Geometric correction method for radiance meter of near-space aerostat

Abstract

The invention provides a method for geometric correction of a radiometer of a near-space aerostat, comprising: obtaining spectral reflectances of different ground objects in a test area and spectral radiances of the ground surface; calculating the spatial position corresponding to a beam of the radiometer according to the relative position offset and rotational geometric relationship between the radiometer and an integrated navigation measurement system; calculating the spatial positioning error of the radiometer; determining the matching range of the ground objects in the test area according to the spatial position and the spatial positioning error; matching the spectral reflectances of different ground objects in the test area with the spectral radiances of the ground surface within the matching range to obtain ground field coordinates corresponding to the spectral reflectance of the ground object with the highest matching degree with the spectral radiance of the ground surface; taking the ground field coordinates corresponding to the highest matching degree as geometric control points, calculating the pointing angle error of the radiometer on the near-space aerostat; and geometrically correcting the radiometer according to the pointing angle error.

Description

Technical Field

[0001] The invention relates to the field of aerospace remote sensing technology, and in particular to a geometric correction method for a radiometer of a near-space aerostat. Background Art

[0002] Space radiation and the aging of components will greatly affect the authenticity and accuracy of remote sensing data. Tracing the satellite platform's onboard observations back to existing benchmarks is an important way to ensure the accuracy and consistency of observations of different aerospace remote sensing payloads. The existing technology has proposed a variety of space radiation benchmark research plans. The main method is to move the radiation benchmark to the space satellite platform to form a "calibration star", and use the ground target benchmark data obtained by the "calibration star" to implement in-orbit calibration of other satellites. However, the method of using a "calibration star" for radiation calibration has the disadvantages of difficulty in synchronization with other satellites and difficulty in eliminating the uniformity of the underlying surface of actual objects, atmospheric environmental disturbances, and time-space matching errors. Summary of the invention

[0003] In view of this, the present invention provides a method for geometric correction of a radiometer of a near-space aerostat, comprising: obtaining spectral reflectances of different objects in a test area and the spectral radiance of the surface; calculating the spatial position corresponding to the radiometer light beam according to the relative position offset and rotational geometric relationship between the radiometer and an integrated navigation measurement system; calculating the spatial positioning error of the radiometer; determining the matching range of objects in the test area according to the spatial position and the spatial positioning error; matching the spectral reflectances of different objects in the test area with the spectral radiance of the surface within the matching range to obtain ground field coordinates corresponding to the spectral reflectance of the object with the highest matching degree with the spectral radiance of the surface; taking the ground field coordinates corresponding to the highest matching degree as geometric control points, calculating the pointing angle error of the radiometer on the near-space aerostat; and geometrically correcting the radiometer according to the pointing angle error.

[0004] According to an embodiment of the present invention, the step of obtaining the spectral reflectance of different objects in the test area includes: measuring the radiant brightness of different objects in the test area and the radiant brightness of a reference plate; obtaining the spectral reflectance of the reference plate; and calculating the spectral reflectance of the objects in the test area based on the radiant brightness of different objects in the test area, the radiant brightness of the reference plate, and the spectral reflectance.

[0005] According to an embodiment of the present invention, the step of acquiring the spectral radiance of the earth's surface comprises: acquiring an earth observation signal using the radiance meter; and performing amplitude correction on the earth observation signal to obtain the spectral radiance of the earth's surface.

[0006] According to an embodiment of the present invention, the calculation of the spatial position corresponding to the radiometer beam according to the relative position offset and rotational geometric relationship between the radiometer and the integrated navigation and measurement system includes: establishing a relationship between the direction vector of the radiometer beam in the WGS84 spatial rectangular coordinate system and the direction vector in the body coordinate system according to the angle between the projection of the center line of the field of view angle of the radiometer on the XOY plane of the body coordinate system and the positive direction of the X-axis, the angle between the center line of the field of view angle of the radiometer and the projection line of the center line of the field of view angle of the radiometer on the XOY plane, and the attitude angle and coordinates of the integrated navigation and measurement system, and obtaining a ground field of view range solution model; determining the direction of the radiometer beam based on the ground field of view range solution model; determining the intersection of the beam direction and the ground, and taking the coordinates of the intersection as the spatial position corresponding to the radiometer beam.

[0007] According to an embodiment of the present invention, the calculating of the spatial positioning error of the radiometer comprises: calculating the spatial positioning error of the radiometer according to a pointing error of an angle between a projection of a center line of the radiometer's field of view angle on an XOY plane of a body coordinate system and a positive direction of an X-axis, a pointing error of an angle between a center line of the radiometer's field of view angle and a projection line of the center line of the radiometer's field of view angle on an XOY plane, and a yaw angle measurement error, a pitch angle measurement error, and a roll angle measurement error of the near-space aerostat.

[0008] According to an embodiment of the present invention, determining the matching range of the ground objects in the test area based on the spatial position and the spatial positioning error includes: taking the spatial position as the center, the range of the spatial positioning error that fluctuates up and down by a preset multiple is the matching range.

[0009] According to an embodiment of the present invention, the spectral reflectance of different objects in the test area within the matching range is matched with the spectral radiance of the surface, including: calculating the spectral radiance of the objects within the matching range based on the spectral reflectance of the objects within the matching range; calculating the degree of matching between the spectral radiance of the objects within the matching range and the spectral radiance of the surface.

[0010] According to an embodiment of the present invention, the method of calculating the pointing angle error of the radiometer on the near-space aerostat by taking the ground field of view coordinates corresponding to the highest matching degree as geometric control points includes: substituting the ground field of view coordinates into the ground field of view range solution model based on the principle of minimizing the distance between the radiometer and the ground field of view coordinates to obtain an error equation corresponding to the pointing angle of the radiometer on the near-space aerostat; and solving the error equation to obtain the pointing angle error.

[0011] According to an embodiment of the present invention, the error equation is:

[0012]

[0013] in:

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020] in, represents the inverse matrix of the attitude matrix of the integrated navigation system, ρ x , y , z are the components of the direction vector of the beam of the radiometer in the body coordinate system in the x, y and z directions respectively, is the distance residual from the center of the radiometer to the ground field of view coordinates, (X wgs84 Y wgs84 Z wgs84 ) represents the coordinates of the integrated navigation system in the WGS84 space rectangular coordinate system, α is the angle between the projection of the center line of the field of view of the radiometer on the XOY plane of the body coordinate system and the positive direction of the X-axis, β is the angle between the center line of the field of view of the radiometer and the projection line of the center line of the field of view of the radiometer on the XOY plane, ρ x0 , y0 , z0 is x , y , z are the initial values ​​of , dα, dβ, and dρ are the corrected values ​​of α, β, and the distance residual, respectively.

[0021] According to an embodiment of the present invention, the solving of the equation comprises: solving the equation less than a preset threshold value. The corresponding dα, dβ, dρ are used as the pointing angle error.

[0022] According to the geometric correction method of the radiometer of the near-space aerostat provided by the present invention, the real ground object coordinates in the field test are used as geometric control points to perform geometric correction on the pointing angle of the radiometer, which can improve the horizontal and elevation positioning accuracy of the instantaneous field of view on the ground. In addition, this method has good reliability and provides effective support for improving the radiation calibration accuracy of multiple series of remote sensing satellites and ensuring the consistency of multi-satellite data quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0024] Figure 1 A flow chart of a method for geometric correction of a radiance meter of a near-space aerostat according to an embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0027] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] In the description of the present invention, it should be understood that the terms "longitudinal", "length", "circumferential", "front", "rear", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the subsystem or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0029] Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present invention. The shapes, sizes, and positional relationships of the components in the drawings do not reflect the actual size, proportion, and actual positional relationship. In addition, in the present invention, any reference symbol between brackets should not be constructed as a limitation to the present invention.

[0030] Similarly, in order to simplify the present invention and help understand one or more of the various disclosed aspects, in the above description of exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. The description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0031] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0032] In the process of implementing the concept of the present invention, it was found that compared with low-orbit satellite platforms, near-space aerostats can operate in an altitude range of 18-30km, and can achieve regional resident repeated observations by adjusting the flight altitude to seek wind fields. Near-space aerostats also have the advantage of being recyclable, which facilitates the calibration and re-observation of the radiation reference payload carried after the flight, thereby improving the traceability accuracy of the reference. Finally, the near-space aerostat has a lower flight altitude than the satellite platform, and has a higher resolution for the observed target under the same camera parameters.

[0033] During the ground development and testing of the near-space aerostat radiometer, the radiometer, integrated navigation system and near-space aerostat are rigidly connected and less affected by the outside world. After calibration in the laboratory, the radiometer and integrated navigation equipment have a high relative installation relationship. However, as the near-space aerostat is launched, the zero-pressure balloon sways and rotates in the stratosphere with the wind field, the air pressure changes from normal atmospheric pressure to 3-5kpa, the temperature changes from normal outdoor temperature to -60℃, and the temperature difference between the sunny side and the shady side caused by solar radiation may change the relative installation relationship between the payload and the platform on the near-space aerostat, thereby causing the pointing angle of the radiometer to change, and finally causing the plane and elevation errors of the instantaneous field of view on the ground.

[0034] Therefore, considering the above influencing factors comprehensively, based on the geometric calibration of the visible shortwave infrared radiance meter of the near-space aerostat, the horizontal and elevation positioning accuracy of the instantaneous field of view on the ground is improved by correcting the pointing angle error of the radiance meter of the near-space aerostat, which provides a solution for improving the geometric calibration accuracy of remote sensing satellites and for the consistency of the quality of subsequent multi-satellite radiance data.

[0035] Figure 1 The flowchart of the method for extracting a target from a remote sensing image according to an embodiment of the present invention is schematically shown.

[0036] like Figure 1 As shown, the remote sensing image target extraction method may include, for example, operations S101 to S106.

[0037] In operation S101, the spectral reflectance of different ground objects and the spectral radiance of the ground surface in the test area are obtained.

[0038] In an embodiment of the present invention, obtaining the spectral reflectance of different objects in the test area includes: measuring the radiance of different objects in the test area and the radiance of a reference plate. Obtaining the spectral reflectance of the reference plate. Calculating the spectral reflectance of the objects in the test area based on the radiance of different objects in the test area, the radiance of the reference plate, and the spectral reflectance.

[0039] Exemplarily, under good atmospheric conditions, the spectral reflectance curves of different ground objects in the test area are obtained by ground measurement using a ground object spectrometer. Among them, the ground measurement can be carried out by a manual handheld spectrometer, or by a drone equipped with a spectrometer and lifted to an altitude of 50-100m above the ground. The spectral reflectance of the ground object needs to be measured with the help of a reference plate. The spectrometer is used to measure the radiant brightness of the ground object and the radiant brightness of the reference plate respectively. When the spectral reflectance of the reference plate itself is known, the spectral reflectance of the ground object is obtained:

[0040]

[0041] Where λ represents the wavelength, which means that the reflectivity is a function of the wavelength. m，g ) represents the radiation brightness of the ground object, (L m，r ) represents the reference panel radiance, (ρ r ) represents the spectral reflectance of the reference plate itself, ρ g (λ) represents the spectral reflectance curve of the ground object.

[0042] In an embodiment of the present invention, obtaining the spectral radiance of the earth's surface includes: obtaining an earth observation signal using a radiance meter, and performing amplitude correction on the earth observation signal to obtain the spectral radiance of the earth's surface.

[0043] Exemplarily, the formula for amplitude correction may be:

[0044] L b (λ)=a(T,t,g,λ)DN(λ)+b(T,t,g,λ)

[0045] Among them, L b is the target radiation brightness observed by the radiometer, λ represents the wavelength position, DN is the value of the electrical signal recorded by the instrument, a and b are the radiation correction gain and bias coefficients, respectively, and a and b are related to the load operating temperature (T), load integration time (t) and load gain gear (g). The coefficients a and b need to be solved according to the observation data of the laboratory or spherical radiation reference source for different load operating temperatures, integration times and gain gears.

[0046] In operation S102, a spatial position corresponding to the radiance meter beam is calculated according to a relative position offset and a rotational geometric relationship between the radiance meter and the integrated navigation measurement system.

[0047] In an embodiment of the present invention, the relationship between the direction vector of the beam of the radiance meter in the WGS84 space rectangular coordinate system and the direction vector in the body coordinate system can be established based on the angle between the projection of the center line of the field of view angle of the radiance meter on the XOY plane of the body coordinate system and the positive direction of the X-axis, the angle between the center line of the field of view angle of the radiance meter and the projection line of the center line of the field of view angle of the radiance meter on the XOY plane, and the attitude angle and coordinates of the combined navigation measurement system, and the ground field of view range solution model can be obtained. The beam direction of the radiance meter is determined based on the ground field of view range solution model. The intersection of the beam direction and the ground is determined, and the coordinates of the intersection are used as the spatial position corresponding to the beam of the radiance meter.

[0048] For example, since the radiometer and the integrated navigation measurement system (GPS+INS) achieve microsecond synchronization through EVENT triggering, the integrated navigation measurement system records the trigger signal of the radiometer data collection time, and then accurately calculates the position and attitude information of each set of data collection time by performing GPS post-differentiation with the ground reference station. Therefore, the spatial position information of the beam direction of the radiometer at the time of collection is provided by the GPS system, and the attitude information is provided by the INS system. According to the relative position offset and rotation geometry relationship calibrated in the laboratory between the radiation reference load and the integrated navigation measurement system, a rigorous ground field of view range solution model of the airship radiation reference load can be constructed, and the observed ground object points can be located and the accuracy analysis can be performed based on the solution model. The model can be, for example, as follows:

[0049]

[0050] in:

[0051]

[0052] In the formula, is the direction vector of the beam of the radiometer in the WGS84 rectangular coordinate system, is the direction vector of the beam of the radiance meter in the body coordinate system, [X wgs84 Y wgs84 Z wgs84 ] T Represents the coordinates of the integrated navigation system in the WGS84 space rectangular coordinate system, R ins2wgs84 represents the attitude matrix of the integrated navigation system, ω, κ is the attitude during the combined navigation flight, which are the yaw angle, pitch angle and roll angle respectively; α is the angle between the projection of the center line of the field of view angle on the XOY plane of the body coordinate system and the positive direction of the X-axis; β is the angle between the center line of the field of view angle of the radiance meter and the projection line of the center line of the field of view angle of the radiance meter on the XOY plane.

[0053] Based on the above model, the beam direction of the radiometer can be determined. In combination with the digital elevation model (DEM) data, the intersection of the beam direction of the radiometer and the ground can be determined. The coordinates of the intersection are the spatial position corresponding to the beam of the radiometer. For example, the beam direction of the radiometer intersects the ground at point A, that is, the position of point A (X spot , Y spot , Z spot ) is the spatial position corresponding to the radiance meter beam.

[0054] In operation S103, a spatial positioning error of the radiometer is calculated.

[0055] Taking into account the installation and adjustment errors between the payloads of the near-space aerostat and the measurement errors of the position and attitude measurement system, it is necessary to perform spatial positioning accuracy statistics after determining the spatial position of the surface reference target of the near-space aerostat, so as to more accurately determine the search range when matching the spectral reflectance curve of the characteristic objects in the test area and improve the efficiency of spectral reflectance curve feature matching.

[0056] In an embodiment of the present invention, the spatial positioning error of the radiometer can be calculated based on the pointing error of the angle between the projection of the center line of the field of view angle of the radiometer on the XOY plane of the body coordinate system and the positive direction of the X-axis, the pointing error of the angle between the center line of the field of view angle of the radiometer and the projection line of the center line of the field of view angle of the radiometer on the XOY plane, the yaw angle measurement error, the pitch angle measurement error and the roll angle measurement error of the near-space aerostat.

[0057] For example, according to the error propagation law, the spatial positioning errors ΔX, ΔY, ΔZ in the three directions of X, Y, and Z of the radiometer surface reference target WGS-84 spatial rectangular coordinate system are mainly caused by the pointing error Δα of the angle between the projection of the center line of the radiometer field angle on the XOY plane of the body coordinate system and the positive direction of the X-axis, the angle Δβ between the center of the radiometer radiation field angle and its projection line on the XOY plane, the measurement errors Δω, ΔY, and ΔZ of the yaw angle, pitch angle, and roll angle during the flight of the near-space aerostat, Therefore, the spatial positioning errors ΔX, ΔY, and ΔZ can be calculated according to the following formula:

[0058]

[0059]

[0060]

[0061] In operation S104, a matching range of the ground object in the test area is determined according to the spatial position and the spatial positioning error.

[0062] In the embodiment of the present invention, the range of spatial positioning error that fluctuates up and down by a preset multiple with the position as the center is the matching range.

[0063] Exemplarily, according to the spatial position (X spot , Y spot , Z spot ) and spatial positioning errors ΔX, ΔY, ΔZ to determine the range of characteristic features in the experimental area, for example, the formula can be as follows:

[0064] X ground_0 =X spot ±3ΔX

[0065] Y ground_0 =Yspot ±3ΔY

[0066] Z ground_0 =Z spot ±3ΔZ

[0067] In operation S105, the spectral reflectances of different ground objects in the test area are matched with the spectral radiance of the ground surface within the matching range to obtain ground field coordinates corresponding to the spectral reflectance of the ground object with the highest matching degree with the spectral radiance of the ground surface.

[0068] In the embodiment of the present invention, the specific matching process may be as follows:

[0069] First, the spectral radiance of the objects within the matching range is calculated according to the spectral reflectance of the objects within the matching range.

[0070] This process is based on the radiation transfer mechanism. According to the radiation transfer equation, the spectral reflectance of different ground objects is pushed up to obtain the spectral radiance L corresponding to a specific ground object. ge (λ):

[0071]

[0072] Among them, ρ g (λ) is the spectral reflectance of the ground object obtained in step 1; L path (λ) is the atmospheric radiation at wavelength λ, S is the albedo of the large balloon surface, E s (λ) is the solar spectral irradiance at the upper boundary of the atmosphere at wavelength λ, τ(μ s ,λ) and τ(μ v ,λ) are the total atmospheric transmittance at wavelength λ on the paths of sun-surface and surface-remote sensing load, μ s With μ v are the cosine of the solar zenith angle and the cosine of the observed zenith angle, respectively. Among them, atmospheric path radiation, large balloon surface albedo, and atmospheric total transmittance can all be simulated using the atmospheric radiation transfer model. The solar spectral irradiance at the upper boundary of the atmosphere is generally taken as a known value, and the corresponding information is built into most atmospheric radiation transfer models.

[0073] Secondly, the matching degree between the spectral radiance of the objects within the matching range and the spectral radiance of the surface is calculated.

[0074] According to the idea of ​​spectral angle matching, the matching degree can be calculated using the following formula:

[0075]

[0076] Where N is the total number of bands, i is the band number, L b (λ) is the radiance observed by the aerostat, L ge(λ) is the radiance of the ground spectrum, m a For matching degree.

[0077] The closer the matching degree is to 1, the more the spectral radiance of the object matches the spectral radiance of the surface. The ground field coordinate corresponding to the spectral radiance of the most matching object is X real , Y real and Z real .

[0078] In operation S106, the ground field coordinates corresponding to the highest matching degree are used as geometric control points, the pointing angle error of the radiometer on the near-space aerostat is calculated, and the radiometer is geometrically corrected according to the pointing angle error.

[0079] In an embodiment of the present invention, based on the principle of minimizing the distance between the radiometer and the ground field of view coordinates, the ground field of view coordinates are substituted into the ground field of view range solution model to obtain the error equation corresponding to the pointing angle of the radiometer on the near-space aerostat, and the error equation is solved to obtain the pointing angle error.

[0080] For example, first, the ground field of view coordinates are substituted into the ground field of view range solution model based on the principle of minimizing the distance between the radiometer and the ground field of view coordinates to obtain the error equation:

[0081]

[0082]

[0083]

[0084] in, represents the inverse matrix of the attitude matrix of the integrated navigation system, ρ x , y , z are the components of the direction vector of the beam of the radiometer in the body coordinate system in the x, y, and z directions, respectively. wgs84 Y wgs84 Z wgs84 ) represents the coordinates of the integrated navigation system in the WGS84 space rectangular coordinate system, α is the angle between the projection of the center line of the field of view angle of the radiometer on the XOY plane of the body coordinate system and the positive direction of the X-axis, and β is the angle between the center line of the field of view angle of the radiometer and the projection line of the center line of the field of view angle of the radiometer on the XOY plane.

[0085] Next, we substitute the initial values ​​of the pointing angles α and β into 0 , β 0 And the ground field coordinate is X real , Y real and Z real The error equation from the previous step is obtained as ρx , y , the initial value of ρz x0 , y0 , z0 , and perform linearization to obtain the following formula:

[0086]

[0087]

[0088]

[0089] Next, during the adjustment, the distance between the center point of the radiometer and the ground foot point is calculated at the same time, and the correction value of ρ is introduced to obtain the following formula:

[0090]

[0091]

[0092]

[0093] Then the indirect adjustment formula is used to perform the least squares adjustment. According to the conditional formula V = AX-L, the final error equation can be obtained as follows:

[0094]

[0095] in:

[0096]

[0097]

[0098]

[0099]

[0100]

[0101]

[0102] in, is the distance residual from the center of the radiometer to the ground field coordinates, and dα, dβ, and dρ are the correction values ​​of α, β, and distance residuals, respectively. They are ρ x , y The partial derivatives of α and β.

[0103] Further, according to the indirect adjustment principle of minimum amount, the final error equation is transformed into the normal equation:

[0104] (A T PA)X=A T PL

[0105] Where P is the unit weight matrix of the observation value;

[0106]

[0107]

[0108]

[0109] List expressions for solutions to the normal equation:

[0110]

[0111] Finally, solve the problem of The corresponding dα, dβ, dρ are used as the pointing angle error.

[0112] In the embodiment of the present invention, an iteration method is adopted to solve the correction values ​​dα, dβ, dρ of the pointing angle and the distance difference.

[0113] Specifically, determine the initial values ​​of the parameters dα, dβ, and dρ, substitute the initial values ​​into the normal equation to solve the X matrix, and substitute the X matrix into the final error equation to obtain the residual vector matrix

[0114] Determine the residual vector matrix of the above steps In Is it greater than the preset threshold? If it is less than the preset threshold, then according to: α 1 =α+dα、β 1 =β+dβ、ρ 1 =ρ+dρ, respectively add dα, dβ, dρ to the previous solved α, β, ρ to update the new α 1 , β 1 , 1 As the optimal parameter. If it is greater than the preset threshold, then according to: α 1 =α+dα、β 1 =β+dβ、ρ 1 =ρ+dρ, respectively add dα, dβ, dρ to the previous solved α, β, ρ to update the new α 1 , β 1 , 1 , and the new α 1 , β 1 , 1 Repeat the above steps as the initial value until is less than a preset threshold.

[0115] In summary, the geometric correction method for a radiometer provided in an embodiment of the present invention, based on the characteristics of a ball-borne visible short-wave infrared radiometer, takes the coordinates of characteristic objects as geometric control points, corrects the pointing angle error of the radiometer on a near-space aerostat through least squares iterative calculation, and finally brings the pointing angle error into the solution model of the instantaneous field of view range of the radiometer on the ground, thereby realizing the near-space geometric calibration of the pointing angle error parameters of the reference payload.

[0116] It will be appreciated by those skilled in the art that the features described in the various embodiments of the present invention may be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments of the present invention may be combined and / or combined in various ways without departing from the spirit and teachings of the present invention. All of these combinations and / or combinations fall within the scope of the present invention.

[0117] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for geometric correction of a radiance meter of a near-space aerostat, comprising: Obtain the spectral reflectance of different ground objects and the spectral radiance of the ground surface in the test area; Calculate the spatial position corresponding to the beam of the radiometer according to the relative position offset and rotational geometric relationship between the radiometer and the integrated navigation measurement system; Calculating a spatial positioning error of the radiometer; Determine a matching range of the ground object in the test area according to the spatial position and the spatial positioning error; Matching the spectral reflectances of different ground objects in the test area with the spectral radiance of the ground surface within the matching range to obtain ground field coordinates corresponding to the spectral reflectance of the ground object with the highest matching degree with the spectral radiance of the ground surface; Taking the ground field coordinates corresponding to the highest matching degree as geometric control points, calculating the pointing angle error of the radiometer on the near-space aerostat; Performing geometric correction on the radiometer according to the pointing angle error; The step of calculating the spatial position corresponding to the beam of the radiometer according to the relative position offset and rotational geometric relationship between the radiometer and the integrated navigation measurement system comprises: According to the angle between the projection of the center line of the field of view angle of the radiometer on the XOY plane of the body coordinate system and the positive direction of the X-axis, the angle between the center line of the field of view angle of the radiometer and the projection line of the center line of the field of view angle of the radiometer on the XOY plane, and the attitude angle and coordinates of the integrated navigation measurement system, a relationship between the direction vector of the light beam of the radiometer in the WGS84 space rectangular coordinate system and the direction vector in the body coordinate system is established to obtain a ground field of view range solution model; Determining the beam direction of the radiance meter based on the ground field of view range solution model; Determine the intersection of the light beam direction and the ground, and use the coordinates of the intersection as the spatial position corresponding to the radiometer light beam; The step of taking the ground field coordinates corresponding to the highest matching degree as geometric control points and calculating the pointing angle error of the radiometer on the near-space aerostat comprises: Based on the principle of minimizing the distance between the radiometer and the ground field of view coordinates, the ground field of view coordinates are substituted into the ground field of view range solution model to obtain an error equation corresponding to the pointing angle of the radiometer on the near-space aerostat; The error equation is solved to obtain the pointing angle error.

2. The method for geometric correction of a radiometer according to claim 1, wherein: The obtaining of spectral reflectances of different objects in the test area includes: Measuring the radiance of different objects in the test area and the radiance of the reference plate; Obtaining the spectral reflectance of the reference plate; The spectral reflectance of the ground objects in the test area is calculated according to the radiance of different ground objects in the test area, the radiance and spectral reflectance of the reference plate.

3. The method for geometric correction of a radiometer according to claim 1, wherein: The obtaining of the spectral radiance of the surface comprises: Acquiring an earth observation signal using the radiometer; Amplitude correction is performed on the earth observation signal to obtain the spectral radiance of the earth's surface.

4. The method for geometric correction of a radiometer according to claim 1, wherein: Calculating the spatial positioning error of the radiometer comprises: The spatial positioning error of the radiometer is calculated according to the pointing error of the angle between the projection of the center line of the field of view angle of the radiometer on the XOY plane of the body coordinate system and the positive direction of the X-axis, the pointing error of the angle between the center line of the field of view angle of the radiometer and the projection line of the center line of the field of view angle of the radiometer on the XOY plane, and the yaw angle measurement error, pitch angle measurement error and roll angle measurement error of the near-space aerostat.

5. The method for geometric correction of a radiometer according to claim 1, wherein: Determining the matching range of the ground object in the test area according to the spatial position and the spatial positioning error includes: The range of the spatial positioning error that fluctuates up and down by a preset multiple with the spatial position as the center is the matching range.

6. The method for geometric correction of a radiometer according to claim 1, wherein: The matching of the spectral reflectance of different ground objects in the test area with the spectral radiance of the ground surface within the matching range includes: Calculating the spectral radiance of the ground objects within the matching range according to the spectral reflectance of the ground objects within the matching range; The degree of matching between the spectral radiance of the ground object within the matching range and the spectral radiance of the ground surface is calculated.

7. The method for geometric correction of a radiometer according to claim 1, wherein: The error equation is: in: ； ； ； ； ； ； in, represents the inverse matrix of the attitude matrix of the integrated navigation system, , , are the components of the direction vector of the beam of the radiometer in the body coordinate system in the x, y and z directions respectively, , , is the distance residual from the center of the radiometer to the ground field of view coordinates, ( ) represents the coordinates of the integrated navigation system in the WGS84 space rectangular coordinate system, is the angle between the projection of the center line of the field of view of the radiometer on the XOY plane of the body coordinate system and the positive direction of the X axis, is the angle between the center line of the field of view of the radiometer and the projection line of the center line of the field of view of the radiometer on the XOY plane, , , for , , The initial value of , , Respectively , , a correction value of the distance residual.

8. The method for geometric correction of a radiometer according to claim 7, wherein: The solving the equation comprises: Solve the problem that the , , Corresponding , , as the pointing angle error.

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