A flight guidance method based on synthetic vision

Abstract

The present invention relates to a flight guidance method based on synthetic vision. First, this method uses multi-source detection images, attitude data, and terrain data of a helicopter to generate a three-dimensional geographical environment, performs real-time calculation in combination with helicopter waypoints and flight routes, extracts the synthetic vision range and conducts information simulation. Then, it comprehensively processes the terrain database and multi-source avionics data to generate terrain and obstacle warning prompts and superimposes them on the vision for display. In the near-ground and landing phases, by identifying threats such as close-range terrain obstacles and long-range terrain conflicts, it provides clear and easy-to-understand vision image output and reliable flight indication information. This method has the characteristics of high calculation efficiency, strong versatility, and easy implementation.

Description

Technical Field

[0001] The present invention belongs to the field of helicopter visual flight guidance applications, and particularly relates to a flight guidance method based on synthetic vision, which is particularly suitable for the comprehensive display of battlefield environments, warning of dangerous terrains and obstacles in complex visual environments. Background Art

[0002] In response to the need of helicopter pilots to enhance the perception of external threats and the ability of safe driving in complex terrains and harsh visual environments, based on the built-in synthetic vision database, multi-source detection images, attitude data and landscape data of the helicopter are used for matching to generate a three-dimensional geographical environment. Combined with the helicopter's waypoints and flight routes, real-time calculations are performed to drive the simulation of synthetic vision information, and to complete the warning prompt of terrain obstacles and the output of flight visualization guidance symbols. Especially in the near-ground stage, through the identification of threats such as close-range terrain obstacles and long-range terrain conflicts, clear and easy-to-understand visual images and reliable flight indication information are provided to assist the pilot in avoiding threats and driving safely. From the actual situation, there has been no such research yet, and the application of the method using synthetic vision generation in the flight guidance of the front cabin of a helicopter is still blank. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to avoid the deficiencies in the above background art and provide a flight guidance method based on synthetic vision. The present invention has high calculation efficiency, strong versatility and is easy to implement, and can be used to reduce the flight operation load of a helicopter in a complex visual field environment and improve the level of safe driving.

[0004] The technical problem to be solved by the present invention is realized by the following technical solutions:

[0005] A flight guidance method based on synthetic vision, comprising the following steps:

[0006] Step 1, before takeoff, the on-board three-dimensional engine loads the synthetic vision database and the helicopter flight route, pre-reads the surrounding terrain data within a fixed range of the current coordinates of the helicopter and stores it in memory, and generates a synthetic vision of the three-dimensional image in front of the pilot's basic perspective;

[0007] Step 2, during the flight of the aircraft, obtain the helicopter position and attitude data and the pilot's helmet orientation information, calculate the pilot's navigation field of view range in real time, update the synthetic vision generated in Step 1 based on the navigation field of view range, and superimpose safety level colors on the terrain data in the synthetic vision to identify the threat level to the helicopter flight altitude;

[0008] Step 3, according to the pilot's navigation field of view range processed in Step 2, perform image registration and obstacle recognition on the helicopter multi-source sensor data, extract the obstacle model and geographical data, and perform matching, fusion loading and rendering in the synthetic vision;

[0009] Step 4: Calculate the minimum flight segment data in front of the helicopter based on the helicopter flight route data and the current position and attitude of the helicopter loaded in Step 1, and perform visual warning processing based on the flight warning envelope model;

[0010] Step 5: Generate corresponding safe flight path information and overlay and display it in the form of a layer in the integrated vision window;

[0011] Step 6: Generate a set of safe driving guidance symbols in the low-altitude flight scene, dynamically calculate the segmented paths within the time period of flying along the expected track, and generate supporting safe operation guidance symbols to indicate and guide the pilot to drive safely;

[0012] Step 7: Based on the current track position and attitude of the helicopter and the flight route, continue to execute Step 2 - Step 6 until a safe landing is achieved, realizing the low-altitude guidance for the entire flight process.

[0013] Further, Step 1 specifically includes the following steps:

[0014] Step 101: Before takeoff, the on-board 3D engine loads the integrated vision database and the helicopter flight route; with the coordinates of the center point of the departure airport as the center, extract the terrain data and tall building models within a set range to complete the initialization display of the vision;

[0015] Step 102: Prefetch 8 pieces of terrain data of the same range around the set vision area and store them in memory;

[0016] Step 103: Initialize the basic perspective information of the pilot in the front cabin of the helicopter based on the coordinates of the aircraft at the airport parking point and the fuselage orientation;

[0017] Step 104: Based on the basic perspective information of the pilot, the on-board 3D engine loads the integrated vision viewpoint data, and loads the terrain, ground object models, and atmospheric lighting data to generate a 3D image integrated vision in front of the basic perspective of the pilot.

[0018] Further, Step 2 specifically includes the following steps:

[0019] Step 201: During flight, receive the on-board bus data to obtain the helicopter position and attitude data and the pilot's helmet orientation information;

[0020] Step 202: Based on the obtained helicopter position and attitude data and the pilot's helmet orientation information, calculate the pilot's navigation field of view direction and range data in real time. When the vision boundary is about to exceed the current vision range, load the pre-fetched surrounding terrain data into the vision window, and at the same time delete the pre-fetched terrain data that has been displayed, so that the data exchange during real-time rendering only occurs in memory, improving the rendering speed;

[0021] Step 203: Update the integrated visual scene display range and viewpoint information based on the navigation field of view direction and range;

[0022] Step 204: Calculate the height difference ΔH1 between all terrain heights within the integrated visual scene display range and the height of the carrier aircraft:

[0023] Step 205: Determine the value range of ΔH1, and use OpenGL shaders to display the terrain in each interval within the integrated visual scene with different safety level colors superimposed;

[0024] Step 206: Based on Step 204, if the value of ΔH1 is less than 0m, it is defined as the threat level, and 50% red is used for interpolation coloring; if the value of ΔH1 is within the interval [0m, 50m), it is defined as the danger level, and 50% yellow is used for interpolation coloring; if the value of ΔH1 is within the interval [50m, 100m), it is defined as the warning level, and 25% yellow is used for interpolation coloring; if the value of ΔH1 is within the interval [100m, 200m), it is defined as the pay attention to safety level, and 25% green is used for interpolation coloring; if the value of ΔH1 is greater than 200m, it is defined as the safety level, and the terrain texture of the integrated visual scene database itself is used;

[0025] Step 207: The airborne 3D engine performs matching rendering on the preset integrated visual scene database according to Steps 204 - 206 to realize visual information on potential dangers to helicopter flight marked by levels.

[0026] Furthermore, Step 3 specifically includes the following steps:

[0027] Step 301: According to the payload parameters of the airborne optical sensor and the pilot's navigation field of view range, perform image denoising, registration, and pixel-level fusion on low-light, infrared, and visible light to generate a fused optical image;

[0028] Step 302: Adopt an intelligent algorithm based on the VGG19 network to fuse the fused optical image with the airborne radar image and radar data, detect, identify, and color-mark the targets, obstacles, and threats within the field of view, and add the processed obstacle model and geographical data platform to the optical image to generate a fused optoelectronic image;

[0029] Step 303: Using the integrated visual scene processed in Step 2 as the background, superimpose and display the fused optical and radar image layers.

[0030] Furthermore, Step 4 specifically includes the following steps:

[0031] Step 401, when the helicopter is flying above a certain radio altitude, select the 120s and 60s warning envelopes to determine the current warning status; calculate the terrain, obstacle height and radio altitude difference within the forward 120s flight time distance, left and right 60s flight time distances based on the latest forward speed, trigger the 120s flight time threshold to display a caution-level prompt, and trigger the 60s flight time threshold to display a warning-level prompt;

[0032] Step 402, when the helicopter is in a descending state and the descent rate exceeds the allowable safety value, select the 60s and 30s warning envelopes to determine the current warning status; if the terrain and obstacles within the 60s flight time envelope are all lower than the aircraft height, no warning signal is output; if there are obstacles equal to or higher than the helicopter height within the 60s flight time envelope, but there are none within the 30s flight time envelope, output the corresponding visual prompt signal, and if there is terrain equal to or higher than the helicopter height, display an amber area identifier; if there are obstacles equal to or higher than the helicopter height within the 30s flight time envelope, output the corresponding visual warning signal, and if there is terrain equal to or higher than the helicopter height, highlight the red area identifier;

[0033] Step 403, when the helicopter enters the near landing phase, select the 40s and 20s flight time warning envelopes to determine the current warning status; at 40s flight time from the obstacle and threatening terrain, it is defined as reaching the caution-level prompt, and display an amber obstacle contour line; at 20s flight time from the obstacle and threatening terrain, it is defined as reaching the warning-level prompt, and display a red obstacle contour line that flashes continuously.

[0034] Furthermore, Step 5 specifically includes the following steps:

[0035] Step 501, load the flight route information as the virtual center line, providing the basis for the calculation of the safe flight tubular channel and the solution of the flight guidance command, and not directly displayed in the synthetic vision;

[0036] Step 502, calculate the virtual waypoints in the safe flight tubular channel according to the data parameters of the aircraft state, and at the same time draw a red connecting line from the target position to the aircraft as the segmented distance guidance line;

[0037] Step 503, according to each virtual waypoint and the track curvature at that point, calculate the end point coordinates of the rectangular plane perpendicular to the route with the virtual waypoint as the center to form the left limit box and the right limit box; connect all the end points in the left limit box and the right limit box in sequence, convert the end point coordinates of the limit box to screen coordinates, obtain the two-dimensional safe flight channel shape of this flight segment, and give the pilot an intuitive track prompt.

[0038] Furthermore, Step 6 specifically includes the following steps:

[0039] Step 601: Calculate each key point for flying along the safety channel based on the position and attitude of the carrier aircraft, mark the expected position 10 seconds after flying along the safe flight channel in chronological order, convert it into screen coordinates for superimposed display, and clear the previously displayed channel information after flying over it.

[0040] Step 602: During the flight, calculate the information of the heading, altitude, and speed that the carrier aircraft should fly according to the current flight attitude; convert the calculated heading, altitude, and speed into flight symbols and display them using dark green linear symbols, and clear the previously displayed information after flying over it.

[0041] Step 603: Through the comparison of visual scene information, assist the pilot in confirming the positional relationship between the flight track of the helicopter and the guiding symbol, and assist in determining that the actual flight track of the helicopter coincides with the planned channel within the error range, so as to achieve visual flight track tracking and safe flight guidance.

[0042] The present invention has the following advantages compared with the background technology:

[0043] 1. Based on the multi-source image matching of the position and attitude of the carrier aircraft, the present invention presents a comprehensive visual scene in the forward view for the pilot, filling the gap in the field of helicopter visual flight guidance.

[0044] 2. The present invention generates corresponding terrain obstacle warning displays, enabling the pilot to visually perceive the relative horizontal and vertical positions of the terrain and other objects with respect to the carrier aircraft, as well as the changes in the relative height difference with the carrier aircraft. The required algorithms are mature, with high calculation efficiency and stability.

[0045] 3. The safe flight channel and guiding symbol generated by the present invention can change during the flight process, enabling the multi-dimensional graphical generation of guiding information, achieving clear flight operation instructions, and facilitating the reduction of track deviation during the flight.

[0046] 4. The present invention also has the characteristics of being easy to implement and debug, easy to expand, and having strong compatibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is an example flowchart of the comprehensive display information of the flight environment.

[0048] Figure 2 It is an example flowchart of the warning display information of dangerous terrain and obstacles.

[0049] Figure 3 It is an example flowchart of the visual near-ground guidance process. DETAILED DESCRIPTION OF THE INVENTION

[0050] Next, the present invention will be further described in conjunction with the accompanying drawings.

[0051] A flight guidance method based on synthetic vision. First, this method uses multi-source detection images, attitude data, and terrain data of a helicopter to match and generate a three-dimensional geographical environment, performs real-time calculations in combination with helicopter waypoints and flight routes, extracts the synthetic vision range and conducts information simulation. Then, it comprehensively processes the terrain database and multi-source avionics data to generate terrain and obstacle warning prompts and superimposes them on the vision for display. In the near-ground and landing phases, by identifying threats such as close-range terrain obstacles and long-range terrain conflicts, it provides clear and easy-to-understand vision image output and reliable flight indication information.

[0052] As Figures 1-3 shown, this method specifically includes the following steps:

[0053] (1) Before takeoff, load the on-board 3D engine to load the synthetic vision database and helicopter flight route data, pre-read the surrounding terrain data within a fixed range adjacent to the current coordinates of the helicopter into the memory, and generate and real-time update the synthetic vision of the three-dimensional image in front of the pilot's basic view; specifically including the following steps:

[0054] (101) Before takeoff, load the on-board 3D engine to load the synthetic vision database and helicopter flight route; at the same time, with the coordinates of the center point of the departure airport as the center, extract the terrain data and large building models within the set range to complete the initial display of the vision.

[0055] (102) At the same time, pre-read 8 pieces of terrain data in the same range around the set vision area and store them in the memory.

[0056] (103) Based on the coordinates of the aircraft's parking point at the airport and the fuselage orientation, initialize the basic view information of the pilot in the front cabin of the helicopter.

[0057] (104) Based on the basic view information of the pilot, the on-board 3D engine loads the synthetic vision viewpoint data, and loads the terrain, ground object models, and atmospheric lighting data to generate the synthetic vision of the three-dimensional image in front of the pilot's basic view.

[0058] (2) During the flight of the aircraft, obtain the position and attitude data of the helicopter and the pilot's helmet orientation information, calculate the pilot's navigation field of view range in real-time, update the pre-read synthetic vision terrain data based on the navigation field of view range, and superimpose safety level colors on the terrain data in the synthetic vision to identify the threat level to the helicopter's flight altitude; specifically including the following steps:

[0059] (201) During the flight, receive the on-board bus data to obtain the position and attitude data of the helicopter and the pilot's helmet orientation information.

[0060] (202) Based on the acquired helicopter position and attitude data and the pilot's helmet orientation information, calculate the pilot's navigation field of view direction and range data in real time. When the visual scene boundary is about to exceed the current visual scene range, load the pre-read adjacent range terrain into the visual scene window, and at the same time delete the pre-read terrain data that has been displayed, so that the data exchange during real-time rendering only occurs in memory, improving the rendering speed;

[0061] (202) Update the integrated visual scene display range and viewpoint information based on the navigation field of view direction and range;

[0062] (203) Calculate the height difference ΔH1 between the heights of all terrains within the integrated visual scene display range and the carrier aircraft:

[0063] (204) Determine the value range of ΔH1, and use the OpenGL shader to display the terrains in each interval within the integrated visual scene with different safety level colors superimposed;

[0064] (205) Based on step (204), if the value of ΔH1 is less than 0m, it is defined as the threat level and interpolated and shaded with 50% red; if the value of ΔH1 is in the interval [0m, 50m), it is defined as the danger level and interpolated and shaded with 50% yellow; if the value of ΔH1 is in the interval [50m, 100m), it is defined as the warning level and interpolated and shaded with 25% yellow; if the value of ΔH1 is in the interval [100m, 200m), it is defined as the pay attention to safety level and interpolated and shaded with 25% green; if the value of ΔH1 is greater than 200m, it is defined as the safety level and the terrain texture of the integrated visual scene database itself is used.

[0065] (206) The airborne 3D engine performs matching rendering on the preset integrated visual scene database in the order of steps (203)-(205), and realizes the visual information of potential hazards to the helicopter flight according to the level identification.

[0066] (3) According to the pilot's navigation field of view range processed in step (2), perform image registration and obstacle recognition on the helicopter multi-source sensor data, extract the obstacle model and geographical data, and perform matching, fusion loading and rendering in the integrated visual scene; specifically including the following steps:

[0067] (301) According to the airborne optical sensor load parameters and the pilot's navigation field of view range, perform image denoising, registration and pixel-level fusion on low-light, infrared and visible light to generate a fused optical image;

[0068] (302) An intelligent algorithm based on the VGG19 network is adopted to fuse the fused optical image with the airborne radar image and radar data, detect, identify and color-mark the targets, obstacles and threats in the field of view, add the processed obstacle model and geographical data platform to the optical image, and generate a fused optoelectronic image;

[0069] (303) Using the visual scene image processed in step (2) as the background, layer-overlay and display the fused optical and radar images;

[0070] (4) According to the flight route data loaded in step (1) and the current position and attitude of the helicopter, calculate the minimum flight segment data in front of the helicopter, and perform visual warning processing based on the flight warning envelope model; specifically including the following steps:

[0071] (401) When the helicopter is flying above a certain radio altitude, select the 120s and 60s warning envelopes to judge the current warning status. Calculate the terrain, obstacle height and the difference from 3 radio altitudes within the forward 120s flight time distance, left and right 60s flight time distances based on the latest forward speed, trigger the 120s flight time threshold to display an attention-level prompt, and trigger the 60s flight time threshold to display an alarm-level prompt.

[0072] (402) When the helicopter is in a descending state and the descending rate exceeds the allowable safety value, select the 60s and 30s warning envelopes to judge the current warning status. If the terrain and obstacles within the 60s flight time envelope are all lower than the altitude of the aircraft, no warning signal is output; if there are obstacles equal to or higher than the helicopter altitude within the 60s flight time envelope, but there are none within the 30s flight time envelope, the corresponding visual (amber information) prompt signal should be output. If there is terrain equal to or higher than the helicopter altitude, the amber area identifier should be displayed; if there are obstacles equal to or higher than the helicopter altitude within the 30s flight time envelope, the corresponding visual (red information) alarm signal should be output. If there is terrain equal to or higher than the helicopter altitude, the red area identifier should be highlighted.

[0073] (403) When the helicopter enters the approach and landing phase, select the 40s and 20s flight time warning envelopes to judge the current warning status. About 40s flight time from the obstacle and threatening terrain is defined as reaching the attention-level prompt, and the amber obstacle contour line is displayed; about 20s flight time from the obstacle and threatening terrain is defined as reaching the alarm-level prompt, and the red obstacle contour line is displayed and flashes continuously.

[0074] (5) Generate the corresponding safe flight path information and overlay and display it in the form of a layer in the integrated visual scene window; specifically including the following steps:

[0075] (501) Load the flight route information as the virtual center line, which is not directly displayed in the integrated visual scene, providing a basic basis for the calculation of the safe flight tubular channel and the solution of the flight guidance command.

[0076] (502) Calculate the virtual waypoints in the safe flight tubular channel according to the data parameters of the carrier aircraft state, and at the same time draw a red connection line from the target position to the carrier aircraft as the segmented distance guidance line.

[0077] (503) According to each virtual waypoint and the track radian at that point, calculate the endpoint coordinates of the rectangular plane perpendicular to the route with the virtual waypoint as the center, forming a left limit box and a right limit box. Connect all the endpoints in the left limit box and the right limit box in turn, convert the endpoint coordinates of the limit box into screen coordinates, obtain the two-dimensional shape of the safe flight channel for this flight segment, and give the pilot an intuitive track hint.

[0078] (6) Generate a set of safe driving guidance symbols in the low-altitude flight scene, dynamically calculate the segmented paths within the time period of flying along the expected track, and generate supporting safe operation guidance symbols, using the real-time generated flight guidance symbols to indicate and guide the pilot to drive safely; specifically including the following steps:

[0079] (601) According to the position and attitude of the carrier aircraft, calculate each key point of flying along the safe channel, mark the expected position 10 s after flying along the safe flight channel in chronological order, convert it into screen coordinates for overlay display, and clear the previously displayed channel information after flying over.

[0080] (602) During the flight, according to the current flight attitude, calculate the elements information such as the heading, altitude, and speed that the carrier aircraft should fly. Convert the calculated heading, altitude, speed, etc. into flight symbols, display them using dark green linear symbols, and clear the previously displayed information after flying over.

[0081] (603) Through the comparison of the visual information, assist the pilot to confirm the positional relationship between the flight track of the helicopter and the guidance symbols. Within the error range, it can be assisted to determine that the actual flight track of the helicopter coincides with the planned channel, realizing visual track tracking and safe flight guidance.

[0082] (7) Based on the current track position, attitude and flight route of the helicopter, continue to execute steps (2) - (6) until a safe landing is achieved, realizing the low-altitude guidance for the entire flight process.

[0083] In summary, in view of the need of helicopter pilots to improve the external threat perception and safe driving ability in complex terrains and harsh visual environments, the present invention drives the onboard integrated vision simulation, provides effective warning displays of dangerous terrains and obstacles and flight guidance information prompts at the near-ground stage, and designs a flight guidance method based on integrated vision. This method features high computational efficiency, strong generality and easy implementation.

Claims

1. A flight guidance method based on synthetic vision, characterized in that, It includes the following steps: Step 1: Before takeoff, the on-board 3D engine loads the integrated visual database and the helicopter flight route, pre-reads the terrain data around the fixed range where the current coordinates of the helicopter are located and stores it in the memory, and generates a 3D image integrated view in front of the pilot's basic perspective; Step 2: During the flight of the aircraft, obtain the helicopter position and attitude data and the pilot's helmet orientation information, calculate the pilot's navigation field of view in real time, update the integrated view generated in Step 1 based on the navigation field of view, and overlay the safety level color on the terrain data in the integrated view to identify the threat level to the helicopter flight altitude; Step 3: According to the pilot's navigation field of view range processed in Step 2, perform image registration and obstacle recognition on the helicopter multi-source sensor data, extract the obstacle model and geographical data, and perform matching, fusion loading and rendering in the integrated view; Step 4: According to the helicopter flight route data and the current position and attitude of the helicopter loaded in Step 1, calculate the minimum flight segment data in front of the helicopter, and perform visual warning processing based on the flight warning envelope model; Step 5: Generate the corresponding safe flight path information and overlay and display it in the integrated view window in the form of a layer; Specifically, it includes the following steps: Step 501: Load the flight route information as the virtual center line, provide the basis for the calculation of the safe flight tubular path and the solution of the flight guidance instruction, and do not directly display it in the integrated view; Step 502: According to the data parameters of the carrier aircraft state, calculate the virtual waypoints in the safe flight tubular path, and at the same time draw a red connection line from the target position to the carrier aircraft as the segmented distance guidance line; Step 503: According to each virtual waypoint and the track curvature at that point, calculate the end point coordinates of the rectangular plane perpendicular to the route with the virtual waypoint as the center to form a left limit box and a right limit box; Connect all the end points in the left limit box and the right limit box in sequence, convert the end point coordinates of the limit box into screen coordinates, obtain the two-dimensional safe flight path shape of this flight segment, and give the pilot an intuitive track prompt; Step 6: Generate a set of safe driving guidance symbols in the low-altitude flight scenario, dynamically calculate the segmented paths within the time period of flying along the expected track, and generate supporting safe operation guidance symbols to indicate and guide the pilot to drive safely; Step 7: Based on the current track position and attitude of the helicopter and the flight route, continue to execute Steps 2 - 6 until a safe landing is achieved, and realize the low-altitude guidance for the entire flight process.

2. The flight guidance method based on synthetic vision according to claim 1, characterized in that, Step 1 specifically includes the following steps: Step 101: Before takeoff, the on-board 3D engine loads the integrated visual database and the helicopter flight route; with the coordinates of the center point of the departure airport as the center, extract the terrain data and large building models within the set range, and complete the initialization display of the view; Step 102: Pre-read 8 pieces of terrain data with the same range around the set view area and store them in the memory; Step 103: Based on the coordinates of the aircraft at the airport parking point and the fuselage orientation, initialize the basic perspective information of the pilot in the front cabin of the helicopter; Step 104: Based on the pilot's basic perspective information, the airborne 3D engine loads the comprehensive visual perspective data, and loads the terrain, ground object models, and atmospheric lighting data to generate a 3D image comprehensive visual perspective in front of the pilot's basic perspective.

3. The flight guidance method based on synthetic vision according to claim 1, characterized in that, Step 2 specifically includes the following steps: Step 201: During flight, receive the airborne bus data to obtain the helicopter's position and attitude data and the pilot's helmet orientation information; Step 202: Based on the obtained helicopter's position and attitude data and the pilot's helmet orientation information, calculate the pilot's navigation field of view direction and range data in real time. When the visual scene boundary is about to exceed the current visual scene range, load the pre-read surrounding terrain data into the visual scene window, and at the same time delete the pre-read terrain data that has been displayed, so that the data exchange during real-time rendering only occurs in memory, improving the rendering speed; Step 203: Update the comprehensive visual scene display range and viewpoint information based on the navigation field of view direction and range; Step 204: Calculate the height difference ΔH1 between the heights of all terrains within the comprehensive visual scene display range and the height of the aircraft; Step 205: Determine the value range of ΔH1, and use the OpenGL shader to display the terrains in each interval in the comprehensive visual scene with different safety level colors superimposed; Step 206: Based on Step 204, if the value of ΔH1 is less than 0m, it is defined as the threat level, and 50% red is used for interpolation coloring; if the value of ΔH1 is in the interval [0m, 50m), it is defined as the danger level, and 50% yellow is used for interpolation coloring; if the value of ΔH1 is in the interval [50m, 100m), it is defined as the warning level, and 25% yellow is used for interpolation coloring; if the value of ΔH1 is in the interval [100m, 200m), it is defined as the pay attention to safety level, and 25% green is used for interpolation coloring; if the value of ΔH1 is greater than 200m, it is defined as the safety level, and the terrain itself texture in the comprehensive visual scene database is used; Step 207: The airborne 3D engine performs matching rendering on the preset comprehensive visual scene database according to Steps 204 - 206 to realize the visual information of potential dangers to the helicopter flight according to the level identification.

4. The flight guidance method based on synthetic vision according to claim 1, characterized in that, Step 3 specifically includes the following steps: Step 301: According to the airborne optical sensor payload parameters and the pilot's navigation field of view range, perform image denoising, registration, and pixel-level fusion on low-light, infrared, and visible light to generate a fused optical image; Step 302: Adopt an intelligent algorithm based on the VGG19 network to fuse the fused optical image with the airborne radar image and radar data, detect, identify, and color-mark the targets, obstacles, and threats within the field of view, and add the processed obstacle models and geographical data platforms to the optical image to generate a fused optoelectronic image; Step 303: Using the comprehensive visual scene processed in Step 2 as the background, superimpose and display the fused optical and radar image layers.

5. The flight guidance method based on synthetic vision according to claim 1, characterized in that, Step 4 specifically includes the following steps: Step 401: When the helicopter is flying above a certain radio altitude, select the 120s and 60s warning envelopes to determine the current warning status; calculate the terrain, obstacle height, and the difference from the radio altitude within the forward 120s flight time distance, and the left and right 60s flight time distances based on the latest forward speed, trigger the 120s flight time threshold to display a caution-level prompt, and trigger the 60s flight time threshold to display a warning-level prompt. Step 402: When the helicopter is in a descending state and the descent rate exceeds the allowable safety value, select the 60s and 30s warning envelopes to determine the current warning status; if the terrain and obstacles within the 60s flight time envelope are all lower than the carrier altitude, no warning signal is output; if there are obstacles equal to or higher than the helicopter altitude within the 60s flight time envelope, but none within the 30s flight time envelope, output the corresponding visual prompt signal. If there is terrain equal to or higher than the helicopter altitude, display an amber area identifier; if there are obstacles equal to or higher than the helicopter altitude within the 30s flight time envelope, output the corresponding visual warning signal. If there is terrain equal to or higher than the helicopter altitude, prominently display a red area identifier. Step 403: When the helicopter enters the near landing phase, select the 40s and 20s flight time warning envelopes to determine the current warning status; at 40s flight time from the obstacle or threatening terrain, it is defined as reaching the caution level prompt, and display an amber obstacle contour line; at 20s flight time from the obstacle or threatening terrain, it is defined as reaching the warning level prompt, and display a red obstacle contour line that flashes continuously.

6. The flight guidance method based on synthetic vision according to claim 1, characterized in that, Step 6 specifically includes the following steps: Step 601: According to the position and attitude of the carrier aircraft, calculate the key points for flying along the safe passage, identify the expected position 10s after flying along the safe flight passage in chronological order, convert it to screen coordinates for overlay display, and clear the previous displayed passage information after flying over. Step 602: During the flight, calculate the information of the heading, altitude, and speed that the carrier aircraft should fly according to the current flight attitude; convert the calculated heading, altitude, and speed to flight symbols and display them using dark green linear symbols, and clear the previous displayed information after flying over. Step 603: Through visual scene information comparison, assist the pilot in confirming the positional relationship between the flight path of the helicopter and the guiding symbol, and assist in determining that the actual flight path of the helicopter coincides with the planned passage within the error range, realizing visual flight path tracking and safe flight guidance.

Images