An airborne synthetic vision-assisted navigation approach method based on a satellite-based augmentation system

Abstract

This invention discloses an airborne synthetic vision-assisted navigation approach method based on a satellite-based augmentation system. Utilizing navigation messages provided by the satellite-based augmentation system, it provides accurate navigation data for the airborne synthetic vision during aircraft approach. Compared to traditional synthetic vision navigation methods without augmentation systems, this method effectively improves the positional accuracy of the aircraft during the approach and landing phase, providing pilots with reliable and intuitive information for precise landing operations, and significantly enhancing aircraft safety.

Description

Technical Field

[0001] This invention relates to airborne synthetic vision, and more particularly, to an airborne synthetic vision-assisted navigation approach method based on a satellite-based augmentation system. Background Technology

[0002] Airborne synthetic vision systems are computer-generated virtual visual environments primarily designed to address flight safety issues arising from insufficient external visibility or unfamiliar environments. Their principle involves using onboard terrain, obstacle, and navigation databases, based on the aircraft's current position, attitude, and heading, to generate a real-time three-dimensional terrain scene in front of the aircraft. This scene is then displayed on the cockpit monitor from the pilot's perspective, providing the pilot with a clear view even under conditions of limited external visibility, enhancing their situational awareness. Currently, airborne synthetic vision systems are increasingly relied upon by pilots due to their intuitive, clear, and natural display methods. However, because this system is highly dependent on positioning accuracy, it has not yet been approved for use as a navigation approach guidance tool.

[0003] Therefore, both domestically and internationally, airborne augmented vision systems are commonly used to compensate for the insufficient navigation and approach accuracy of synthetic vision systems. This involves switching from synthetic vision to augmented vision for navigation and approach when the aircraft is below a certain altitude. However, augmented vision systems are greatly affected by weather conditions, have limited detection range, and generate images that are far less clear than those from synthetic vision systems. Therefore, improving the navigation and approach performance of synthetic vision systems has become an important research topic in the field of synthetic vision systems.

[0004] A satellite-based augmentation system (SBA) is a global navigation satellite system (GNSS) augmentation system that broadcasts SBAS navigation messages to users, including corrections and integrity information. Users use these messages to correct deviations in GNSS satellite signals, thereby improving the positioning accuracy of the GNSS system. Currently, globally deployed or under-construction SBAs include: the Wide Area Augmentation System (WAAS) and Local Augmentation System (LAAS) of the United States; the Geostationary Satellite Navigation Overlap Service (EGNOS) of Europe; the Differential Correction and Monitoring System (SDCM) of Russia; the Multifunctional Satellite Augmentation System (MSAS) of Japan; the GPS-Assisted Geostationary Orbit Augmentation System (GAGAN) of India; the Korea Satellite Augmentation System (KASS) of South Korea; and the BeiDou Satellite-Based Augmentation System (BDSBAS) of my country. These widely distributed, globally covering SBAs not only provide users with accurate positioning and navigation information but also offer low cost and high availability, making them ideal for improving the navigation and approach performance of synthetic vision systems. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of insufficient approach navigation accuracy in existing synthetic vision technology, and to provide a novel airborne synthetic vision-assisted navigation approach method for satellite-based augmentation systems.

[0006] To achieve this objective, the technical solution of the present invention is as follows: an airborne synthetic vision-assisted navigation approach method for a satellite-based augmentation system, comprising the following steps.

[0007] Step S1: During flight, the airborne GNSS receiver receives in real time the broadcast ephemeris, basic GNSS navigation messages and SBAS navigation messages transmitted by the Global Navigation Satellite System.

[0008] Step S2: Determine the non-differential measurement from the broadcast ephemeris and the GNSS navigation message;

[0009] Step S3: Determine the differential correction number from the SBAS navigation message, and use the differential correction number to correct the non-differential observation, thereby obtaining the corrected aircraft position information;

[0010] Step S4: During the aircraft approach phase, the range of data to be retrieved from the system database is determined by the aircraft position information and the current aircraft flight parameters. The system database includes a terrain database, an obstacle database, and a navigation database.

[0011] Step S5: Retrieve the required data from the system database according to the data range, and generate a 3D scene image and navigation approach guidance markers.

[0012] As a preferred embodiment of an airborne synthetic vision-assisted navigation approach method based on a satellite-based augmentation system, step S2 includes the following sub-steps:

[0013] Sub-step S21: Read the broadcast ephemeris, the GNSS navigation message, and the SBAS navigation message;

[0014] Sub-step S22: For GNSS satellites, based on the broadcast ephemeris and the GNSS navigation message, establish the pseudorange non-differential observation equation shown in equation (1) and the carrier phase non-differential observation equation shown in equation (2).

[0015] equation:

[0016] L=R+cδt-cδt s +D tro +D ion +D rel +D ant +D mul +D oth +ε L (1)

[0017] P = R + cδt - cδt s -λN+D tro -D ion +D rel +D ant +D mul +D oth +ε P (2)

[0018] Where L represents the measured pseudorange observation; R represents the geometric distance between the observation station and the satellite; c represents the speed of light; δt is the receiver clock error; δt s For satellite clock bias; D tro Indicates tropospheric delay; D ion Indicates ionospheric delay; D rel Represents relativistic effects; D ant D represents the antenna phase center error; mul Indicates multipath error; D oth Indicates other errors; ε L ε represents pseudorange observation noise; P represents the measured phase observation value; λ represents the carrier wavelength; N represents the ambiguity of the initial phase between the satellite and the receiver; ε P This indicates phase observation noise.

[0019] As a preferred embodiment of an airborne synthetic vision-assisted navigation approach method based on a satellite-based augmentation system, step S3 includes the following sub-steps:

[0020] Sub-step S31, based on the differential corrections, including satellite orbit error correction ΔR and satellite clock error correction Δδt s Tropospheric delay correction ΔD tro and the ionospheric delay correction ΔD ion By performing SBAS difference correction on the observation equations in S22, we obtain equations (3) and (4):

[0021] L'=R+ΔR+cδt-c(δt s +Δδt s )+D tro +ΔD tro +D ion +ΔD ion +D rel +D ant +D mul +D oth +ε L (3)

[0022] P'=R+ΔR+cδt-c(δt s +Δδt s )-λN+D tro+ΔD tro -(D ion +ΔD ion )+D rel +D ant +D mul +D oth +ε P (4)

[0023] In sub-step S32, a dual-frequency receiver scheme is used to construct an ionosphere-free combination, resulting in the pseudorange shown in equation (5).

[0024] Combined observations, and carrier phase combined observations as shown in equation (6):

[0025]

[0026]

[0027] Where f1 and f2 represent the frequency points of the dual-frequency receiver; L'1, L'2 and P'1, P'2 represent the pseudorange observations and carrier phase observations at frequencies f1 and f2, respectively.

[0028] In sub-step S33, based on the combined observation equation, equations (5) and (6) are solved jointly for at least 4 effective satellites to obtain the corrected receiver positioning result.

[0029] As a preferred embodiment of an airborne synthetic vision-assisted navigation approach method based on a satellite-based augmentation system, step S4 includes the following sub-steps:

[0030] Sub-step S41: Calculate the visible field of view of the aircraft based on the aircraft's current location (longitude and latitude), altitude, attitude, heading, and other information, combined with parameters such as the field of view angle and field of view range of the airborne synthetic vision system.

[0031] Sub-step S42: Calculate the terrain data, obstacle data, and navigation data that the visible field system needs to retrieve.

[0032] As a preferred embodiment of an airborne synthetic vision-assisted navigation approach method based on a satellite-based augmentation system, step S5 includes the following sub-steps:

[0033] Sub-step S51 generates a three-dimensional terrain scene and navigation guidance markers in real time based on the results of S4 throughout the flight.

[0034] Sub-step S52: When the target airport enters the visible field of view of the synthetic scene, the airport logo is superimposed on the 3D scene image.

[0035] Sub-step S53: When the horizontal distance between the aircraft and the runway start point is no more than 20 nautical miles, the composite visual display screen uses line segments and arrows to guide the straight path from the aircraft's current position to the runway start point, and displays the outline of the runway and the runway side in quadrilaterals.

[0036] Sub-step S54: When the horizontal distance between the aircraft and the runway starting point is no more than 2 nautical miles and the vertical distance is no more than 1,000 feet, and the aircraft is within a 30° horizontal field of view of the runway starting point center viewpoint, display the runway surface, runway centerline and various road surface guidance symbols.

[0037] Compared with the prior art, the beneficial effects of the present invention are at least as follows: (1) the airborne synthetic vision obtains the aircraft’s accurate position, attitude and heading information by using the correction data sent by the satellite-based augmentation system, thereby improving the navigation guidance performance of the airborne synthetic vision during flight.

[0038] (2) Compared with airborne augmentation systems, satellite-based augmentation systems have the characteristics of all-weather operation, wide coverage, low cost and high flexibility, which expands the application scope of airborne synthetic vision.

[0039] (3) Airborne synthetic vision based on satellite-based augmentation system has the function of precision approach, which enables aircraft to achieve a high level of safety landing similar to instrument landing at airports without instrument landing systems. Attached Figure Description

[0040] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. It should be noted that these descriptions are for the purpose of aiding understanding the invention and do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the invention described below can be combined with each other as long as they do not conflict with each other.

[0042] Please see Figure 1 The figure shows an airborne synthetic vision-assisted navigation approach method for a satellite-based augmentation system.

[0043] S1: During flight, the airborne GNSS receiver receives broadcast ephemeris, GNSS navigation messages and SBAS navigation messages transmitted by the Global Navigation Satellite System in real time;

[0044] S2: Obtain nondifferential measurements based on broadcast ephemeris and GNSS navigation messages transmitted by the Global Navigation Satellite System;

[0045] S3: Obtain correction values ​​from the SBAS navigation message of the satellite-based augmentation system, and use this information to correct the non-differential measurements, thereby obtaining the corrected aircraft position information;

[0046] S4: During the aircraft approach phase, the aircraft position information obtained in S3 is used in combination with the aircraft flight parameters to calculate the range of terrain database, obstacle database and navigation database to be retrieved.

[0047] S5: Retrieve the required data from the system database based on the database range calculated in S4, generate a 3D scene image, and navigation approach guidance signs.

[0048] Step S2 includes:

[0049] S21: Read the broadcast ephemeris, GNSS navigation messages and SBAS navigation messages transmitted by the Global Navigation Satellite System;

[0050] S22: For GNSS satellites, based on the broadcast ephemeris and basic navigation message read in S21, establish the pseudorange non-differential observation equation shown in equation (1) and the carrier phase non-differential observation equation shown in equation (2):

[0051] L=R+cδt-cδt s +D tro +D ion +D rel +D ant +D mul +D oth +ε L (1)

[0052] P = R + cδt - cδt s -λN+D tro -D ion +D rel +D ant +D mul +D oth +ε P (2)

[0053] Where L represents the measured pseudorange observation; R represents the geometric distance between the observation station and the satellite; c represents the speed of light; δt is the receiver clock error; δt s For satellite clock bias; D tro Indicates tropospheric delay; D ion Indicates ionospheric delay; D rel Represents relativistic effects; D ant D represents the antenna phase center error; mul Indicates multipath error; D oth Indicates other errors; ε Lε represents pseudorange observation noise; P represents the measured phase observation value; λ represents the carrier wavelength; N represents the ambiguity of the initial phase between the satellite and the receiver; ε P This indicates phase observation noise.

[0054] Step S3 includes:

[0055] S31: Obtain the differential corrections based on the SBAS navigation message read from S2, including satellite orbit error correction ΔR and satellite clock error correction Δδt. s Tropospheric delay correction ΔD tro and the ionospheric delay correction ΔD ion By performing SBAS difference correction on the observation equations in S22, we obtain equations (3) and (4):

[0056] L'=R+ΔR+cδt-c(δt s +Δδt s )+D tro +ΔD tro +D ion +ΔD ion +D rel +D ant +D mul +D oth +ε L (3)

[0057] P'=R+ΔR+cδt-c(δt s +Δδt s )-λN+D tro +ΔD tro -(D ion +ΔD ion )+D rel +D ant +D mul +D oth +ε P (4)

[0058] S32: As a further preferred embodiment of the airborne synthetic vision-assisted navigation approach method based on a satellite-based augmentation system of the present invention, in step S32, a dual-frequency receiver scheme is adopted to construct an ionosphere-free combination, obtaining the phase combination observation value shown in equation (5) and the pseudorange combination observation value shown in equation (6):

[0059]

[0060]

[0061] Where f1 and f2 represent the frequency points of the dual-frequency receiver; L'1, L'2 and P'1, P'2 represent the pseudorange observations and carrier phase observations at frequencies f1 and f2, respectively.

[0062] S33: Based on the combined observation equations obtained in S32, equations (5) and (6) are solved together for at least 4 effective satellites to obtain the corrected receiver positioning results.

[0063] In step S4: the positioning result corrected by SBAS in S3 is used as the current position input of the aircraft, thereby calculating the range of databases required for navigation approach, specifically:

[0064] S41: Calculate the visible field of view of the aircraft based on the aircraft's current location (longitude and latitude), altitude, attitude, heading, and other information, combined with parameters such as the field of view angle and field of view range of the airborne synthetic vision system.

[0065] S42: Based on the visual field calculation system obtained in S41, the terrain data, obstacle data, and navigation data that need to be retrieved.

[0066] 5. The synthetic vision-assisted navigation approach method based on a satellite-based augmentation system according to claim 1, characterized in that, in step S5: retrieving the corresponding database information according to the calculation results of S4, and generating a three-dimensional scene image and navigation approach guidance markers, specifically:

[0067] S51: During the entire flight, three-dimensional terrain scenes and navigation guidance signs are generated in real time based on the results of S4;

[0068] S52: When the target airport enters the visible field of view of the synthetic scene, the airport logo is overlaid on the 3D scene image;

[0069] S53: When the horizontal distance between the aircraft and the runway start point is no more than 20 nautical miles, the composite visual display shows a straight path from the aircraft’s current position to the runway start point with lines and arrows, and displays the outline of the runway and the runway side with quadrilaterals.

[0070] S54: When the horizontal distance between the aircraft and the runway starting point is no more than 2 nautical miles and the vertical distance is no more than 1,000 feet, and the aircraft is within a 30° horizontal field of view of the runway starting point center viewpoint, display the runway surface, runway centerline and various road surface guidance symbols.

[0071] The above description merely illustrates embodiments of the present invention and is quite specific and detailed; however, it should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An airborne synthetic vision-assisted navigation approach method based on a satellite-based augmentation system, characterized in that, It includes the following steps, Step S1: During the flight of the aircraft, the airborne GNSS receiver receives in real time the broadcast ephemeris and GNSS navigation messages sent by the Global Navigation Satellite System and the SBAS navigation messages sent by the Satellite-based Augmentation System. Step S2: Determine the non-differential measurement from the broadcast ephemeris and the GNSS navigation message; Step S3: Determine the differential correction number from the SBAS navigation message, and use the differential correction number to correct the non-differential observation, thereby obtaining the corrected aircraft position information; Step S4: During the aircraft approach phase, the range of data to be retrieved from the system database is determined based on the aircraft position information and current aircraft flight parameters. The system database includes a terrain database, an obstacle database, and a navigation database; and... Step S5: Retrieve the required data from the system database according to the data range, and generate a 3D scene image and navigation guidance markers; Step S2 includes the following sub-steps. Sub-step S21: Read the broadcast ephemeris, the GNSS navigation message, and the SBAS navigation message; Sub-step S22: For GNSS satellites, based on the broadcast ephemeris and the GNSS navigation message, establish the pseudorange non-differential observation equation shown in equation (1) and the carrier phase non-differential observation equation shown in equation (2): （1） （2） in, This represents the measured pseudorange observation value; Indicates the geometric distance between the observation station and the satellite; Represents the speed of light; For receiver clock bias; For satellite clock bias; Indicates tropospheric delay; Indicates ionospheric delay; Represents relativistic effects; This indicates the antenna phase center error; Indicates multipath error; Indicates other errors; Indicates pseudorange observation noise; This represents the measured phase observation value; Indicates the carrier wavelength; This indicates the ambiguity of the initial phase between the satellite and the receiver; This indicates phase observation noise.

2. The airborne synthetic vision-assisted navigation approach method based on a satellite-based augmentation system according to claim 1, characterized in that, Step S3 includes the following sub-steps. Sub-step S31: Based on the differential corrections in the SBAS navigation message, including satellite orbit error corrections. Satellite clock correction Tropospheric delay correction and ionospheric delay correction By performing difference correction on the observation equations in S22, we obtain equations (3) and (4): （3） （4） In sub-step S32, a dual-frequency receiver scheme is used to construct an ionospheric-free combination, obtaining the pseudorange combination observation value shown in equation (5) and the carrier phase combination observation value shown in equation (6): （5） （6） in, , Indicates the frequency point of the dual-frequency receiver; , and , They represent , Pseudorange and carrier phase observations at frequency; In sub-step S33, according to the combined observation equation, equations (5) and (6) are solved together for at least 4 effective satellites to obtain the corrected receiver positioning result.

3. The airborne synthetic vision-assisted navigation approach method based on a satellite-based augmentation system according to claim 1, characterized in that, Step S4 includes the following sub-steps. Sub-step S41: Calculate the visible field of view of the aircraft based on the longitude and latitude of the aircraft's current position, the aircraft's altitude, attitude, and heading, combined with the field of view angle and field of view range of the airborne synthetic visual scene. Sub-step S42: Calculate the terrain data, obstacle data, and navigation data that the visible field calculation system needs to retrieve.

4. The airborne synthetic vision-assisted navigation approach method based on a satellite-based augmentation system according to claim 1, characterized in that, Step S5 includes the following sub-steps. Sub-step S51 generates a three-dimensional terrain scene and navigation guidance markers in real time based on the results of S4 throughout the flight. Sub-step S52: When the target airport enters the visible field of view of the synthetic scene, the airport logo is superimposed on the 3D scene image. Sub-step S53: When the horizontal distance between the aircraft and the runway start point is no more than 20 nautical miles, the composite visual display screen uses line segments and arrows to guide the straight path from the aircraft's current position to the runway start point, and displays the outline of the runway and the runway side in quadrilaterals. Sub-step S54: When the horizontal distance between the aircraft and the runway starting point is no more than 2 nautical miles and the vertical distance is no more than 1,000 feet, and the aircraft is within a 30° horizontal field of view of the runway starting point center viewpoint, display the runway surface, runway centerline and various road surface guidance symbols.

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