Digital target field system for comprehensive calibration of optical remote sensing payload

Abstract

The present application relates to a digital target field system for comprehensive calibration of optical remote sensing payloads, which includes calibration field targets and measuring equipment. The calibration field targets include a calibration field and various targets arranged on the calibration field; the measuring equipment is used to monitor the position parameters, radiation parameters and spatial parameters of various targets, and determine the corresponding time parameters based on the position parameters, radiation parameters and spatial parameters of various targets; wherein the position parameters include the coordinate information of the calibration field and the coordinate information of various targets; the radiation parameters include the reflectivity, flatness, Lambertianity and contrast of various targets; the spatial parameters include the target scale of various targets and the non-uniformity corresponding to the target scale; the time parameters include the target sedimentation rate and the target radiation attenuation rate of various targets. The system can monitor the calibration field performance parameters in real time.

Description

Technical Field

[0001] The present application relates to the field of aerospace remote sensing technology, and in particular to a digital target field system for comprehensive calibration of optical remote sensing payloads. Background Art

[0002] With the rapid growth in the number of high-resolution optical remote sensing satellites and the diversification of their functions, the existing on-orbit calibration technology based on a few calibration fields faces many challenges, especially in terms of the timeliness and adaptability of calibration. It is difficult to meet the calibration requirements of different payload characteristics and to achieve calibration over a full dynamic range. In particular, the radiation characteristics of the existing calibration fields are relatively single, making it difficult to adapt to the differentiated requirements of different satellite payloads. In addition, current technology lacks an effective solution to monitor the performance parameters of the calibration fields in real time, such as reflectivity, temperature changes, etc., which may lead to deviations in the calibration results, thereby affecting the accuracy and reliability of satellite remote sensing data.

[0003] In view of this, there is an urgent need to develop a comprehensive calibration digital target field system that can support the on-orbit performance detection and evaluation of optical remote sensing satellites. The system not only needs to have high-precision, high-frequency, and full-dynamic range calibration capabilities, but also needs to integrate the function of real-time monitoring of the calibration field performance parameters to ensure the stability and accuracy of the calibration process. Summary of the invention

[0004] Based on this, it is necessary to provide an optical remote sensing payload comprehensive calibration digital target field system that can monitor the calibration field performance parameters in real time to address the above technical problems.

[0005] The present application provides a digital target field system for comprehensive calibration of optical remote sensing payloads, the system comprising:

[0006] Calibration field targets, which include the calibration field and various targets set on the calibration field;

[0007] A measuring device, used for monitoring the position parameters, radiation parameters and space parameters of the calibration field target, and determining the corresponding time parameters based on the position parameters, radiation parameters and space parameters of the calibration field target;

[0008] Among them, the position parameters include the coordinate information of the calibration field and the coordinate information of various targets; the radiation parameters include the reflectivity, flatness, Lambertianness and contrast of various targets; the spatial parameters include the target scale of various targets and the non-uniformity corresponding to the target scale; the time parameters include the target sedimentation rate and target radiation attenuation rate of various targets.

[0009] In one embodiment, the coordinate information of the calibration field includes the longitude, latitude, and elevation coordinates of the corner points of the calibration field; the coordinate information of each type of target includes the longitude, latitude, and elevation coordinates of the corner points of each type of target, and the longitude, latitude, and elevation coordinates of the feature points of each type of target.

[0010] In one embodiment, the corner points of the calibration field include four corner points and a center point of the calibration field;

[0011] Various types of targets include cross-opposite angle targets, grayscale targets, knife-edge targets, radial targets, spectral targets and reflective point source arrays, and the corner points of various types of targets include the four corner points and edge black and white intersection points of the cross-opposite angle targets, the four corner points of the grayscale targets, the four corner points of each target in the knife-edge targets, the four corner points of the edge of the radial targets, the four corner points of each color spectral target in the spectral targets and the four corner points of the boundary of the reflective point source array; the characteristic points of various types of targets include the center point of the cross-opposite angle targets, the intersection point between the inner and outer edges of the black and white spokes of the radial targets and the center point of the circle, and the rotation center point of the reflective point source array.

[0012] In one embodiment, the target sedimentation rate is determined based on the longitude, latitude and elevation coordinates of the characteristic points of each type of target each year; the target radiation attenuation rate is determined based on the reflectivity change, flatness change, Lambertian change, contrast change and non-uniformity change of each type of target each year.

[0013] In one embodiment, the time parameters of various targets satisfy the following conditions:

[0014] The target sedimentation rate is less than or equal to 1 cm / year, and the radiation attenuation rate is less than or equal to 2% / year.

[0015] In one embodiment, the radiation parameters of various targets satisfy the following conditions:

[0016] The reflectivity of each type of target includes at least one or more of 5%, 20%, 40%, 60%, and 80%; the flatness of each type of target is less than or equal to 5%; the change in the bidirectional reflectance factor of each type of target within the range of ±30° of the target normal is less than or equal to 2%; the contrast of each type of target is greater than or equal to 12:1.

[0017] In one embodiment, each type of target satisfies the following conditions:

[0018] The cross-vertical angle target is composed of cross-vertical angle sub-targets with reflectivity of 5% and 60% respectively and a scale of not less than 7 ground pixel resolutions intersecting in straight lines;

[0019] The grayscale target is composed of multiple reflectivity grayscale sub-targets with reflectivity of 5%, 20%, 40% and 60% and a scale of no less than 20 ground pixel resolutions;

[0020] The knife edge target is composed of knife edge sub-targets with reflectivity of 5% and 60% and a scale of not less than 20 ground pixel resolutions intersecting in a straight line;

[0021] The radial target is a fan-shaped pattern with an opening angle of 110° formed by alternately coating trapezoidal targets with reflectivity of 5% and 60%;

[0022] The spectral target is composed of spectral sub-targets with colors of red, yellow, blue, green, purple and orange and a scale of not less than 20 ground pixel resolutions;

[0023] The reflection point source array consists of a 3*12 circulant matrix with a reflectivity of 80% and a spacing of no less than 10.2 ground pixel resolution.

[0024] In one embodiment, the spatial parameters of various targets satisfy the following conditions:

[0025] The target scale of each type of target is greater than or equal to 20 times the ground pixel resolution of the optical remote sensing payload, and the non-uniformity within the target scale is less than or equal to 1%.

[0026] In one embodiment, the cross-vertex angle target is perpendicular to the imaging direction of the remote sensing payload within the width of the remote sensing payload, the angle between the edge target and the imaging direction of the remote sensing payload is 5° to 7°, the angle between the radial target and the imaging direction of the remote sensing payload is 10°, and the grayscale target, spectral target and reflection point source array are all along the imaging direction of the remote sensing payload.

[0027] In one embodiment, the calibration field target is a multi-coating structure, the thickness of the multi-coating structure is greater than or equal to 3 mm, and the multi-coating structure includes a base layer, a bottom coating layer, an elastic layer, a reinforcement layer and a target surface layer;

[0028] Among them, the base layer is cement concrete or asphalt formed by mechanical automatic pouring and compaction; the base coating is a permeable alkali-resistant material; and the target surface layer includes various targets.

[0029] The above optical remote sensing payload comprehensive calibration digital target field system has at least the following beneficial effects:

[0030] By setting up measuring equipment, the calibration performance of the calibration field target is monitored to obtain the changes in the calibration performance of the calibration field target with the years of use, so as to ensure the stability and accuracy of the calibration process. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0032] FIG1 is a schematic diagram of the structure of a digital target field system for comprehensive calibration of optical remote sensing payloads in one embodiment;

[0033] FIG2 is a schematic diagram of the structure of corner points of a calibration field, corner points of various targets, and feature points in one embodiment;

[0034] FIG3 is a schematic diagram of the structure of a cross diagonal target in one embodiment;

[0035] FIG4 is a schematic diagram of the structure of a grayscale target and a knife edge target in one embodiment;

[0036] FIG5 is a schematic diagram of the structure of a radial target in one embodiment;

[0037] FIG6 is a schematic diagram of the structure of a spectral target in one embodiment;

[0038] FIG7 is a schematic diagram of the structure of a reflection point source array in one embodiment;

[0039] FIG8 is a schematic diagram of a reflectivity curve of a non-spectral target in a calibration field target in one embodiment;

[0040] FIG9 is a schematic diagram of a reflectivity curve of a spectral target in a calibration field target in one embodiment;

[0041] FIG10 is a schematic diagram of a Lambertian curve of a non-spectral target in a calibration field target in one embodiment;

[0042] FIG11 is a schematic diagram of a Lambertian curve of a spectral target in a calibration field target in one embodiment;

[0043] FIG12 is a schematic diagram showing the uniformity of reflectivity of various types of targets in a calibration field target according to an embodiment;

[0044] FIG. 13 is a schematic diagram of a multi-coating structure of a calibration field target in one embodiment. DETAILED DESCRIPTION

[0045] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0047] It can be understood that the terms "first", "second", etc. used in the present application can be used in this article to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element.

[0048] Spatially relative terms such as "under", "beneath", "below", "under", "above", "above", etc., may be used herein to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that in addition to the orientations shown in the figures, spatially relative terms also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is turned over, the element or feature described as "under other elements" or "under it" or "under it" will be oriented as "on" the other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptors used herein are interpreted accordingly.

[0049] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element, or connected to the other element through an intermediate element. In addition, the "connection" in the following embodiments should be understood as "electrical connection", "communication connection", etc. if there is transmission of electrical signals or data between the connected objects.

[0050] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" etc. specify the presence of stated features, wholes, steps, operations, components, parts or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof.

[0051] In an exemplary embodiment, as shown in FIG1 , the present application provides a digital target field system for integrated calibration of optical remote sensing payloads, which includes a calibration field target and a measuring device 500. The calibration field target includes a calibration field 300 and various targets arranged on the calibration field 300; the measuring device 500 is used to monitor the position parameters, radiation parameters and spatial parameters of the calibration field target, and determine the corresponding time parameters based on the position parameters, radiation parameters and spatial parameters of the calibration field target; wherein the position parameters include the coordinate information of the calibration field and the coordinate information of various targets; the radiation parameters include the reflectivity, flatness, Lambertianity and contrast of various targets; the spatial parameters include the target scale of various targets and the non-uniformity corresponding to the target scale; the time parameters include the target sedimentation rate and the target radiation attenuation rate of various targets.

[0052] As shown in FIG1 , various types of targets may include one or more of a cross diagonal target 2, a grayscale target 4, a knife edge target 6, a radial target 8, a spectral target 10, and a reflective point source array 12, and the specific selection may be selected according to the calibration requirements of the optical remote sensing payload, and is not limited here. The calibration field 300 refers to the carrier of various types of targets, which may be the ground or a cloth surface. The measuring equipment 500 may include measuring equipment using RTK-GPS (Real-Time Kinematic-GlobalPositioning System, real-time dynamic positioning) technology, a high-precision spectral radiometer, a bidirectional reflectance distribution function measuring instrument, a laser rangefinder, and the like.

[0053] For example, on the target of the calibration field, by using a measuring device equipped with RTK-GPS technology, the coordinate information of the calibration field and the coordinate information of various targets can be measured; for example, after the above-mentioned measuring device is turned on and stabilized, it is connected to the global positioning system satellite through an antenna. After completion, it is placed at the calibration field or the point to be measured of various targets, and its level is adjusted. After being left still for a period of time, an alarm will be immediately sounded when the acquisition of the coordinate information of the point to be measured is completed. At this time, the target type and time corresponding to the point to be measured can also be recorded. The reflectivity of various targets can be measured by using a high-precision spectroradiometer to simultaneously measure the reflectivity of the diffuse reflectance standard reference plate and the target, so as to obtain the target reflectivity by comparative measurement. Flatness refers to the change in the reflectivity of the target in the solar reflection band, which is represented by the difference between the maximum and minimum values ​​of the reflectivity. The flatness of various targets can be determined based on the target reflectivity obtained by the above measurement. Lambertian property is the change of the reflected radiance observed by the target at different illumination angles, which is expressed by BRF (bidirectional reflectance factor). By using a bidirectional reflectance distribution function measuring instrument, the reflectivity of the target is measured at different incident and exit angles. If the reflectivity does not change with the angle, it means that the target has good Lambertian property. The contrast can be calculated by measuring the reflectivity of each part using a spectroradiometer. The target scale of various targets can be measured by a laser rangefinder to measure the physical size of the target (such as length and width) to obtain the target scale. Non-uniformity is the mean square error of the reflectivity measured at multiple positions of the target scale, which can be calculated from the reflectivity obtained by the above measurement. It can be seen that by using high-precision spectroradiometers, bidirectional reflectance distribution function measuring instruments, laser rangefinders and other measuring equipment, the performance parameters such as reflectivity, flatness, Lambertian property, contrast, target scale and non-uniformity of various targets can be obtained in real time to determine whether the optical remote sensing calibration requirements are met. Furthermore, based on the coordinate information obtained annually by measuring equipment equipped with RTK-GPS technology, the target settlement rate of various targets can be calculated to obtain the changes in the geometric position of the target over time due to factors such as foundation settlement, high temperature in summer, low temperature due to rain and snow in winter, and solar radiation; at the same time, based on the above performance parameters measured annually, the target radiation attenuation rate is calculated to obtain the attenuation of radiation performance, thereby further understanding the impact of changes in geometric position and attenuation of radiation performance on the calibration process.

[0054] The optical remote sensing payload comprehensive calibration digital target field system monitors the calibration performance of the calibration field target by setting up measuring equipment to obtain changes in the calibration performance of the calibration field target with the service life, thereby ensuring the stability and accuracy of the calibration process.

[0055] In an exemplary embodiment, the coordinate information of the calibration field includes the longitude, latitude, and elevation coordinates of the corner points of the calibration field; the coordinate information of each type of target includes the longitude, latitude, and elevation coordinates of the corner points of each type of target, and the longitude, latitude, and elevation coordinates of the feature points of each type of target.

[0056] Among them, the corner points of the calibration field may include but are not limited to the points at the four corners of the terrain boundary of the calibration field, that is, the points at the upper left corner, upper right corner, lower left corner and lower right corner of the terrain, which are used to define the spatial range of the calibration field. The corner points of various targets may refer to the points at the four corners of the edge of the target shape, which are used to define the size and shape of the target. For example, for a rectangular target, the corner points may be its four corners. The feature points of various targets may be specific marking points on the target, or some key points in the target design, which have an important impact on the performance of the target.

[0057] In this embodiment, the coordinate information of the calibration field includes the longitude, latitude, and elevation coordinates of the corner points of the calibration field, so as to accurately know the position of the calibration field in the entire geographic space. Similarly, the coordinate information of various targets also includes the longitude, latitude, and elevation coordinates of the corner points of various targets, as well as the longitude, latitude, and elevation coordinates of the feature points of various targets, so that the specific position of each target can be accurately understood. By regularly measuring the above coordinate information through measuring equipment, any position changes of the calibration field targets over time can be monitored, such as changes in the target position caused by factors such as foundation settlement, seasonal temperature changes, weather effects, or solar radiation. This continuous monitoring helps to promptly discover and deal with problems that may affect the calibration process, thereby ensuring the stability and accuracy of the calibration process.

[0058] In an exemplary embodiment, as shown in FIG2 , the corner points of the calibration field 300 include the four corner points and the center point of the calibration field 300; various types of targets include a cross-opposite corner target 2, a grayscale target 4, a knife edge target 6, a radial target 8, a spectral target 10 and a reflective point source array 12, and the corner points of various types of targets include the four corner points and edge black and white intersection points of the cross-opposite corner target 2, the four corner points of the grayscale target 4, the four corner points of each target in the knife edge target 6, the four corner points of the edge of the radial target 8, the four corner points of each color spectral target 10 in the spectral target 10 and the four corner points of the boundary of the reflective point source array 12; the feature points of various types of targets include the center point of the cross-opposite corner target 2, the intersection point between the inner and outer edges of the black and white spokes of the radial target 8 and the center point of the circle, and the rotation center point of the reflective point source array 12.

[0059] The corner points of the calibration field 300 include the points at the four corners of the calibration field 300 and the three center points at the midline position (as shown by the red dots of the calibration field 300 in FIG2 ). The corner points of various targets include: the points at the four corners of the cross-vertical target 2 and the five points at the black and white intersection of the edge (as shown by the red dots of the cross-vertical target 2 in FIG2 ), the points at the four corners of each grayscale sub-target in the grayscale target 4 (as shown by the red dots of the grayscale target 4 in FIG2 ), the points at the four corners of each edge sub-target in the edge target 6 (as shown by the red dots of the edge target 6 in FIG2 ), the four corner points of the edge of the radial target 8 (as shown by the red dots of the radial target 8 in FIG2 ), and the points at each color in the spectral target 10. The points at the four corners of the spectral sub-target (as shown by the red dots of the spectral target 10 in FIG2 ) and the four corner points of the boundary of the reflection point source array 12; and the characteristic points of various targets include: the center point of the cross-vertical target 2 (as shown by the purple dots of the cross-vertical target 2 in FIG2 ), the intersection point of the inner and outer edges of the black and white spokes of the radial target 8 and the center point of the circle (as shown by the purple dots of the radial target 8 in FIG2 ), and the rotation center point of the reflection point source array 12 (as shown by the red dots of each reflection point source in the reflection point source array 12 in FIG2 ).

[0060] In this embodiment, the corner points of the calibration field are set as four corner points and a center point, which can better grasp the overall layout and positional relationship of the calibration field, and facilitate subsequent measurement and analysis. According to the different characteristics of different types of targets, corresponding corner points and feature points are set respectively, which can more comprehensively cover the key parts of each target, and facilitate accurate positioning and measurement. The feature points of various targets, such as the center point of the cross-vertex target, the intersection point of the inner and outer edges of the black and white spokes of the radial target, the center point of the circle, and the rotation center point of the reflection point source array, are all important characteristics of the target. Accurate measurement of them can reflect the performance status of the target, which is conducive to improving the accuracy of the calibration results.

[0061] In an exemplary embodiment, the target sedimentation rate is determined based on the longitude, latitude and elevation coordinates of the characteristic points of each type of target each year; the target radiation attenuation rate is determined based on the reflectivity change, flatness change, Lambertian change, contrast change and non-uniformity change of each type of target each year.

[0062] Exemplarily, the target sedimentation rate is determined based on the longitude, latitude and elevation coordinates of the characteristic points of various types of targets each year. Specifically, the data measured this year and last year are compared, and the sedimentation is determined based on the data difference between the two years. The average sedimentation for many years, such as three or five years, is the sedimentation rate. In other words, by measuring the longitude, latitude and elevation coordinates of the characteristic points of various types of targets each year, the position changes of these characteristic points between different years can be obtained, and then the target sedimentation rate can be obtained by calculating the average value of these changes. On the other hand, the target radiation attenuation rate is determined based on the reflectivity change, flatness change, Lambertian change, contrast change and non-uniformity change of various types of targets each year. Among them, the reflectivity change is the difference between the reflectivity this year and the reflectivity last year. The calculation method of the change in other parameters can also refer to the calculation method of the reflectivity change, which will not be repeated here. The radiation attenuation rate mainly refers to the mean of the target reflectivity change over the years. That is to say, by measuring the performance parameters such as reflectivity, flatness, Lambertianity, contrast and non-uniformity of various targets each year, the changes in these parameters between different years can be obtained, and then by calculating the average value of these changes, the target radiation attenuation rate can be obtained.

[0063] In this embodiment, by accurately measuring the longitude, latitude and elevation coordinates of the characteristic points of various targets, the geometric position changes of the targets can be effectively monitored, and then the target settlement rate can be calculated to evaluate the stability of the target position during long-term use; at the same time, by continuously monitoring the reflectivity change, flatness change, Lambertian change, contrast change and non-uniformity change of various targets each year, the degradation degree of the target radiation performance can be accurately evaluated, and the target radiation attenuation rate can be calculated to ensure the stability and accuracy of the calibration process. It is helpful to timely discover and solve the problem of target performance degradation, and can also improve the reliability and effectiveness of the entire optical remote sensing payload comprehensive calibration digital target field system, thereby providing a solid foundation for high-quality remote sensing data.

[0064] In an exemplary embodiment, the time parameters of various types of targets meet the following conditions: the target sedimentation rate is less than or equal to 1 cm / year, and the radiation attenuation rate is less than or equal to 2% / year.

[0065] In this embodiment, the target sedimentation rate of the calibration field target is designed to be less than or equal to 1 cm / year, and the radiation attenuation rate is designed to be less than or equal to 2% / year. By strictly controlling the target sedimentation rate and radiation attenuation rate, the position stability and radiation performance reliability of the calibration field target are ensured during its service life, thereby providing an accurate and stable benchmark for the comprehensive calibration of the optical remote sensing payload, effectively ensuring the stability and accuracy of the calibration process, and thus improving the quality and reliability of the remote sensing data.

[0066] In an exemplary embodiment, the radiation parameters of various types of targets meet the following conditions: the reflectivity of various types of targets includes at least one or more of 5%, 20%, 40%, 60%, and 80%; the flatness of various types of targets is less than or equal to 5%; the bidirectional reflectance factor variation of various types of targets within the range of ±30° of the target normal is less than or equal to 2%; the contrast of various types of targets is greater than or equal to 12:1.

[0067] Among them, the reflectivity of various targets includes at least one or more of 5%, 20%, 40%, 60%, and 80%. Specifically, it can be understood that, for example, a grayscale target can include grayscale sub-targets with reflectivities of 5%, 20%, 40% and 60% respectively, and for example, a knife-edge target can include knife-edge sub-targets with reflectivities of 5% and 60% respectively.

[0068] In this embodiment, the setting of the above conditions ensures that the target has a wide reflectivity range and can simulate different types of ground objects, thereby improving the applicability and accuracy of the calibration results; the high flatness of the target ensures spectral consistency and reduces the measurement error caused by the uneven spectrum of the ground object; the smaller change in the bidirectional reflectance factor ensures the stability of the reflective characteristics of the target at different observation angles and enhances the reliability of the calibration results; and the higher contrast is conducive to reducing the mutual influence between adjacent targets, ensuring the independence and distinguishability of each target, and ultimately improving the stability and accuracy of the entire calibration system.

[0069] In an exemplary embodiment, various types of targets meet the following conditions: the cross-vertex target is composed of cross-vertex sub-targets with reflectivity of 5% and 60% respectively and a scale of not less than 7 ground pixel resolutions intersecting in straight lines; the grayscale target is composed of grayscale sub-targets with multiple reflectivity of 5%, 20%, 40% and 60% respectively and a scale of not less than 20 ground pixel resolutions; the knife edge target is composed of knife edge sub-targets with reflectivity of 5% and 60% respectively and a scale of not less than 20 ground pixel resolutions intersecting in straight lines; the radial target is composed of a fan-shaped pattern with an angle of 110° formed by alternating trapezoidal targets with reflectivity of 5% and 60% respectively; the spectral target is composed of spectral sub-targets with colors of red, yellow, blue, green, purple and orange respectively and a scale of not less than 20 ground pixel resolutions; the reflection point source array is composed of a 3*12 circulant matrix with a reflectivity of 80% and a spacing of not less than 10.2 ground pixel resolutions.

[0070] Among them, the specific composition and structure of the cross-vertex target 2, grayscale target 4, edge target 6, radial target 8, spectral target 10 and reflective point source array 12 can be referred to by those skilled in the art as shown in Figures 3 to 7, and will not be repeated here. It should be noted that the target of the calibration field 300 follows the principle of compact layout and one target for multiple uses, and according to the planning area and target type of the calibration field 300, the area of ​​each type of target should be maximized as much as possible, and the grayscale target 4 and the edge target 6 can be shared. The grayscale target 4 and the edge target 6 can be shared specifically means that during design and layout, the grayscale target 4 and the edge target 6 can share functions in the same physical area. Specifically, the grayscale target and the edge target 6 can be on the same target surface, including both grayscale sub-targets of different reflectivity levels and a smooth transition area from one reflectivity level to another reflectivity level (i.e., the edge sub-target) to meet different calibration requirements, as shown in Figure 4.

[0071] Exemplarily, for the calibration field targets in this embodiment, the reflectivity of non-spectral targets (including cross-vertex targets, grayscale targets, edge targets, radial targets and reflective point source arrays) to light of different wavelengths is shown in FIG8, and the reflectivity of spectral targets to light of different wavelengths is shown in FIG9. It can be seen that the calibration field targets in this embodiment have a small change in reflectivity within the solar reflection band and good flatness. The Lambertian property of the non-spectral target is shown in FIG10, and the Lambertian property of the spectral target is shown in FIG11. It can be seen that the calibration field targets in this embodiment, whether they are non-spectral targets or spectral targets, have good Lambertian properties. The uniformity of various targets is shown in FIG12, where the number in the horizontal axis represents nine different positions evenly distributed on the target. It can be seen that the reflectivity uniformity of various targets in the calibration field targets in this embodiment is good.

[0072] In this embodiment, the design and construction of the cross-vertex target, grayscale target, edge target, radial target, spectral target and reflective point source array not only covers a wide range of reflectivity, ensuring that the calibration field can simulate a variety of surface reflection characteristics, but also these targets can be integrated in a limited space to improve the calibration efficiency. The target design follows the principle of compact layout and one target for multiple uses, ensuring the maximum utilization of the target area, while maintaining good flatness, Lambertian and reflectivity uniformity, which helps to reduce measurement errors and improve calibration accuracy.

[0073] In an exemplary embodiment, the spatial parameters of each type of target meet the following conditions: the target scale of each type of target is greater than or equal to 20 times the ground pixel resolution of the optical remote sensing payload, and the non-uniformity within the target scale is less than or equal to 1%.

[0074] In this embodiment, the target scale of each type of target is greater than or equal to 20 times the ground pixel resolution of the optical remote sensing payload, and the non-uniformity within the target scale is less than or equal to 1%. This design ensures that the target is large enough to be clearly distinguished by the optical remote sensing payload, avoiding the problem of insufficient pixel sampling due to the target being too small. At the same time, the non-uniformity inside the target is extremely low, effectively reducing the measurement error introduced by the inconsistent reflective characteristics of the target surface. Under the combined effect of the above conditions, the accuracy and stability of the calibration process can be improved, ensuring the acquisition of high-quality remote sensing data, thereby improving the accuracy and reliability of remote sensing image processing and analysis.

[0075] In an exemplary embodiment, the cross-vertex angle target is perpendicular to the imaging direction of the remote sensing payload within the width of the remote sensing payload, the angle between the edge target and the imaging direction of the remote sensing payload is 5° to 7°, the angle between the radial target and the imaging direction of the remote sensing payload is 10°, and the grayscale target, spectral target and reflection point source array are all along the imaging direction of the remote sensing payload.

[0076] In this embodiment, the above target layout ensures that the target can match the imaging characteristics of the remote sensing payload in the best way. The design of the cross-vertex target perpendicular to the imaging direction facilitates edge detection and geometric correction; the small angle offset of the edge target from the imaging direction helps to evaluate the directional dependence of the sensor; the specific angle setting of the radial target from the imaging direction can simulate different observation angles, which is used to evaluate and correct the influence of the field of view angle; and the arrangement of the grayscale target, spectral target and reflective point source array along the imaging direction ensures the uniform distribution of different reflectivity levels during the calibration process, which is conducive to the accuracy of radiation calibration. In summary, this target layout not only improves the calibration efficiency, but also enhances the comprehensiveness and accuracy of the calibration, providing a solid guarantee for obtaining high-quality remote sensing data.

[0077] In an exemplary embodiment, as shown in FIG13 , the calibration field target is a multi-coating structure having a thickness greater than or equal to 3 mm, and the multi-coating structure includes a base layer 101, a primer layer 103, an elastic layer 105, a reinforcing layer 107 and a target surface layer 109; wherein the base layer 101 is cement concrete or asphalt formed by mechanical automatic pouring and compaction; the primer layer 103 is a permeable alkali-resistant material; and the target surface layer 109 includes various types of targets.

[0078] Among them, the base layer 101 can be a large area of ​​cement concrete foundation with temperature expansion joints, or it can be an asphalt foundation. The base layer 101 can be polished to improve the adhesion. The base layer 103 is formed by rolling with a strong permeability and alkali-resistant material as the basis, which is used to close the pores of the base layer 101 and improve the adhesion to prevent peeling. The elastic layer 105 and the reinforcing layer 107 are a mixture of the base layer 103 and the target surface layer 109. The scraping method is adopted to ensure the surface flatness and play a role in buffering the target surface layer 109. The target surface layer 109 is the main body of the calibration field target. After the calibration field is divided and marked, different types of targets (grayscale targets, edge targets, radial targets and spectral targets) are coated by scraping or rolling, and the reflection point source array is placed in the low reflectivity area of ​​the calibration field after coating. Among them, the target coating of the target surface layer 109 is mainly a modified acrylic material with weather resistance and flexibility.

[0079] In this embodiment, the multi-layer structure design ensures that the target has excellent physical properties and durability. The base layer, as a solid supporting layer, is specially treated to improve the adhesion; the base layer uses permeable alkali-resistant materials to enhance the bonding strength with the base layer, and closes the pores to prevent moisture erosion; the addition of the elastic layer and the reinforcement layer not only ensures the flatness of the target surface, but also provides additional buffer protection, increasing the service life of the target; the target surface layer constitutes the main body of the calibration field target, and different types of targets are coated by scraping or rolling, and the reflective point source array is placed in the low reflectivity area. The target surface layer adopts a modified acrylic material with good weather resistance and flexibility, which ensures that the target can maintain good reflective properties and appearance quality under various climatic conditions. In summary, the multi-coating structure design improves the durability and stability of the target, ensures the stability of the reflectivity and geometric properties of the target during long-term use, and thus provides a more reliable and accurate reference standard for the comprehensive calibration of optical remote sensing payloads.

[0080] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", "ideal embodiments", 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 descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0081] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0082] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. An optical remote sensing payload comprehensive calibration digital target field system, characterized in that: The system comprises: A calibration field target, wherein the calibration field target comprises a calibration field and various targets arranged on the calibration field; A measuring device, used for monitoring the position parameters, radiation parameters and space parameters of the calibration field target, and determining the corresponding time parameters based on the position parameters, radiation parameters and space parameters of the calibration field target; Wherein, the position parameters include the coordinate information of the calibration field and the coordinate information of the various targets; the radiation parameters include the reflectivity, flatness, Lambertianity and contrast of the various targets; the spatial parameters include the target scale of the various targets and the non-uniformity corresponding to the target scale; the time parameters include the target sedimentation rate and the target radiation attenuation rate of the various targets; The coordinate information of the calibration field includes the longitude, latitude, and elevation coordinates of the corner points of the calibration field; the coordinate information of each type of target includes the longitude, latitude, and elevation coordinates of the corner points of each type of target, and the longitude, latitude, and elevation coordinates of the feature points of each type of target; Among them, the target sedimentation rate is determined according to the longitude, latitude and elevation coordinates of the characteristic points of the various targets each year; the target radiation attenuation rate is determined according to the reflectivity change, flatness change, Lambertian change, contrast change and non-uniformity change of the various targets each year.

2. The optical remote sensing payload comprehensive calibration digital target field system according to claim 1 is characterized in that: The corner points of the calibration field include the four corner points and the center point of the calibration field; The various types of targets include cross-opposite angle targets, grayscale targets, edge targets, radial targets, spectral targets and reflective point source arrays, and the corner points of the various types of targets include the four corner points and edge black and white intersection points of the cross-opposite angle targets, the four corner points of the grayscale targets, the four corner points of each target in the edge targets, the four corner points of the edge of the radial targets, the four corner points of each color spectral target in the spectral targets and the four corner points of the boundary of the reflective point source array; the characteristic points of the various types of targets include the center point of the cross-opposite angle targets, the intersection points of the inner and outer edges of the black and white spokes of the radial targets and the center point of the circle, and the rotation center point of the reflective point source array.

3. The optical remote sensing payload comprehensive calibration digital target field system according to claim 1 is characterized in that: The time parameters of the various targets meet the following conditions: The target sedimentation rate is less than or equal to 1 cm / year, and the radiation attenuation rate is less than or equal to 2% / year.

4. The optical remote sensing payload comprehensive calibration digital target field system according to claim 1 is characterized in that: The radiation parameters of the various targets meet the following conditions: The reflectivity of each type of target includes at least one or more of 5%, 20%, 40%, 60%, and 80%; the flatness of each type of target is less than or equal to 5%; the bidirectional reflectance factor of each type of target within the range of ±30° of the target normal is less than or equal to 2%; the contrast of each type of target is greater than or equal to 12:

1.

5. The optical remote sensing payload comprehensive calibration digital target field system according to claim 2 is characterized in that: The various targets meet the following conditions: The cross-vertex target is composed of cross-vertex sub-targets with reflectivity of 5% and 60% respectively and a scale of not less than 7 ground pixel resolutions intersecting in a straight line; The grayscale target is composed of multiple reflectivity grayscale sub-targets with reflectivity of 5%, 20%, 40% and 60% respectively and a scale of not less than 20 ground pixel resolutions; The knife edge target is composed of knife edge sub-targets with reflectivity of 5% and 60% respectively and a scale of not less than 20 ground pixel resolutions intersecting in a straight line; The radial target is a fan-shaped pattern with an opening angle of 110° formed by alternately coating trapezoidal targets with reflectivity of 5% and 60% respectively; The spectral target is composed of spectral sub-targets with colors of red, yellow, blue, green, purple and orange and a scale of not less than 20 ground pixel resolutions; The reflection point source array is composed of a 3*12 circulant matrix with a reflectivity of 80% and a spacing of no less than 10.2 ground pixel resolutions.

6. The optical remote sensing payload comprehensive calibration digital target field system according to claim 1 is characterized in that: The spatial parameters of the various targets satisfy the following conditions: The target scale of each type of target is greater than or equal to 20 times the ground pixel resolution of the optical remote sensing payload, and the non-uniformity within the target scale is less than or equal to 1%.

7. The optical remote sensing payload comprehensive calibration digital target field system according to claim 2 is characterized in that: The cross-vertex angle target is perpendicular to the imaging direction of the remote sensing payload within the width range of the remote sensing payload, the angle between the edge target and the imaging direction of the remote sensing payload is 5° to 7°, the angle between the radial target and the imaging direction of the remote sensing payload is 10°, and the grayscale target, the spectral target and the reflection point source array are all along the imaging direction of the remote sensing payload.

8. The optical remote sensing payload comprehensive calibration digital target field system according to claim 1 is characterized in that: The calibration field target is a multi-coating structure, the thickness of the multi-coating structure is greater than or equal to 3 mm, and the multi-coating structure includes a base layer, a bottom coating layer, an elastic layer, a reinforcement layer and a target surface layer; Wherein, the base layer is cement concrete or asphalt formed by mechanical automatic pouring and compaction; the base coating is a permeable alkali-resistant material; and the target surface layer includes the various targets.

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