CN113538595B - Method for improving geometric precision of remote sensing stereo image by using laser height measurement data in auxiliary manner - Google Patents

Method for improving geometric precision of remote sensing stereo image by using laser height measurement data in auxiliary manner Download PDF

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CN113538595B
CN113538595B CN202110797215.0A CN202110797215A CN113538595B CN 113538595 B CN113538595 B CN 113538595B CN 202110797215 A CN202110797215 A CN 202110797215A CN 113538595 B CN113538595 B CN 113538595B
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CN113538595A (en
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刘昌儒
岳庆兴
赵世湖
刘书含
王霞
张恒
王艺颖
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Ministry Of Natural Resources Land Satellite Remote Sensing Application Center
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    • G06T7/85—Stereo camera calibration
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Abstract

The invention discloses a method for improving geometric precision of a remote sensing stereo image by using laser height measurement data in an auxiliary manner, and relates to the technical field of geometric processing of the remote sensing stereo image; the method fully utilizes the advantage of extremely high elevation precision of high-resolution seven-grade laser height measurement data and the characteristics of same-platform acquisition and relatively good precision of the laser height measurement data, the footprint image and the stereoscopic image, realizes the rapid extraction of the position information of the laser height measurement point on the stereoscopic image, and restrains the front intersection error of the stereoscopic image by taking the elevation of the laser height measurement point as a reference, thereby realizing the optimization of the geometric imaging model parameters of the stereoscopic image and further improving the geometric positioning precision of the stereoscopic image.

Description

Method for improving geometric precision of remote sensing stereo image by using laser height measurement data in auxiliary manner
Technical Field
The invention relates to the technical field of geometric processing of remote sensing stereoscopic images, in particular to a method for assisting in improving geometric accuracy of remote sensing stereoscopic images by utilizing laser height measurement data.
Background
At present, the parameters of the geometric imaging model of the satellite image are updated mainly by a ground calibration field method. The method is based on high-precision reference data of a ground calibration field, and control point information of a satellite image and a reference base map is obtained in an image matching mode, so that internal and external parameters of an imaging model are solved. The method based on the checking field has the characteristics of high calculation precision and quick solution, but has obvious defects, the maintenance cost of the checking field is high, the method is a huge examination in the aspects of manpower and financial resources, in addition, due to weather reasons and the limitation of a satellite revisit period, the time interval for acquiring the transit images of the checking field is long, the checking timeliness is poor, and in addition, along with the continuous improvement of the resolution of the satellite images and the requirement of high positioning precision of the images, higher requirements are provided for the resolution and precision of the checking field. Therefore, how to update the geometric imaging model parameters of the satellite images with high precision, low cost, rapidness and convenience on the premise of not using a ground calibration field is an important subject currently facing. The current research focus is to fully utilize the design characteristics and imaging characteristics of the satellite and carry out geometric self-checking correction without a control field.
The high-resolution seven-grade satellite is the first civil sub-meter optical transmission type three-dimensional mapping satellite in China, is provided with a front-view optical camera and a back-view optical camera, is provided with a laser height indicator, is the satellite with the highest civil mapping precision at present, and can realize the high-precision satellite three-dimensional mapping with the 1:10000 scale in China under the support of laser height measurement data. After post-processing, the elevation precision of the laser height measurement data of the high-resolution seven-model satellite can reach 0.1m, even higher than that of a conventional calibration field, and the plane precision of the high-resolution seven-model satellite can also reach 6 m. The advantage that the elevation precision of the laser height measurement point is extremely high is fully utilized, and the characteristic that the relative precision of the three-dimensional image and the laser height measurement point obtained by the same platform is high is fully utilized, so that the updating of the geometric imaging model parameters of the satellite image is very important and meaningful research.
Disclosure of Invention
The invention aims to provide a method for improving the geometric accuracy of a remote sensing stereo image by using laser height measurement data in an auxiliary manner, so that the problems in the prior art are solved.
It should be noted that the definition of the stereoscopic image mentioned in the present application refers to a sliced CCD image in which original data uploaded and downloaded by a satellite are physically sliced, cropped, and subjected to radiation correction, but no geometric processing is performed; the stereo image applied in this embodiment may be not only the stereo image acquired by the high-resolution seven satellite, but also the stereo image acquired by other satellites.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method for improving geometric accuracy of remote sensing stereoscopic images by using laser altimetry data in an auxiliary mode comprises the following steps:
s1, constructing a geometric imaging model of the stereoscopic image by utilizing internal and external parameters of the geometric imaging model calibrated in a laboratory according to attitude and orbit data downloaded by the satellite;
s2, acquiring the image point coordinates of the laser height measurement point on the stereoscopic image through image matching based on the object space coordinates, the footprint image and the image point coordinates of the laser height measurement point footprint image of the height-dividing seven laser height measurement point and the geometric imaging model constructed in the step S1;
s3, carrying out connection point matching on the stereo image, particularly paying attention to the connection point acquisition condition at the connection edges of different CCDs of the same camera, acquiring connection points which are uniformly distributed and enough in quantity, and acquiring the object space coordinates of the connection points by front intersection of the geometric imaging model established in the step S1;
s4, according to the image space coordinates and the object space coordinates of the connection points, respectively solving partial derivatives of the internal and external parameters of the geometric imaging model and the object space plane coordinates and elevation coordinates of the connection points, and constructing a connection point error equation;
s5, respectively solving partial derivatives of the internal and external parameters of the geometric imaging model and the object space coordinates of the laser height measurement point according to the image space coordinates and the object space coordinates of the laser height measurement point, and constructing a laser height measurement point error equation;
s6, according to the least square principle, the error equations constructed in the steps S4 and S5 are normalized, a normal equation is constructed, and the internal and external parameters and the connection points of the geometric imaging model and the object coordinate correction number of the laser height measurement point are solved;
s7, updating the inside and outside parameters of the geometric imaging model, the coordinates of the object space of the connecting point and the coordinates of the object space of the laser height measurement point according to the correction number obtained in the step S6, and continuing the steps S4-S6 until the iteration is finished to obtain the inside and outside parameters of the final geometric imaging model;
and S8, updating the geometric imaging model of the stereoscopic image according to the internal and external parameters of the newly solved geometric imaging model, and improving the geometric precision of the stereoscopic image.
Preferably, the geometric imaging model constructed in step S1 is expressed by formula (1):
Figure BDA0003163179600000031
wherein the content of the first and second substances,
Figure BDA0003163179600000032
is the object coordinates of the image point in the WGS84 coordinate system,
Figure BDA0003163179600000033
is the coordinate of the phase center of the satellite GPS receiver in the WGS84 coordinate system, m is a scale factor,
Figure BDA0003163179600000034
is a transformation matrix from the camera coordinate system to the satellite body coordinate system,
Figure BDA0003163179600000035
is a transformation matrix from the satellite body coordinate system to the J2000 inertial coordinate system,
Figure BDA0003163179600000036
is a transformation matrix from the J2000 inertial coordinate system to the WGS84 coordinate system, (psi)x,ψy) The pointing angle of the image probe represents the internal precision of the image;
Figure BDA0003163179600000037
in the formula (2), s is the column coordinate of the image, ai,bj(i, j is less than or equal to 5) is an internal parameter of the geometric imaging model needing to be solved;
Figure BDA0003163179600000038
in the formula (3), the first and second groups,
Figure BDA0003163179600000039
the rotation angles of Y, X and Z axes of a coordinate system surrounding the satellite body are external parameters of a geometric imaging model to be solved.
Preferably, the method for acquiring the coordinates of the image points of the laser height finding point on the stereoscopic image in step S2 specifically includes:
s21, substituting the object coordinates of the laser height measurement point into the geometric imaging model of the three-dimensional image, calculating to obtain the initial position of the current laser height measurement point on the three-dimensional image, and setting the coordinates of the image point as (x, y), then the coordinates of the image point of the current laser height measurement point and the coordinates of the image point of the footprint image of the laser height measurement point (x, y)0,y0) Forming a conjugate point pair;
s22, using the image point coordinate (x, y) as the center, using the laser spot radius as the maximum searching window, calculating point by point according to the formula (4) and using the laser height measuring point footprint image point coordinate (x)0,y0) Taking the maximum correlation coefficient point (x) as the correlation coefficient of the central area image1’,y1’) As pixel-level registration points:
Figure BDA0003163179600000041
wherein g and g' are the gray values of the footprint image and the stereoscopic image respectively,
Figure BDA0003163179600000042
the W, h sub-table represents the width and height of a correlation coefficient search window for the average gray value of the matching window;
s23, in terms of coordinate (x)0,y0),(x1’,y1’) For the initial value, carrying out least square matching according to a formula (5) to obtain a sub-pixel level registration point position (x)1,y1) And obtaining the coordinates of the image points of the laser height measuring points on the current image:
Figure BDA0003163179600000043
in the formula, h0,h1As a distortion parameter of image radiationi,biThe image geometric transformation parameters are obtained;
s24, repeating the steps S21-S23, and obtaining the coordinates of the image points of the current laser height measuring point on all the drop point images;
s25, repeating the steps S21-S24, and obtaining the image point coordinates of all the laser height measuring points in the stereo image.
Preferably, before the error equation is established, the formula (1) needs to be modified to obtain the formula (1-1):
Figure BDA0003163179600000044
order to
Figure BDA0003163179600000045
Then:
Figure BDA0003163179600000051
the above equation is developed to obtain the following equation:
Figure BDA0003163179600000052
in the formula:
Figure BDA0003163179600000053
for each connecting point, solving the partial derivatives of the internal and external parameters of the geometric imaging model and the coordinates and the elevations of the object space of the connecting point by using a formula (1-3), and establishing an error equation of the connecting point, wherein the error equation is shown in a formula (6):
Figure BDA0003163179600000054
writing equation (6) in matrix form:
V1＝A1t+B1x1-L1,P1 (7)
wherein the content of the first and second substances,
Figure BDA0003163179600000055
is the parameter correction number, x, of the image geometric imaging model1＝(ΔXΔYΔZ)TIs the object space plane coordinate and elevation correction number of the connecting point, A1,B1For a corresponding matrix of coefficient of correction, L1And P1Respectively, an initial value computation constant and a weight matrix.
Preferably, in step S6, for each laser height measurement point, the equation (1-3) is used to calculate the deviation of the internal and external parameters of the geometric imaging model and the object-side plane coordinates of the laser height measurement point, so as to establish an error equation of the laser height measurement point, as shown in equation (8):
Figure BDA0003163179600000061
writing equation (8) in matrix form as:
V2＝A2t+B2x2-L2,P2 (9)
wherein the content of the first and second substances,
Figure BDA0003163179600000062
is the parameter correction number, x, of the image geometric imaging model2＝(ΔXΔY)TIs the correction number of the object space plane coordinate of the laser height measuring point, A2,B2For a corresponding matrix of coefficient of correction, L2And P2Respectively, an initial value computation constant and a weight matrix.
Preferably, step S6 specifically includes:
s61, combining the error equation of the connecting point constructed in the step S4 and the error equation of the laser height measuring point constructed in the step S5 to construct an overall error equation:
V＝At+Bx-L,P (10)
wherein x is (x)1 x2)TRepresenting object coordinate correction numbers of the connecting point and the laser height measuring point;
s62, the error equation is normalized according to the least square adjustment principle to obtain a normal equation, as shown in formula (11):
Figure BDA0003163179600000063
and solving the equation to obtain the internal and external parameters and the connection points of the geometric imaging model and the object coordinate correction number of the laser height measurement point.
The invention has the beneficial effects that:
the invention discloses a method for assisting in improving geometric precision of a remote sensing stereo image by using laser height measurement data, which fully utilizes the advantage of extremely high precision of height measurement data of high-grade seven laser height measurement data and the characteristics of same platform acquisition and better relative precision of the laser height measurement data, a footprint image and the stereo image, realizes the rapid extraction of position information of a laser height measurement point on the stereo image, and restricts forward intersection errors of the stereo image by taking the height of the laser height measurement point as a reference, thereby realizing the optimization of geometric imaging model parameters of the stereo image and further improving the geometric positioning precision of the stereo image.
Drawings
FIG. 1 is a schematic diagram of a test carried out by using a laser height measuring system of high-resolution seven in example 1;
fig. 2 is a method for improving geometric accuracy of a remote sensing stereoscopic image with the assistance of laser altimetry data provided in embodiment 1.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
Example 1
When the remote sensing satellite is observed on the ground, because the inclination angles of the cameras are different, a certain included angle is formed when the remote sensing satellite shoots the same area, and stereo observation is formed, for example, a high-resolution seven-numbered satellite is used, the inclination angles of the front and rear view cameras carried by the high-resolution seven-numbered satellite are respectively 26 degrees and 5 degrees, and the observation mode is shown in fig. 1.
Ideally, the same-name rays of the cameras mounted on the satellites should meet at the same point, such as ground point a in fig. 1. However, due to the influence of various errors, the front and rear view camera rays of the same name actually meet at the ground point B. The error sources at this time are errors on the satellite, including attitude orbit measurement errors and internal camera distortion, and also elevation errors of ground intersection points. It is therefore difficult to determine which error or errors the front-rear view camera intersection error is generated by without any exact information.
The laser height measurement data adopted in the embodiment is acquired by a high-resolution seven-satellite laser height measuring instrument, so that the high-altitude precision is very high, meanwhile, the footprint camera and the front-back stereo camera are shot synchronously, so that the ground image of the laser spot can be acquired, and two rows of 16 laser height measurement points can be acquired in a standard image range. The advantage that the elevation precision of the laser height measurement data is extremely high is fully utilized, a height value is provided for a stereo camera intersection point, the influence of the elevation error of a ground point on the stereo intersection error can be eliminated, and the optimization and the promotion of the parameters of a geometric imaging model of the stereo camera are facilitated. Therefore, the present embodiment provides a method for improving geometric accuracy of a remote sensing stereoscopic image by using laser altimetry data, as shown in fig. 2, the method mainly includes the following steps:
s1, constructing a geometric imaging model of the stereoscopic image by utilizing internal and external parameters of the geometric imaging model calibrated in a laboratory according to attitude and orbit data downloaded by the satellite;
s2, acquiring the image point coordinates of the laser height measurement point on the stereoscopic image through image matching based on the object space coordinates, the footprint image and the image point coordinates of the laser height measurement point footprint image of the height-dividing seven laser height measurement point and the geometric imaging model constructed in the step S1;
s3, carrying out connection point matching on the stereo image, particularly paying attention to the connection point acquisition condition at the connection edges of different CCDs of the same camera, acquiring connection points which are uniformly distributed and enough in quantity, and acquiring the object space coordinates of the connection points by front intersection of the geometric imaging model established in the step S1;
s4, according to the image space coordinates and the object space coordinates of the connection points, respectively solving partial derivatives of the internal and external parameters of the geometric imaging model and the object space plane coordinates and elevation coordinates of the connection points, and constructing a connection point error equation;
s5, respectively solving partial derivatives of the internal and external parameters of the geometric imaging model and the object space coordinates of the laser height measurement point according to the image space coordinates and the object space coordinates of the laser height measurement point, and constructing a laser height measurement point error equation;
s6, according to the least square principle, the error equations constructed in the steps S4 and S5 are normalized, a normal equation is constructed, and the internal and external parameters and the connection points of the geometric imaging model and the object coordinate correction number of the laser height measurement point are solved;
s7, updating the inside and outside parameters of the geometric imaging model, the coordinates of the object space of the connecting point and the coordinates of the object space of the laser height measurement point according to the correction number obtained in the step S6, and continuing the steps S4-S6 until the iteration is finished to obtain the inside and outside parameters of the final geometric imaging model;
and S8, updating the geometric imaging model of the stereoscopic image according to the internal and external parameters of the newly solved geometric imaging model, and improving the geometric precision of the stereoscopic image.
It should be noted that the stereoscopic image referred to in the present application refers to a sliced CCD image in which original data uploaded and downloaded by a satellite are physically sliced, and subjected to radiation correction but not subjected to any geometric processing; the stereo image applied in this embodiment includes, but is not limited to, stereo images acquired by high-resolution seven satellites, and stereo images acquired by other satellites may also be used.
The geometric imaging model constructed in step S1 in the present embodiment is expressed by formula (1):
Figure BDA0003163179600000091
wherein the content of the first and second substances,
Figure BDA0003163179600000092
is the object coordinates of the image point in the WGS84 coordinate system,
Figure BDA0003163179600000093
is the coordinate of the phase center of the satellite GPS receiver in the WGS84 coordinate system, m is a scale factor,
Figure BDA0003163179600000094
is a transformation matrix from the camera coordinate system to the satellite body coordinate system,
Figure BDA0003163179600000095
is a transformation matrix from the satellite body coordinate system to the J2000 inertial coordinate system,
Figure BDA0003163179600000096
is a transformation matrix from the J2000 inertial coordinate system to the WGS84 coordinate system, (psi)x,ψy) The pointing angle of the image probe represents the internal precision of the image;
Figure BDA0003163179600000097
in the formula (2), s is the column coordinate of the image, ai,bj(i, j is less than or equal to 5) is an internal parameter of the geometric imaging model needing to be solved;
Figure BDA0003163179600000098
in the formula (3), the first and second groups,
Figure BDA0003163179600000099
the rotation angles of Y, X and Z axes of a coordinate system surrounding the satellite body are external parameters of a geometric imaging model to be solved.
In this embodiment, the method for acquiring the coordinates of the image points of the laser height finding point on the stereoscopic image in step S2 specifically includes:
s21, substituting the object coordinates of the laser height measurement point into the geometric imaging model of the three-dimensional image, calculating to obtain the initial position of the current laser height measurement point on the three-dimensional image, and setting the coordinates of the image point as (x, y), then the coordinates of the image point of the current laser height measurement point and the coordinates of the image point of the footprint image of the laser height measurement point (x, y)0,y0) Forming a conjugate point pair;
s22, using the image point coordinate (x, y) as the center, using the laser spot radius as the maximum searching window,calculating point-by-point according to formula (4) and measuring the coordinates (x) of the footprint image point by laser0,y0) Taking the maximum correlation coefficient point (x) as the correlation coefficient of the central area image1’,y1’) As pixel-level registration points:
Figure BDA0003163179600000101
wherein g and g' are the gray values of the footprint image and the stereoscopic image respectively,
Figure BDA0003163179600000102
the W, h sub-table represents the width and height of a correlation coefficient search window for the average gray value of the matching window;
s23, in terms of coordinate (x)0,y0),(x1’,y1’) For the initial value, carrying out least square matching according to a formula (5) to obtain a sub-pixel level registration point position (x)1,y1) And obtaining the coordinates of the image points of the laser height measuring points on the current image:
Figure BDA0003163179600000103
in the formula, h0,h1As a distortion parameter of image radiationi,biThe image geometric transformation parameters are obtained;
s24, repeating the steps S21-S23, and obtaining the coordinates of the image points of the current laser height measuring point on all the drop point images;
s25, repeating the steps S21-S24, and obtaining the image point coordinates of all the laser height measuring points in the stereo image.
Before the error equation is established, the formula (1) needs to be deformed to obtain the formula (1-1):
Figure BDA0003163179600000104
order to
Figure BDA0003163179600000105
Then:
Figure BDA0003163179600000111
the above equation is developed to obtain the following equation:
Figure BDA0003163179600000112
in the formula:
Figure BDA0003163179600000113
for each connecting point, solving the partial derivatives of the internal and external parameters of the geometric imaging model and the coordinates and the elevations of the object space of the connecting point by using a formula (1-3), and establishing an error equation of the connecting point, wherein the error equation is shown in a formula (6):
Figure BDA0003163179600000114
writing equation (6) in matrix form:
V1＝A1t+B1x1-L1,P1 (7)
wherein the content of the first and second substances,
Figure BDA0003163179600000115
is the parameter correction number, x, of the image geometric imaging model1＝(ΔXΔYΔZ)TIs the object space plane coordinate and elevation correction number of the connecting point, A1,B1For a corresponding matrix of coefficient of correction, L1And P1Respectively, an initial value computation constant and a weight matrix.
In this embodiment, in step S6, for each laser height measurement point, the equation (1-3) is used to calculate the deviation of the internal and external parameters of the geometric imaging model and the object-side plane coordinates of the laser height measurement point, and establish an error equation of the laser height measurement point, as shown in equation (8):
Figure BDA0003163179600000121
writing equation (8) in matrix form as:
V2＝A2t+B2x2-L2,P2 (9)
wherein the content of the first and second substances,
Figure BDA0003163179600000122
is the parameter correction number, x, of the image geometric imaging model2＝(ΔXΔY)TIs the correction number of the object space plane coordinate of the laser height measuring point, A2,B2For a corresponding matrix of coefficient of correction, L2And P2Respectively, an initial value computation constant and a weight matrix.
Step S6 in this embodiment specifically includes:
s61, combining the error equation of the connecting point constructed in the step S4 and the error equation of the laser height measuring point constructed in the step S5 to construct an overall error equation:
V＝At+Bx-L,P (10)
wherein x is (x)1 x2)TRepresenting object coordinate correction values of the connecting point and the laser height measuring point;
s62, the error equation is normalized according to the least square adjustment principle to obtain a normal equation, as shown in formula (11):
Figure BDA0003163179600000123
and solving the equation to obtain the internal and external parameters and the connection points of the geometric imaging model and the object coordinate correction number of the laser height measurement point.
In this embodiment, the iteration process in step S7 includes setting the iteration number setting number and the geometric imaging model internal and external parameter correction value setting threshold, and in the iteration process, when the iteration number is greater than the setting number or the geometric imaging model internal and external parameter correction value is smaller than the setting threshold, the geometric imaging model internal and external parameters are output.
By adopting the technical scheme disclosed by the invention, the following beneficial effects are obtained:
the invention discloses a method for assisting in improving geometric precision of a remote sensing stereo image by using laser height measurement data, which fully utilizes the advantage of extremely high precision of height measurement data of high-grade seven laser height measurement data and the characteristics of same platform acquisition and better relative precision of the laser height measurement data, a footprint image and the stereo image, realizes the rapid extraction of position information of a laser height measurement point on the stereo image, and restricts forward intersection errors of the stereo image by taking the height of the laser height measurement point as a reference, thereby realizing the optimization of geometric imaging model parameters of the stereo image and further improving the geometric positioning precision of the stereo image.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and improvements can be made without departing from the principle of the present invention, and such modifications and improvements should also be considered within the scope of the present invention.

Claims (5)

1. A method for improving geometric accuracy of remote sensing stereoscopic images by using laser altimetry data in an auxiliary manner is characterized by comprising the following steps:
s1, constructing a geometric imaging model of the stereoscopic image by utilizing internal and external parameters of the geometric imaging model calibrated in a laboratory according to attitude and orbit data downloaded by the satellite;
s2, acquiring the image point coordinates of the laser height measurement point on the stereoscopic image through image matching based on the object space coordinates, the footprint image and the image point coordinates of the laser height measurement point footprint image of the height-dividing seven laser height measurement point and the geometric imaging model constructed in the step S1;
s3, carrying out connection point matching on the stereo image, and acquiring connection points which are uniformly distributed and enough in quantity, wherein the object space coordinates of the connection points are acquired by the front intersection of the geometric imaging model established in the step S1;
s4, according to the image space coordinates and the object space coordinates of the connection points, respectively solving partial derivatives of the internal and external parameters of the geometric imaging model and the object space plane coordinates and elevation coordinates of the connection points, and constructing a connection point error equation;
s5, respectively solving partial derivatives of the internal and external parameters of the geometric imaging model and the object space coordinates of the laser height measurement point according to the image space coordinates and the object space coordinates of the laser height measurement point, and constructing a laser height measurement point error equation;
s6, according to the least square principle, the error equations constructed in the steps S4 and S5 are normalized, a normal equation is constructed, and the internal and external parameters and the connection points of the geometric imaging model and the object coordinate correction number of the laser height measurement point are solved;
s7, updating the inside and outside parameters of the geometric imaging model, the coordinates of the object space of the connecting point and the coordinates of the object space of the laser height measurement point according to the correction number obtained in the step S6, and continuing the steps S4-S6 until the iteration is finished to obtain the inside and outside parameters of the final geometric imaging model;
s8, updating the geometric imaging model of the stereoscopic image according to the internal and external parameters of the newly solved geometric imaging model, and improving the geometric precision of the stereoscopic image;
the method for acquiring the image point coordinates of the laser height finding point on the stereoscopic image in the step S2 specifically includes:
s21, substituting the object coordinates of the laser height measurement point into the geometric imaging model of the three-dimensional image, calculating to obtain the initial position of the current laser height measurement point on the three-dimensional image, and setting the coordinates of the image point as (x, y), then the coordinates of the image point of the current laser height measurement point and the coordinates of the image point of the footprint image of the laser height measurement point (x, y)0,y0) Forming a conjugate point pair;
s22, using the image point coordinate (x, y) as the center, using the laser spot radius as the maximum searching window, calculating point by point according to the formula (4) and using the laser height measuring point footprint image point coordinate (x)0,y0) Taking the maximum correlation coefficient point (x) as the correlation coefficient of the central area image1’,y1’) As pixel-level registration points:
Figure FDA0003357505640000021
wherein g and g' are the gray values of the footprint image and the stereoscopic image respectively,
Figure FDA0003357505640000022
the average gray value of the matching window, w and h respectively represent the width and height of the correlation coefficient search window;
s23, in terms of coordinate (x)0,y0),(x1’,y1’) For the initial value, carrying out least square matching according to a formula (5) to obtain a sub-pixel level registration point position (x)1,y1) And obtaining the coordinates of the image points of the laser height measuring points on the current image:
Figure FDA0003357505640000023
in the formula, h0,h1As a distortion parameter of image radiationi,biThe image geometric transformation parameters are obtained;
s24, repeating the steps S21-S23, and obtaining the coordinates of the image points of the current laser height measuring point on all the drop point images;
s25, repeating the steps S21-S24, and obtaining the image point coordinates of all the laser height measuring points in the stereo image.
2. The method for improving the geometric accuracy of the remote sensing stereoscopic images with the assistance of the laser altimetry data according to claim 1, wherein the geometric imaging model constructed in the step S1 is expressed as formula (1):
Figure FDA0003357505640000024
wherein the content of the first and second substances,
Figure FDA0003357505640000025
is the object coordinates of the image point in the WGS84 coordinate system,
Figure FDA0003357505640000026
is the coordinate of the phase center of the satellite GPS receiver in the WGS84 coordinate system, m is a scale factor,
Figure FDA0003357505640000027
is a transformation matrix from the camera coordinate system to the satellite body coordinate system,
Figure FDA0003357505640000031
is a transformation matrix from the satellite body coordinate system to the J2000 inertial coordinate system,
Figure FDA0003357505640000032
is a transformation matrix from the J2000 inertial coordinate system to the WGS84 coordinate system, (psi)x,ψy) The pointing angle of the image probe represents the internal precision of the image;
Figure FDA0003357505640000033
where s is the column coordinate of the image, ai,bj(i, j is less than or equal to 5) is an internal parameter of the geometric imaging model needing to be solved;
Figure FDA0003357505640000034
in the formula (I), the compound is shown in the specification,
Figure FDA0003357505640000035
and omega and kappa are rotation angles around Y, X and Z axes of a satellite body coordinate system respectively and are external parameters of the geometric imaging model to be solved.
3. The method for improving the geometric accuracy of the remote sensing stereoscopic images with the assistance of the laser altimetry data according to claim 1, wherein the connection point error equation constructed in the step S4 is shown in formula (6);
Figure FDA0003357505640000036
written in matrix form as:
V1＝A1t+B1x1-L1,P1 (7)
wherein the content of the first and second substances,
Figure FDA0003357505640000037
is the parameter correction number, x, of the image geometric imaging model1＝(△X △Y △Z)TIs the object space plane coordinate and elevation correction number of the connecting point, A1,B1For a corresponding matrix of coefficient of correction, L1And P1Respectively, an initial value computation constant and a weight matrix.
4. The method for improving the geometric accuracy of the remote sensing stereoscopic images with the assistance of the laser altimetry data according to claim 1, wherein the laser altimetry error equation constructed in the step S6 is as shown in formula (8):
Figure FDA0003357505640000041
written in matrix form as:
V2＝A2t+B2x2-L2,P2 (9)
wherein the content of the first and second substances,
Figure FDA0003357505640000042
is the parameter correction number, x, of the image geometric imaging model2＝(△X △Y)TIs the correction number of the object space plane coordinate of the laser height measuring point, A2,B2For a corresponding matrix of coefficient of correction, L2And P2Respectively, an initial value computation constant and a weight matrix.
5. The method for improving the geometric accuracy of the remote sensing stereoscopic images with the assistance of the laser altimetry data according to claim 1, wherein the step S6 specifically comprises:
s61, combining the error equation of the connecting point constructed in the step S4 and the error equation of the laser height measuring point constructed in the step S5 to construct an overall error equation:
V＝At+Bx-L,P (10)
wherein x is (x)1 x2)TRepresenting object coordinate correction numbers of the connecting point and the laser height measuring point;
s62, the error equation is normalized according to the least square adjustment principle to obtain a normal equation, as shown in formula (11):
Figure FDA0003357505640000043
and (5) solving the equation (11) to obtain the internal and external parameters and the connection points of the geometric imaging model and the object-side coordinate correction number of the laser height measurement point.
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