CN100481133C - RPC model forward transform method - Google Patents

Abstract

This method leads the result of the counter conversion to the conversion process to iteratively convert. It includes steps of: (1) setting the altitude and the RPC model parameters, setting the land rectangle area (LRA); (2) calculating the pixel coordinate of four angle points and the center point of LRA; (3) calculating the simulation conversion coefficient; (4) calculating the near longitude/ latitude coordinate (LC) corresponding with the test image point coordinate (IPC); (5) calculating the theory IPC and the remained difference (RD); (6) if RD is within the preset value (PV), outputting the near LC as the LC corresponding with the test IPC; (7) otherwise, regulating LRA, returning to iteration until RD is within PV. This scheme ensures to obtain accurate land point position under the limited condition presented by the image producer. It possesses significant meaning in the remote sensing image application area.

Description

Direct transform method based on the rational polynominal imaging model

Technical field

The invention belongs to the photographic imagery technical field, particularly based on the direct transform method of rational polynominal imaging model.

Background technology

Because tight imaging geometry model has high orientation precision, is the first-selection of photogrammetry therefore always, satellite remote-sensing image is handled and usually will be utilized tight imaging geometry model.Yet, though some high performance sensing systems have been realized commercialization, but because critical technical parameters such as satellite platform and useful load are the technology secrets of spacefaring nation, the core information of high resolution sensor and satellite orbit parameter are also unexposed, as satellites such as IKONOS, can't utilize strict imaging geometry model to handle; The variation of sensor imaging mode has simultaneously also proposed the unitized requirement of model to photogrammetric software, when designing, software frame just needn't determine the form of its strict geometric model like this for various types of sensors existing or that may occur in the future one by one, and can unify to adopt universal model to handle, thereby greatly reduce the complicacy of program design, be easier to software upgrading and maintenance, when handling multi-source satellite remote-sensing image data especially at the same time, the universal imaging geometric model more can demonstrate its advantage.

Common universal imaging geometric model has following several: polynomial expression, direct linear transformation, affined transformation, rational function model etc.The RPC model is wherein a kind of of universal imaging geometric model of satellite remote-sensing image, and it is applicable to that various kinds of sensors comprises up-to-date aerospace sensor model.Based on the imaging model of RPC and do not require actual characteristic and the imaging process of understanding sensor, be a kind of can obtain and strict imaging model is similar to the simple broad sense imaging model of form of consistent precision.

The concrete definitional relation of RPC model is as follows:

$X=\frac{{\mathrm{Num}}_L(P,L,H)}{{\mathrm{Den}}_L(P,L,H)}$

$Y=\frac{{\mathrm{Num}}_s(P,L,H)}{{\mathrm{Den}}_s(P,L,H)}$

Wherein (X, Y) for the image coordinate of regularization, (P, L H) are the topocentric coordinates of regularization.

Num _L(P, L, H), Den _L(P, L, H), Num _s(P, L, H), Den _s(P, L H) are cubic polynomial:

Num _L(P，L，H)＝a ₁+a ₂L+a ₃P+a ₄H+a ₅LP+a ₆LH+a ₇PH+a ₈L ²+a ₉P ²

+a ₁₀H ²+a ₁₁PLH+a ₁₂L ³+a ₁₃LP ²+a ₁₄LH ²+a ₁₅L ²P+a ₁₆P ³+a ₁₇PH ²

+a ₁₈L ²H+a ₁₉P ²H+a ₂₀H ³

Den _L(P，L，H)＝b ₁+b ₂L+b ₃P+b ₄H+b ₅LP+b ₆LH+b ₇PH+b ₈L ²+b ₉P ²

+b ₁₀H ²+b ₁₁PLH+b ₁₂L ³+b ₁₃LP ²+b ₁₄LH ²+b ₁₅L ²P+b ₁₆P ³+b ₁₇PH ²

+b ₁₈L ²H+b ₁₉P ²H+b ₂₀H ³

Num _s(P，L，H)＝c ₁+c ₂L+c ₃P+c ₄H+c ₅LP+c ₆LH+c ₇PH+c ₈L ²+c ₉P ²

+c ₁₀H ²+c ₁₁PLH+c ₁₂L ³+c ₁₃LP ²+c ₁₄LH ²+c ₁₅L ²P+c ₁₆P ³+c ₁₇PH ²

+c ₁₈L ²H+c ₁₉P ²H+c ₂₀H ³

Den _s(P，L，H)＝d ₁+d ₂L+d ₃P+d ₄H+d ₅LP+d ₆LH+d ₇PH+d ₈L ²+d ₉P ²

+d ₁₀H ²+d ₁₁PLH+d ₁₂L ³+d ₁₃LP ²+d ₁₄LH ²+d ₁₅L ²P+d ₁₆P ³+d ₁₇PH ²

+d ₁₈L ²H+d ₁₉P ²H+d ₂₀H ³

Wherein, the coefficient a of cubic polynomial ₁..., a ₂₀, b ₁..., b ₂₀, c ₁..., c ₂₀Be the model parameter that provides in the RPC file, b ₁And d ₁Be generally 1, l, s are respectively image columns value and line number value.

So-called regularization, be one handle infinitely great, disperse and the method for some unreasonable expressions, its method sees through introduces a complementary notion---the regularization factor.This method of utilization is handled the coordinate of ground point and imaging point in the RPC model.

Regularization topocentric coordinates defined formula is

$P=\frac{\mathrm{Latitude}-\mathrm{LAT}\_\mathrm{OFF}}{\mathrm{LAT}\_\mathrm{SCALE}}$

$L=\frac{\mathrm{Longitude}-\mathrm{LONG}\_\mathrm{OFF}}{\mathrm{LONG}\_\mathrm{SCALE}}$

$H=\frac{\mathrm{Height}-\mathrm{HEIGHT}\_\mathrm{OFF}}{\mathrm{HEIGHT}\_\mathrm{SCALE}}$

Wherein, regularization factor LAT_OFF, LAT_SCALE, LONG_OFF, LONG_SCALE, HEIGHT_OFF, HEIGHT_SCALE are the topocentric coordinates regularization model parameters that comprises in the RPC file.Latitude represents that longitude, Longitude represent that latitude, Height represent elevation, can represent topocentric volume coordinate for these three.Annotate: the distance of certain point along the pedal line direction to geoid surface, be commonly referred to absolute elevation or height above sea level, elevation is called for short in the present technique field.

Regularization image coordinate defined formula is

$X=\frac{\mathrm{Sample}-\mathrm{SAMP}\_\mathrm{OFF}}{\mathrm{SAMP}\_\mathrm{SCALE}}$

$Y=\frac{\mathrm{Line}-\mathrm{LINE}\_\mathrm{OFF}}{\mathrm{LINE}\_\mathrm{SCALE}}$

Wherein, regularization factor S AMP_OFF, SAMP_SCALE, LINE_OFF, LINE_SCALE also are the image coordinate regularization model parameters that comprises in the RPC file, and sample represents image row coordinate, and its numerical value is s, line represents the image row-coordinate, and its numerical value is l.

At first need be in based on how much application of RPC model based on the positive inverse transformation of RPC model.The RPC direct transform is meant the relational expression according to the RPC model, the conversion process from the Ground Control point coordinate to the remote sensing image planimetric coordinates.The RPC inverse transformation then is the relational expression according to the RPC model, and the altitude figures of each pixel correspondence is to the conversion process of certain map projection from original remote sensing image and image.

But in the prior art, direct transform based on the RPC model all is to utilize the theoretical realization of least square adjustment direct transform, at first suppose initial position on ground, iterative then, because the initial position of supposition is not necessarily accurate, and convergent controlled condition not necessarily is optimum, might cause restraining the inaccurate of position.Therefore the technological means that in the practical application of RPC model, needs application of advanced in a hurry, improve the reliability of RPC model direct transform, and provide a kind of method of direct transform of new RPC model so that obtain higher precision and reliability based on the geometric manipulations of RPC model.

Summary of the invention

The object of the invention is to solve the prior art deficiency, has proposed a kind of brand-new direct transform method based on RPC model inverse transformation, the bottleneck problem in having solved present RPC model direct transform iteration not necessarily convergent RPC model being used.

Technical scheme of the present invention is: rational polynominal imaging model inverse transformation result introduced rational polynominal imaging model direct transform process carries out iterated transform, promptly adopt computing machine to carry out following steps,

Step 1 is provided with elevation numerical value D _HeiWith rational polynominal imaging model parameter, setting the central point latitude and longitude coordinates is (D _{Lat_off}, D _{Lon_off}), the length of side is D _{Lat_scale}And D _{Lon_scale}The rectangular area, ground, wherein the latitude and longitude coordinates of 4 angle points is

(D _{lat_off}+D _{lat_scale}/2.0，D _{lon_off}+D _{lon_scale}/2.0)；

(D _{lat_off}-D _{lat_scale}/2.0，D _{lon_off}+D _{lon_scale}/2.0)；

(D _{lat_off}+D _{lat_scale}/2.0，D _{lon_off}-D _{lon_scale}/2.0)；

(D _{lat_off}-D _{lat_scale}/2.0，D _{lon_off}-D _{lon_scale}/2.0)；

Step 2 is utilized 4 angle points in rectangular area, inverse transformation Model Calculation ground and the central point corresponding image picpointed coordinate of rational polynominal imaging model;

Step 3 is utilized the latitude and longitude coordinates and the image picpointed coordinate of above-mentioned 5 points, according to the affine transformation relationship formula $\begin{array}{c}{D}_{\mathrm{lat}}=f_0+f_{1}x+f_{2}y\\ D_{\mathrm{lon}}=g_0+g_{1}x+g_{2}y\end{array},$ Utilize the principle of least square to calculate the approximate affine transformation parameter f of image ₀, f ₁, f ₂, g ₀, g ₁, g ₂, x, y represent the columns value and the line number value of the image picpointed coordinate of regularization, D respectively _Lat, D _LonLatitude numerical value and the longitude numerical value of representing the topocentric coordinates of regularization respectively;

Step 4 is according to the approximate affine transformation parameter f of image ₀, f ₁, f ₂, g ₀, g ₁, g ₂Find the solution and measure given measurement picpointed coordinate (x _a, y _a) corresponding approximate latitude and longitude coordinates

Step 5 is according to the inverse transformation Model Calculation topocentric coordinates of rational polynominal imaging model

Corresponding theoretical picpointed coordinate (x _b, y _b);

Step 6 is calculated residual error e, computing formula be e=(| x _a-x _b|) ²+ (| y _a-y _b|) ²If residual error e satisfies the difference range of setting, directly output

As measuring picpointed coordinate (x _a, y _a) corresponding latitude and longitude coordinates

Otherwise with Dwindle rectangular area, ground scope for the central point latitude and longitude coordinates, return the operation of step 2 iteration then, satisfy the difference range of setting up to residual error e.

And step 6.1 is according to formula PS=θ * D _{Lat_scale}/ sqrt ((x ₁-x ₂) * (x ₁-x ₂)+(y ₁-y ₂) * (y ₁-y ₂)) calculate (

D _Hei) near the position the pixel size PS of image,

Picpointed coordinate (x wherein ₁, y ₁) be ground point ( D _Hei) pairing picpointed coordinate, picpointed coordinate (x ₂, y ₂) be ground point $(D_{{\mathrm{lat}}_a}+\mathrm{\θ}\×D_{\mathrm{lat}\_\mathrm{scale}},D_{{\mathrm{lon}}_a},D_{\mathrm{hei}})$ Pairing picpointed coordinate, θ is for dwindling the value coefficient;

Step 6.2 is adjusted rectangular area, ground scope according to pixel size PS, and the latitude and longitude coordinates of 4 angle points in rectangular area, ground is $(D_{{\mathrm{lat}}_a}+e_s\×{\mathrm{PS},D}_{{\mathrm{lon}}_a}+e_l\×\mathrm{PS}),$ $(D_{{\mathrm{lat}}_a}-e_s\×{\mathrm{PS},D}_{{\mathrm{lon}}_a}+e_l\×\mathrm{PS}),$ $(D_{{\mathrm{lat}}_a}+e_s\×{\mathrm{PS},D}_{{\mathrm{lon}}_a}-e_l\×\mathrm{PS}),$ $(D_{{\mathrm{lat}}_a}-e_s\×{\mathrm{PS},D}_{{\mathrm{lon}}_a}-e_l\×\mathrm{PS}),$

E wherein _s=| x _a-x _b|, the residual error of expression column direction, e _l=| y _a-y _b|, the residual error of expression line direction.

And the value of dwindling value coefficient θ is 0.001～0.05.

The present invention proposes a kind of brand-new direct transform method based on RPC model inverse transformation, iteration is carried out in inverse transformation result introducing, overcome prior art convergence difficulty, improved the reliability of RPC model direct transform, made geometric manipulations obtain higher precision and reliability based on the RPC model.And realization of the present invention can be finished under the existing model parameter that provides, and it is convenient to realize.Scheme provided by the invention can be all to vital role in various work that satellite remote-sensing image is handled, for example the geometric correction of image, image coupling and examine aspects such as line arrangement.

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

Embodiment

The present invention introduces RPC model direct transform process with RPC model inverse transformation result and carries out iterated transform, can adopt computer program to finish when specifically implementing, and flow process can be referring to accompanying drawing.The positive change procedure of RPC model of the present invention may further comprise the steps,

Step 1 is provided with elevation numerical value D _HeiWith the RPC model parameter, setting the central point latitude and longitude coordinates is (D _{Lat_off}, D _{Lon_off}), the length of side is D _{Lat_scale}And D _{Lon_scale}The rectangular area, ground, wherein the latitude and longitude coordinates of 4 angle points is

(D _{lat_off}+D _{lat_scale}/2.0，D _{lon_off}+D _{lon_scale}/2.0)；

(D _{lat_off}-D _{lat_scale}/2.0，D _{lon_off}+D _{lon_scale}/2.0)；

(D _{lat_off}+D _{lat_scale}/2.0，D _{lon_off}-D _{lon_scale}/2.0)；

(D _{lat_off}-D _{lat_scale}/2.0，D _{lon_off}-D _{lon_scale}/2.0)。

The implication of latitude and longitude coordinates: in earth coordinates, certain some geodetic longitude, the dihedral angle that meridian ellipse and initial meridian ellipse constituted by this point exactly.Start at by initial meridian ellipse, for just, be east longitude eastwards, for negative, be west longitude westwards.The normal of this point and the angle of the equatorial plane are called geodetic latitude, are started at by the equatorial plane, for just, are north latitude northwards, and be to the south for negative, is south latitude.Just become latitude and longitude coordinates by geodetic longitude and the represented topocentric coordinates of geodetic latitude.Latitude and longitude coordinates adds that elevation can mark topocentric coordinate.In order to satisfy the design conditions of the following step, the present invention is provided with elevation numerical value D earlier _Hei, the RPC model parameter is then provided by image supplier, and input gets final product when specifically implementing.The rectangular area of setting, ground can be adjusted when needing iteration.

Step 2 is utilized 4 angle points in rectangular area, RPC inverse transformation Model Calculation ground and central point corresponding image picpointed coordinate.

Step 3 is utilized the latitude and longitude coordinates and the image picpointed coordinate of above-mentioned 5 points, according to the affine transformation relationship formula $\begin{array}{c}{D}_{\mathrm{lat}}=f_0+f_{1}x+f_{2}y\\ D_{\mathrm{lon}}=g_0+g_{1}x+g_{2}y\end{array},$ Utilize the principle of least square to calculate the approximate affine transformation parameter f of image ₀, f ₁, f ₂, g ₀, g ₁, g ₂, x, y represent the columns value and the line number value of the image picpointed coordinate of regularization, D respectively _Lat, D _LonLatitude numerical value and the longitude numerical value of representing the topocentric coordinates of regularization respectively;

Affined transformation is the combination of computings such as translation, rotation, convergent-divergent, and the coefficient of affine transformation relationship formula is affine transformation parameter.

Step 4 is according to the approximate affine transformation parameter f of image ₀, f ₁, f ₂, g ₀, g ₁, g ₂Find the solution and measure given measurement picpointed coordinate (x _a, y _a) corresponding approximate latitude and longitude coordinates

So-called picpointed coordinate (the x that measures _a, y _a), measure certain picture point according to satellite image when specifically implementing and obtain, the latitude and longitude coordinates that it is corresponding

Can be value to be found the solution, the result that this step obtains be an approximate value, also need look and satisfy this value of the direct output of accuracy requirement decision for waiting the value of finding the solution or iteration correction.

Step 5, according to the inverse transformation Model Calculation topocentric coordinates of RPC model ( D _Hei) corresponding theoretical picpointed coordinate (x _b, y _b);

Theory of computation picpointed coordinate (x _a, y _a), be to be used for the inverse transformation result is introduced the direct transform process so that revise.

The inverse transformation model of RPC model is a formula $\begin{array}{c}X=\frac{\mathrm{Nu}{m}_L(P,L,H)}{{\mathrm{Den}}_L(P,L,H)}\\ Y=\frac{{\mathrm{Num}}_s(P,L,H)}{{\mathrm{Den}}_s(P,L,H)}\end{array}$

The approximate latitude and longitude coordinates that in step 4, obtains

In conjunction with elevation numerical value D _Hei, can bring following formula into as P, L, H respectively and find the solution X, Y value, obtain corresponding theoretical picpointed coordinate (x _b, y _b).Step 6 is calculated residual error e, computing formula be e=(| x _a-x _b|) ²+ (| y _a-y _b|) ²If residual error e satisfies the difference range of setting, directly output

As measuring picpointed coordinate (x _a, y _a) corresponding latitude and longitude coordinates

Otherwise with

Dwindle rectangular area, ground scope for the central point latitude and longitude coordinates, return the operation of step 2 iteration then, satisfy the difference range of setting up to residual error e.

Because elevation numerical value D _HeiCan be given, the present invention is by obtaining the latitude and longitude coordinates of given elevation numerical value correspondence behind the interative computation

Measure picpointed coordinate (x so _a, y _a) corresponding topocentric coordinates promptly $(D_{{\mathrm{lat}}_b},D_{{\mathrm{lon}}_b},D_{\mathrm{hei}}).$

During the invention process, can set difference range according to the precision needs, for example be set at residual error e less than 0.01 pixel, residual error is meant the poor of the true value of variable and observed reading.e _s=| x _a-x _b|, the residual error of expression column direction, e _l=| y _a-y _b|, the residual error of expression line direction, e=(| x _a-x _b|) ²+ (| y _a-y _b|) ², the residual error that the expression distance is last.

In order to improve each interative computation precision as a result, guarantee convergence process, when also providing iteration, the present invention adjusts the concrete grammar of rectangular area, ground:

Step 6.1 is according to formula PS=θ * D _{Lat_scale}/ sqrt ((x ₁-x ₂) * (x ₁-x ₂)+(y ₁-y ₂) * (y ₁-y ₂)) calculate (

D _Hei) near the position the pixel size PS of image,

Picpointed coordinate (x wherein ₁, y ₁) be ground point (

D _Hei) pairing picpointed coordinate, and numerical value is (x _b, y _b); Picpointed coordinate (x ₂, y ₂) be ground point $(D_{{\mathrm{lat}}_a}+\mathrm{\θ}\×D_{\mathrm{lat}\_\mathrm{scale}},D_{{\mathrm{lon}}_a},D_{\mathrm{hei}})$ Pairing picpointed coordinate, θ is for dwindling the value coefficient, and sqrt represents extraction of square root; Dwindling the span of value coefficient θ can choose as the case may be, and for example 0.001～0.05, the embodiment of the invention selects 0.01 for use, then PS=0.01 * D _{Lat_scale}/ sqrt ((x ₁-x ₂) * (x ₁-x ₂)+(y ₁-y ₂) * (y ₁-y ₂))

During concrete enforcement, the calculating of the pixel size PS of image is not limited to this kind mode, for example adjusts latitude numerical value, calculate $(D_{{\mathrm{lat}}_a}+0.01\×D_{\mathrm{lat}\_\mathrm{scale}},D_{{\mathrm{lon}}_a},D_{\mathrm{hei}})$ Corresponding picpointed coordinate; If change the adjustment longitude into, corresponding making into calculated $(D_{{\mathrm{lat}}_a},D_{{\mathrm{lon}}_a}+0.01\×D_{\mathrm{lat}\_\mathrm{scale}},D_{\mathrm{hei}})$ Corresponding picpointed coordinate; Perhaps latitude, longitude is adjusted simultaneously and also can.Accordingly, molecule also needs corresponding change in the formula.

Step 6.2 is adjusted rectangular area, ground scope according to pixel size PS, and the latitude and longitude coordinates of rectangular area, ground central point and 4 angle points is $(D_{{\mathrm{lat}}_a}+e_s\×{\mathrm{PS},D}_{{\mathrm{lon}}_a}+e_l\×\mathrm{PS}),$ $(D_{{\mathrm{lat}}_a}-e_s\×{\mathrm{PS},D}_{{\mathrm{lon}}_a}+e_l\×\mathrm{PS}),$ $(D_{{\mathrm{lat}}_a}+e_s\×{\mathrm{PS},D}_{{\mathrm{lon}}_a}-e_l\×\mathrm{PS}),$ $(D_{{\mathrm{lat}}_a}-e_s\×{\mathrm{PS},D}_{{\mathrm{lon}}_a}-e_l\×\mathrm{PS}).$

Claims (2)

1. based on the direct transform method of rational polynominal imaging model, it is characterized in that: rational polynominal imaging model inverse transformation result is introduced rational polynominal imaging model direct transform process carry out iterated transform, promptly adopt computing machine to carry out following steps, step 1 is provided with elevation numerical value D _HeiWith rational polynominal imaging model parameter, setting the central point latitude and longitude coordinates is (D _{Lat_off}, D _{Lon_off}), the length of side is D _{Lat_scale}And D _{Lon_scale}The rectangular area, ground, wherein the latitude and longitude coordinates of 4 angle points is

(D _{lat_off}+D _{lat_scale}/2.0，D _{lon_off}+D _{lon_scale}/2.0)；

(D _{lat_off}-D _{lat_scale}/2.0，D _{lon_off}+D _{lon_scale}/2.0)；

(D _{lat_off}+D _{lat_scale}/2.0，D _{lon_off}-D _{lon_scale}/2.0)；

(D _{lat_off}-D _{lat_scale}/2.0，D _{lon_off}-D _{lon_scale}/2.0)；

Step 2 is utilized 4 angle points in rectangular area, inverse transformation Model Calculation ground and the central point corresponding image picpointed coordinate of rational polynominal imaging model;

Step 3 is utilized the latitude and longitude coordinates and the image picpointed coordinate of above-mentioned 5 points, according to the affine transformation relationship formula $\begin{array}{c}{D}_{\mathrm{lat}}=f_0+f_{1}x+f_{2}y\\ D_{\mathrm{lon}}=g_0+g_{1}x+g_{2}y\end{array},$ Utilize the principle of least square to calculate the approximate affine transformation parameter f of image ₀, f ₁, f ₂, g ₀, g ₁, g ₂, x, y represent the columns value and the line number value of the image picpointed coordinate of regularization, D respectively _Lat, D _LonLatitude numerical value and the longitude numerical value of representing the topocentric coordinates of regularization respectively;

Step 4 is according to the approximate affine transformation parameter f of image ₀, f ₁, f ₂, g ₀, g ₁, g ₂Find the solution and measure given measurement picpointed coordinate (x _a, y _a) corresponding approximate latitude and longitude coordinates

Step 5 is according to the inverse transformation Model Calculation topocentric coordinates of rational polynominal imaging model

Corresponding theoretical picpointed coordinate (x _b, y _b);

Step 6 is calculated residual error e, computing formula be e=(| x _a-x _b|) ²+ (| y _a-y _b|) ²If residual error e satisfies the difference range of setting, directly output As measuring picpointed coordinate (x _a, y _a) corresponding latitude and longitude coordinates

Otherwise with Dwindle rectangular area, ground scope for the central point latitude and longitude coordinates, return the operation of step 2 iteration then, satisfy the difference range of setting up to residual error e,

With

The concrete steps of dwindling rectangular area, ground scope for the central point latitude and longitude coordinates are as follows, and step 6.1 is according to formula PS=θ * D _{Lat_scale}/ sqrt ((x ₁-x ₂) * (x ₁-x ₂)+(y ₁-y ₂) * (y ₁-y ₂)) calculate $(D_{{\mathrm{lat}}_a},D_{{\mathrm{lon}}_a},D_{\mathrm{hei}})$ Near the pixel size PS of the image the position,

Picpointed coordinate (x wherein ₁, y ₁) be ground point

Pairing picpointed coordinate, picpointed coordinate (x ₂, y ₂) be ground point $(D_{{\mathrm{lat}}_a}+\mathrm{\θ}\×D_{\mathrm{lat}\_\mathrm{scale}},D_{{\mathrm{lon}}_a},D_{\mathrm{hei}})$ Pairing picpointed coordinate, θ is for dwindling the value coefficient;

Step 6.2 is adjusted rectangular area, ground scope according to pixel size PS, and the latitude and longitude coordinates of 4 angle points in rectangular area, ground is $(D_{{\mathrm{lat}}_a}+e_s\×\mathrm{PS},D_{{\mathrm{lon}}_a}+e_l\×\mathrm{PS}),$ $(D_{{\mathrm{lat}}_a}-e_s\×\mathrm{PS},D_{{\mathrm{lon}}_a}+e_l\×\mathrm{PS}),$ $(D_{{\mathrm{lat}}_a}+e_s\×\mathrm{PS},D_{{\mathrm{lon}}_a}-e_l\×\mathrm{PS}),$ $(D_{{\mathrm{lat}}_a}-e_s\×\mathrm{PS},D_{{\mathrm{lon}}_a}-e_l\×\mathrm{PS}),$

E wherein _s=| x _a-x _b|, the residual error of expression column direction, e _l=| y _a-y _b|, the residual error of expression line direction.

2. according to the described direct transform method based on the rational polynominal imaging model of claim 1, it is characterized in that: the span of dwindling value coefficient θ is 0.001～0.05.

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