阅读说明：本技术 一种基于轨道约束的卫星影像立体区域网平差方法 (Satellite image three-dimensional area network adjustment method based on orbit constraint ) 是由 张过 于 2021-08-06 设计创作，主要内容包括：本发明提供了一种基于轨道约束的卫星影像立体区域网平差方法,其包括通过同轨道内相邻影像重叠区域的偏移量计算原始单景影像的像点在轨道影像坐标系下的坐标,对同轨拼接条件进行检查,满足拼接条件后进行拼接,对拼接后的轨道影像在物方生成虚拟控制网格,通过网格点计算轨道影像的RFM,将控制点的像方和物方坐标视为真值,经区域网平差求解RFM的仿射变换系数以及目标点的物方空间坐标,从而大大的提高了区域网平差的精度。(The invention provides a satellite image stereo regional net adjustment method based on orbit constraint, which comprises the steps of calculating the coordinates of image points of an original single-scene image under an orbit image coordinate system through the offset of an adjacent image overlapping region in the same orbit, checking the same-orbit splicing condition, splicing after the splicing condition is met, generating a virtual control grid for the spliced orbit image in an object space, calculating the RFM of the orbit image through grid points, regarding the image space and object space coordinates of control points as true values, and solving the affine transformation coefficient of the RFM and the object space coordinates of a target point through regional net adjustment, thereby greatly improving the precision of regional net adjustment.)

1. A satellite image stereo area network adjustment method based on orbit constraint is characterized by comprising the following steps:

calculating the coordinates of the image points of the original single-scene image in the track image coordinate system through the offset of the overlapping area of the adjacent images in the same track;

checking the same-rail splicing condition, and splicing after meeting the splicing condition;

generating a virtual control grid for the spliced track image in an object space, and calculating the RFM of the track image through grid points;

and (3) regarding the image space coordinates and the object space coordinates of the control points as true values, and solving the affine transformation coefficient of the RFM and the object space coordinates of the target point through block adjustment.

2. The orbital constraint-based satellite image stereo regional block adjustment method as recited in claim 1, wherein if the RFM fitting accuracy obtained by calculating the RFM of the orbital image through the grid points is poor, virtual control grid points are established and grid compensation is performed.

3. The orbital constraint-based satellite image stereo regional net adjustment method according to claim 1, wherein the RFM is in the general form of:

in the formula, x and y are coordinates of image points; x, Y, Z are ground point coordinates; the sum of the powers of the individual coordinate components of each term in the polynomial Pi (i ═ 1,2,3, 4) and the power thereof does not exceed 3 at most. Then the polynomial is of the form:

P_i＝a_i0+a_i1Z+a_i2Y+a_i3X+a_i4ZY+a_i5ZX+a_i6YX+a_i7Z²+a_i8Y²+aⁱ⁹X²+a_i10ZYX+a_i11Z²Y+a_i12Z²X+a_i13Y²Z+a_i14Y²X+a_i15ZX₂+a_i16YX₂+a_i17Z³+a_i18Y³+a_i19X³

in the formula, aij (i is 1,2,3, 4; j is 0,1, 9) is a polynomial coefficient of a rational function.

4. The orbit constraint-based satellite image stereo area network adjustment method according to claim 3, wherein a preset image space compensation scheme is adopted to eliminate the influence on the image geometric positioning result when the RPC parameters contain errors, the preset image space compensation scheme is to adopt an image space compensation RFM with an affine transformation model, and the image space compensation RFM with the affine transformation model is:

in the formula, e_iAnd f_i(i is 0,1, 2) is an affine transformation parameter. Transforming affine parameters (e)_i，f_i) And object space coordinates (X, Y, Z) of the target point are used as unknown numbers, the affine transformation parameters are affine transformation parameters of the track image, and the adjustment error square of the track image area network based on the RFM can be obtained through the formulaThe process is as follows:

Technical Field

The invention relates to the technical field of photogrammetry and remote sensing, in particular to a satellite image three-dimensional block adjustment method based on orbit constraint.

Background

With the successful emission of the high-resolution three-dimensional mapping satellite resource III, the high-resolution earth observation capability of China is gradually enhanced, and the mapping and updating of a large-scale topographic map by using a satellite remote sensing image become possible. The block adjustment is used as a method for carrying out precise geodetic positioning by utilizing an aviation or aerospace remote sensing image and a small number of ground control points, and plays a role in lifting weight in the topographic map surveying and mapping process.

In reality, most satellite image providers do not provide the attitude, orbit, camera mounting and other parameters at the image imaging time, but only provide RPC parameters, and a rigorous geometric model is difficult to establish. Therefore, the co-orbit constraint method based on the rigorous geometric model has no applicability to satellite imagery that only provides RPC parameters. On the premise of fully considering a data source, aiming at satellite image data only providing RPC parameters, a resource No. three standard scene satellite image block adjustment method (called orbit adjustment for short) based on orbit constraint is provided by taking a resource No. three sensor corrected standard scene image product (only RPC parameters) as a test object. And then, the orientation parameters of the obtained orbit image are re-planned to obtain the orientation parameters of the original single-scene image. Finally, the block adjustment test of image data in different areas proves that the method achieves better precision level under sparse control, and the precision result is obviously superior to that of the conventional RFM-based single-view satellite image block adjustment

Disclosure of Invention

In order to solve the above problems, the present invention aims to provide a satellite image stereo block adjustment method based on orbit constraint, and aims to improve block adjustment accuracy of a satellite image under an orbit constraint condition.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

the invention provides a satellite image stereo regional net adjustment method based on orbit constraint, which comprises the following steps

Calculating the coordinates of the image points of the original single-scene image in the track image coordinate system through the offset of the overlapping area of the adjacent images in the same track;

checking the same-rail splicing condition, and splicing after meeting the splicing condition;

generating a virtual control grid for the spliced track image in an object space, and calculating the RFM of the track image through grid points;

and (3) regarding the image space coordinates and the object space coordinates of the control points as true values, and solving the affine transformation coefficient of the RFM and the object space coordinates of the target point through block adjustment.

Further, if the fitting accuracy of the RFM obtained by calculating the RFM of the orbit image through the grid points is poor, establishing virtual control grid points and carrying out grid compensation.

According to the embodiment of the invention, the coordinates of the image points of the original single-scene image under the track image coordinate system are calculated through the offset of the overlapping areas of the adjacent images in the same track, the same-track splicing condition is checked, splicing is carried out after the splicing condition is met, a virtual control grid is generated on the spliced track image in the object space, the RFM of the track image is calculated through grid points, the image space and object space coordinates of the control points are regarded as true values, and the affine transformation coefficient of the RFM and the object space coordinates of the target point are solved through block network adjustment, so that the accuracy of the block network adjustment is greatly improved.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 is a schematic diagram of splicing in-orbit adjacent images of a satellite image stereo block adjustment method based on orbit constraint according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a virtual control grid of a satellite image stereo area block adjustment method based on orbit constraint according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It is also to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be further understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

The invention provides a structural schematic diagram of a satellite image stereo area network adjustment method based on orbit constraint, which comprises the following steps of S101-S104:

step S101: and calculating the coordinates of the image points of the original single-scene image in the track image coordinate system through the offset of the overlapping area of the adjacent images in the same track.

Step S102: and checking the same-rail splicing condition, and splicing after the splicing condition is met.

Step S103: and generating a virtual control grid for the spliced track image at an object space, and calculating the RFM of the track image through grid points.

Step S104: and (3) regarding the image space coordinates and the object space coordinates of the control points as true values, and solving the affine transformation coefficient of the RFM and the object space coordinates of the target point through block adjustment.

Specifically, the coordinates of image points of an original single-scene image under an orbit image coordinate system are calculated through the offset of an adjacent image overlapping area in the same orbit, the same-orbit splicing condition is checked, splicing is carried out after the splicing condition is met, a virtual control grid is generated on the spliced orbit image in an object space, the RFM of the orbit image is calculated through grid points, the image space and object space coordinates of control points are regarded as true values, the affine transformation coefficient of the RFM and the object space coordinates of a target point are solved through block network adjustment, and therefore the accuracy of block network adjustment is greatly improved.

Specifically, the primary goal of performing track adjustment is to logically splice the images in the same track into a virtual image in a strip, i.e., all the images in the same track are considered to be a scene, but are not physically spliced in practice. The image coordinates of all the image points in the orbit image coordinate system need to be recalculated and the RFM of the orbit image needs to be regenerated. Referring to fig. 1, the coordinates of the image point of the original monoscopic image in the track image coordinate system can be calculated by the offset of the overlapping area of the adjacent images in the same track, and the specific calculation method is as follows,

wherein i represents the ith scene image in the track; height represents the height of the image; bisa_iIndicating the offset of the ith scene image relative to the previous scene image, i.e. the length of the overlap of the two scenes, and defining the bias when i is 0₀＝0；x_iAnd y_iRespectively representing the column coordinates and the row coordinates of the image point in the orbital coordinate system.

In addition, in order to ensure that the spliced track images can be logically spliced into a scene and ensure that the RFM fitting precision of the track images is high, the same-track splicing condition check is required. Checking the same-rail splicing condition, and splicing after meeting the splicing condition; that is, the image point of the overlapped area on the image a (fig. 1) is projected to the elevation of the object, and then the object point is back projected to the image plane of the lower scene image B adjacent to the same track, so that the difference between the coordinate of the image point of the "same-name point" (the same-name point is actually represented as the same point because the cutting production of the standard scene image adjacent to the same track leads to the division on the two scenes, and the two points do not actually have the intersection condition), and the deviation should not exceed the limit (the threshold value can be set to 1 pixel, for example). If the image exceeds the limit, the track image of one scene is divided into two scenes, and so on. Referring to fig. 2, for the calculation of the spliced orbit image RFM, a terrain-independent scheme is adopted for solution. Firstly, the orbit image generates a virtual control grid on the object space, and then the RFM of the orbit image is calculated by utilizing the grid points. And generating a virtual control grid for the spliced track image in an object space, calculating the RFM of the track image through grid points, and if the obtained RFM has poor fitting precision (if the fitting precision is more than 5% of pixels), establishing the virtual control grid points and compensating the grid points in order to ensure that the track image RFM has higher internal geometric precision.

The Rational Function Model (RFM) is a ratio of polynomials expressing the image point coordinates (X, Y) as ground point coordinates (X, Y, Z), generally in the form,

in the formula, x and y are coordinates of image points; x, Y, Z are ground point coordinates; the sum of the powers of the individual coordinate components of each term in the polynomial Pi (i ═ 1,2,3, 4) and the power thereof does not exceed 3 at most. Then each polynomial is of the form

P_i＝a_i0+a_i1Z+a_i2Y+a_i3X+a_i4ZY+a_i5ZX+a_i6YX+a_i7Z²+a_i8Y²+a_i9X²+a_i10ZYX+a_i11Z²Y+a_i12Z²X+a_i13Y²Z+a_i14Y²X+a_i15ZX²+a_i16YX²+a_i17Z³+a_i18Y³+a_i19X³ (3)

In the formula, aij (i ═ 1,2,3, 4; j ═ 0, 1.., 19) is a polynomial coefficient (RPCs) of a rational function.

Generally, the RPC parameters are attached to the high-resolution satellite remote sensing images. Or its RPC parameters can be found by fitting to a rigorous geometric model using a terrain-independent approach, which is usually considered to be a known value. The RPC parameters used herein are RPC parameters of the orbit image. Research shows that RPC parameters often contain errors, and the influence of the RPC parameters on the image geometric positioning result can be well eliminated by adopting an image-space-based compensation scheme. The common image space compensation RFM with affine transformation model is:

in the formula, e_iAnd f_i(i is 0,1, 2) is an affine transformation parameter. Transforming affine parameters (e)_i，f_i) And the object coordinates (X, Y, Z) of the target point are used as unknown numbers, wherein the affine transformation parameters are affine transformation parameters of the track image. From the above equation, the adjustment error equation of the orbit image area network based on RFM is obtained as

Writing the formula into a matrix form V ═ At + Bx-l

In the formula, V is an observed value residual vector of the image point coordinate; t ═ Δ a₀Δa₁Δa₂Δb₀Δb₁Δb₂]^TAn affine transformation parameter increment vector; x ═ Δ X Δ Y Δ Z]^TAn object space coordinate increment vector of a target point; A. b is a coefficient matrix, namely a partial derivative matrix to an unknown number; l ═ x-x⁰y－y⁰]^TIs a constant term, where (x, y) is the observation of the coordinates of the image point; (x)⁰，y⁰) The image plane coordinate value of the image point calculated by the formula (2) is substituted by an unknown number approximate value.

Establishing a normal equation by a matrix form according to the least square adjustment principle

The image space and object space coordinates of the control points are taken as true values, and the image orientation parameters, namely the affine transformation coefficient of the RFM and the object space coordinates of the target point can be integrally solved through adjustment of the area network.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.