CN1303431C - Airborne synthetic aperture radar surveying area positioning system - Google Patents

Abstract

The airborne Synthetic Aperture Radar (SAR) measurement area positioning system involves radar technology and consists of a global positioning system, a geographic information positioning platform and a measurement area positioning system. The global positioning system is wirelessly connected to the geographic information positioning platform, and the geographic information positioning platform is The measurement area positioning system is electrically connected; the measurement area positioning system includes a measurement area positioning module, a reference target parameter calculation module in the measurement zone, an earth model module and a coordinate conversion module. The invention can accurately locate the ground measurement area of the airborne synthetic aperture radar, and complete the position parameter measurement of the reference target in the area, and can be used for the pre-establishment of the optimal flight track and the projection transformation from the synthetic aperture radar image to the ground coordinate system , and the application of ground standard reference targets in radiometric and geometric calibration of radar images, etc.

Description

Airborne synthetic aperture radar measured zone positioning system

Technical field

The present invention relates to Radar Technology, particularly relate to the location technology of the definite and regional internal reference target of aperture radar measured zone.

Background technology

Airborne synthetic aperture radar occupies absolute consequence in imaging radar, have a wide range of applications and development potentiality, as active system, round-the-clock, the round-the-clock ability to work of airborne synthetic aperture radar and it can obtain the high-definition picture of target under different frequency range, different polarization, for people provide various very Useful Informations.These information are widely used in fields such as geology, the hydrology, agricultural, city, ocean, mapping and military surveillance, measure for large tracts of land especially, and airborne synthetic aperture radar has the incomparable advantage of other kind sensor.There is a measured zone in the airborne synthetic aperture radar earth observation, and this measured zone is determined by the performance and the flight track of airborne synthetic aperture radar.Before carrying out earth observation, how to determine that measured zone becomes very important, observation area as required, the flight path that we can designing optimal is adjusted the duty of radar system; If being set, reference target is used for quantitative radar remote sensing in the observation area, then need to determine the accurate position of reference target, therefore, research aircraft borne synthetic aperture radar (SAR) measured zone positioning system is just significant, it provides theoretic witness mark, can instruct the carrying out of whole surveying work.

At present, when the finger Beijiao of determining ground normative reference target is spent, be by on the longitude and latitude figure of ground, for changing, tolerance obtains to refer to the urecholine chloride vector in the same longitude of target reference point place, make to exist certain shortcoming like this, it does not consider the existence of earth curvature and magnetic declination, so its precision is not the most accurately.

Summary of the invention

The objective of the invention is to set up a kind of airborne synthetic aperture radar (SAR) measured zone positioning system, be used for the accurate location with regional internal reference target of pre-determining of measured zone.

For achieving the above object, technical solution of the present invention is for providing a kind of airborne synthetic aperture radar measured zone positioning system, by GPS, geography information locating platform and measured zone positioning system are formed, its GPS and the wireless connections of geography information locating platform, the geography information locating platform is electrically connected with the measured zone positioning system; The measured zone positioning system comprises the measured zone locating module, measures band internal reference target component computing module, earth model module and coordinate transferring; The input end of measured zone locating module directly is electrically connected with the geography information locating platform, its output terminal is electrically connected with measuring band internal reference target component computing module, and the output terminal of earth model module and coordinate transferring also is electrically connected with the measured zone locating module.

Described measured zone positioning system, its to the location of measured zone by finishing with following step:

After the beginning, airborne synthetic aperture radar is read in data such as the initial longitude and latitude of aircraft that GPS sends, aircraft altitude, perigee oblique distance, apogee oblique distance by the receiving interface of geography information locating platform, and input measurement zone location module; Simultaneously, the measured zone locating module with the initial longitude and latitude of aircraft by with the coordinate transferring swap data, and convert the inertial coordinates system coordinate to, and calculate point under the machine of aircraft starting point, be initial value with point coordinate under the machine of aircraft again, ask low coverage point, the remote point of aircraft starting point ground mapping band; The low coverage point that the measured zone locating module is with the mapping of aircraft starting point ground, remote point inertial coordinates system coordinate data are by exchanging with coordinate transferring, and convert latitude and longitude coordinates to, again according to antenna attitude, determine that the mapping of the side that aircraft is identical with the antenna tilt direction is with each end points, and will survey and draw and be with each end points to be arranged on the map continuously, in display screen, show, finish.

Described measured zone positioning system, it is to measurement band internal reference target measurement the time, and the location of reference target is by finishing with following step:

After the beginning, by the some position of geography information locating platform to measured zone locating module input angle reverberator, the measured zone locating module is put corner reflector the data of position by exchanging with coordinate transferring, and converting the inertial coordinates system coordinate to, the data in inertial coordinates system are imported into and are measured band internal reference target component computing module with these data and earth model module; Measure band internal reference target component computing module and calculate the aircraft point that corner reflector is aimed at earlier, calculate point under the machine of this aircraft point again, computed altitude angle then, and then the subpoint on corner reflector is ordered tangent plane is excessively selected in the calculating arctic, calculate the finger Beijiao, last, the position of measuring band internal reference target is input on the map, in display screen, show, finish.

Described measured zone positioning system, it has adopted the adaptive iteration algorithm when asking the ground subpoint.

Described measured zone positioning system, what it pointed in the ground reference target location determines, has proofreaied and correct the influence of magnetic declination and earth curvature, the finger Beijiao of Que Dinging thus, accuracy is higher.

The present invention relates to earth model, general measurement and positioning system thinks that aircraft is the same with it at the longitude and latitude of ground subpoint, and is actual when using earth model, and height error can cause aircraft and its ground subpoint longitude and latitude inconsistent.For more accurate measurement, the influence that needs the consideration aircraft altitude to bring, the variation of longitude and latitude data when the present invention has considered the aircraft differing heights.

Calculate the finger Beijiao degree of target, can obtain to refer to the urecholine chloride vector in the same longitude of target reference point place for tolerance changes by at ground longitude and latitude figure; Do like this and have certain shortcoming, it does not consider the existence of earth curvature and magnetic declination, so its precision is not the most accurately.The present invention considers the influence of earth curvature and magnetic declination, obtains measurement result more accurately.

Description of drawings

Fig. 1 airborne synthetic aperture radar measured zone of the present invention positioning system;

The ground survey regional map that Fig. 2 airborne synthetic aperture radar measured zone of the present invention positioning system is taken when actual aerial survey;

Fig. 3 inertia geocentric coordinate system;

Fig. 4 invention measured zone positioning flow;

The measured zone that Fig. 5 invention is measured in advance;

Fig. 6 the present invention measures the positioning flow of band internal reference target;

Fig. 7 measured zone internal reference of the present invention target distribution.

Embodiment

The principal feature of airborne synthetic aperture radar measured zone positioning system of the present invention is to utilize GPS (GPS) and Geographic Information System (GIS), in conjunction with the aircraft flight flight path, set up the vacant lot geometric relationship, utilize software algorithm to calculate ground subpoint coordinate again.The composition of this system is with reference to figure 1, it is by GPS (GPS) 1, geography information locating platform (GIS) 2 and measured zone positioning system 3 are formed (part in the empty frame of Fig. 1), wherein, GPS (GPS) 1 and geography information locating platform (GIS) 2 wireless connections, geography information locating platform (GIS) 2 is electrically connected with measured zone positioning system 3; Measured zone positioning system 3 comprises measured zone locating module 4, measures band internal reference target component computing module 5, earth model module 6 and coordinate transferring 7; The input end of measured zone locating module 4 directly is electrically connected with geography information locating platform (GIS) 2, its output terminal is electrically connected with measuring band internal reference target component computing module 5, and the output terminal of earth model module 6 and coordinate transferring 7 also is electrically connected with measured zone locating module 4.

The present invention relates to earth model, general measurement and positioning system thinks that aircraft is the same with it at the longitude and latitude of ground subpoint.Actual when using earth model, height error can cause aircraft and its ground subpoint longitude and latitude inconsistent.For more accurate measurement, the influence that needs the consideration aircraft altitude to bring, the variation of longitude and latitude data when the present invention has considered the aircraft differing heights.

The present invention has adopted the adaptive iteration algorithm when finding the solution the ground subpoint, to three-dimensional quadratic equation, adopt the newton-La Fei Senn process of Nonlinear System of Equations, and wherein selection of initial value is solution convergence and stable key.In the present invention, this selection of initial value has been used the priori of radar system itself, makes this selection of initial value reasonable, and convergence as a result and the stability of finding the solution subpoint are better.

When determining that it refers to northern position, not on map longitude and latitude plane, to calculate it to refer to Beijiao, but considered the influence of earth curvature and magnetic declination that the finger Beijiao accuracy of Que Dinging is higher thus for the ground reference target in the measured zone.

At first set up inertia geocentric coordinate system (see figure 3), all calculating are unified in the inertia geocentric coordinate system and finish.

Airborne synthetic aperture radar measured zone positioning system of the present invention when measuring, to the location of measured zone by finishing with following step:

As shown in Figure 4, after the beginning, airborne synthetic aperture radar is read in data such as the initial longitude and latitude of aircraft that GPS (GPS) 1 sends, aircraft altitude, perigee oblique distance, apogee oblique distance by the receiving interface of geography information locating platform (GIS) 2, and input measurement zone location module 4; Simultaneously, measured zone locating module 4 with the initial longitude and latitude of aircraft by with coordinate transferring 7 swap datas, and convert the inertial coordinates system coordinate to, and calculate point under the machine of aircraft starting point, be initial value with point coordinate under the machine of aircraft again, ask low coverage point, the remote point of aircraft starting point ground mapping band with the adaptive iteration algorithm; The low coverage point that measured zone locating module 4 is with the mapping of aircraft starting point ground, remote point inertial coordinates system coordinate data are by exchanging with coordinate transferring 7, and convert latitude and longitude coordinates to, again according to antenna attitude, determine that the mapping of the side that aircraft is identical with the antenna tilt direction is with each end points, and will survey and draw and be with each end points to be arranged on the map continuously, in display screen, show, see Fig. 5, finish.

The computing of described measured zone locating module 4 is to be unified in the inertia geocentric coordinate system, and utilizes geography information locating platform (GIS) 2 to finish, and its specific algorithm is as follows:

Consider the height selection flight starting point coordinate (x of earth model and aircraft ₁, y ₁, z ₁) and terminal point coordinate (x ₂, y ₂, z ₂), determine their each self-corresponding terrestrial beam point coordinate (x then _G11, y _G11, z _G11) and (x _G21, y _G21, z _G21).Each beam spot coordinate satisfies following three conditions:

(1) during positive side-looking mode of operation, vector is vertical, promptly

(x _g11-x ₁)(x ₂-x ₁)+(y _g11-y ₁)(y ₂-y ₁)+(z _g11-z ₁)(z ₂-z ₁)＝0 (1)

(2) beam spot is positioned on the ground sphere

$\frac{{x_{g11}}^2+{y_{g11}}^2}{a^2}+\frac{{z_{g11}}^2}{b^2}=1---\left(2\right)$

Wherein, a=6378.145km, b=6356.76km.

(3) the low coverage point of radar system measurement or remote point distance are set by radar system, satisfy

(x _g11-x ₁) ²+(y _g11-y ₁) ²+(z _g11-z ₁) ²＝R _near (3)

(x _g11-x ₁) ²+(y _g11-y ₁) ²+(z _g11-z ₁) ²＝ _Rfar (4)

Wherein, R _NearBe low coverage point distance, R _FarBe the remote point distance

According to above-mentioned rule, can obtain a three-dimensional quadratic equation group.Separate this Nonlinear System of Equations and adopt newton-La Fei Senn process.For Nonlinear System of Equations

f _i(x ₁，x ₂…，x _n)＝0，i＝1，2，…，N (5)

Newton-La Fei Senn process is as follows:

Make x=(x ₁, x ₁..., x _n) ^T, i= ¹, ²..., N does Taylor expansion at the neighborhood of x, omits the above item of secondary and secondary,

$f_i(x^{\left(0\right)}+\mathrm{\δ}{x}^{\left(0\right)})\≈f_i(x^{\left(0\right)}+\underset{j=1}{\overset{N}{\mathrm{\Σ}}}\frac{{\∂f}_i}{{\∂x}_j}\mathrm{\δ}{x}_j^{\left(0\right)})---\left(6\right)$

$\mathrm{\α}\≡{\left[{\mathrm{\α}}_{\mathrm{ij}}^{\′}\right]}_{N\×N},\mathrm{\β}\≡{({\mathrm{\β}}_1,...,{\mathrm{\β}}_n)}^T$

${\mathrm{\α}}_{\mathrm{ij}}=\frac{\∂f_i}{\∂x_i},\mathrm{\β}=-f_i---\left(7\right)$

If det is α ≠ and 0, iterative formula is so

$x_i^{\mathrm{new}}=x_i^{\mathrm{old}}+\mathrm{\δ}{x}_i,i=\mathrm{1,2},...,N---\left(8\right)$

(δ x wherein ₁, δ x ₂..., δ x _N) ^T≡ δ x is separating of system of linear equations α δ x=β.In sum, the step of using newton-La Fei Senn process to separate Nonlinear System of Equations is:

(1) gives the initial approximation x of normal root x ⁽⁰⁾(near x), permissible error is ε ₁, ε ₂, suppose to obtain approximate x the k time ^(k)

(2) calculate

${\mathrm{\α}}_{\mathrm{ij}}^{\left(k\right)}\≡\∂f_i\left(x^{\left(k\right)}\right)/{\∂x}_j,i,j=\mathrm{1,2},...,N---\left(9\right)$

${\mathrm{\β}}_i^{\left(k\right)}=-f_i\left(x^{\left(k\right)}\right),i=\mathrm{1,2},...,N$

Can get ${\mathrm{\α}}^{\left(k\right)}={\left[{\mathrm{\α}}_{\mathrm{ij}}^{\left(k\right)}\right]}_{N\×N}$ And ${\mathrm{\β}}^{\left(k\right)}={({\mathrm{\β}}_1^{\left(k\right)}{\mathrm{\β}}_2^{\left(k\right)},...,{\mathrm{\β}}_N^{\left(k\right)})}^T.$

(3) calculate

S1＝|f ₁(x ^(k))|+|f ₂(x ^(k))|+…|f _N(x ^(k))| (10)

If S1＜ε ₁, then calculate and finish x ^(k)As the approximate solution that satisfies accuracy requirement; Otherwise, carry out (4).

(4) ask the linear algebraic equation group with LU factorization

α ^(k)·δx ^(k)＝β ^(k) (11)

${\mathrm{\δx}}^{\left(k\right)}\≡{({\mathrm{\δx}}_1^{\left(k\right)},{\mathrm{\δx}}_2^{\left(k\right)},...{\mathrm{\δx}}_N^{\left(k\right)})}^T$

(5) calculate x ^(k+1)=x ^(k)+ δ x ^(k)And

$\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="C0215588500111.png"\; state="\{\{state\}\}">S</figure-callout>}2=\left|{\mathrm{\&epsiv;x}}_1^{\left(k\right)}\right|+\left|{\mathrm{\&epsiv;x}}_2^{\left(k\right)}\right|+...+\left|{\mathrm{\&epsiv;x}}_N^{\left(k\right)}\right|---\left(12\right)$

If S2＜ε ₂, then calculate and finish x ^(k+1)As the approximate solution that satisfies accuracy requirement; Otherwise, $k\&DoubleLeftArrow;k+1,$ Turn to (2) continue to calculate, till satisfying accuracy requirement or iterations and having reached given iterations.

Through top computing, finish determining of coordinate conversion and subpoint, correspondingly finished determine (as shown in Figure 5) of measured zone.

After measured zone is determined, need determine its azimuth direction for the ground standard reference target that wherein is provided with, airborne synthetic aperture radar measured zone positioning system of the present invention, to measurement band internal reference target measurement the time, the location of reference target is by finishing with following step:

As shown in Figure 6, after the beginning, by the some position of geography information locating platform (GIS) 2 to measured zone locating module 4 input angle reverberators, measured zone locating module 4 is put corner reflector the data of position by exchanging with coordinate transferring 7, and converting the inertial coordinates system coordinate to, the data in inertial coordinates system are imported into and are measured band internal reference target component computing module 5 with these data and earth model module 6; Measure band internal reference target component computing module 5 and calculate the aircraft point that corner reflector is aimed at earlier, calculate point under the machine of this aircraft point again, computed altitude angle then, and then calculate the arctic and select subpoint on the mistake corner reflector is ordered tangent plane, on this basis, after having proofreaied and correct magnetic declination and earth curvature, calculate the finger Beijiao, last, the position of measuring band internal reference target is input on the map, in display screen, show, see Fig. 7, finish.

Embodiment 1:

The present invention's many successes is used for the flight measurement work of airborne synthetic aperture radar, and predetermined measured zone (as shown in Figure 5) is coincide with the practical flight result.Once found in the work that measured zone did not meet the demands, found through the analysis of this system that the flight track of aircraft did not meet the demands, found the reason of problem, in time revised, retrieved unnecessary loss.The system that uses in the experiment is used to calculate the location parameter of ground reference target, is used further in the actual experiment, has obtained ground reference target image values result accurately on radar image, as shown in Figure 7.

Embodiment 2:

Figure 2 shows that airborne synthetic aperture radar measured zone positioning system of the present invention, the ground survey regional map of when actual aerial survey, taking.

Claims (5)

1. airborne synthetic aperture radar measured zone positioning system, by GPS, geography information locating platform and measured zone positioning system are formed, it is characterized in that, GPS and the wireless connections of geography information locating platform, the geography information locating platform is electrically connected with the measured zone positioning system; The measured zone positioning system comprises the measured zone locating module, measures band internal reference target component computing module, earth model module and coordinate transferring; The input end of measured zone locating module directly is electrically connected with the geography information locating platform, its output terminal is electrically connected with measuring band internal reference target component computing module, and the output terminal of earth model module and coordinate transferring also is electrically connected with the measured zone locating module.

2. measured zone positioning system as claimed in claim 1 is characterized in that, the location of measured zone is finished with following step:

After the beginning, airborne synthetic aperture radar reads in the initial longitude and latitude of aircraft, aircraft altitude, perigee oblique distance, the apogee oblique distance data that GPS sends by the receiving interface of geography information locating platform, and input measurement zone location module; Simultaneously, the measured zone locating module with the initial longitude and latitude of aircraft by with the coordinate transferring swap data, and convert the inertial coordinates system coordinate to, and calculate point under the machine of aircraft starting point, be initial value with point coordinate under the machine of aircraft again, ask low coverage point, the remote point of aircraft starting point ground mapping band; The low coverage point that the measured zone locating module is with the mapping of aircraft starting point ground, remote point inertial coordinates system coordinate data are by exchanging with coordinate transferring, and convert latitude and longitude coordinates to, again according to antenna attitude, determine that the mapping of the side that aircraft is identical with the antenna tilt direction is with each end points, and will survey and draw and be with each end points to be arranged on the map continuously, in display screen, show, finish.

3. measured zone positioning system as claimed in claim 1 is characterized in that, to measurement band internal reference target measurement the time, finish with following step the location of reference target:

After the beginning, by the some position of geography information locating platform to measured zone locating module input angle reverberator, the measured zone locating module is put corner reflector the data of position by exchanging with coordinate transferring, and converting the inertial coordinates system coordinate to, the data in inertial coordinates system are imported into and are measured band internal reference target component computing module with these data and earth model module; Measure band internal reference target component computing module and calculate the aircraft point that corner reflector is aimed at earlier, calculate point under the machine of this aircraft point again, computed altitude angle then, and then the subpoint on corner reflector is ordered tangent plane is excessively selected in the calculating arctic, calculate the finger Beijiao, last, the position of measuring band internal reference target is input on the map, in display screen, show, finish.

4. measured zone positioning system as claimed in claim 3 is characterized in that, when asking the ground subpoint, has adopted the adaptive iteration algorithm.

5. measured zone positioning system as claimed in claim 3 is characterized in that, that points in the ground reference target location determines, has proofreaied and correct the influence of magnetic declination and earth curvature, the finger Beijiao of Que Dinging thus, and accuracy is higher.

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