating can see document: Aunifiedalgorithmforphaseandcross-talkcalibrationofpolar imetricdata-theoryandobservations-1994.

Step 2, the process of POLSAR radar image piecemeal.

Because same polarization channel imbalance k to be solved is plural number, two different covariance matrixes are at least needed to solve as observed reading.This embodiment to POLSAR radar image in orientation to being divided into 64 pieces, adjusting the distance to being divided into 100 pieces, namely POLSAR radar image is divided into 64*100 block.Due to same polarization channel imbalance in orientation to comparatively stable, comparatively violent to change in distance, therefore can think that each distance upwards affects to little image blocks by identical unknown number k in 64 orientation.

During concrete enforcement, for each distance to 64 orientation corresponding to block to block, by the orientation covariance matrix C that all exposed soil pixels are corresponding in block ₃be averaging processing, by in each orientation covariance matrix that all exposed soil pixels are corresponding in block corresponding element be added after divided by each orientation to exposed soil pixel quantity in block, using 64 after average treatment, an average covariance matrices C is as distance to the observed reading of block, and each distance is to all corresponding 64 observed readings of block.

Definition average covariance matrices is C:

$C=\left[\begin{array}{ccc}{C}_{11}& C_{12}& C_{13}\\ C_{12}^{*}& C_{22}& C_{23}\\ C_{13}^{*}& C_{23}^{*}& C_{33}\end{array}\right]=\left[\begin{array}{ccc}{C}_{11}& C_{12\mathrm{re}}+j\·C_{12\mathrm{im}}& C_{13\mathrm{re}}+j\·C_{13im}\\ C_{12\mathrm{re}}-j\·C_{12\mathrm{im}}& C_{22}& C_{23\mathrm{re}}+j\·C_{23\mathrm{im}}\\ C_{13\mathrm{re}}-j\·C_{13\mathrm{im}}& C_{23\mathrm{re}}-j\·C_{23\mathrm{im}}& C_{33}\end{array}\right]---\left(7\right)$

In formula (7), j represents imaginary symbols; Re and im represents real part and imaginary part respectively, that is, C _12rerepresent C ₁₂real part, C _12imrepresent C ₁₂imaginary part.

Step 3, with the low conveyor screw composition of true soil for optimization aim builds majorized function, adopts the majorized function built to solve each distance to same polarization channel imbalance corresponding to block.

With each distance to 64 average covariance matrices C corresponding to block for distance is to the observed reading of block, build majorized function f _uZHEX:

$f_{\mathrm{UZHEX}}=\frac{1}{\sqrt{2}}\mathrm{Im}\left(\right|p|p{C}_{12}+\frac{1}{\left|p\right|}p{C}_{23})=0---\left(8\right)$

In formula (8), p=k ^-1=a+ib, a and b are real part and the imaginary part of p, and i is imaginary symbols, and k is same polarization channel imbalance to be solved; Im operates for asking imaginary part; C ₁₂with C ₂₃for the element in average covariance matrices C.

Majorized function f _uZHEXbe conveyor screw composition, specifically can see document: Four-componentscatteringmodelforpolarimetricSARimagedeco mposition-2005.This step solves and makes conveyor screw composition and fUZHEX be the p of 0, thus obtains same polarization channel imbalance estimated value.

For the reliable solving result of quick obtaining, the partial derivative of having derived needed for Newton process of iteration during concrete enforcement:

$\begin{array}{c}\frac{{\∂f}_{\mathrm{UZHEX}}}{\∂A}=\frac{1}{\sqrt{2}}[\frac{a(a{C}_{12\mathrm{im}}+b{C}_{12\mathrm{re}})+C_{23\mathrm{im}}}{\sqrt{a^2+b^2}}+]\sqrt{a^2+b^2}{C}_{12\mathrm{im}}-\frac{a(a{C}_{23\mathrm{im}}+b{C}_{23\mathrm{re}})}{\sqrt{{(a^2+b^2)}^3}}\\ \frac{{\∂f}_{\mathrm{UZHEX}}}{\∂b}=\frac{1}{\sqrt{2}}[\frac{b(a{C}_{12\mathrm{im}}+b{C}_{12\mathrm{re}})+C_{23\mathrm{re}}}{\sqrt{a^2+b^2}}+]\sqrt{a^2+b^2{C}_{12\mathrm{re}}}-\frac{b(a{C}_{23\mathrm{im}}+b{C}_{23\mathrm{re}})}{\sqrt{{(a^2+b^2)}^3}}\end{array}---\left(9\right)$

For each distance to block, each distance of Newton solution by iterative method is adopted to see Fig. 2 to the same polarization channel imbalance process of block respectively, specific as follows:

A, iteration initial value p is set _x=a _x+ jb _x, bring iteration initial value and distance into majorized function f to 64 observed readings of block _uZHEX, build system of linear equations (10) and solve corrected value Δ a _xwith Δ b _y:

$\mathrm{BM}=L\→\left[\begin{array}{cc}\frac{{\∂f}_{\mathrm{UZHEX}}^1}{{\∂a}_x}& \frac{{\∂f}_{\mathrm{UZHEX}}^1}{{\∂b}_x}\\ \·& \·\\ \·& \·\\ \·& \·\\ \frac{{\∂f}_{\mathrm{UZHEX}}^{64}}{{\∂a}_x}& \frac{{\∂f}_{\mathrm{UZHEX}}^{64}}{{\∂b}_x}\end{array}\right]\left[\begin{array}{c}{\mathrm{\Δa}}_x\\ {\mathrm{\Δb}}_x\end{array}\right]=\left[\begin{array}{c}{-f}_{\mathrm{UZHEX}}^1\\ \·\\ \·\\ \·\\ {-f}_{\mathrm{UZHEX}}^{64}\end{array}\right]---\left(10\right)$

In formula (10), subscript represents that distance is to 64 orientation corresponding to block to block, represent that distance is to m orientation corresponding to block to fast majorized function, m=1,2 ..., 64.

B, employing corrected value Δ a _xwith Δ b _yupgrade parameter a to be solved _x=a _x+ Δ a _x, b _y=b _y+ Δ b _y, with the parameter a after upgrading _x, b _yfor parameter current, the corrected value Δ a adopting this to solve _x, Δ b _yand parameter current a _x, b _ycalculating solves residual error || BM-L|| ₂if solve residual error || BM-L|| ₂be less than threshold value 10 ^-6, parameter current a _x, b _ybe solving result, finishing iteration, export solving result and solve residual error; If the residual error of solving || BM-L|| ₂be not less than threshold value 10 ^-6, perform step c;

C, by parameter current a _x, b _ywith 64 the observed readings substitution majorized function fs of distance to block _uZHEX, build system of linear equations (10) and solve corrected value Δ a _xwith Δ b _y, then, perform step b.

Seeing Fig. 2, for eliminating the impact of iteration initial value, in embodiment ,-3dB being divided into separately 30 parts to 3dB ,-pi to pi respectively as a and b initial value input Newton process of iteration, using minimum solving result corresponding to residual error that solve as last solution.Pi is standard round frequency.

Said method is adopted to solve the estimated value of 100 distances to same polarization channel imbalance corresponding to block respectively.

Step 4, adjusts the distance and carries out the linear fit of intensity and phase place to the same polarization channel imbalance estimated value that block is corresponding, obtains closely end and arrives same polarization channel imbalance corresponding to remote each pixel, complete the elimination that distortion factor is final.

Specific embodiment described herein is only to the explanation for example of the present invention's spirit.Those skilled in the art can make various amendment or supplement or adopt similar mode to substitute to described specific embodiment, but can't depart from spirit of the present invention or surmount the scope that appended claims defines.

Claims (3)

1., based on the polarimetric synthetic aperture radar calibrating method of natural exposed soil, it is characterized in that, comprise step:

Step 1, with exposed soil in Synthetic Aperture Radar images for observed object, estimate and eliminate crosstalk and the cross polarization channel imbalance of polarimetric synthetic aperture radar image, this step comprises sub-step further:

1.1 windows opening size n × n respectively in polarimetric synthetic aperture radar image centered by each pixel, adopt grey scale pixel value in window to build polarization coherence matrix corresponding to window, n value is artificial default;

1.2 with exposed soil pixel in Synthetic Aperture Radar images for observed object, adopt Qugen scaling method to eliminate crosstalk and the cross polarization channel imbalance of the polarization coherence matrix built;

Step 2, the acquisition of covariance matrix observed reading, this step comprises sub-step further:

2.1 by polarimetric synthetic aperture radar image in orientation to be divided into P block orientation to block, in distance to being divided into N block distance to block, that is, each distance is to the corresponding P block orientation of block to block;

2.2 for each distance to block, adjust the distance respectively to each orientation that block is corresponding and be averaging processing to the polarization covariance matrix of exposed soil pixel in block, obtain the average polarization covariance matrix of each orientation to block, using P average polarization covariance matrix of acquisition as distance to the observed reading of block;

Step 3, estimate same polarization channel imbalance, this step comprises sub-step further:

3.1 with soil conveyor screw composition for optimization aim builds majorized function wherein, p=k ^-1=a+jb, a and b are real part and the imaginary part of p, and j is imaginary symbols, and k is same polarization channel imbalance to be solved; Im operates for asking imaginary part; C ₁₂for the element that the 1st row the 2nd in average covariance matrices C arranges, C ₂₃for the element that the 2nd row the 3rd in average covariance matrices C arranges;

3.2 according to the observed reading of distance to block, adopts Newton solution by iterative method majorized function to obtain the estimated value of a and b, thus obtain the same polarization channel imbalance estimated value of each distance to block;

Step 4, carries out the matching of intensity and phase place to the same polarization channel imbalance estimated value of block to each distance, obtain closely end to same polarization channel imbalance corresponding to remote each pixel, eliminate distortion factor.

2., as claimed in claim 1 based on the polarimetric synthetic aperture radar calibrating method of natural exposed soil, it is characterized in that:

Sub-step 3.2 comprises further:

A) system of linear equations BM=L is built, wherein, $B=\left[\begin{array}{cc}\frac{\∂f_{UZHEX}^1}{\∂a_x}& \frac{\∂f_{UZHEX}^1}{\∂b_x}\\ \·& \·\\ \·& \·\\ \·& \·\\ \frac{\∂f_{UZHEX}^P}{\∂a_x}& \frac{\∂f_{UZHEX}^P}{\∂b_x}\end{array}\right];$ $M=\left[\begin{array}{c}\mathrm{\Δ}{a}_x\\ {\mathrm{\Δb}}_x\end{array}\right],$ Δ a _xwith Δ b _yfor corrected value to be solved; $L=\left[\begin{array}{c}-f_{UZHEX}^1\\ .\\ .\\ .\\ -f_{UZHEX}^P\end{array}\right];$ represent that distance is to m orientation of block to the majorized function of block, m=1,2 ..., P;

B) iteration initial value p is set _x=a _x+ jb _x, bring iteration initial value and distance into system of linear equations BM=L to the P group observations of block, solve Δ a _xwith Δ b _y;

C) Δ a is adopted _xwith Δ b _yundated parameter a _x=a _x+ Δ a _x, b _y=b _y+ Δ b _y, with the parameter a after upgrading _xand b _yfor parameter current, the corrected value Δ a adopting this to solve _x, Δ b _yand parameter current a _x, b _ycalculating solves residual error || BM-L|| ₂, and compare and solve residual error || BM-L|| ₂with predetermined threshold value size, if the residual error of solving || BM-L|| ₂be less than predetermined threshold value, parameter current a _x, b _ybe solving result, finishing iteration; Otherwise, perform steps d);

D) by parameter current a _x, b _yand distance is to the P group observations substitution system of linear equations BM=L of block, continues to solve corrected value Δ a _xwith Δ b _y, then, perform step c).

3., as claimed in claim 2 based on the polarimetric synthetic aperture radar calibrating method of natural exposed soil, it is characterized in that:

The iteration initial value p that many groups are different is set _x=a _x+ jb _x, the step described in employing a) ~ d) obtain solving result corresponding to many group iteration initialization respectively, will residual error be solved || BM-L|| ₂minimum solving result is as last solution.