CN103363960B - A kind of based on DLT coefficient large format digital air photo instrument image splicing method - Google Patents

Abstract

The invention discloses a kind of based on DLT coefficient large format digital air photo instrument image splicing method, this method is mainly used in large format digital air photo instrument sub-image splicing virtual image, comprising: obtain four sub-images to synchronization exposure; The tie point coupling of four sub-images is carried out in cruciform overlay region, according to the tie point between sub-image, and the initial platform calibration parameter of each sub-image, calculate the elements of exterior orientation often opening sub-image; According to the elements of exterior orientation of four sub-images of synchronization exposure, determine the relative position relation of four cameras, calculate DLT platform calibration parameter according to described relative position relation; Spliced virtual image is generated from sub-image according to described DLT platform calibration parameter.Provided by the invention based on DLT coefficient large format digital air photo instrument image splicing method, avoid complicated data operation process, therefore this joining method is more simple, is more conducive to image splicing method fast processing.

Description

A kind of based on DLT coefficient large format digital air photo instrument image splicing method

Technical field

The present invention relates to photogrammetric measurement technical field, particularly relate to a kind of based on DLT coefficient large format digital air photo instrument image splicing method.

Background technology

Practical digital air photo instrument requires to possess high resolving power and large format covering simultaneously.But when film size is certain, in inverse relation between the spatial resolution of image and covered ground, the effective way of both solutions contradiction increases film size size.The digital aerial surveying camera film size of little film size is little, and data volume is large, and add the workload of aftertreatment, base-height ratio is little, reduces vertical accuracy.Multiaspect battle array digital air photo instrument is compared with one side battle array, under same boat takes the photograph condition (flying height, degree of overlapping is identical), film size becomes large, baseline elongates, base-height ratio increases, and vertical accuracy large format improves, and can improve work unit work efficiency, reduce workload, shorten working hours, save huge financial resources, material resources and manpower, huge impetus is served for photogrammetric development.

In prior art, in June, 2007, the Research Team headed by the first woods academician of Liu is proposed the large film size digital aerial surveying camera SWDC series of products of China's independent development first.The digital aerial surveying camera of the large film size of SWDC adopt directly by traditional platform calibration parameter by carrying out being spliced to form virtual image as plane transformation method.Existing platform calibration parameter is by needing as plane transformation to calculate rotation matrix, and therefore operand is large, is unfavorable for data splicing on a large scale.

Summary of the invention

The object of the present invention is to provide a kind of based on DLT coefficient large format digital air photo instrument image splicing method, to solve the problem.

In order to achieve the above object, technical scheme of the present invention is achieved in that

A kind of based on DLT coefficient large format digital air photo instrument image splicing method, comprise the steps:

Four sub-images are obtained to synchronization exposure;

The tie point coupling of four sub-images is carried out in cruciform overlay region, according to the tie point between sub-image, and the platform calibration initial value of each sub-image, calculate the elements of exterior orientation often opening sub-image;

According to the elements of exterior orientation of four sub-images of synchronization exposure, determine the relative position relation of four cameras, calculate DLT platform calibration parameter according to described relative position relation;

Spliced virtual image is generated from sub-image according to described DLT platform calibration parameter.Compared with prior art, the advantage of the embodiment of the present invention is:

One provided by the invention, based on DLT coefficient large format digital air photo instrument image splicing method, comprises the steps:

First, obtain four sub-images to synchronization exposure, this is the element task realizing obtaining digitized video, is preserved by above-mentioned corresponding sub-image.

Then, in cruciform overlay region, carry out the tie point coupling of multiple sub-image, according to the tie point between sub-image, and the platform calibration initial value of each sub-image, calculate the elements of exterior orientation often opening sub-image.Particularly, utilize above-mentioned steps can realize calculating the data such as elements of exterior orientation, elements of interior orientation, data basis can be provided for follow-up calibration platform model of setting up like this.

Then, according to the elements of exterior orientation of four sub-images of synchronization exposure, determine the relative position relation of four cameras, calculate DLT(direct linear transformation solution according to described relative position relation) platform calibration parameter; Here step its essence is the foundation of carrying out mathematical model and solves.Establish the mathematical model of calibration, adopt the mathematical model based on space resection, based on collinearity equation (namely object point, picture point and photo centre are positioned on straight line), solution tries to achieve out the DLT coefficient (namely each picture plane of single camera is to the DLT conversion coefficient of virtual representation plane) of every platform camera.

Finally, spliced virtual image is generated according to described DLT platform calibration parameter from sub-image.

Provided by the invention based on DLT coefficient large format digital air photo instrument image splicing method, by the introducing of DLT coefficient, can be DLT coefficient by platform calibration Parameter Switch, thus set up one camera as the relation between plane to virtual representation plane, only need to calculate simple multiplication and division plus and minus calculation, namely can be virtual representation planimetric coordinates as two-dimensional assemblage by one camera, complete image joint, avoid complicated data operation process, therefore this joining method is more simple, is more conducive to image splicing method fast processing.

Accompanying drawing explanation

The schematic flow sheet based on DLT coefficient large format digital air photo instrument image splicing method that Fig. 1 provides for the embodiment of the present invention.

Embodiment

Also by reference to the accompanying drawings the present invention is described in further detail below by specific embodiment.

See Fig. 1, embodiments provide a kind of based on DLT coefficient large format digital air photo instrument image splicing method, comprise the steps:

Step S100, to synchronization exposure obtain four sub-images;

Step S200, in cruciform overlay region, carry out the tie point coupling of four sub-images, according to the tie point between sub-image, and the platform calibration initial value of each sub-image, calculate the elements of exterior orientation often opening sub-image;

Step S300, the elements of exterior orientation of four sub-images according to synchronization exposure, determine the relative position relation of four cameras, calculate DLT platform calibration parameter according to described relative position relation;

Step S400, generate spliced virtual image according to described DLT platform calibration parameter from sub-image.

In embodiments of the present invention, it should be noted that, the enforcement of each step above-mentioned has come by application system, and this application system comprises calibration platform, the digital picture splicing device (comprising software section) that four cameras are formed.This processor can Automatic solution elements of relative orientation, sets up area adjustment model and carries out resolving of aerotriangulation, analytical photogrammetry.

For large format multiaspect battle array digital camera, higher calibration precision be obtained, the method for controlling filed calibration should be adopted, the object obtaining sub-image elements of exterior orientation and other distortion factors can be reached by calibration.The error (namely comprising optical parallax, machine error and electricity error etc.) of digital camera can be determined by calibration, thus carry out follow-up process.

The digital air photo instrument image splicing method that the embodiment of the present invention provides, first, obtain four sub-images to the exposure of (same subject) synchronization, this is the element task realizing obtaining digitized video, is preserved by above-mentioned corresponding sub-image.

Then, in cruciform overlay region, carry out the tie point coupling of four sub-images, according to the tie point between sub-image, and the platform calibration initial value of each sub-image, calculate the elements of exterior orientation often opening sub-image.Particularly, utilize above-mentioned steps can realize calculating the data such as elements of exterior orientation, elements of interior orientation, data basis can be provided for follow-up calibration platform model of setting up like this.

Then, according to the elements of exterior orientation of four sub-images of synchronization exposure, determine the relative position relation of four cameras, calculate DLT((directlineartransformation, DLT according to described relative position relation) direct linear transformation's solution) platform calibration parameter; Here step its essence is the foundation of carrying out mathematical model and solves.Establish the mathematical model of calibration, adopt the mathematical model based on space resection, based on collinearity equation (namely object point, picture point and photo centre are positioned on straight line), solution tries to achieve out the DLT coefficient (namely each picture plane of single camera is to the DLT conversion coefficient of virtual representation plane) of every platform camera.Finally, spliced virtual image is generated according to described DLT platform calibration parameter from sub-image.

The embodiment of the present invention provide based on DLT coefficient large format digital air photo instrument image splicing method, by the introducing of DLT coefficient, can be DLT coefficient by platform calibration Parameter Switch, thus set up one camera as the relation between plane to virtual representation plane, only need to calculate simple multiplication and division plus and minus calculation, namely can be virtual representation planimetric coordinates as two-dimensional assemblage by one camera, complete image joint.Avoid complex calculations in prior art, therefore this joining method is more simple, is conducive to image splicing method fast processing.

Below each step above-mentioned based on DLT coefficient large format digital air photo instrument image splicing method that the embodiment of the present invention provides is described in detail:

Particularly, in step S300, the elements of exterior orientation of described four sub-images according to synchronization exposure, determines the relative position relation of four cameras, calculates DLT platform calibration parameter, comprise the steps: according to described relative position relation

Step S310, calculate the DLT conversion coefficient of each picture plane to virtual representation plane of every platform camera in four cameras respectively;

Step S320, DLT conversion coefficient according to four cameras, determine the relative position relation of four cameras, calculates DLT platform calibration parameter according to the relative position relation of four cameras.

Preferably, in step S310, in described calculating respectively four cameras, each picture plane of every platform camera is to the DLT conversion coefficient of virtual representation plane, comprises the steps:

Step S311, calculating single camera are to the perspective transform of surface level;

If the elements of exterior orientation of camera is X _s1, Y _s1, Z _s1, ω ₁, κ ₁, elements of interior orientation is x ₀₁, y ₀₁, f ₁, be x as coordinate ₁, y ₁, corresponding surface level is (X, Y, H), and rotation matrix is R1, obtains formula one according to collinearity equation:

$\left(\begin{array}{c}{x}_1-x_{01}\\ y_1-y_{01}\\ -f_1\end{array}\right)={\mathrm{\λ}}_1{R}_1\left(\begin{array}{c}X-X_{s1}\\ Y-Y_{s1}\\ H-Z_{s1}\end{array}\right);$

Rotation matrix: $R_1=\left[\begin{array}{ccc}{a}_1& a_2& a_3\\ b_1& b_2& b_3\\ c_1& c_2& c_3\end{array}\right];$

During coordinates computed, if k ₀₁=a ₃/ (H-Z _s1), k ₀₂=b ₃/ (H-Z _s1),

k ₀₃=-(a ₃x ₀₁+b ₃y ₀₁+c ₃f ₁)/(H-Z _s1)；

λ ₁=(a ₃(x ₁-x ₀₁)+b ₃(y ₁-y ₀₁)-c ₃f ₁)/(H-Z _s1)=k ₀₁x+k ₀₂y+k ₀₃；

Wherein, it should be noted that, k ₀₁, k ₀₂, k ₀₃coefficient be required hypothesis numerical value when calculating, not there is any practical significance, will be used in follow-up computation process.

Step S312, calculated level face are to the perspective transform of virtual representation plane;

If the elements of exterior orientation of virtual camera is X _s0, Y _s0, Z _s0, ω ₀, κ ₀, focal length is f, is x, y as coordinate, and corresponding surface level is (X, Y, 0), and rotation matrix is R' ₁;

Wherein, described elements of exterior orientation is all through the numerical value after centralization process:

X _s0=(X _s1+X _s2)/2

Y _s0=(Y _s1+Y _s2)/2

Z _s0=(Z _s1+Z _s2)/2

ω _s0=(ω _s1+ω _s2)/2

κ _s0=(κ _s1+κ _s2)/2

Formula two is obtained according to collinearity equation:

$\left(\begin{array}{c}x\\ y\\ -f\end{array}\right)={\mathrm{\λ}}_1^{\′}{R}_1^{\′}\left(\begin{array}{c}X-X_{s0}\\ Y-Y_{s0}\\ H-Z_{s0}\end{array}\right);$

Wherein, rotation matrix is ${R_1}^{\′}=\left[\begin{array}{ccc}{c}_{00}& c_{01}& c_{02}\\ c_{10}& c_{11}& c_{12}\\ c_{20}& c_{21}& c_{22}\end{array}\right];$

Obtain thus:

$\left(\begin{array}{c}X-X_{s0}\\ Y-Y_{s0}\\ H-Z_{s0}\end{array}\right)=R_1^{{\′}^{-1}}/{\text{\λ}}_1^{\′}\left(\begin{array}{c}x\\ y\\ -f\end{array}\right);$

Obtain perspective transform coefficient: λ ' ₁=(C ₂₀x+C ₂₁y-C ₂₂f)/(H-Z _s0);

In calculating ${\mathrm{\λ}}_1{R}_1\left(\begin{array}{c}{X}_{s1}-X_{s0}\\ Y_{s1}-Y_{s0}\\ Z_{s1}-Z_{s0}\end{array}\right)$ Time, if its be ${\mathrm{\λ}}_1\left(\begin{array}{c}{k}_{11}\\ k_{12}\\ k_{13}\end{array}\right),$ Then calculate:

k ₁₁=C ₀₀(X _s1-X _s0)+C ₀₁(Y _s1-Y _s0)+C ₀₂(Z _s1-Z _s0)；

k ₁₂=C ₁₀(X _s1-X _s0)+C ₁₁(Y _s1-Y _s0)+C ₁₂(Z _s1-Z _s0)；

k ₁₃=C ₂₀(X _s1-X _s0)+C ₂₁(Y _s1-Y _s0)+C ₂₂(Z _s1-Z _s0)；

Step S313, according to single camera to the perspective transform coefficient of surface level and surface level to the perspective transform of virtual representation plane, ask for the DLT conversion coefficient of single camera to the Relative Transformation of virtual camera;

Can be obtained by formula one:

Formula three $\left(\begin{array}{c}X-X_{s1}\\ Y-Y_{s1}\\ H-Z_{s1}\end{array}\right)={R_1}^{-1}/{\mathrm{\λ}}_1\left(\begin{array}{c}{x}_1-x_{01}\\ y_1-y_{01}\\ -f_1\end{array}\right);$

Obtain formula four thus:

$\left(\begin{array}{c}X\\ Y\\ H\end{array}\right)={R_1}^{-1}/{\mathrm{\λ}}_1\left(\begin{array}{c}{x}_1-x_{01}\\ y_1-y_{01}\\ {-f}_1\end{array}\right)+\left(\begin{array}{c}{X}_{s1}\\ Y_{s1}\\ Z_{s1}\end{array}\right);$

Formula four is substituted into formula two and obtains formula five:

Formula five is:

$\left(\begin{array}{c}x\\ y\\ -f\end{array}\right)={\mathrm{\λ}}_1^{\′}/{\mathrm{\λ}}_1{R}_1^{\′}{R_1}^{-1}(\left(\begin{array}{c}{x}_1-x_{01}\\ y_1-y_{01}\\ {-f}_1\end{array}\right)+{\mathrm{\λ}}_1{R}_1\left(\begin{array}{c}{X}_{s1}-X_{s0}\\ Y_{s1}-Y_{s0}\\ Z_{s1}-Z_{s0}\end{array}\right));$

Wherein: ${R_1}^{\′}{R}_1^{-1}=\left[\begin{array}{ccc}{M}_{00}& M_{01}& M_{02}\\ M_{10}& M_{11}& M_{12}\\ M_{20}& M_{21}& M_{22}\end{array}\right];$

Calculate $\left(\begin{array}{c}x\\ y\\ -f\end{array}\right)$ Time, if its be $\left(\begin{array}{c}{k}_{20}x+k_{21}y+k_{22}\\ k_{23}x+k_{24}y+k_{25}\\ k_{26}+k_{27}y+k_{28}\end{array}\right),$ Then calculate nine coefficients:

k ₂₀=M ₀₀(1+k ₁₁k ₀₁)+M ₀₁k ₀₁k ₁₂+M ₀₂k ₀₁k ₁₃；

k ₂₁=M ₀₁(1+k ₁₂k ₀₂)+M ₀₀k ₁₁k ₀₂+M ₀₂k ₀₂k ₁₃；

k ₂₂=M ₀₂(-f+k ₁₃k ₀₃)+M ₀₁k ₀₃k ₁₂+M ₀₀k ₀₃k ₁₁-M ₀₀x ₁-M ₀₁y ₁；

k ₂₃=M ₁₀(1+k ₁₁k ₀₁)+M ₁₁k ₀₁k ₁₂+M ₁₂k ₀₁k ₁₃；

k ₂₄=M ₁₁(1+k ₁₂k ₀₂)+M ₁₀k ₁₁k ₀₂+M ₁₂k ₀₂k ₁₃；

k ₂₅=M ₁₂(-f+k ₁₃k ₀₃)+M ₁₁k ₀₃k ₁₂+M ₁₀k ₀₃k ₁₁-M ₁₀x ₁-M ₁₁y ₁；

k ₂₆=M ₂₀(1+k ₁₁k ₀₁)+M ₂₁k ₀₁k ₁₂+M ₂₂k ₀₁k ₁₃；

k ₂₇=M ₂₁(1+k ₁₂k ₀₂)+M ₂₀k ₁₁k ₀₂+M ₂₂k ₀₂k ₁₃；

k ₂₈=M ₂₂(-f+k ₁₃k ₀₃)+M ₂₁k ₀₃k ₁₂+M ₂₀k ₀₃k ₁₁-M ₂₀x ₁-M ₂₁y ₁；

Step S314, by the first eight coefficient k ₂₀, k ₂₁, k ₂₂, k ₂₃, k ₂₄, k _25,k ₂₆, k ₂₇respectively to the 9th coefficient k ₂₈carry out division arithmetic and obtain one group of totally eight DLT conversion coefficient;

Described eight DLT conversion coefficients as each picture plane of single camera to the DLT conversion coefficient of virtual representation plane.

Preferably, in step S400, describedly generate spliced virtual image according to described DLT platform calibration parameter from sub-image, comprise the steps:

According to the DLT conversion coefficient of each picture plane to virtual representation plane, calculating each one camera respectively as two-dimensional assemblage is virtual representation planimetric coordinates, determine the overlapping region of four sub-images, the virtual representation planimetric coordinates of every two sub-images is weighted on average as the coordinate of new virtual image, completes the concatenation of virtual image according to the coordinate of described new virtual representation.

Further, after generating spliced virtual image according to described DLT platform calibration parameter from sub-image, also comprise the steps:

Step S500, the smoothing process of virtual image splicing reconstructed, obtain central projection virtual image.

Wherein, spliced virtual image also needs to carry out the operations such as dodging, and to obtain stitching image, the embodiment of the present invention repeats no more this.

It should be noted that, in the joining method that the embodiment of the present invention provides, can also formula six be obtained:

$\left(\begin{array}{c}{x}_1-x_{01}\\ y_1-y_{01}\\ {-f}_1\end{array}\right)={\mathrm{\λ}}_1/{\mathrm{\λ}}_1^{\′}{R}_1{R}_1^{{\′}^{-1}}(\left(\begin{array}{c}x\\ y\\ -f\end{array}\right)+{\mathrm{\λ}}_1^{\′}{R}_1^{\′}\left(\begin{array}{c}{X}_{s0}-X_{s1}\\ Y_{s0}-Y_{s1}\\ Z_{s0}-Z_{s1}\end{array}\right));$

Utilizing formula six, equally also can obtain the DLT conversion coefficient of each virtual representation plane to picture plane by calculating.The joining method that the embodiment of the present invention provides, repeats no longer one by one to this.

Those skilled in the art are to be understood that, the embodiment of the present invention provide based on DLT coefficient large format digital air photo instrument image splicing method, by the introducing of DLT coefficient, can be DLT coefficient by platform calibration Parameter Switch, thus set up one camera as the relation between plane to virtual representation plane, only need to calculate simple multiplication and division plus and minus calculation, can be namely virtual representation planimetric coordinates as two-dimensional assemblage by one camera, complete image joint.Avoid complex calculations in prior art, therefore this joining method is more simple, is conducive to image splicing method fast processing.

The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, for a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (3)

1., based on a DLT coefficient large format digital air photo instrument image splicing method, it is characterized in that, comprise the steps:

Four sub-images are obtained to synchronization exposure;

The tie point coupling of four sub-images is carried out in cruciform overlay region, according to the tie point between sub-image, and the platform calibration initial value of each sub-image, calculate the elements of exterior orientation often opening sub-image;

According to the elements of exterior orientation of four sub-images of synchronization exposure, determine the relative position relation of four cameras, calculate DLT platform calibration parameter according to described relative position relation;

Spliced virtual image is generated from sub-image according to described DLT platform calibration parameter;

The elements of exterior orientation of described four sub-images according to synchronization exposure, determines the relative position relation of four cameras, calculates DLT platform calibration parameter, comprise the steps: according to described relative position relation

Calculate the DLT conversion coefficient of each picture plane to virtual representation plane of every platform camera in four cameras respectively;

According to the DLT conversion coefficient of four cameras, determine the relative position relation of four cameras, calculate DLT platform calibration parameter according to the relative position relation of four cameras;

In described calculating respectively four cameras, each picture plane of every platform camera is to the DLT conversion coefficient of virtual representation plane, comprises the steps:

Calculate the perspective transform of single camera to surface level;

If the elements of exterior orientation of camera is X _s1, Y _s1, Z _s1, ω ₁, κ ₁, elements of interior orientation is x ₀₁, y ₀₁, f ₁, be x as coordinate ₁, y ₁, corresponding surface level is (X, Y, H), and rotation matrix is R1, obtains formula one according to collinearity equation:

Rotation matrix:

During coordinates computed, if k ₀₁=a ₃/ (H-Z _s1), k ₀₂=b ₃/ (H-Z _s1), k ₀₃=-(a ₃x ₀₁+ b ₃y ₀₁+ c ₃f ₁)/(H-Z _s1);

λ ₁＝(a ₃(x ₁-x ₀₁)+b ₃(y ₁-y ₀₁)-c ₃f ₁)/(H-Z _s1)＝k ₀₁x ₁+k ₀₂y ₁+k ₀₃；

Calculated level face is to the perspective transform of virtual representation plane;

If the elements of exterior orientation of virtual camera is X _s0, Y _s0, Z _s0, ω _s0, κ _s0, focal length is f, is x, y as coordinate, and corresponding surface level is (X, Y, 0), and rotation matrix is R ' ₁:

X _s0＝(X _s1+X _s2)/2

Y _s0＝(Y _s1+Y _s2)/2

Z _s0＝(Z _s1+Z _s2)/2

ω _s0＝(ω _s1+ω _s2)/2

κ _s0＝(κ _s1+κ _s2)/2

Formula two is obtained according to collinearity equation:

Wherein, rotation matrix is

Obtain thus:

Obtain perspective transform coefficient: λ ' ₁=(C ₂₀x+C ₂₁y-C ₂₂f)/(H-Z _s0);

In calculating time, if its be then calculate:

k ₁₁＝C ₀₀(X _s1-X _s0)+C ₀₁(Y _s1-Y _s0)+C ₀₂(Z _s1-Z _s0)；

k ₁₂＝C ₁₀(X _s1-X _s0)+C ₁₁(Y _s1-Y _s0)+C ₁₂(Z _s1-Z _s0)；

k ₁₃＝C ₂₀(X _s1-X _s0)+C ₂₁(Y _s1-Y _s0)+C ₂₂(Z _s1-Z _s0)

；

According to single camera to the perspective transform coefficient of surface level and surface level to the perspective transform coefficient of virtual representation plane, ask for the DLT conversion coefficient of single camera to the Relative Transformation of virtual camera;

Can be obtained by formula one:

Formula three

Obtain formula four thus:

Formula four is substituted into formula two and obtains formula five:

Formula five is:

Wherein:

Calculate time, if its be then calculate nine coefficients:

k ₂₀＝M ₀₀(1+k ₁₁k ₀₁)+M ₀₁k ₀₁k ₁₂+M ₀₂k ₀₁k ₁₃；

k ₂₁＝M ₀₁(1+k ₁₂k ₀₂)+M ₀₀k ₁₁k ₀₂+M ₀₂k ₀₂k ₁₃；

k ₂₂＝M ₀₂(-f+k ₁₃k ₀₃)+M ₀₁k ₀₃k ₁₂+M ₀₀k ₀₃k ₁₁-M ₀₀x ₁-M ₀₁y ₁；

k ₂₃＝M ₁₀(1+k ₁₁k ₀₁)+M ₁₁k ₀₁k ₁₂+M ₁₂k ₀₁k ₁₃；

k ₂₄＝M ₁₁(1+k ₁₂k ₀₂)+M ₁₀k ₁₁k ₀₂+M ₁₂k ₀₂k ₁₃；

k ₂₅＝M ₁₂(-f+k ₁₃k ₀₃)+M ₁₁k ₀₃k ₁₂+M ₁₀k ₀₃k ₁₁-M ₁₀x ₁-M ₁₁y ₁；

k ₂₆＝M ₂₀(1+k ₁₁k ₀₁)+M ₂₁k ₀₁k ₁₂+M ₂₂k ₀₁k ₁₃；

k ₂₇＝M ₂₁(1+k ₁₂k ₀₂)+M ₂₀k ₁₁k ₀₂+M ₂₂k ₀₂k ₁₃；

k ₂₈＝M ₂₂(-f+k ₁₃k ₀₃)+M ₂₁k ₀₃k ₁₂+M ₂₀k ₀₃k ₁₁-M ₂₀x ₁-M ₂₁y ₁；

By the first eight coefficient k ₂₀, k ₂₁, k ₂₂, k ₂₃, k ₂₄, k ₂₅, k ₂₆, k ₂₇respectively to the 9th coefficient k ₂₈carry out division arithmetic and obtain one group of totally eight DLT conversion coefficient;

Described eight DLT conversion coefficients as each picture plane of single camera to the DLT conversion coefficient of virtual representation plane.

2., as claimed in claim 1 based on DLT coefficient large format digital air photo instrument image splicing method, it is characterized in that,

Generate spliced virtual image according to described DLT platform calibration parameter from sub-image, comprise the steps:

According to the DLT conversion coefficient of each picture plane to virtual representation plane, calculating each one camera respectively as two-dimensional assemblage is virtual representation planimetric coordinates, determine the overlapping region of four sub-images, the virtual representation planimetric coordinates of every two sub-images is weighted on average as the coordinate of new virtual image, completes the concatenation of virtual image according to the coordinate of described new virtual image.

3., as claimed in claim 2 based on DLT coefficient large format digital air photo instrument image splicing method, it is characterized in that,

According to described DLT platform calibration parameter from after sub-image generates spliced virtual image, also comprise the steps:

By the smoothing process of virtual image of splicing reconstruct, obtain smooth and seamless central projection image.