CN108375682A - Ground target object speed measurement method and device based on apparent time sequence image under space base - Google Patents
Ground target object speed measurement method and device based on apparent time sequence image under space base Download PDFInfo
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Abstract
The invention discloses a kind of ground target object speed measurement methods and device based on apparent time sequence image under space base, this method introduces element of time in sequential image dynamic imaging model, obtain the instantaneous projection model of sequential image between apparent time under aviation, and obtain the relationship of object image space movement velocity and object space movement velocity, with simple and efficient, it is accurate to calculate, and makes full use of the effect of image space measurement result.
Description
Technical Field
The invention relates to a ground target speed measuring method and device based on an empty-base downward-looking time sequence image, and belongs to the field of empty-base downward-looking time sequence images.
Background
There are 3 time items in the time series image, exposure time interval, exposure start time, exposure time. The interval between two adjacent exposure start times is an exposure interval T (unit is s), the exposure Frequency (FPS) is F (unit is FPS), and F and T are in inverse relation.
The aviation time sequence image and the conventional navigation film contain information and have different purposes. The study of time-series images is mainly divided into two technical approaches:
on one hand, the method originates from the theory and application of machine vision, mainly takes the optical flow algorithm as a main part, improves the precision of the optical flow algorithm, enhances the stability of the dense optical flow algorithm through structural features and contour features, analyzes the optical flow features in regions like space, and researches the smoothness of the optical flow based on the characteristics of the motion of a target object. The existing method improves the performances of the homonymous point tracking algorithm such as precision, speed and stability around the image space change characteristics of the time sequence image, and applies the optical flow algorithm to ground feature classification, static ground surface background identification, distance measurement and the like. For example, CN201710546833.1 discloses "method for detecting a ground object distance under a power line based on monocular time series images of unmanned aerial vehicles".
On the other hand, in photogrammetry research, a strict imaging model is taken as a research means, the time sequence image homonymy point extraction precision is improved based on a geometric constraint condition, the camera precision is optimized from the lens distortion angle of a video camera, and the video data calibration is carried out by adopting a traditional area-array camera method. These prior art photogrammetry methods process dynamic time series image data using a static image processing concept and do not make full use of the resulting data.
The application of the existing downward-looking time sequence images mainly focuses on processing images obtained by long-time shooting, but in an actual environment, a flight platform is easily influenced by uncertain factors such as power, airflow and the like in various aspects, the motion track of the platform is complex, and the long-time irregular motion condition is difficult to accurately describe by using a motion equation in the existing model.
Disclosure of Invention
According to one aspect of the invention, the ground target object speed measurement method based on the space-based downward-looking time sequence image accurately reflects the conversion relation between object space motion and image space motion of a flight platform under the condition of long-term irregular motion, so that various motion conditions and elevations of a monitored image space can be accurately obtained from the obtained downward-looking time sequence image.
The method comprises the following steps:
step S100: defining the image coordinates of an image space point P of a downward-looking time sequence image acquired by a flight platform as X and y, and defining the t-time coordinate of an object space point P corresponding to a target object as (X)t,Yt,Zt) The coordinates of the camera station S are (X)S、YS、ZS) Starting point P of movement of object0Coordinate (X) of0、Y0、Z0) And constructing an image space projection relation of the object space motion speed:
where Δ X and Δ Y are the components of the object velocity on the X-axis and Y-axis, respectively, f is the focal length of the camera, VX、VYIs the component on the X, Y axis of the image space motion velocity, VCAMThe speed of movement of the camera in the longitudinal direction of the object, Z0Is a target ofStarting point P of object movement0Z-axis coordinates of (a);
step S200: measuring image space motion parameters, and constructing an object space instantaneous position equation:
wherein, Xt,Yt,ZtIs the coordinate of the object point P at time t, X0、Y0、Z0Is the starting point P of the movement of the object0Coordinate of (a), VX、VYThe speed components of the X axis and the Y axis of the movement speed of the target object are shown, and t is the movement time;
step S300: obtaining the mapping relation between the target object image space speed and the object space motion speed by the formula (7) and the formula (9):
and (5) substituting the image space motion parameters into the formula (11) to calculate the ground motion speed of the target object.
Preferably, when the target object is stationary, the t-time coordinate of the object point P corresponding to the target object is the starting point P of the target object motion0The high Z of the stationary object0Comprises the following steps:
preferably, step S100 includes the steps of:
step S110: constructing a time sequence image dynamic imaging model containing time elements, wherein the time sequence image dynamic imaging model comprises the following steps: a collinearity equation, a target object motion equation, a camera motion equation and a camera attitude equation;
step S120: at tnTo tn+1Obtaining an instantaneous camera motion equation, an instantaneous camera attitude equation and an instantaneous target object motion equation according to the time sequence image dynamic imaging mode in the instantaneous sampling interval;
step S130: and obtaining an image space projection relation of the object space motion speed according to the instantaneous camera motion equation, the instantaneous camera attitude equation and the instantaneous target object motion equation.
Preferably, the instantaneous camera motion equation is:
wherein K is the altitude.
Preferably, the instantaneous camera pose equation is:
wherein,ωS、κSis the instantaneous pose parameter of the camera.
Preferably, the instantaneous target object motion equation:
when the target object is static:
when the target object moves:
the invention also provides a ground target speed measuring device based on the space-based downward viewing time sequence image, which comprises:
defining a projection module: the method is used for defining the image coordinates of an image space point P of a downward-looking time sequence image acquired by a flight platform as X and y, and the t-time coordinate of an object space point P corresponding to a target object as (X)t,Yt,Zt) The coordinates of the camera station S are (X)S、YS、ZS) Starting point P of movement of object0Coordinate (X) of0、Y0、Z0) And constructing an image space projection relation of the object space motion speed:
where Δ x and Δ y are the components of the object-side velocity on the image-side horizontal and longitudinal axes, respectively, f is the focal length of the camera, and VX、VYIs the component on the X, Y axis of the image space motion velocity, VCAMThe speed of movement of the camera in the longitudinal direction of the object, Z0Is the starting point P of the movement of the object0Z-axis coordinates of (a);
the measurement module is used for measuring the motion parameters of the image space and constructing an object space instantaneous position equation:
wherein, Xt,Yt,ZtIs the coordinate of the object point P at time t, X0、Y0、Z0Is the starting point P of the movement of the object0Coordinate of (a), VX、VYThe speed components of the X axis and the Y axis of the movement speed of the target object are shown, and t is the movement time;
the calculating module is used for obtaining the mapping relation between the target object image space speed and the object space motion speed according to the formula (7) and the formula (9):
and (5) substituting the image space motion parameters into the formula (11) to calculate the ground motion speed of the target object.
Preferably, when the target object is stationary, the t-time coordinate of the object point P corresponding to the target object is the starting point P of the target object motion0The high Z of the stationary object0Comprises the following steps:
preferably, defining the projection module comprises:
the modeling module is used for constructing a time sequence image dynamic imaging model containing time elements, and the time sequence image dynamic imaging model comprises: a collinearity equation, a target object motion equation, a camera motion equation and a camera attitude equation;
transient module for at tnTo tn+1Obtaining an instantaneous camera motion equation, an instantaneous camera attitude equation and an instantaneous target object motion equation according to the time sequence image dynamic imaging mode in the instantaneous sampling interval;
and the projection module is used for obtaining the image space projection relation of the object space motion speed according to the instantaneous camera motion equation, the instantaneous camera attitude equation and the instantaneous target object motion equation.
Preferably, the instantaneous camera motion equation is:
wherein K is the altitude;
preferably, the instantaneous camera pose equation is:
wherein,ωS、κSinstantaneous pose parameters of the camera;
instantaneous target motion equation:
when the target object is static:
when the target object moves:
the invention can produce the beneficial effects that:
1) the ground target object speed measuring method based on the space-based downward-looking time sequence image, provided by the invention, has the advantages that the time element is introduced into the dynamic imaging model of the time sequence image, the instantaneous projection model of the aviation downward-looking time sequence image is obtained, the relation between the moving speed of the image space of the target object and the moving speed of the object space is obtained, the method is simple, convenient and fast, the calculation is accurate, and the effect of fully utilizing the image space measuring result is achieved.
2) The ground target object speed measuring device based on the space-based downward-looking time sequence image can accurately obtain the movement speed of the target object in the object space only by measuring the movement speed of the target object in the image space, and is simple, rapid and small in calculation amount.
Drawings
FIG. 1 is a flow chart of a method for measuring a velocity of a ground target based on an aerial look-down time-series image according to a preferred embodiment of the present invention;
FIG. 2 is a schematic diagram of object-side and image-side coordinate systems in a preferred embodiment of the present invention, wherein (a) is an object-side rectangular coordinate system, O is an object-side starting point, and t isnThe camera at the moment is an object space starting point O, Q is tn+1The object space terminal point of (a), (b) is an image plane coordinate system;
FIG. 3 is a schematic block diagram of a ground object velocity measurement device based on an aerial look-down time-series image according to a preferred embodiment of the present invention;
FIG. 4 is a schematic view of a simulated aerial downward-looking timing image scene of a verification test of the present invention;
FIG. 5 is a 10 th frame of a simulation image for a verification test according to the present invention;
fig. 6 is a schematic diagram of the image space motion characteristics of the simulated dynamic target in the verification test of the present invention.
Detailed Description
The present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.
The object space refers to a real three-dimensional world and includes the characteristics of object space coordinates, object space elevation and the like. The image space refers to a target object image in each picture of the air-based downward-looking time sequence image obtained by shooting by the flight platform, and comprises the characteristics of image space speed, image space height and the like.
Referring to fig. 1, the present invention provides a ground object velocity measurement method based on an aerial downward viewing time sequence image, comprising the following steps:
step S100: defining the image coordinates of an image space point P of a downward-looking time sequence image acquired by a flight platform as X and y, and defining the t-time coordinate of an object space point P corresponding to a target object as (X)t,Yt,Zt) The coordinates of the camera station S are (X)S、YS、ZS) Starting point P of movement of object0Coordinate (X) of0、Y0、Z0) And constructing an image space projection relation of the object space motion speed:
where Δ x and Δ y are the components of the object velocity on the horizontal and vertical axes of the image, f is the focal length of the camera, VX、VYIs the component on the X, Y axis of the image space motion velocity, VCAMThe speed of movement of the camera in the longitudinal direction of the object, Z0Is the starting point P of the movement of the object0Z-axis coordinates of (a);
step S200: measuring image space motion parameters, and constructing an object space instantaneous position equation:
wherein, Xt,Yt,ZtIs the coordinate of the object point P at time t, X0、Y0、Z0Is the starting point P of the movement of the object0Coordinate of (a), VX、VYThe speed components of the X axis and the Y axis of the movement speed of the target object are shown, and t is the movement time;
step S300: obtaining the mapping relation between the target object image space speed and the object space motion speed by the formula (7) and the formula (9):
and (5) substituting the image space motion parameters into the formula (11) to calculate the ground motion speed of the target object.
According to the invention, the dynamic imaging model of the time-series image is improved, so that the instantaneous image conversion relation is obtained, and the motion condition of the target object can be more accurately described. The flight platform comprises but is not limited to an unmanned aerial vehicle and other autonomous controllable flight devices, and shooting is carried out through camera equipment additionally arranged on the flight platform. The camera in this context is the flying platform as a whole.
Preferably, when the target object is stationary, the t-time coordinate of the object point P corresponding to the target object is the moving start of the target objectStarting point P0The high Z of the stationary object0Comprises the following steps:
according to the invention, the instantaneous image conversion relation is obtained by improving the time-series image dynamic imaging model, and the accurate height of the target object can be obtained only by measuring the image space speed and the height.
Preferably, step S100 includes the steps of:
step S110: constructing a time sequence image dynamic imaging model containing time elements, wherein the time sequence image dynamic imaging model comprises the following steps: a collinearity equation, a target object motion equation, a camera motion equation and a camera attitude equation;
step S120: at tnTo tn+1Obtaining an instantaneous camera motion equation, an instantaneous camera attitude equation and an instantaneous target object motion equation according to the time sequence image dynamic imaging mode in the instantaneous sampling interval;
step S130: and obtaining an image space projection relation of the object space motion speed according to the instantaneous camera motion equation, the instantaneous camera attitude equation and the instantaneous target object motion equation.
Specifically, the method comprises the following steps:
in an aviation environment, the time interval T of the exposure of the visual sequence image is short, and the visual sequence image has the characteristics of instantaneity, relativity and dispersion.
1) The dispersion characteristic is as follows: the time sequence images are discretization sampling of continuous real world, exposure starting time is an isolated point on a continuous time axis, and changes between adjacent time sequence images cannot be recorded.
2) Instantaneous characteristics; the exposure interval T is short, the various motions are described linearly, and the long-time motion process can be represented as a concatenation of multiple instantaneous linear motions.
3) The method has the relative characteristics that: the time-series images are images arranged in chronological order, and the image space difference refers to the change of a subsequent image relative to a previous image. From another perspective, the motion recorded by the time-series image is the motion of the environment (static object, dynamic object) relative to the camera, and the surrounding environment can be perceived from the time-series image.
The invention fully utilizes the characteristics, changes the sampling point of the flight platform into instantaneous sampling, reduces the calculated amount and can obtain better side face results.
Preferably, the instantaneous camera motion equation is:
wherein K is the altitude.
Preferably, the instantaneous camera pose equation is:
wherein,ωS、κSis the instantaneous pose parameter of the camera.
Preferably, the instantaneous target object motion equation:
when the target object is static:
when the target object moves:
based on the instantaneous sudden change of the surface moving target object, the ground is taken as a static reference target object, and the surface target object has the following 2 typical motion modes. The position coordinates of the static object on the earth surface are independent of time, and the moving speed is 0.
The method specifically comprises the following steps:
the formula (1) comprises a collinear equation, an object motion equation, a camera motion equation and a camera font change equation, wherein a camera exposure time point t represents a one-dimensional time axis, and the object, the camera position and the camera posture are changed along with the time. Defining the image coordinates of an image space point P of the time sequence image as X and y, and the time t coordinate of an object space point P corresponding to the ground target object as (X)t,Yt,Zt) (ii) a The coordinates of the camera station S are (X)S、YS、ZS) (ii) a Attitude angle of camera station S is
In the collinearity equation of formula (1), f is the focal length of the area-array camera, x0、y0Is like a main point. Equation 1 for the motion of the target, X0、Y0、Z0Is the starting point P of the movement of the object0Three-dimensional coordinates of (a). VX、VY、VZAre the three-axis velocity components of the object motion. Equation (1) Camera equation of motion, XS0、YS0、ZS0Is the starting point S of the movement of the object0Three-dimensional coordinates of (V)CAMX、VCAMY、VCAMZIs the three-axis velocity component.ωS0、κS0Is the pose angle of the camera at the initial position,ωS、κSthe instantaneous pose parameters of the camera are represented,VCAM_ω、VCAM_κis the camera attitude angle change speed. Collinearity equation adoptionω, κ rotation angle system.
Changes caused by elevation, horizontal motion speed, attitude angle and instantaneous sudden change of the camera in the instantaneous time interval are small and are ignored here. Instantaneous camera attitude angle
Based on the temporal characteristics of the time-series image, a coordinate system as shown in fig. 2 is set within the exposure time interval of the time-series image. With tnThe time camera is the origin of object space O, tn+1The time is the object space end point Q, and the image principal point in FIG. 2(b) is x0＝0、y0So that the camera image plane coordinate system coincides with the object coordinate system, the camera moves from point O to point Q of fig. 2(a) at a constant height, and the camera motion equation in equation (1) is:
wherein, VCAMShows the moving speed, V, of the camera in the longitudinal direction of FIG. 2(a)CAMAnd K is greater than 0 and is the altitude.
Will be provided withAnd (5) substituting the equation into a collinear equation, and based on the instantaneous characteristics of the time sequence image, the instantaneous dynamic imaging model of the object space target object is shown as the equation (8).
And (8) projecting the instantaneous position of the object space moving target object to the image space, and obtaining the motion track of the image space target object through continuous projection along with the time t.
Referring to fig. 3, another aspect of the present invention further provides a ground object speed measuring device based on an aerial base downward viewing time series image, including:
defining a projection module: the method is used for defining the image coordinates of an image space point P of a downward-looking time sequence image acquired by a flight platform as X and y, and the t-time coordinate of an object space point P corresponding to a target object as (X)t,Yt,Zt) The coordinates of the camera station S are (X)S、YS、ZS) Starting point P of movement of object0Coordinate (X) of0、Y0、Z0) And constructing an image space projection relation of the object space motion speed:
where Δ x and Δ y are the components of the object velocity on the horizontal and vertical axes of the image, f is the focal length of the camera, VX、VYIs the component on the X, Y axis of the image space motion velocity, VCAMThe speed of movement of the camera in the longitudinal direction of the object, Z0Is the starting point P of the movement of the object0Z-axis coordinates of (a);
the measurement module is used for measuring the motion parameters of the image space and constructing an object space instantaneous position equation:
wherein, Xt,Yt,ZtIs the coordinate of the object point P at time t, X0、Y0、Z0Is the starting point P of the movement of the object0Coordinate of (a), VX、VYIs the X-axis and Y-axis velocity components of the motion velocity of the target object, and t isThe time of the exercise;
the calculating module is used for obtaining the mapping relation between the target object image space speed and the object space motion speed according to the formula (7) and the formula (9):
and (5) substituting the image space motion parameters into the formula (11) to calculate the ground motion speed of the target object.
Preferably, when the target object is stationary, the t-time coordinate of the object point P corresponding to the target object is the starting point P of the target object motion0The high Z of the stationary object0Comprises the following steps:
preferably, defining the projection module comprises:
the modeling module is used for constructing a time sequence image dynamic imaging model containing time elements, and the time sequence image dynamic imaging model comprises: a collinearity equation, a target object motion equation, a camera motion equation and a camera attitude equation;
transient module for at tnTo tn+1Obtaining an instantaneous camera motion equation, an instantaneous camera attitude equation and an instantaneous target object motion equation according to the time sequence image dynamic imaging mode in the instantaneous sampling interval;
and the projection module is used for obtaining the image space projection relation of the object space motion speed according to the instantaneous camera motion equation, the instantaneous camera attitude equation and the instantaneous target object motion equation.
Preferably, the instantaneous camera motion equation is:
wherein K is the altitude;
preferably, the instantaneous camera pose equation is:
wherein,ωS、κSis the instantaneous pose parameter of the camera;
instantaneous target motion equation:
when the target object is static:
when the target object moves:
in order to verify the effect of the method provided by the invention, a simulation test is adopted to record the specific motion condition of the ground target object, and then the specific motion condition is compared with the result obtained by the method provided by the invention to verify the detection accuracy of the method provided by the invention.
Simulation tests are carried out in the simulation test scene shown in fig. 2 and 4, including simulation in terms of time, surface static target, surface moving target, downward-looking time series camera and the like, wherein the surface target simulation parameters are listed in table 1.
TABLE 1 simulation target location and motion parameter table
Downward-looking camera simulation parameters:
the downward-looking time sequence image camera comprises three aspects of simulation of a camera, shooting and moving. Inner orientation element (undistorted image principal point is the image frame midpoint), outer orientation element (flight height 100m, moving to point Q along point O in fig. 2a, speed 1m/s), and equal interval sequence imaging (exposure interval 1 s). The artificial lens focal length (0.018m), the pixel number (4000 × 3000), and the imaging sensor size (36 × 27 mm); pixel size (0.000009 m/pixel); the imaging GSD is 0.05 m/pixel; the frame rate of the time-series image is 1 Frane/s.
The simulation scene acquires 1s to 40s time series images, wherein 1 frame is shown in fig. 5. The coded targets in the simulation images respectively represent 14 simulation targets in the table 1, and the target measurement accuracy is better than 1/10 pixels.
1) The moving speed feature of the image side can be obtained by measuring the image side moving speed of the target in the time-series image, as shown in fig. 6. The image-wise motion characteristics of various simulated targets are shown in fig. 6. The device comprises a static target, dynamic targets with the same direction and different speeds and dynamic targets with different directions. As can be seen from FIG. 6, the results obtained by the method provided by the present invention are consistent with the instantaneous dynamic feature projection relationship of the simulation data.
2) From the object-side motion characteristic parameters simulated in table 1, the theoretical value of the image-side motion characteristic is calculated by equation (9). The results obtained and the results of the simulation tests are shown in Table 2.
TABLE 2 projection transformation result table from object space to image space for motion characteristics
As can be seen from Table 2, the difference between the theoretical calculation result and the simulation image measurement result is very small, and the expression (9) is consistent with the time sequence image simulation test, and the accuracy is high.
3) Obtaining the height of the earth surface static target object from the image space change characteristics
According to the formula (10), the height information of the simulated surface target object is calculated according to the image space change characteristics of the simulated time-sequence images, and the height information is compared with the known height of the simulated target object and is listed in the table 3.
TABLE 3 calculation of surface stationary object height from image dynamic characteristics
In table 3, the elevation information of the simulated static target object can be estimated through the image space motion characteristics, and the difference between the calculation result and the simulation result is small. The method provided by the invention can effectively and accurately obtain the elevation of the earth surface static target object through the image space motion characteristics.
4) Obtaining the motion characteristics of the moving target object space from the image space change characteristics
The moving speed of the surface moving object and the true value of the simulation test are calculated according to the formula (11) by the image space change characteristics, and are listed in the table 4 for comparison.
TABLE 4 calculation of object motion characteristics from image space variation characteristics
Table 4 the simulated image side motion characteristics recorded in fig. 6 were calculated to obtain the object side motion velocity, and the conversion accuracy was lower than 0.001 m/s. This experiment verifies that the motion characteristics of the moving object are obtained from the image space variation characteristics according to formula (11) in the method provided by the present invention.
Although the present invention has been described with reference to a few embodiments, it should be understood that the present invention is not limited to the above embodiments, but rather, the present invention is not limited to the above embodiments.
Claims (10)
1. A ground target speed measurement method based on an empty-base downward-looking time sequence image is characterized by comprising the following steps:
step S100: defining the image coordinates of an image space point P of a downward-looking time sequence image acquired by a flight platform as X and y, and defining the t-time coordinate of an object space point P corresponding to a target object as (X)t,Yt,Zt) The coordinates of the camera station S are (X)S、YS、ZS) The starting point P of the movement of the object0Coordinate (X) of0、Y0、Z0) Building of physical exercisesImage-side projection relationship of velocity:
where Δ X and Δ Y are the components of the object velocity on the X-axis and Y-axis, respectively, f is the focal length of the camera, VX、VYIs the component on the X, Y axis of the image space motion velocity, VCAMThe speed of movement of the camera in the longitudinal direction of the object, Z0Is the starting point P of the movement of the object0Z-axis coordinates of (a);
step S200: measuring image space motion parameters, and constructing an object space instantaneous position equation:
wherein, Xt,Yt,ZtIs the coordinate of the object point P at time t, X0、Y0、Z0Is the movement starting point P of the target object0Coordinate of (a), VX、VYThe speed components of the X axis and the Y axis of the movement speed of the target object are obtained, and t is the movement time;
step S300: obtaining the mapping relation between the target object image space speed and the object space motion speed through a formula (7) and a formula (9):
and substituting the image space motion parameters into a formula (11) to calculate the ground motion speed of the target object.
2. The method for measuring the speed of a ground target object based on an aerial downward viewing time series image according to claim 1, wherein when the target object is stationary, the t-time coordinate of the object space point P corresponding to the target object is the starting point P of the movement of the target object0The high Z of the stationary object0Comprises the following steps:
3. the method for measuring the velocity of a ground target object based on an aerial downward viewing time series image according to claim 1 or 2, wherein the step S100 comprises the steps of:
step S110: constructing a time sequence image dynamic imaging model containing a time element, wherein the time sequence image dynamic imaging model comprises the following steps: a collinearity equation, a target object motion equation, a camera motion equation and a camera attitude equation;
step S120: at tnTo tn+1Obtaining an instantaneous camera motion equation, an instantaneous camera attitude equation and an instantaneous target object motion equation according to the time sequence image dynamic imaging mode in the instantaneous sampling interval;
step S130: and obtaining the image space projection relation of the object space motion speed according to the instantaneous camera motion equation, the instantaneous camera attitude equation and the instantaneous target object motion equation.
4. The method of claim 3, wherein the instantaneous camera motion equation is as follows:
wherein K is the altitude.
5. The method of claim 3, wherein the instantaneous camera pose equation is:
ωS＝0、κS＝0
wherein,ωS、κSis the instantaneous pose parameter of the camera.
6. The method of claim 3, wherein the instantaneous target object motion equation is:
when the target object is static:
when the target object moves:
7. a ground object speed measuring device based on an empty-base downward-looking time sequence image is characterized by comprising:
defining a projection module: the method is used for defining the image coordinates of an image space point P of a downward-looking time sequence image acquired by a flight platform as X and y, and the t-time coordinate of an object space point P corresponding to a target object as (X)t,Yt,Zt) The coordinates of the camera station S are (X)S、YS、ZS) The starting point P of the movement of the object0Coordinate (X) of0、Y0、Z0) And constructing an image space projection relation of the object space motion speed:
where Δ x and Δ y are the components of the object-side velocity on the image-side horizontal and longitudinal axes, respectively, f is the focal length of the camera, and VX、VYIs the component on the X, Y axis of the image space motion velocity, VCAMThe speed of movement of the camera in the longitudinal direction of the object, Z0Is the starting point P of the movement of the object0Z-axis coordinates of (a);
the measurement module is used for measuring the motion parameters of the image space and constructing an object space instantaneous position equation:
wherein, Xt,Yt,ZtIs the coordinate of the object point P at time t, X0、Y0、Z0Is the movement starting point P of the target object0Coordinate of (a), VX、VYThe speed components of the X axis and the Y axis of the movement speed of the target object are obtained, and t is the movement time;
the calculation module is used for obtaining the mapping relation between the target object image space speed and the object space motion speed according to a formula (7) and a formula (9):
and substituting the image space motion parameters into a formula (11) to calculate the ground motion speed of the target object.
8. The apparatus according to claim 7, wherein the t-time coordinate of the object space point P corresponding to the object is the starting point P of the movement of the object when the object is still0The high Z of the stationary object0Comprises the following steps:
9. the apparatus of claim 7, wherein the defining projection module comprises:
the modeling module is used for constructing a time sequence image dynamic imaging model containing time elements, and the time sequence image dynamic imaging model comprises: a collinearity equation, a target object motion equation, a camera motion equation and a camera attitude equation;
transient module for at tnTo tn+1Obtaining an instantaneous camera motion equation, an instantaneous camera attitude equation and an instantaneous target object motion equation according to the time sequence image dynamic imaging mode in the instantaneous sampling interval;
and the projection module is used for obtaining the image space projection relation of the object space motion speed according to the instantaneous camera motion equation, the instantaneous camera attitude equation and the instantaneous target object motion equation.
10. The ground target speed measurement device based on space-based downward-looking time-series images of claim 7, wherein the instantaneous camera motion equation is as follows:
wherein K is the altitude;
preferably, the instantaneous camera pose equation is:
ωS＝0、κS＝0
wherein,ωS、κSis the instantaneous pose parameter of the camera;
the instantaneous target object motion equation:
when the target object is static:
when the target object moves:
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