A multi-sensor based aviation coaxial remote sensing device and method

Abstract

The present invention relates to an aviation coaxial remote sensing device and method based on multiple sensors, wherein a gyro-stabilized platform is fixedly connected to an oblique-flying remote sensing aircraft; a remote sensing device is fixedly connected to the gyro-stabilized platform; a GNSS antenna is fixedly connected to the top of the remote sensing aircraft; an industrial computer is fixedly connected to the floor of the oblique-flying remote sensing aircraft; a radome is fixedly connected to the oblique-flying remote sensing aircraft; a SAR antenna is fixedly connected to the oblique-flying remote sensing aircraft; a SAR antenna turntable is fixedly connected to the oblique-flying remote sensing aircraft; a GNSS receiver is fixedly connected to the industrial computer; the GNSS receiver is connected to the industrial computer; the industrial computer is connected to the remote sensing device through a data line; the industrial computer is connected to the SAR antenna; and the industrial computer is connected to the gyro-stabilized platform. By using the oblique-flying remote sensing aircraft, the industrial computer is used to design and display the flight route, control the gyro-stabilized platform and the SAR antenna, so that different sensors can simultaneously acquire data for the same surface area, realize coaxial remote sensing, and improve the efficiency of aviation remote sensing data acquisition and sensor utilization.

Description

Technical Field

[0001] The present invention relates to the field of remote sensing technology, and in particular to an aerial coaxial remote sensing device and method based on multiple sensors. Background Art

[0002] Aerial remote sensing, also known as airborne remote sensing, refers to the technology of using flying platforms such as airplanes, airships and balloons as sensor carriers to conduct remote sensing in the air. It is a multifunctional comprehensive detection technology developed from aerial photographic reconnaissance. The traditional aerial remote sensing system uses an aircraft to carry a sensor for ground observation. With the improvement of aircraft performance, the improvement of sensor integration and the demand for high-efficiency remote sensing operations, the use of a remote sensing aircraft carrying a variety of different types of sensors to observe the ground in the air is the current development trend of aerial remote sensing. Among them, different types of sensors include multispectral cameras, hyperspectral imagers, infrared cameras, lidar, synthetic aperture radar (SAR), etc. Different types of sensors have different perspectives for earth observation. Some are downward looking, that is, perpendicular to the sea level, such as multispectral cameras, hyperspectral imagers, thermal infrared cameras, lidar, etc. Some are side looking, that is, downward at a certain angle to the sea level, such as SAR. In this case, different types of sensors cannot meet co-axial remote sensing when conducting earth observation at the same time, that is, they cannot meet the requirements of conducting earth observation on the same surface area at the same time, resulting in inconsistency in remote sensing data obtained by downward looking sensors and side looking sensors. In addition, in order to ensure that all sensors can obtain remote sensing data of the same surface area, remote sensing aircraft need to fly multiple routes to make up for the differences caused by downward looking and side looking, which will lead to redundancy of flight routes and reduced flight efficiency. Summary of the invention

[0003] The purpose of the present invention is to provide an aerial coaxial remote sensing device and method based on multiple sensors. The present invention adopts a special flight method during the flight and controls different equipment through an industrial computer, so that different types of sensors can realize coaxial remote sensing, that is, to realize ground observation of the same surface area under the same space-time environment, reduce redundant flights, improve the working efficiency of aerial remote sensing, and can complete aerial remote sensing tasks based on multiple sensors faster and more conveniently.

[0004] In order to achieve the above object, the present invention has the following technical solutions:

[0005] The invention discloses an aviation coaxial remote sensing device based on multiple sensors, comprising an oblique flying remote sensing aircraft, a gyro-stabilized platform, a remote sensing device, an industrial computer, a radome, a SAR antenna, a SAR antenna turntable, a GNSS antenna, and a GNSS receiver. The gyro-stabilized platform is fixedly connected to a downward-looking remote sensing window of the oblique flying remote sensing aircraft; the remote sensing device is fixedly connected to the gyro-stabilized platform; the GNSS antenna is fixedly connected to the top of the oblique flying remote sensing aircraft; the industrial computer is fixedly connected to the floor of the oblique flying remote sensing aircraft; the radome is fixedly connected to the belly and the bottom of the oblique flying remote sensing aircraft. The SAR antenna is respectively connected to the side of the oblique-flying remote sensing aircraft and the SAR antenna turntable; the SAR antenna turntable is connected to the belly of the oblique-flying remote sensing aircraft; the GNSS receiver is connected to the industrial computer; the GNSS antenna is connected to the GNSS receiver through a data line; the GNSS receiver is connected to the industrial computer through a data line; the industrial computer is connected to the remote sensing equipment through a data line; the industrial computer is connected to the SAR antenna through a data line; the industrial computer is connected to the gyro-stabilized platform through a data line;

[0006] The oblique-flying remote sensing aircraft is a remote sensing aircraft capable of oblique flight, and the angle between the horizontal axis of the oblique-flying remote sensing aircraft and the plane parallel to the sea level is: 15°-30°; the oblique-flying remote sensing aircraft comprises a structural installation platform, a downward-looking optical window, optical glass and a camera cabin door, wherein the structural installation platform is located above the downward-looking optical window, the optical glass is located on the downward-looking optical window, and the camera cabin door is located below the optical glass;

[0007] The remote sensing equipment includes sensors of SAR, multi-spectral aerial camera, hyperspectral aerial camera, infrared aerial camera and airborne laser radar; wherein the incident beam of the SAR antenna is offset as the oblique-flying remote sensing aircraft tilts; and when the oblique-flying remote sensing aircraft tilts, the sensors of the multi-spectral aerial camera, hyperspectral aerial camera, infrared aerial camera and airborne laser radar are adjusted by the gyro-stabilized platform to be vertical to the sea level downward to perform ground remote sensing observation, thus forming downward-looking ground remote sensing observation without being affected by the angular motion of the aircraft; the gyro-stabilized platform can be used to control the attitude of the remote sensing equipment;

[0008] Among them, SAR performs remote sensing observation of the ground by looking sideways, that is, downward at a certain angle to the ground normal; the angle between the incident beam emitted by the SAR antenna and the ground normal is 30°-60°; multispectral aerial cameras, hyperspectral aerial cameras, infrared aerial cameras and airborne laser radars all perform remote sensing observation of the ground by looking downward, that is, vertically downward from the sea level;

[0009] Among them, the gyro-stabilized platform is installed on the structural mounting platform; the remote sensing equipment of the multi-spectral aerial camera, hyper-spectral aerial camera, infrared aerial camera and airborne laser radar are all installed on the gyro-stabilized platform, and the SAR is installed separately from the gyro-stabilized platform;

[0010] The radome refers to an airborne radar radome, of which there are three, one belly radome is arranged under the belly of the aircraft, and a left SAR radome and a right SAR radome are arranged on both sides of the fuselage;

[0011] Among them, the three radomes are all installed on the front half of the aircraft fuselage. Among them, the belly radome is symmetrical with respect to the symmetry plane of the aircraft; the left and right SAR radomes overlap with the effective section of the belly radome in the front-to-back direction.

[0012] The SAR antenna turntable is installed on the belly of the oblique flying remote sensing aircraft and is used to control the azimuth of the belly SAR antenna so that it can tilt to the left or right.

[0013] There are three SAR antennas, one is mounted on the SAR antenna turntable, and the other two are mounted on the left and right sides of the oblique flying remote sensing aircraft. The belly SAR antenna is located inside the belly radome, and the left and right SAR antennas are located inside the left and right SAR radomes respectively.

[0014] Among them, the three SAR antennas can obtain SAR data of four bands, namely, P, L, C, and X. The data obtained by the left and right SAR antennas are the same.

[0015] The GNSS antenna can receive GNSS signals and send them to a GNSS receiver. The GNSS receiver processes the GNSS signals and then outputs GNSS data to an industrial computer.

[0016] The industrial computer includes a control device and a display device, wherein the control device is used to control sensors such as a gyro-stabilized platform, a SAR antenna turntable, SAR, a multi-spectral aerial camera, a hyperspectral aerial camera, an infrared aerial camera, and an airborne laser radar; and the display device is used to display maps, flight routes, aircraft flight trajectories, and aircraft position information, etc.

[0017] The industrial computer can prepare a flight plan for an oblique-flying remote sensing aircraft for an aerial remote sensing operation area, so that all remote sensing equipment on the oblique-flying remote sensing aircraft can perform ground remote sensing observation along a designated flight route. The steps are:

[0018] 1) Coordinate transformation

[0019] Coordinate transformation can improve the accuracy and efficiency of the system in route design, because it can process data in different coordinate systems. Currently, commonly used coordinate systems include WGS84 global coordinate system, National 2000 coordinate system, Xi'an 80 coordinate system, Beijing 54 coordinate system and local coordinate system. Different coordinate system data sometimes need to be converted. Since the nodes in the flight survey area generally use the longitude and latitude coordinates of WGS84, the longitude and latitude coordinates are not convenient for calculating the azimuth and the distance between points, lines and surfaces, while the plane coordinates are easy to calculate, so the conversion between longitude and latitude coordinates and plane rectangular coordinates is inevitable.

[0020] First, you need to use GPS to obtain the geodetic coordinates of the point (B 84 L 84 H 84 ) T , and then convert it to spatial rectangular coordinates (XYZ) according to the reference ellipsoid parameters of WGS84 using formula (1) T Then, according to the reference ellipsoid parameters of Beijing 54 or Xi'an 80 or the local independent coordinate system, (XYZ) is converted by formula (2) T Convert to geodetic coordinates (B 54 L 54 H 54 ) T or (B 80 L 80 H 80 ) T or (B local L local H local ) T Finally, according to the central meridian, the projection surface elevation and the north-east offset, (B 54 L 54 ) T or (B 80 L 80 ) T or (B local L local ) T Projection is Gaussian coordinates (X g Y g ) T ;

[0021]

[0022]

[0023]

[0024] in,

[0025] X=C0B+(C2 cosB+C4 cos 3 B+C6cos 5 B+C8cos 7 B)sin B (4)

[0026]

[0027] t=tanB (6)

[0028]

[0029] l″=L-L0 (8)

[0030] In the formula, L and B are the latitude and longitude coordinates before conversion; H is the elevation

[0031] x, y are the transformed Gaussian coordinates;

[0032] a is the major radius of the ellipsoid, and e is the first eccentricity of the ellipsoid;

[0033] L0 is the longitude of the central meridian of the projection zone;

[0034] C0, C2, C4, C6, and C8 are constant values ​​related only to the ellipsoid parameters;

[0035] The use of coordinate transformation in flight route design can improve the efficiency of flight strip design compared to conventional manual route design. Although manual calculations are relatively complete and stable, if the number of flight strips is too large, it will bring greater computing intensity. At the same time, manual flight strip calculations cannot use high-precision electronic maps. Therefore, route design using coordinate transformation has obvious advantages, making the scope of the survey area clearer. The application of coordinate transformation improves the accuracy and efficiency of flight strip design, and also improves the system's ability to process various coordinate system data.

[0036] 2) Automatic route determination

[0037] Introducing buffer analysis in geographic information systems into multi-sensor-based aviation remote sensing flight management systems can simplify the amount of calculation and improve the quality of air flight to a certain extent. Buffers are polygons with a certain width range around entities such as points, lines, and surfaces. Multi-sensor-based aviation remote sensing flight management systems can generate judgment buffers of specific shapes according to flight missions. When the system automatically shoots a predetermined area, it is necessary to judge the relative position between the aircraft and the survey area and the flight route. However, due to the complexity of the actual situation (the pilot will adjust to a suitable angle for level flight according to the airflow state), the correct judgment of the relative position of the aircraft requires many judgment conditions, and the amount of calculation required for real-time calculation is relatively large. In order to ensure the smooth operation of the system, the system needs to generate some buffers in advance to judge the relative position, so that the relative position of the oblique flying remote sensing aircraft and the route can be determined by only judging whether the oblique flying remote sensing aircraft is in the buffer, thereby greatly reducing the amount of calculation. When the oblique remote sensing aircraft enters the buffer zone and meets the flight altitude restriction conditions to enter the route, it can be considered as an effective entry; when the oblique remote sensing aircraft takes pictures after entering the route, if it flies off the scheduled route and exceeds the flight zone buffer zone, the system will give a prompt and automatically stop the aerial sensor from taking pictures accordingly, thereby avoiding flight waste that does not meet the route design. Therefore, establishing a buffer zone can ensure the quality of the flight route to a certain extent.

[0038] At present, with the improvement of the accuracy of GNSS equipment, the relative position of the aircraft and the scheduled route can be determined through the feedback information of GNSS equipment, so as to make automatic judgments and perform relevant operations on aviation sensors in a timely manner.

[0039] 3) Route position calculation

[0040] First, the coordinate system is rotated according to the route layout direction so that the X′ axis of the rotated coordinate system is parallel to the route direction; therefore, to calculate the position of the route, it is only necessary to find the heading centerline of the survey area and the number of routes, and then other routes are laid symmetrically on both sides parallel to the heading centerline of the survey area; the ordinate of the heading centerline is:

[0041] Y′=(Y′ max +Y′ min ) / 2 (9)

[0042] Where, Y′ max , Y′ min are the maximum and minimum values ​​of the ordinate of the circumscribed rectangle of the polygon in the X′Y′ coordinate system respectively;

[0043] According to the requirements of the national standard topographic map aerial photogrammetry internal specifications, the lateral coverage beyond the boundary line of the shooting area is generally not less than 50% of the image frame, and at least not less than 30% of the image frame; Yis the lateral coverage width of the image frame on the ground, the designed minimum total coverage width is:

[0044] W min =Y′ max -Y′ min +2L Y (10)

[0045] Assuming the number of routes in the survey area is n, the total coverage width of all routes is:

[0046] W=((1-S)(n-1)+1)×L Y (11)

[0047] Where S is the lateral overlap ratio; from formula (11) we can calculate n = 1 + (WL Y ) / (L Y -SL Y ); n must be an integer and the coverage width must be guaranteed. n is rounded up and added by 1, that is,

[0048] n=[1+(WL Y ) / (L Y -SL Y )]+1 (12)

[0049] The brackets in the above formula indicate rounding. Let W = W min Substitute it in and calculate the total number of routes that meet the requirements;

[0050] Regardless of whether n is an odd number or an even number, all routes are parallel to the center line and symmetrically distributed on both sides. Combined with the schematic diagram, the calculation formula of the ordinate of each route can be derived based on the relevant knowledge of photogrammetry:

[0051] Y′ m =(Y′ max +Y′ min ) / 2+(m-(n+1) / 2)(1-S)×L Y (13)

[0052] Where m is the number of the route from bottom to top, 1≤m≤n;

[0053] 4) Exposure point coordinate calculation

[0054] For flat areas, the baseline length of the aerial photogrammetry area remains basically unchanged; the coordinates of the center point of the polygon in the X′ direction of the measurement area are X′0 = (X′ max +X′ min ) / 2, where X′ max and X′ min The maximum and minimum values ​​of the horizontal coordinates of the circumscribed rectangle of the polygon in the X′Y′ coordinate system;

[0055] To calculate the coordinates of the exposure point on a certain route, we can first calculate the intersection of the route and the survey area polygon, and then use the center point (X′0, Y′ m ) is the starting point, and within the range of the maximum and minimum values ​​of the horizontal coordinate of the intersection point, the integer multiples of the photographic baseline are extended to the left and right to obtain a series of intersection points, which are the exposure points;

[0056] X′ k =X′0±B k ×k(k=0,1,2...) (14)

[0057] Where B k is the baseline length;

[0058] If the route has no intersection with the polygon or has only one intersection, that is, the route is laid out outside the polygon of the survey area, or intersects at a node at the top or bottom of the polygon, then the center point (X′0, Y′ m ) is the starting point, at (X′ min X′ max ) interval is extended to the left and right by integer multiples of the photographic baseline to obtain a series of points. These points are taken as exposure centers in turn to calculate the coverage area of ​​the film on the ground. If the area overlaps with the measurement area polygon, the point is used as the exposure point.

[0059] At the same time, the requirements of aerial photography specifications should be taken into consideration. The heading coverage should exceed the boundary line of the shooting area by a certain range, with two more baseline lengths. Therefore, a corresponding number of exposure points should be added outside the boundary.

[0060] 5) Route design based on DEM

[0061] DEM-based route design is to combine DEM with GIS, fully consider the important role of terrain factors in aerial photography route design, use DEM data as the basis, GIS as the technical support, use grids and vector graphs as the visualization background, and through mathematical operations and conditional judgments, solve the problems of survey area division, parameter calculation and route laying in the current actual design, and realize high-precision and high-quality aerial photography route design;

[0062] According to the aerial photogrammetry specifications, there needs to be a certain overlap between adjacent aerial photographs to cover the survey area and facilitate subsequent stereo mapping; the overlap rate is divided into heading overlap rate and lateral overlap rate, and the formula is as follows:

[0063]

[0064] In the formula, P and Q are the heading and lateral overlap rates, respectively, x and y are the overlapping parts of the heading and lateral adjacent images, respectively, l x , l y are image length and width respectively;

[0065] The terrain undulation will directly affect the heading and lateral overlap rate, and its influence can be analyzed by formula (15). In addition, the terrain undulation will also cause a series of changes in the photographic baseline and photographic interval.

[0066]

[0067] Where h is the height difference relative to the mean elevation datum, H 摄 is the relative altitude of aerial photography, P and Q are the actual heading and lateral overlap rate, P′ and Q′ are the planned heading and lateral overlap rate. DEM can most effectively reflect the terrain undulations, can quickly obtain the h value of the required point and provide fast computer calculation;

[0068] The elevation values ​​of the flight route and the main image point can be obtained from the digital elevation model by computer. According to formula (16), the change of the heading lateral overlap rate can be calculated, and then the positions of the adjacent main image points and the adjacent flight routes can be calculated;

[0069] For areas with undulating terrain, the influence of DEM needs to be considered. First, the actual overlap rate of the images on the average surface is calculated based on the planned heading overlap rate of the images and the photographic baseline length B is calculated. Then, the position of the next image principal point O is calculated based on the position of the image principal point and the heading overlap rate. i Similarly, the interval D of the photography routes is calculated according to the lateral overlap rate, and finally the position O of each image principal point on each other route is obtained according to the interval D of the photography routes and B. j ;

[0070]

[0071]

[0072] Where: b x , B x It is the length of the photographic baseline on the film and in the field;

[0073] d x , D y The width of the flight line interval on the image and on the ground;

[0074] L x , L y is the length and width of the photographic image;

[0075] p x ,q y is the heading and lateral overlap ratio;

[0076] m 航 is the denominator of the aerial photography scale.

[0077] The industrial control computer can display maps, flight routes, flight tracks and position information of oblique remote sensing aircraft in real time. Based on the displayed information, the onboard operator can control the timing of turning on and off the remote sensing equipment, so that all remote sensing equipment can synchronously perform remote sensing observation of the ground. The method steps are:

[0078] 1) Load and display the electronic map of administrative divisions;

[0079] 2) Load the flight plan file to display the flight route on the electronic map;

[0080] 3) Obtain the longitude and latitude coordinates and time information of the oblique-flying remote sensing aircraft through a GNSS receiver, convert the longitude and latitude coordinates into plane rectangular coordinates corresponding to the electronic map, and display the position of the oblique-flying remote sensing aircraft on the electronic map;

[0081] 4) Display the oblique flying remote sensing aircraft symbol - obtain the current position of the oblique flying remote sensing aircraft; call the symbol library; define the symbol object, set the properties; draw the symbol object;

[0082] 5) Dynamic display of the flight trajectory of the oblique flying remote sensing aircraft - the coordinate points of the oblique flying remote sensing aircraft arranged in time series form line segments, and the line segments representing the aircraft's motion trajectory are drawn through the map control DrawShape function;

[0083] 6) The onboard operator determines the time when the oblique flying remote sensing aircraft enters the route based on the aircraft position, flight route and flight trajectory of the oblique flying remote sensing aircraft, and uses the industrial computer to turn on the remote sensing equipment; determines the time when the oblique flying remote sensing aircraft leaves the route, and uses the industrial computer to turn off the remote sensing equipment.

[0084] Among them, the observation mode of the SAR is to look sideways for ground remote sensing observation, and the angle range between the incident beam of its antenna and the ground normal is set to 30°-60°, wherein the sampling angle range of the incident beam of the left SAR antenna is -30°--60°, and the sampling angle range of the incident beam of the right SAR antenna is set to 30°-60°; while the observation mode of the multispectral aerial camera, hyperspectral aerial camera, infrared aerial camera and airborne laser radar remote sensing equipment on the gyro-stabilized platform is to look downward, and the angle range between the incident beam of its sensor head and the ground normal is set to -30°-30°, and the sampling angle range of the incident beam is -30°-30°; it can be seen that the ground observation range of the side-looking remote sensing equipment and the downward-looking remote sensing equipment under the same conditions is different. In order to ensure that the ground observation range of SAR and other remote sensing equipment is consistent, the following method steps are taken:

[0085] 1) Open the gyro stabilized platform control software in the industrial computer, click "Communication Settings", and set the angle parameters. The roll angle range is set to: -30°-+30°; the pitch angle range is set to: -8°-+6°; the yaw angle range is set to: -30°-+30°;

[0086] 2) Determine the lateral overlap rate between 50% and 75% according to the mission plan setting, make a flight plan according to this requirement, and generate a flight route; display the map, flight route, aircraft flight track and aircraft position information in the industrial computer according to this requirement;

[0087] 3) When the first route 1 of the aircraft is located at the westernmost or southernmost part of the operation area, notify the pilot to tilt the oblique remote sensing aircraft around the longitudinal axis of the aircraft 15°-30° to the lower left, forming an oblique remote sensing aircraft with an inclination of 15°-30° to the lower left, and keep flying along the first route 1 in this state. At this time, the gyro-stabilized platform will automatically correct the roll angle so that the remote sensing equipment on the gyro-stabilized platform maintains a downward-looking ground observation state;

[0088] 4) Open the SAR antenna turntable control software in the industrial computer, set the turntable to tilt to the lower left, and set the sampling angle range of the SAR antenna incident beam on the turntable to -30°--60°; at this time, the sampling angle range of the incident beam of the belly SAR antenna and the left SAR antenna is both -30°-0°;

[0089] 5) When the oblique flying remote sensing aircraft displayed on the industrial computer enters the flight route, all remote sensing devices are turned on. When the oblique flying remote sensing aircraft maintains this state and flies out of the route, all remote sensing devices are turned off and the oblique flying remote sensing aircraft resumes parallel flight;

[0090] 6) The oblique remote sensing aircraft turns and prepares to fly the second route 5. The pilot is notified to tilt the oblique remote sensing aircraft 30° to the lower right around the longitudinal axis of the aircraft, forming an oblique remote sensing aircraft with an inclination of 15°-30° to the lower right, and maintain this state to fly along the second route 5. At this time, the gyro-stabilized platform will automatically correct the roll angle, so that the remote sensing equipment on the gyro-stabilized platform maintains a downward-looking ground observation state;

[0091] 7) Open the SAR antenna turntable control software in the industrial computer, set the turntable to tilt to the lower right, and set the sampling angle range of the SAR antenna incident beam on the turntable to 30°-60°. At this time, the sampling angle range of the incident beam of the belly SAR antenna and the right SAR antenna is 0°-30°;

[0092] 8) When the aircraft displayed on the industrial computer enters the flight route, all remote sensing devices are turned on. When the oblique flying remote sensing aircraft maintains this state and flies out of the route, all remote sensing devices are turned off and the oblique flying remote sensing aircraft resumes parallel flight;

[0093] 9) Repeat steps 3) to 8) until all routes in the operation area are completed, thus completing the flight mission;

[0094] 10) When the first route 1 of the aircraft is located at the easternmost or northernmost part of the operation area, notify the pilot to tilt the oblique remote sensing aircraft around the longitudinal axis of the aircraft 15°-30° downward to the right, forming an oblique remote sensing aircraft with an inclination of 15°-30° downward to the right, and keep flying along the first route 1 in this state. At this time, the gyro-stabilized platform will automatically correct the roll angle so that the remote sensing equipment on the gyro-stabilized platform maintains a downward-looking ground observation state;

[0095] 11) Open the SAR antenna turntable control software in the industrial computer, set the turntable to tilt to the lower right, and set the sampling angle range of the SAR antenna incident beam on the turntable to 30°-60°; at this time, the sampling angle range of the incident beam of the belly SAR antenna and the right SAR antenna is 0°-30°;

[0096] 12) When the aircraft displayed on the industrial computer enters the flight route, all remote sensing devices are turned on. When the oblique flying remote sensing aircraft maintains this state and flies out of the route, all remote sensing devices are turned off and the oblique flying remote sensing aircraft resumes parallel flight;

[0097] 13) The oblique remote sensing aircraft turns and prepares to fly the second route 5. The pilot is notified to tilt the oblique remote sensing aircraft 30° to the lower left around the longitudinal axis of the aircraft, forming an oblique remote sensing aircraft with an inclination of 15°-30° to the lower left, and maintain this state to fly along the second route 5. At this time, the gyro-stabilized platform will automatically correct the roll angle, so that the remote sensing equipment on the gyro-stabilized platform maintains a downward-looking ground observation state;

[0098] 14) Open the SAR antenna turntable control software in the industrial computer, set the turntable to tilt to the lower left, and set the sampling angle range of the SAR antenna incident beam on the turntable to -30°--60°. At this time, the sampling angle range of the incident beam of the belly SAR antenna and the left SAR antenna is -30°-0°;

[0099] 15) When the aircraft displayed on the industrial computer enters the flight route, all remote sensing devices are turned on. When the oblique remote sensing aircraft maintains this state and flies out of the route, all remote sensing devices are turned off and the oblique remote sensing aircraft resumes parallel flight;

[0100] 16) Repeat steps 10) to 15) until all routes in the operation area are flown, thus completing the flight mission.

[0101] Among them, the range of the angle between the incident beam of the SAR antenna and the ground normal can also be set to other ranges, not limited to 30°-60°, but also 20°-50° or 25°-55°, etc., and the length of the range is less than 40°; the side-view remote sensing equipment is not limited to SAR, and other side-view remote sensing equipment such as oblique photography aerial cameras are also applicable.

[0102] Wherein, the distance resolution of the remote sensing device SAR is:

[0103]

[0104] Where τ is the pulse width of the SAR, C is the speed of light, and θ is the SAR antenna incident beam side view;

[0105] Due to the tilted flight of the oblique remote sensing aircraft, θ changes from ±45° to ±15°, which will cause ΔR to become larger, that is, the distance resolution is reduced. In order to ensure that the distance resolution is not reduced, the linear frequency modulation pulse width and amplitude are modulated to reduce τ, thereby ensuring that the distance resolution is not reduced. The method steps are as follows:

[0106] The harmonic is subjected to linear frequency modulation to generate a linear frequency modulation pulse, and then the pulse is transmitted. After receiving the echo, the pulse is passed through a matching filter having opposite frequency characteristics in terms of frequency and time as those during transmission, so that the delay of the received low-frequency echo in the filter is first made greater than the delay of the high-frequency echo, thereby extracting the received pulse signal in the form of reduced pulse width and increased pulse amplitude;

[0107] Within the pulse width, the instantaneous frequency is linearly proportional to f min Change to f max , FM bandwidth Δf = f max -f min The envelope of the waveform function generated by the matched filter (the envelope is a graph formed by many elliptical curves interwoven, and looks like it is wrapped. The envelope has its own unique meaning in mathematics, signal processing, literature, economics, and traditional Chinese medicine) is The main lobe of its waveform is larger than the side lobe, and the half-power width is That is, the compressed pulse width τ0, so the pulse width is compressed to the original The larger Δf is, the smaller the compressed pulse width is, the smaller ΔR is, and the higher the distance resolution is;

[0108] Among them, f min is the minimum instantaneous frequency, f max is the maximum instantaneous frequency; sinc is the Sinker function,

[0109] Wherein, when the sampling angle range of the incident beam of the left SAR antenna in the above step 4) is -30°-0°, the corresponding sampling angle range of the incident beam of the right SAR antenna becomes 60°-90°, and the side viewing angle of the incident beam of the right SAR antenna is 75°; according to the principle of trigonometric function, when the sampling angle changes from 30° to 60°, the corresponding ground coverage range changes from H tan 30° to H tan 60°;

[0110] Where H is the relative altitude of the aircraft, tan 90°=∞, it can be calculated that the ground coverage is 3 times the original; if the coverage corresponding to the sampling angle -30°-30° is the nth route 30 in the flight plan, then the coverage corresponding to the sampling angle 60°-90° is the (3+n)th to nth routes 30 in the flight plan, which is equivalent to obtaining the data corresponding to these routes in advance; at the same time, the side angle of the incident beam of the right SAR antenna changes from 45° to 75°, and the side angle increases. According to the above formula (19), the distance resolution ΔR of the remote sensing data corresponding to the (3+n)th to nth routes 30 becomes smaller, that is, the distance resolution is improved. (According to the previous steps, SAR data obtains half a line less than other remote sensing equipment, which can not only make up for the lack of lines, but also fly a wider range than other remote sensing equipment, and ensure the distance resolution). Similarly, steps 7), 11) and 14) all have the characteristics of step 4).

[0111] According to the previous method, if only the SAR antenna on the side of the aircraft tilted downward is considered, when the oblique remote sensing aircraft flies the first route 1, the SAR obtains the ground data corresponding to the angle between the incident beam of the SAR antenna and the ground normal of -30°-0°, and other remote sensing equipment obtains the ground data corresponding to the angle between the longitudinal axis of the sensor head of other remote sensing equipment and the ground normal of -30°-+30°. SAR obtains less ground data corresponding to 0°-30° than other remote sensing equipment, that is, the data of half a route; because the lateral overlap rate between routes is 50%-75%, the aircraft flies the second route 5, SAR obtains ground data corresponding to 0°-30°, and the overlap rate of this data with the data obtained by SAR on the previous route is between 0% and 25%; other remote sensing equipment still obtains ground data corresponding to the angle between the longitudinal axis of the sensor head of other remote sensing equipment and the ground normal -30°-+30°, and the overlap rate of this data with the data obtained by other remote sensing equipment on the previous route is between 50% and 75%. SAR still obtains less data for half a route than other remote sensing equipment; therefore, when all routes are completed, SAR still obtains less data for half a route than other remote sensing equipment. Now with the data obtained by the SAR antenna on the upward tilted side, the missing data of half a route can be compensated in advance; due to the increase in the side viewing angle of the left or right SAR antenna due to tilted flight, the data obtained will be much more than half a route, and according to formula (19), the distance resolution is higher than before; other remote sensing equipment refers to multispectral aerial cameras, hyperspectral aerial cameras, infrared aerial cameras and airborne laser radars, but is not limited to these equipment.

[0112] Due to the adoption of the above technical solution, the advantages of the present invention are:

[0113] 1. One machine can be used for multiple purposes. Through one flight, multiple remote sensing data can be obtained, replacing the traditional industry model of one machine for one use for aerial remote sensing;

[0114] 2. Realize coaxial remote sensing under the background of time-space consistency, avoid redundant flights, reduce flight routes, reduce aircraft flight time and fuel consumption, reduce the intensity of aerial operations, the difficulty of post-data processing, and save costs and time;

[0115] 3. Improved the technical level of aviation remote sensing industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0116] Figure 1 It is a flight schematic diagram of the present invention;

[0117] Figure 2 A schematic diagram of the overlapping parts of the earth observation of SAR and other remote sensing equipment formed after the first to third routes 9 of the present invention are flown;

[0118] Figure 3It is a schematic diagram of the device connection of the present invention;

[0119] Figure 4 It is a schematic diagram of the ground observation angle of the SAR side view and other remote sensing equipment downward view of the present invention, and the oblique flying remote sensing aircraft parallel flight;

[0120] Figure 5 This is a schematic diagram of the ground observation angle of the SAR side view and other remote sensing equipment downward view of the present invention, with the oblique-flying remote sensing aircraft tilting downward to the left;

[0121] Figure 6 It is a schematic diagram of the installation of the radome of the present invention;

[0122] Figure 7 for Figure 6 Schematic diagram of AA direction;

[0123] Figure 8 It is a flow chart of the on-board operation of the present invention.

[0124] In the figure:

[0125] 1. The first route; 2. The overlapping area of ​​SAR and other remote sensing equipment for earth observation on the first route; 3. The area of ​​earth observation of other remote sensing equipment on the first route; 4. The oblique flying remote sensing aircraft on the first route; 5. The second route; 6. The overlapping area of ​​SAR and other remote sensing equipment for earth observation on the second route; 7. The area of ​​earth observation of other remote sensing equipment on the second route; 8. The oblique flying remote sensing aircraft on the second route; 9. The third route; 10. The overlapping area of ​​SAR and other remote sensing equipment for earth observation on the third route; 11. The oblique flying remote sensing aircraft on the third route; 12. The area of ​​earth observation of other remote sensing equipment on the third route; 13. The oblique flying remote sensing aircraft; 14. Display; 15. Industrial computer; 16. Belly antenna; 17. SAR antenna cover on the left; 18. Right SAR antenna cover; 19, 20, 21: remote sensing equipment; 22, left side SAR earth observation area; 25, right side SAR earth observation area; 26, SAR and remote sensing equipment earth observation overlapping area; 27, right side SAR earth observation area; 28, remote sensing equipment earth observation area; 29, no data area; 30, nth route; 31, n+1th route; 32, n+2th route; 33, n+3th route; 36, left side antenna; 37, left side antenna mounting plate; 38, belly antenna cover; 39, belly antenna mounting plate; 40, SAR antenna turntable; 41, belly antenna; 43, right side antenna mounting plate; 44, right side antenna; 45, buckle; 46, fixing rod; 47, angle mark; 48, bearing. DETAILED DESCRIPTION

[0126] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0127] See attached Figure 1-Figure 8 , an aviation coaxial remote sensing method and device based on multiple sensors, including an oblique flying remote sensing aircraft 13, a gyro-stabilized platform, a remote sensing device 19, an industrial computer 15, antenna covers 17, 18 and 38, a SAR antenna, a GNSS antenna, and a GNSS receiver. The gyro-stabilized platform is fixedly connected to the downward-looking remote sensing window of the oblique-flying remote sensing aircraft 13; the remote sensing device 19 is fixedly connected to the gyro-stabilized platform; the GNSS antenna is fixedly connected to the top of the oblique-flying remote sensing aircraft 13; the industrial computer 15 is fixedly connected to the floor of the oblique-flying remote sensing aircraft 13; the antenna covers 17, 18 and 38 are fixedly connected to the oblique-flying remote sensing aircraft 13; the SAR antenna is fixedly connected to the oblique-flying remote sensing aircraft 13; the SAR antenna turntable 40 is fixedly connected to the oblique-flying remote sensing aircraft 13; the GNSS receiver is fixedly connected to the industrial computer 15; the GNSS antenna is connected to the GNSS receiver via a data line; the GNSS receiver is connected to the industrial computer 15 via a data line; the industrial computer 15 is connected to the remote sensing device 19 via a data line; the industrial computer 15 is connected to the SAR antenna via a data line; the industrial computer 15 is connected to the gyro-stabilized platform via a data line.

[0128] The oblique-flying remote sensing aircraft 13 comprises a structural mounting platform, a downward-looking optical window, optical glass and a camera door, wherein the structural mounting platform is located above the downward-looking optical window, the optical glass is located on the downward-looking optical window, and the camera door is located below the optical glass.

[0129] The gyro-stabilized platform enables the remote sensing device 19 to perform remote sensing observation of the earth vertically downward from the sea level without being affected by the angular motion of the aircraft; the gyro-stabilized platform can be used to control the attitude of the remote sensing device 19;

[0130] The remote sensing equipment 19 includes sensors such as SAR, multi-spectral aerial camera, hyperspectral aerial camera, infrared aerial camera and airborne laser radar.

[0131] Among them, SAR conducts remote sensing observations of the ground by looking sideways, that is, downward at a certain angle to the ground normal; multispectral aerial cameras, hyperspectral aerial cameras, infrared aerial cameras and airborne lidar all conduct remote sensing observations of the ground by looking downward, that is, vertically downward from the sea level.

[0132] Among them, the gyro-stabilized platform is installed on the structural mounting platform; remote sensing equipment such as multi-spectral aerial cameras, hyperspectral aerial cameras, infrared aerial cameras and airborne lidar 19 are all installed on the gyro-stabilized platform, and SAR has no connection with the gyro-stabilized platform.

[0133] Among them, the radome refers to an airborne radar radome, including a left SAR radome 17, a right SAR radome 18, and a belly radome 38, wherein the belly radome 38 is arranged under the belly, and the left SAR radome 17 and the right SAR radome 18 are respectively arranged on both sides of the fuselage.

[0134] The SAR antennas include a SAR antenna on the belly of the oblique flying remote sensing aircraft 13, and SAR antennas on the left and right sides of the oblique flying remote sensing aircraft;

[0135] The SAR antenna on the belly of the oblique flying remote sensing aircraft 13 comprises a belly antenna 16, a SAR antenna turntable 40, a belly antenna mounting plate 39, and a belly radome 38. The belly antenna mounting plate 39 is mounted on the belly of the oblique flying remote sensing aircraft 13. The SAR antenna turntable 40 is mounted on the belly antenna mounting plate 39. The belly antenna 41 is mounted on the SAR antenna turntable 40. The belly radome 38 is mounted on the belly of the oblique flying remote sensing aircraft 13, and the belly antenna 16 is wrapped in the belly radome 38. The SAR antenna turntable 40 is used to control the orientation of the belly antenna 16 so that it can tilt to the left or right.

[0136] The SAR antennas on the left and right sides of the oblique flying remote sensing aircraft are symmetrically installed on the left and right sides of the belly of the oblique flying remote sensing aircraft 13. The left SAR antenna includes a left antenna 36, ​​a left antenna mounting plate 37, and a left SAR antenna cover 17. The left antenna mounting plate 37 is installed on the belly of the oblique flying remote sensing aircraft 13. The left antenna 36 is installed on the left antenna mounting plate 37. The left SAR antenna cover 17 is installed on the left side of the belly of the oblique flying remote sensing aircraft 13, and the left antenna 36 is wrapped in the left SAR antenna cover 17. The right SAR antenna includes a right antenna 44, a right antenna mounting plate 43, and a right SAR antenna cover 18. The mounting plate of the right antenna 44 is installed on the belly of the oblique flying remote sensing aircraft 13. The right antenna 44 is installed on the right antenna mounting plate 43. The right SAR antenna cover 18 is installed on the right side of the belly of the oblique flying remote sensing aircraft 13, and the right antenna 44 is wrapped in the right SAR antenna cover 18.

[0137] Among them, the SAR antenna turntable 40 includes a turntable column, a bearing 48, a fixing rod 46, a buckle 45, and an angle mark 47. The turntable column is connected to the belly antenna mounting plate 39 through the bearing 48. The belly antenna 16 is mounted on the turntable column and can rotate. The upper surface of the turntable column is provided with the angle mark 47. One end of the fixing rod 46 is fixed to the upper surface of the turntable column, and the other end of the fixing rod 46 can be fixed with the buckle 45 on the belly antenna mounting plate 39, so that the belly antenna 16 is fixed after the ground observation angle is set by the angle mark 47 on the upper surface of the turntable column.

[0138] The left SAR radome 17, the right SAR radome 18, and the belly radome 38 are all installed on the front half of the aircraft fuselage. The belly radome 38 is symmetrical with respect to the symmetry plane of the aircraft; the left SAR radome 17 and the right SAR radome 18 overlap with the effective section of the belly radome 38 in the front-to-back direction.

[0139] The SAR antenna turntable 40 is installed on the belly of the oblique flying remote sensing aircraft 13, and is used to control the azimuth of the belly SAR antenna so that it can tilt to the left or right.

[0140] There are three SAR antennas, one of which is mounted on the SAR antenna turntable 40, and the other two are respectively mounted on the left and right sides of the oblique flying remote sensing aircraft 13. The belly SAR antenna is located inside the belly radome 38, and the left and right SAR antennas are respectively located inside the left SAR radome 17 and the right SAR radome 18.

[0141] Among them, the three SAR antennas can obtain SAR data of four bands, namely, P, L, C, and X. The data obtained by the left and right SAR antennas are the same.

[0142] The GNSS antenna can receive GNSS signals and send them to a GNSS receiver. The GNSS receiver processes the GNSS signals and then outputs GNSS data to the industrial computer 15 .

[0143] The industrial computer 15 includes a control device and a display device, wherein the control device is used to control sensors such as a gyro-stabilized platform, a SAR antenna turntable 40, SAR, a multi-spectral aerial camera, a hyperspectral aerial camera, an infrared aerial camera, and an airborne laser radar; the display device is used to display maps, flight routes, aircraft flight trajectories, and aircraft position information, etc.

[0144] The industrial computer 15 can make a flight plan for the operation area of ​​aerial remote sensing, so that all remote sensing equipment 19 can perform ground remote sensing observation along the designated flight route, and the method is:

[0145] 1) Coordinate transformation

[0146] Coordinate transformation can improve the accuracy and efficiency of the system in route design, because it can process data in different coordinate systems. Currently, commonly used coordinate systems include WGS84 global coordinate system, National 2000 coordinate system, Xi'an 80 coordinate system, Beijing 54 coordinate system and local coordinate system. Different coordinate system data sometimes need to be converted. Since the nodes in the flight survey area generally use the longitude and latitude coordinates of WGS84, the longitude and latitude coordinates are not convenient for calculating the azimuth and the distance between points, lines and surfaces, while the plane coordinates are easy to calculate, so the conversion between longitude and latitude coordinates and plane rectangular coordinates is inevitable.

[0147] First, you need to use GPS to obtain the geodetic coordinates of the point (B 84 L 84 H 84 ) T , and then convert it to spatial rectangular coordinates (XYZ) according to the reference ellipsoid parameters of WGS84 using formula (1) T Then, according to the reference ellipsoid parameters of Beijing 54 or Xi'an 80 or the local independent coordinate system, (XYZ) is converted by formula (2) T Convert to geodetic coordinates (B 54 L 54 H 54 ) T or (B 80 L 80 H 80 ) T or (B local L local H local ) T Finally, according to the central meridian, the projection surface elevation and the north-east offset, (B 54 L 54 ) T or (B 80 L 80 ) T or (B local L local ) T Projection is Gaussian coordinates (X g Y g ) T .

[0148]

[0149]

[0150]

[0151] in,

[0152] X=C0B+(C2 cos B+C4 cos 3 B+C6 cos 5 B+C8 cos 7 B)sin B (4)

[0153]

[0154] t=tan B (6)

[0155]

[0156] l″=L-L0 (8)

[0157] Where, L and B are the longitude and latitude coordinates before conversion;

[0158] x, y are the transformed Gaussian coordinates;

[0159] a is the major radius of the ellipsoid, and e is the first eccentricity of the ellipsoid;

[0160] L0 is the longitude of the central meridian of the projection zone;

[0161] C0, C2, C4, C6, and C8 are constant values ​​that are only related to the ellipsoid parameters.

[0162] Using coordinate transformation in flight route design can improve the efficiency of flight strip design compared to conventional manual route design. Although manual calculation is relatively complete and stable, if the number of flight photos is too large, it will bring greater calculation intensity. At the same time, manual flight strip calculation cannot use high-precision electronic maps. Therefore, route design using coordinate transformation has obvious advantages, making the scope of the survey area clearer. The application of coordinate transformation improves the accuracy and efficiency of flight strip design, and also improves the system's ability to process various coordinate system data.

[0163] 2) Automatic route determination

[0164] Introducing buffer analysis in geographic information systems into multi-sensor-based aerial remote sensing flight management systems can simplify the amount of calculation and improve the quality of air flight to a certain extent. Buffers are polygons with a certain width range built around entities such as points, lines, and surfaces. Multi-sensor-based aerial remote sensing flight management systems can generate judgment buffers of specific shapes according to flight missions. When the system automatically shoots a predetermined area, it is necessary to judge the relative position between the aircraft and the survey area and the flight route. However, due to the complexity of the actual situation (the pilot will adjust to a suitable angle for level flight according to the airflow state), the correct judgment of the relative position of the aircraft requires many judgment conditions, and the amount of calculation required for real-time calculation is relatively large. In order to ensure the smooth operation of the system, the system needs to generate some buffers in advance to judge the relative position, so that it only needs to judge whether the aircraft is in the buffer to determine the relative position of the aircraft and the route, thereby greatly reducing the amount of calculation. When the aerial photography aircraft enters the buffer zone and meets the flight altitude restriction conditions to enter the route, it can be considered as an effective entry. When the aircraft takes pictures after entering the route, if it flies away from the predetermined route and exceeds the flight zone buffer zone, the system will give a prompt and automatically stop the shooting of the aerial sensor accordingly, thereby avoiding flight waste that does not meet the route design. Therefore, establishing a buffer zone to a certain extent can ensure the quality of the flight route.

[0165] At present, with the improvement of the accuracy of GNSS equipment, the relative position of the aircraft and the scheduled route can be determined through the feedback information of GNSS equipment, so as to make automatic judgments and perform relevant operations on aviation sensors in a timely manner.

[0166] 3) Route position calculation

[0167] First, rotate the coordinate system according to the route layout direction so that the X' axis of the rotated coordinate system is parallel to the route direction; therefore, to calculate the position of the route, it is only necessary to find the heading centerline of the survey area and the number of routes, and then other routes are laid symmetrically on both sides parallel to the heading centerline of the survey area. The ordinate of the heading centerline is:

[0168] Y′=(Y′ max +Y′ min ) / 2 (9)

[0169] Where, Y′ max , Y′ min They are respectively the maximum and minimum values ​​of the ordinate of the polygon's circumscribed rectangle in the X′Y′ coordinate system.

[0170] According to the requirements of the national standard topographic map aerial photogrammetry internal industry specifications, the lateral coverage beyond the boundary line of the shooting area is generally not less than 50% of the image frame, and at least not less than 30% of the image frame. Yis the lateral coverage width of the image frame on the ground, the designed minimum total coverage width is:

[0171] W min =Y′ max -Y′ min +2L Y (10)

[0172] Assuming the number of routes in the survey area is n, the total coverage width of all routes is:

[0173] W=((1-S)(n-1)+1)×L Y (11)

[0174] Where S is the lateral overlap rate. From formula (11), we can get n=1+(WL Y ) / (L Y -SL Y ). n must be an integer and the coverage width must be guaranteed. Round n up and add 1, that is,

[0175] n=[1+(WL Y ) / (L Y -SL Y )]+1 (12)

[0176] (The brackets in the above formula indicate rounding), let W = W min Substitute the values ​​into the formula to calculate the total number of routes that meet the requirements.

[0177] Regardless of whether n is an odd number or an even number, all routes are parallel to the center line and symmetrically distributed on both sides. Combined with the schematic diagram, the calculation formula of the ordinate of each route can be derived based on the relevant knowledge of photogrammetry:

[0178] Y′ m =(Y′ max +Y′ min ) / 2+(m-(n+1) / 2)(1-S)×L Y (13)

[0179] Wherein, m is the number of the route from bottom to top, 1≤m≤n.

[0180] 4) Exposure point coordinate calculation

[0181] For flat areas, the baseline length of the aerial photogrammetry area remains basically unchanged. Take the coordinates of the center point of the polygon in the X′ direction of the measurement area as X′0 = (X′ max +X′ min ) / 2, where X′ max and X′ min It is the maximum and minimum value of the horizontal coordinate of the circumscribed rectangle of the polygon in the X′Y′ coordinate system.

[0182] To calculate the coordinates of the exposure point on a certain route, we can first calculate the intersection of the route and the survey area polygon, and then use the center point (X′0, Y′ m ) is the starting point. Within the range of the maximum and minimum values ​​of the horizontal coordinate of the intersection point, extend the integer multiples of the photographic baseline to the left and right to obtain a series of intersection points, which are the exposure points.

[0183] X′ k =X′0±B k ×k(k=0,1,2...) (14)

[0184] Where B k is the baseline length.

[0185] If the route has no intersection with the polygon or has only one intersection, that is, the route is laid out outside the polygon of the survey area, or intersects at a node at the top or bottom of the polygon, then the center point (X′0, Y′ m ) is the starting point, at (X′ min X′ max ) interval is extended to the left and right by integer multiples of the photographic baseline to obtain a series of points. These points are taken as exposure centers in turn, and the coverage area of ​​the film on the ground is calculated. If the area overlaps with the survey area polygon, this point is used as the exposure point.

[0186] At the same time, the requirements of aerial photography specifications should be taken into consideration. The heading coverage should exceed the boundary line of the shooting area to a certain extent, such as two more baseline lengths. Therefore, a corresponding number of exposure points should be added outside the boundary.

[0187] 5) Route design based on DEM

[0188] DEM-based route design is to combine DEM with GIS, fully consider the important role of terrain factors in aerial photography route design, use DEM data as the basis, GIS as the technical support, use raster and vector graphics as the visualization background, and through mathematical operations and conditional judgment, solve the problems existing in the current actual design such as survey area division, parameter calculation and route laying, and realize high-precision and high-quality aerial photography route design.

[0189] According to the aerial photogrammetry specifications, there needs to be a certain overlap between adjacent aerial photographs to cover the survey area and facilitate subsequent stereo mapping. The overlap rate is divided into heading overlap rate and lateral overlap rate, and the formula is as follows:

[0190]

[0191] In the formula, P and Q are the heading and lateral overlap rates, respectively, x and y are the overlapping parts of the heading and lateral adjacent images, respectively, l x , l y They are the image length and width respectively.

[0192] The terrain undulation will directly affect the heading and lateral overlap rate, and its influence can be analyzed by formula (15). In addition, the terrain undulation will also cause a series of changes in the photographic baseline and photographic interval.

[0193]

[0194] Where h is the height difference relative to the mean elevation datum, H 摄 is the relative altitude of aerial photography, P and Q are the actual heading and lateral overlap rate, P′ and Q′ are the planned heading and lateral overlap rate. DEM can most effectively reflect the terrain undulations, and can quickly obtain the h value of the required point and provide fast computer calculation.

[0195] The elevation values ​​of the flight route and the main image point can be obtained from the digital elevation model by computer. According to formula (16), the change of the heading lateral overlap rate can be calculated, and then the positions of adjacent main image points and adjacent flight routes can be calculated.

[0196] For areas with undulating terrain, the influence of DEM needs to be considered. First, the actual overlap rate of the images on the average surface is calculated based on the planned heading overlap rate of the images and the photographic baseline length B is calculated. Then, the position of the next image principal point O is calculated based on the position of the image principal point and the heading overlap rate. i Similarly, the interval D of the photography routes is calculated according to the lateral overlap rate, and finally the position O of each image principal point on each other route is obtained according to the interval D of the photography routes and B. j .

[0197]

[0198]

[0199] Where: b x , B x It is the length of the photographic baseline on the film and in the field;

[0200] d x , D y The width of the flight line interval on the image and on the ground;

[0201] L x , L y is the length and width of the photographic image;

[0202] p x ,q y is the heading and lateral overlap ratio;

[0203] m 航 is the denominator of the aerial photography scale.

[0204] The industrial computer 15 can display maps, flight routes, aircraft flight tracks and aircraft position information in real time. Based on the displayed information, the onboard operator can control the timing of turning on and off the remote sensing equipment 19, so that all remote sensing equipment 19 can synchronously perform remote sensing observation of the ground. The method is:

[0205] 1) Load and display the electronic map of administrative divisions;

[0206] 2) Load the flight plan file to display the flight route on the electronic map;

[0207] 3) Obtain the longitude and latitude coordinates and time information of the aircraft through the GNSS receiver, convert the longitude and latitude coordinates into plane rectangular coordinates corresponding to the electronic map, and display the aircraft position on the electronic map;

[0208] 4) Display aircraft symbols - obtain the current aircraft location; call the symbol library; define symbol objects, set properties; draw symbol objects;

[0209] 5) Dynamic display of aircraft flight trajectory - the coordinate points of the aircraft arranged in time series form line segments, and the line segments representing the aircraft's movement trajectory are drawn through the map control DrawShape function.

[0210] 6) The onboard operator determines the time when the aircraft enters the route according to the aircraft position, flight route and flight trajectory, and uses the industrial computer 15 to turn on the remote sensing device 19; determines the time when the aircraft leaves the route, and uses the industrial computer 15 to turn off the remote sensing device 19.

[0211] Among them, the observation mode of the SAR is side-view, and the range of the angle between the incident beam of its antenna and the ground normal is set to 30°-60°, that is, the sampling angle range of the incident beam of the left SAR antenna is -30°--60°, and the sampling angle range of the incident beam of the right SAR antenna is set to 30°-60°; while the observation mode of other remote sensing devices 19 is downward-view, and the range of the angle between the incident beam of its sensor head and the ground normal is set to -30°-30°, that is, the sampling angle range of the incident beam is -30°-30°. It can be seen that the ground observation range of the side-view remote sensing device 19 and the downward-view remote sensing device 19 under the same conditions is different. In order to ensure that the ground observation range of all remote sensing devices 19 is consistent, the following method is adopted:

[0212] 1) Open the gyro-stabilized platform control software in the industrial computer 15, click "Communication Settings", and set the angle parameters. The range of the roll angle is set to: -30°-+30°; the range of the pitch angle is set to: -8°-+6°; the range of the yaw angle is set to: -30°-+30°;

[0213] 2) Determine the lateral overlap rate between 50% and 75% according to the mission situation, make a flight plan, and generate a flight route; display the map, flight route, aircraft flight track, and aircraft position information in the industrial computer 15;

[0214] 3) When the first route 1 of the aircraft is located at the westernmost or southernmost part of the operation area, the pilot is notified to tilt the oblique remote sensing aircraft 13 around the longitudinal axis of the aircraft 30° to the lower left, and keep flying along the first route 1 in this state. At this time, the gyro-stabilized platform will automatically correct the roll angle so that the remote sensing equipment 19 on the platform maintains a downward-looking ground observation state;

[0215] 4) Open the SAR antenna turntable 40 control software in the industrial computer 15, set the turntable to tilt to the lower left, and set the sampling angle range of the SAR antenna incident beam on the turntable to -30°--60°. At this time, the sampling angle range of the incident beam of the belly SAR antenna and the left SAR antenna is both -30°-0°;

[0216] 5) When the aircraft displayed on the industrial computer 15 enters the flight route, all remote sensing devices 19 are turned on, and when the aircraft maintains this state and flies out of the route, all remote sensing devices 19 are turned off;

[0217] 6) The oblique remote sensing aircraft 13 turns and prepares to fly the second route. The pilot is notified to tilt the oblique remote sensing aircraft 13 30° to the lower right around the longitudinal axis of the aircraft and keep flying along the second route 5. At this time, the gyro-stabilized platform will automatically correct the roll angle so that the remote sensing equipment 19 on the platform maintains a downward-looking ground observation state;

[0218] 7) Open the SAR antenna turntable 40 control software in the industrial computer 15, set the turntable to tilt to the lower right, and set the sampling angle range of the SAR antenna incident beam on the turntable to 30°-60°. At this time, the sampling angle range of the incident beam of the belly SAR antenna and the right SAR antenna is 0°-30°;

[0219] 8) When the aircraft displayed on the industrial computer 15 enters the flight route, all remote sensing devices 19 are turned on, and when the aircraft maintains this state and flies out of the route, all remote sensing devices 19 are turned off;

[0220] 9) Repeat steps 3)-8) until all routes in the operating area are flown and the flight mission is completed.

[0221] 10) When the first route 1 of the aircraft is located at the easternmost or northernmost part of the operation area, the pilot is notified to tilt the oblique remote sensing aircraft 13 around the longitudinal axis of the aircraft 30° to the lower right, and keep flying along the first route 1 in this state. At this time, the gyro-stabilized platform will automatically correct the roll angle so that the remote sensing equipment 19 on the platform maintains a downward-looking ground observation state;

[0222] 11) Open the SAR antenna turntable 40 control software in the industrial computer 15, set the turntable to tilt to the lower right, and set the sampling angle range of the SAR antenna incident beam on the turntable to 30°-60°. At this time, the sampling angle range of the incident beam of the belly SAR antenna and the right SAR antenna is 0°-30°;

[0223] 12) When the aircraft displayed on the industrial computer 15 enters the flight route, all remote sensing devices 19 are turned on. When the aircraft maintains this state and flies out of the route, all remote sensing devices 19 are turned off;

[0224] 13) The oblique remote sensing aircraft 13 turns and prepares to fly the second route 5. The pilot is notified to tilt the oblique remote sensing aircraft 13 30° to the lower left around the longitudinal axis of the aircraft and keep flying along the second route 5. At this time, the gyro-stabilized platform will automatically correct the roll angle so that the remote sensing equipment 19 on the platform maintains a downward-looking ground observation state;

[0225] 14) Open the SAR antenna turntable 40 control software in the industrial computer 15, set the turntable to tilt to the lower left, and set the sampling angle range of the incident beam of the SAR antenna on the turntable to -30°--60°. At this time, the sampling angle range of the incident beam of the belly SAR antenna and the left SAR antenna is both -30°-0°;

[0226] 15) When the aircraft displayed on the industrial computer 15 enters the flight route, all remote sensing devices 19 are turned on, and when the aircraft maintains this state and flies out of the route, all remote sensing devices 19 are turned off;

[0227] 16) Repeat steps 10)-15) until all routes in the operation area are flown, thus completing the flight mission.

[0228] Among them, the range of the angle between the incident beam of the SAR antenna and the ground normal can also be set to other ranges, not limited to 30°-60°, but can also be 20°-50° or 25°-55°, etc., and the length of the range interval is less than 40°; the side-view remote sensing equipment 19 is not limited to SAR, and other side-view remote sensing equipment 19 such as oblique photography aerial cameras are also applicable.

[0229] Among them, the distance resolution of the remote sensing equipment 19SAR is:

[0230]

[0231] Where τ is the pulse width of the SAR, C is the speed of light, and θ is the SAR antenna incident beam side view.

[0232] According to the above method, θ changes from ±45° to ±15°, which will cause ΔR to become larger, that is, the distance resolution is reduced. In order to ensure that the distance resolution is not reduced, the linear frequency modulation technology can be used to modulate the wider pulse into a pulse with large amplitude and narrow width, that is, to reduce τ, thereby ensuring that the distance resolution is not reduced. The method is:

[0233] The harmonic is modulated by linear frequency to produce a linear frequency modulated pulse, and then the pulse is transmitted. After receiving the echo, the pulse is passed through a matching filter with opposite frequency characteristics in frequency and time relationship to those during transmission. The received low-frequency echo is first delayed by a large amount on the filter, and then the high-frequency echo is delayed by a small amount, thereby extracting the received pulse signal in a narrower width and larger amplitude form.

[0234] Within the pulse width, the instantaneous frequency is linearly proportional to f min Change to f max , FM bandwidth Δf = f max -f min The envelope of the waveform function generated by the matched filter (the envelope is a graph formed by many elliptical curves interwoven, and looks like it is wrapped. The envelope has its own unique meaning in mathematics, signal processing, literature, economics, and traditional Chinese medicine) is The main lobe of the waveform is large, the side lobes are small, and the half-power width is That is, the compressed pulse width τ0, so the pulse width is compressed to the original The larger Δf is, the smaller the compressed pulse width is, the smaller ΔR is, and the higher the distance resolution is.

[0235] Among them, f min is the minimum instantaneous frequency, f max is the maximum instantaneous frequency; sinc is the Sinker function,

[0236] Among them, when the sampling angle range of the incident beam of the left SAR antenna in step 4) is -30°-0°, the corresponding sampling angle range of the incident beam of the right SAR antenna becomes 60°-90°, that is, the side viewing angle of the incident beam of the right SAR antenna is 75°. According to the principle of trigonometric function, when the sampling angle changes from 30° to 60°, the corresponding ground coverage changes from H tan 30° to H tan 60°.

[0237] Where H is the relative altitude of the aircraft, tan 90°=∞, it can be calculated that the ground coverage is 3 times the original. If the coverage corresponding to the sampling angle -30°-30° is the nth route 30 in the flight plan, then the coverage corresponding to the sampling angle 60°-90° is the (3+n)th to nth routes 30 in the flight plan, which is equivalent to obtaining the data corresponding to these routes in advance; at the same time, according to the above method, the side viewing angle of the incident beam of the right SAR antenna changes from 45° to 75°, which improves the distance resolution of the remote sensing data corresponding to the (3+n)th to nth routes 30 (according to the previous steps, SAR data obtains half a line less than other remote sensing equipment 19, which can not only make up for the lack of lines, but also fly a wider range than other remote sensing equipment 19 and ensure the distance resolution). Similarly, step 7), step 11) and step 14) all have the characteristics of step 4).

[0238] The present invention adopts a special flight method during the flight and controls different devices through the industrial computer 15, so that different types of sensors can realize coaxial remote sensing, that is, realize ground observation of the same surface area in the same space-time environment, reduce redundant flights, improve the work efficiency of aerial remote sensing, and can complete aerial remote sensing tasks based on multiple sensors faster and more conveniently.

[0239] The present invention can complete remote sensing monitoring tasks faster and more conveniently than traditional aerial remote sensing, and can obtain two results: 1) multi-source remote sensing data results; 2) coaxial remote sensing data results. Therefore, work efficiency is improved.

[0240] Co-axial remote sensing: refers to the use of multiple different types of sensors to achieve remote sensing earth observation of the same area in the same space-time environment.

[0241] Oblique flying remote sensing aircraft: a remote sensing aircraft with the ability to fly obliquely. This aircraft can fly at a certain angle around the longitudinal axis of the aircraft without malfunctioning, while ensuring that the pilot's seat, crew seats, and equipment and instruments on board are fixed.

[0242] Gyro-stabilized platform: abbreviated as gyro platform or inertial platform, is a device that uses the characteristics of a gyroscope to maintain the stability of the platform's orientation.

[0243] Positioning and orientation system: The Positioning and Orientation System (POS) integrates DGPS (Differential GPS) technology and Inertial Navigation System (INS) technology. It can obtain the spatial position and three-axis attitude information of moving objects and is widely used in the navigation and positioning of aircraft, ships and missiles.

[0244] IMU: A device that measures the three-axis attitude angle and acceleration of an object. Generally, an IMU includes a three-axis gyroscope and a three-axis accelerometer. Some 9-axis IMUs also include a three-axis magnetometer.

[0245] GNSS: The full name of GNSS is Global Navigation Satellite System, which refers to all satellite navigation systems, including global, regional and enhanced, such as the United States' GPS, Russia's Glonass, Europe's Galileo, China's BeiDou Satellite Navigation System, and related enhancement systems, such as the United States' WAAS (Wide Area Augmentation System), Europe's EGNOS (European Geostationary Navigation Overlay System) and Japan's MSAS (Multifunctional Transport Satellite Augmentation System), etc., also covers other satellite navigation systems under construction and to be built in the future.

[0246] PWM: Pulse Width Modulation. Pulse Width Modulation is an analog control method that modulates the bias of the transistor base or MOS gate according to the change of the corresponding load to achieve the change of the transistor or MOS tube conduction time, thereby achieving the change of the output of the switching regulated power supply.

[0247] TNC: An antenna interface.

[0248] BNC: A connector for coaxial cable.

[0249] FMS: Short for Flight Management System.

[0250] RS-232: One of the commonly used serial communication interface standards, it was jointly developed by the American Electronics Industries Association (EIA) in conjunction with Bell System, modem manufacturers and computer terminal manufacturers in 1970. Its full name is "Technical Standard for Serial Binary Data Exchange Interface between Data Terminal Equipment (DTE) and Data Communications Equipment (DCE)".

[0251] COM: Serial communication port, also known as serial port.

[0252] LPT: Line print terminal, a parallel communication port used to connect a printer or scanner.

[0253] Obviously, the above embodiments of the present invention are merely examples for clearly explaining the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all implementation methods here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. An aerial coaxial remote sensing device based on multiple sensors, It is characterized in that include: Oblique flying remote sensing aircraft, gyro-stabilized platform, remote sensing equipment, industrial computer, radome, SAR antenna, SAR antenna turntable, GNSS antenna, GNSS receiver; The gyro-stabilized platform is fixedly connected to the downward-looking remote sensing window of the oblique-flying remote sensing aircraft, the remote sensing device is fixedly connected to the gyro-stabilized platform, the GNSS antenna is fixedly connected to the top of the oblique-flying remote sensing aircraft, the industrial computer is fixedly connected to the floor of the oblique-flying remote sensing aircraft, the radome is fixedly connected to the belly and side of the oblique-flying remote sensing aircraft, the SAR antenna is respectively fixedly connected to the side of the oblique-flying remote sensing aircraft and the SAR antenna turntable, the SAR antenna turntable is fixedly connected to the belly of the oblique-flying remote sensing aircraft, the GNSS receiver is fixedly connected to the industrial computer, the GNSS antenna is connected to the GNSS receiver via a data line, the GNSS receiver is connected to the industrial computer via a data line, the industrial computer is connected to the remote sensing device via a data line, the industrial computer is connected to the SAR antenna via a data line, and the industrial computer is connected to the gyro-stabilized platform via a data line; The angle between the horizontal axis of the oblique flying remote sensing aircraft and the plane parallel to the sea level is , the incident beam of the SAR antenna deviates with the inclination of the obliquely flying remote sensing aircraft, and the angle between the incident beam emitted by the SAR antenna and the ground normal is ; The oblique-flying remote sensing aircraft comprises a structural mounting platform, a downward-looking optical window, optical glass and a photographic cabin door, wherein the structural mounting platform is located above the downward-looking optical window, the optical glass is located on the downward-looking optical window, and the photographic cabin door is located below the optical glass; The relative position of the oblique-flying remote sensing aircraft and the planned route is determined by the feedback information of the GNSS equipment.

2. The multi-sensor based aerial coaxial remote sensing device according to claim 1, It is characterized in that The remote sensing equipment includes sensors of SAR, multispectral aerial camera, hyperspectral aerial camera, infrared aerial camera and airborne laser radar; The multi-spectral aerial camera, the hyperspectral aerial camera, the infrared aerial camera and the airborne laser radar sensors are all mounted on the gyro-stabilized platform. When the oblique-flying remote sensing aircraft tilts, the gyro-stabilized platform is adjusted to be vertical to the sea level downward to perform ground remote sensing observation, thereby forming downward-looking ground remote sensing observation without being affected by the angular motion of the aircraft. The SAR is installed separately from the gyro-stabilized platform and performs ground remote sensing observation by side viewing.

3. The multi-sensor based aerial coaxial remote sensing device according to claim 1, It is characterized in that The gyro-stabilized platform is mounted on the structural mounting platform and is used to control the attitude of the remote sensing device; The SAR antennas include a SAR antenna on the belly of the oblique flying remote sensing aircraft, and SAR antennas on the left and right sides of the oblique flying remote sensing aircraft; The SAR antenna on the belly of the oblique flying remote sensing aircraft comprises a belly antenna, a SAR antenna turntable, a belly antenna mounting plate, and a belly radome, wherein the belly antenna mounting plate is mounted on the belly of the oblique flying remote sensing aircraft, the SAR antenna turntable is mounted on the belly antenna mounting plate, the belly antenna is mounted on the SAR antenna turntable, the belly radome is mounted on the belly of the oblique flying remote sensing aircraft, and the belly antenna is wrapped in the belly radome, and the SAR antenna turntable is used to control the azimuth of the belly antenna so that it can tilt left or right; The SAR antennas on the left and right sides of the oblique flying remote sensing aircraft are symmetrically installed on the left and right sides of the belly of the oblique flying remote sensing aircraft, the left SAR antenna includes a left antenna, a left antenna mounting plate, and a left SAR radome, the left antenna mounting plate is installed on the belly of the oblique flying remote sensing aircraft, the left antenna is installed on the left antenna mounting plate, the left SAR radome is installed on the left side of the belly of the oblique flying remote sensing aircraft, and the left antenna is wrapped in the left SAR radome, the right SAR antenna includes a right antenna, a right antenna mounting plate, and a right SAR radome, the right antenna mounting plate is installed on the belly of the oblique flying remote sensing aircraft, the right antenna is installed on the right antenna mounting plate, the right SAR radome is installed on the right side of the belly of the oblique flying remote sensing aircraft, and the right antenna is wrapped in the right SAR radome; Among them, the SAR antenna turntable includes a turntable column, a bearing, a fixing rod, a buckle, and an angle mark. The turntable column is connected to the belly antenna mounting plate through the bearing. The belly antenna is mounted on the turntable column and can rotate. The upper surface of the turntable column is provided with the angle mark. One end of the fixing rod is fixed to the upper surface of the turntable column, and the other end of the fixing rod can be fixed with the buckle on the belly antenna mounting plate, so that the belly antenna is fixed after the ground observation angle is set by the angle mark on the upper surface of the turntable column.

4. An aerial coaxial remote sensing method based on the multi-sensor based aerial coaxial remote sensing device according to claim 1, It is characterized in that The industrial computer can prepare a flight plan for an oblique-flying remote sensing aircraft for an aerial remote sensing operation area, so that all remote sensing equipment on the oblique-flying remote sensing aircraft can perform ground remote sensing observation along a designated flight route. The method includes: Step 1: First use GPS to obtain the geodetic coordinates of the point , and then converted to spatial rectangular coordinates using formula (1) based on the reference ellipsoid parameters of WGS84 , and then according to the reference ellipsoid parameters of Beijing 54 or Xi'an 80 or local independent coordinate system, the formula (2) is used to convert Convert to geodetic coordinates or or Finally, according to the central meridian, the projection surface elevation and the north-east offset, the formula (3) is used to convert or or Projection to Gaussian coordinates ; （1） （2） （3） in, （4） （5） （6） （7） （8） in, , are the latitude and longitude coordinates before conversion; H is the elevation, , is the transformed Gaussian coordinate, is the major radius of the ellipsoid, is the first eccentricity of the ellipsoid, is the longitude of the central meridian of the projection zone, , , , , is a constant value related only to the ellipsoid parameters; Step 2: Generate a buffer zone to determine the relative position. When the oblique remote sensing aircraft enters the buffer zone and meets the flight altitude restriction condition to enter the route, it is considered to be effectively entered. When the oblique remote sensing aircraft takes pictures after entering the route, if it flies off the scheduled route and exceeds the flight zone buffer zone, the system will give a prompt and automatically stop the shooting of the aviation sensor accordingly, thereby avoiding flight waste that does not meet the route design; Step 3: First, rotate the coordinate system according to the route layout direction so that the rotated coordinate system The axis is parallel to the route direction. To calculate the position of the route, you only need to find the heading centerline of the survey area and the number of routes. Then other routes are laid symmetrically on both sides parallel to the heading centerline of the survey area. The ordinate of the heading centerline is: （9） In the formula, , They are The maximum and minimum values ​​of the ordinate of the polygon's circumscribed rectangle in the coordinate system; According to the requirements of the national standard topographic map aerial photogrammetry internal specifications, the lateral coverage beyond the boundary line of the shooting area shall be no less than 50% of the image frame, and at least no less than 30% of the image frame; is the lateral coverage width of the image frame on the ground, the designed minimum total coverage width is: （10） The number of routes in the measurement area is , then the total coverage width of all routes is: （11） In the formula is the lateral overlap ratio; calculated from formula (11): ; Must be an integer and ensure coverage width. Round up and add 1, that is （12） The brackets in the above formula indicate rounding. Substitute in and calculate the total number of routes that meet the requirements; According to the relevant knowledge of photogrammetry, the calculation formula of the ordinate of each route is derived: （13） In the formula, The route is numbered from bottom to top. ; Step 4: For flat areas, the baseline length of the aerial photogrammetry area remains unchanged; take the polygon of the measurement area Center point coordinates of the direction ,in, and for The maximum and minimum values ​​of the horizontal coordinates of the circumscribed rectangle of the polygon in the coordinate system; Calculate the coordinates of the exposure points on the preset route, first calculate the intersection of the route and the measurement area polygon, and then use the center point As the starting point, within the range of the maximum and minimum values ​​of the horizontal coordinate of the intersection point, extend the integer multiples of the photographic baseline to the left and right respectively to obtain a series of intersection points, which are the exposure points; （14） In the formula is the baseline length; If the route has no intersection with the polygon or has only one intersection, the route is laid out outside the polygon of the survey area, or intersects at a node at the top or bottom of the polygon. As the starting point, Extend the integer multiples of the photographic baseline to the left and right within the interval to obtain a series of points. These points are taken as exposure centers in turn to calculate the coverage area of ​​the film on the ground. If the area overlaps with the measurement area polygon, the point is used as the exposure point. Step 5: According to the aerial photogrammetry specifications, adjacent aerial photographs need to overlap to cover the survey area and facilitate subsequent stereo mapping. The overlap rate is divided into heading overlap rate and lateral overlap rate. The formula is as follows: （15） In the formula, , are the heading and lateral overlap rates, , are the overlapping parts of the heading and lateral adjacent images, , are image length and width respectively; The terrain undulation will directly affect the heading and lateral overlap rate, and its influence can be analyzed by formula (15). In addition, the terrain undulation will also cause a series of changes in the photographic baseline and photographic interval. （16） In the formula is the height difference relative to the mean elevation datum, is the relative altitude of aerial photography, , is the actual heading and lateral overlap rate, , is the planned heading and lateral overlap ratio; The elevation values ​​of the flight route and the main image point can be obtained from the digital elevation model by computer. According to formula (16), the change of the heading lateral overlap rate is calculated, and then the positions of the adjacent main image points and the adjacent flight routes are calculated; For areas with undulating terrain, first calculate the actual overlap rate of the images on the average surface based on the planned heading overlap rate of the images and calculate the photographic baseline length. Then, the position of the next image principal point is calculated based on the position of the image principal point and the heading overlap rate. ; Similarly, the photography flight interval is calculated based on the lateral overlap rate Finally, according to the interval of the photography route as well as Find the position of each image principal point on other routes ; （17） （18） Where: , is the photographic baseline length on the film and on the ground, , is the route spacing width on the image and on the ground, , are the length and width of the photographic image, , is the heading and lateral overlap ratio, is the denominator of the aerial photography scale.

5. The multi-sensor based aerial coaxial remote sensing method according to claim 4, It is characterized in that in, Load and display the electronic map of administrative divisions; Load the flight plan file to display the flight route on the electronic map; The latitude and longitude coordinates and time information of the oblique-flying remote sensing aircraft are obtained through a GNSS receiver, and the latitude and longitude coordinates are converted into plane rectangular coordinates corresponding to an electronic map, so that the position of the oblique-flying remote sensing aircraft can be displayed on the electronic map; Get the current position of the oblique flying remote sensing aircraft, call the symbol library, and display the oblique flying remote sensing aircraft symbol; The coordinate points of the oblique-flying remote sensing aircraft arranged in time series form line segments, and the line segments representing the motion trajectory of the oblique-flying remote sensing aircraft are drawn through the map control DrawShape function; The onboard operator determines the time when the oblique flying remote sensing aircraft enters the route based on the aircraft position, flight route and flight trajectory of the oblique flying remote sensing aircraft, and uses the industrial computer to turn on the remote sensing equipment; determines the time when the oblique flying remote sensing aircraft leaves the route, and uses the industrial computer to turn off the remote sensing equipment.

6. The multi-sensor based aerial coaxial remote sensing method according to claim 4, It is characterized in that in The SAR observation method is to perform side-view remote sensing observation of the ground, and the range of the angle between the incident beam of the SAR antenna and the ground normal is set to , where the sampling angle range of the incident beam of the left SAR antenna is , the sampling angle range of the incident beam of the right SAR antenna is set to ; The observation mode of the multispectral aerial camera, hyperspectral aerial camera, infrared aerial camera and airborne laser radar remote sensing equipment on the gyro-stabilized platform is downward looking. The range of the angle between the incident beam of the multispectral aerial camera, hyperspectral aerial camera, infrared aerial camera and airborne laser radar remote sensing equipment and the ground normal is set to , the sampling angle range of the incident beam is ; To ensure that the Earth observation range of SAR and other remote sensing equipment is consistent, the following methods and steps are taken: 1) Open the gyro stabilized platform control software in the industrial computer, click "Communication Settings", and set the angle parameters. The range of the roll angle is set to: ; The range of pitch angle is set to: ; The range of the declination angle is set to: ; 2) According to the task plan setting Determine the lateral overlap rate, make a flight plan and generate a flight route according to this requirement; display the map, flight route, aircraft flight track and aircraft position information on the industrial computer according to this requirement; 3) When the first route 1 of the aircraft is located at the westernmost or southernmost part of the operation area, notify the pilot to tilt the oblique remote sensing aircraft to the lower left around the longitudinal axis of the aircraft. , forming a downward left tilt The remote sensing aircraft is tilted and kept flying along the first route 1. At this time, the gyro-stabilized platform will automatically correct the roll angle so that the remote sensing equipment on the gyro-stabilized platform can keep looking down to observe the ground. 4) Open the SAR antenna turntable control software in the industrial computer, set the turntable to tilt to the lower left, and set the sampling angle range of the SAR antenna incident beam on the turntable to ; At this time, the sampling angle range of the incident beam of the belly SAR antenna and the left SAR antenna is ; 5) When the oblique flying remote sensing aircraft displayed on the industrial computer enters the flight route, turn on all remote sensing equipment. When the oblique flying remote sensing aircraft maintains this state and flies out of the route, turn off all remote sensing equipment and resume the oblique flying remote sensing aircraft's parallel flight; 6) The oblique remote sensing aircraft turns and prepares to fly the second route 5, notifying the pilot to tilt the oblique remote sensing aircraft around the aircraft's longitudinal axis to the lower right. , forming a downward right tilt The remote sensing aircraft is tilted and kept flying along the second route 5. At this time, the gyro-stabilized platform will automatically correct the roll angle so that the remote sensing equipment on the gyro-stabilized platform can keep looking down to observe the ground. 7) Open the SAR antenna turntable control software in the industrial computer, set the turntable to tilt to the lower right, and set the sampling angle range of the SAR antenna incident beam on the turntable to At this time, the sampling angle ranges of the incident beams of the belly SAR antenna and the right SAR antenna are both ; 8) When the aircraft displayed on the industrial computer enters the flight route, all remote sensing devices are turned on. When the oblique flying remote sensing aircraft maintains this state and flies out of the route, all remote sensing devices are turned off and the oblique flying remote sensing aircraft resumes parallel flight; 9) Repeat steps 3) to 8) until all routes in the operation area are completed and the flight mission is completed; 10) When the first route 1 of the aircraft is located at the easternmost or northernmost part of the operation area, notify the pilot to tilt the remote sensing aircraft around the longitudinal axis of the aircraft to the lower right. , forming a downward right tilt The remote sensing aircraft is tilted and kept flying along the first route 1. At this time, the gyro-stabilized platform will automatically correct the roll angle so that the remote sensing equipment on the gyro-stabilized platform can keep looking down to observe the ground. 11) Open the SAR antenna turntable control software in the industrial computer, set the turntable to tilt to the lower right, and set the sampling angle range of the SAR antenna incident beam on the turntable to ; At this time, the sampling angle range of the incident beam of the belly SAR antenna and the right SAR antenna is ; 12) When the aircraft displayed on the industrial computer enters the flight route, all remote sensing devices are turned on. When the oblique remote sensing aircraft maintains this state and flies out of the route, all remote sensing devices are turned off and the oblique remote sensing aircraft resumes parallel flight; 13) The oblique remote sensing aircraft turns and prepares to fly the second route 5. Inform the pilot to tilt the oblique remote sensing aircraft around the aircraft's longitudinal axis to the lower left. , forming a downward left tilt The remote sensing aircraft is tilted and kept flying along the second route 5. At this time, the gyro-stabilized platform will automatically correct the roll angle so that the remote sensing equipment on the gyro-stabilized platform can keep looking down to observe the ground. 14) Open the SAR antenna turntable control software in the industrial computer, set the turntable to tilt to the lower left, and set the sampling angle range of the SAR antenna incident beam on the turntable to At this time, the sampling angle range of the incident beam of the belly SAR antenna and the left SAR antenna is ; 15) When the aircraft displayed on the industrial computer enters the flight route, all remote sensing equipment is turned on. When the oblique remote sensing aircraft maintains this state and flies out of the route, all remote sensing equipment is turned off and the oblique remote sensing aircraft resumes parallel flight; 16) Repeat steps 10) to 15) until all routes in the operation area are flown and the flight mission is completed.

7. The multi-sensor based aerial coaxial remote sensing method according to claim 4, It is characterized in that The distance resolution of the remote sensing device SAR is: （19） in, is the pulse width of the SAR, is the speed of light, is the SAR antenna incident beam side viewing angle; The harmonic is subjected to linear frequency modulation to generate a linear frequency modulation pulse, and then the pulse is transmitted. After receiving the echo, the pulse is passed through a matching filter having opposite frequency characteristics in terms of frequency and time as those during transmission, so that the delay of the received low-frequency echo in the filter is first made greater than the delay of the high-frequency echo, thereby extracting the received pulse signal in the form of reduced pulse width and increased pulse amplitude; Within the pulse width, the instantaneous frequency is linearly determined by Change to , FM bandwidth ; The envelope of the waveform function generated by the echo after the matched filter is , the main lobe of the waveform is larger than the side lobe, and the half-power width is , that is, the compressed pulse width , so the pulse width is compressed to the original ,and The larger it is, the smaller the compressed pulse width is. The smaller it is, the higher the distance resolution; in, is the minimum instantaneous frequency, is the maximum instantaneous frequency; is the Symle function, .

8. The multi-sensor based aerial coaxial remote sensing method according to claim 4, It is characterized in that When the sampling angle range of the incident beam of the left SAR antenna is When , the corresponding sampling angle range of the incident beam of the right SAR antenna becomes , the side viewing angle of the incident beam of the right SAR antenna is ; According to the principle of trigonometric function, when the sampling angle is becomes When , the corresponding ground coverage is become ; in, is the relative altitude of the aircraft, , , .

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