Low-altitude satellite navigation signal enhancement method

Abstract

The invention belongs to the technical field of satellite navigation signal processing, and discloses a low-altitude satellite navigation signal enhancement method which comprises the following steps: acquiring GNSS original satellite navigation data in real time through a high-precision GNSS base station network located on the ground, and performing error analysis and navigation enhancement data generation; after being coded and compressed, navigation enhancement data are transmitted to low-orbit satellites in a coverage area through a ground uploading link, and broadcast rhythms are dynamically scheduled in combination with sub-satellite point tracks and revisit periods of the low-orbit satellites; the low-orbit satellite broadcasts navigation enhancement data to the ground user by using the navigation enhancement load; and the user terminal simultaneously receives GNSS original satellite navigation data and navigation enhancement data sent by the low-orbit satellite, carries out data fusion, carries out correction processing by using an integrated navigation calculation algorithm, and outputs a high-precision positioning result. According to the invention, high-frequency and high-precision navigation enhancement broadcasting is carried out on the low-altitude flight platform serving as the user terminal through the low-orbit satellite, so that continuous, stable and high-precision navigation service in a low-altitude airspace is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of satellite navigation signal processing, and particularly relates to a low-altitude satellite navigation signal enhancement method. BACKGROUND

[0002] To improve low-altitude navigation performance, common signal enhancement technical solutions include a ground-based augmentation system (GBAS) and a satellite-based augmentation system (SBAS).

[0003] Among them, the ground-based augmentation system (GBAS) monitors GNSS satellite signal errors in real time through the layout of ground reference stations, and broadcasts correction information to users through very high frequency (VHF) or other communication links. For example, the GBAS CAT I system recommended by ICAO is widely used in airport precision approach guidance, and its core function is to improve positioning accuracy and reliability through differential technology. However, GBAS usually relies on ground reference stations laid in airports or specific areas to improve local navigation accuracy by broadcasting differential corrections. However, its broadcast range is limited, usually only covering a range of tens of kilometers, and it does not have wide-area navigation enhancement capability, which cannot meet the navigation needs of large-scale low-altitude aircraft. In addition, GBAS has high construction cost and large site deployment density, and it is difficult to widely spread in complex low-altitude environments such as cities, towns and mountains.

[0004] The satellite-based augmentation system (SBAS) (such as the WAAS in the United States and the EGNOS in Europe) monitors and corrects GNSS signal errors through space relay satellites, and broadcasts correction data to user terminals. Although SBAS has the advantages of wide coverage and does not rely on ground communication networks, its error correction accuracy is limited by data update rate and spatial delay, making it difficult to meet the high-precision navigation needs of complex low-altitude environments. However, SBAS broadcasts correction numbers through medium-high orbit relay satellites, and its original design is mainly aimed at civil aviation route navigation, with positioning accuracy generally at the level of 1 meter, and correction information update period is long (usually 5-15 seconds), which is not suitable for fast maneuvering and dynamic low-altitude flight scenarios. The long SBAS signal link and large system inertia make it difficult to reflect the rapid changes of ionospheric disturbances or signal blockage in time, thereby reducing the real-time reliability and navigation safety in low-altitude applications.

[0005] In recent years, there have also been studies attempting to combine GNSS with other auxiliary navigation means, such as hybrid positioning technology based on ground cellular communication base station assistance (see Zhang et al., "GNSS / Cellular Hybrid Positioning for UAV Navigation in Urban Canyon," Sensors, 2021, 21(4): 1302), but due to the limitations of infrastructure deployment density and reliability, it is still difficult to form a widely feasible engineering solution.

[0006] Therefore, a low-altitude satellite navigation signal enhancement method is provided to overcome the problems of small coverage or slow update rate of traditional navigation enhancement systems relying on ground-based (such as GBAS) or medium-high orbit / stationary orbit satellites (such as SBAS) for error broadcasting. SUMMARY

[0007] In view of the deficiencies of the prior art, the purpose of the present application is to provide a low-altitude satellite navigation signal enhancement method.

[0008] To achieve the above technical purpose, the technical solution adopted by the present application is as follows:

[0009] A low-altitude satellite navigation signal enhancement method, comprising the following contents,

[0010] (I) Real-time acquisition of GNSS original satellite navigation data by a high-precision GNSS reference station network located on the ground, error analysis and navigation enhancement data generation;

[0011] (II) After the navigation enhancement data is encoded and compressed, it is transmitted to the low-orbit satellite covering the area through the ground upload link, and combined with the sub-satellite track and revisit period of the low-orbit satellite, the broadcast rhythm is dynamically scheduled;

[0012] (III) The low-orbit satellite broadcasts the navigation enhancement data to the ground user using the navigation enhancement load;

[0013] (IV) The user terminal simultaneously receives the GNSS original satellite navigation data and the navigation enhancement data broadcast by the low-orbit satellite and performs data fusion, uses an integrated navigation solution algorithm for correction processing, and outputs high-precision positioning results.

[0014] In the present application, the GNSS original satellite provides the basic positioning and timing signal;

[0015] The high-precision GNSS reference station network acquires GNSS original satellite navigation data in real time, performs error analysis and navigation enhancement data generation;

[0016] The low-orbit satellite carries the navigation enhancement load for receiving the navigation enhancement data uploaded from the ground and broadcasting it in the coverage area through the broadcast link;

[0017] The user terminal receives GNSS original satellite navigation data and navigation enhancement data sent by the low-orbit satellite and performs fusion positioning calculation;

[0018] Specifically, the high-precision GNSS reference station network arranged on the ground acquires GNSS original satellite navigation data, performs error analysis and navigation enhancement data generation, and broadcasts high-frequency and high-precision navigation enhancement to the low-altitude flight platform as the user terminal through the low-orbit satellite, so that continuous, stable and high-precision navigation service in the low-altitude airspace is realized.

[0019] The application can improve the availability and continuity of low-altitude navigation, introduce multiple low-orbit satellites, and form a low-orbit satellite constellation with dense coverage and strong visibility, thereby significantly improving the number of visible navigation satellites and signal quality in a complex low-altitude environment and reducing the problem of positioning interruption or loss of lock caused by blocking of medium and high-orbit satellites.

[0020] The application enhances navigation precision and reliability, realizes wide-area perception and real-time correction of GNSS positioning errors (including orbit errors, ionospheric delay, multipath errors, etc.) with the aid of the navigation enhancement load carried by the low-orbit satellite, and improves the positioning precision and stability in urban canyons, hills and other environments.

[0021] The application provides high-time-efficiency navigation information service, utilizes the rapid revisit characteristics and near-earth communication link of the low-orbit satellite, realizes rapid update and real-time broadcast of navigation enhancement information, and meets the demand of low-altitude dynamic flight platforms (such as unmanned aerial vehicles, electric aircrafts, etc.) for high-dynamic navigation.

[0022] The application reduces system deployment and use cost, does not depend on a large-scale ground differential station network, can effectively reduce the investment in ground infrastructure, and has cross-regional and wide-area navigation enhancement capability.

[0023] As a preferred technical solution of the application, in step (I), the specific content of error analysis includes that the high-precision GNSS reference station network acquires GNSS original satellite navigation data in combination with precise ephemeris, ionospheric model and clock error model, separates and models the GNSS original satellite orbit error, ionospheric delay and multipath error; in step (I), the specific content of navigation enhancement data generation includes generating navigation enhancement parameters covering different regions based on the differential technique and the spatial grid interpolation algorithm; the navigation enhancement parameters include satellite orbit correction, clock error correction, ionospheric delay correction and residual error estimation.

[0024] As a preferred technical solution of the present application, in step (III), the low-orbit satellite broadcasts navigation enhancement data to ground users using an L-band or Ka-band navigation enhancement load; in step (IV), the integrated navigation solution algorithm selects an RTK solution algorithm or a PPP solution algorithm or a PPP-RTK hybrid solution algorithm.

[0025] As a preferred technical solution of the present application, according to the low-orbit satellite and regional requirements, at least one low-orbit satellite in any region provides navigation enhancement services at any time.

[0026] As a preferred technical solution of the present application, data fusion is performed through extended Kalman filtering (EKF), unscented Kalman filtering (UKF), or a deep learning auxiliary model.

[0027] The beneficial effects of the present application are as follows:

[0028] 1. A high-precision GNSS reference station network laid on the ground acquires GNSS original satellite navigation data, performs error analysis and navigation enhancement data generation, and broadcasts high-frequency and high-precision navigation enhancement to low-altitude flight platforms as user terminals through low-orbit satellites, thereby realizing continuous, stable, and high-precision navigation services in low-altitude airspace;

[0029] 2. The availability and continuity of low-altitude navigation can be improved. By introducing multiple low-orbit satellites, the multiple low-orbit satellites form a low-orbit satellite constellation with dense coverage and strong visibility, significantly improving the number of visible navigation satellites and signal quality in complex low-altitude environments, and reducing the problem of positioning interruption or loss of lock caused by blocking of medium and high-orbit satellites.

[0030] 3. Navigation precision and reliability are enhanced. With the aid of the navigation enhancement load carried by the low-orbit satellite, wide-area perception and real-time correction of GNSS positioning errors (including orbit errors, ionospheric delays, multipath errors, etc.) are realized, and positioning precision and stability in urban canyons, hills, and other environments are improved.

[0031] 4. High-time navigation information services are provided. The rapid revisit characteristics and near-earth communication links of low-orbit satellites are used to realize rapid updating and real-time broadcasting of navigation enhancement information, meeting the needs of low-altitude dynamic flight platforms (such as drones, electric aircraft, etc.) for high-dynamic navigation.

[0032] 5. System deployment and use costs are reduced. The system does not rely on large-scale ground differential station networks, can effectively reduce ground infrastructure investment, and has cross-regional and large-scale navigation enhancement capabilities. BRIEF DESCRIPTION OF DRAWINGS

[0033] The present application can be further illustrated by the non-limiting examples shown in the accompanying drawings;

[0034] Figure 1Flow chart for error analysis and navigation enhancement data generation in the embodiment of the present application;

[0035] Figure 2 Flow chart for fusion solution in the embodiment of the present application. DETAILED DESCRIPTION

[0036] The technical solutions of the present application will be described in detail below with reference to specific embodiments and the accompanying drawings. The embodiments described herein are specific and concrete embodiments of the present application, which are used to illustrate the concept of the present application; these descriptions are all explanatory and exemplary, and should not be understood as limiting the embodiments of the present application and the protection scope of the present application. In addition to the embodiments described herein, those skilled in the art can also employ other technical solutions that are obvious based on the content disclosed in the claims and the specification of the present application, which include technical solutions that make any obvious substitutions and modifications to the embodiments described herein.

[0037] Example 1

[0038] As shown in Figure 1 , 2 , the present embodiment provides a low-altitude satellite navigation signal enhancement method, which comprises (I) collecting GNSS original satellite navigation data in real time through a high-precision GNSS reference station network located on the ground, and performing error analysis and navigation enhancement data generation;

[0039] (II) After the navigation enhancement data is encoded and compressed, it is transmitted to the low-orbit satellite covering the area through the ground upload link, and combined with the sub-satellite track and revisit period of the low-orbit satellite, the broadcast rhythm is dynamically scheduled;

[0040] (III) The low-orbit satellite broadcasts navigation enhancement data to the ground user using the navigation enhancement load. According to the low-orbit satellite and the regional demand, at least one low-orbit satellite in different regions performs navigation enhancement service at any time, and multiple low-orbit satellites form a low-orbit satellite constellation with dense coverage and strong visibility;

[0041] (IV) The user terminal simultaneously receives the GNSS original satellite navigation data and the navigation enhancement data transmitted by the low-orbit satellite and performs data fusion, uses an integrated navigation solution algorithm for correction processing, and outputs high-precision positioning results.

[0042] In the present embodiment, the GNSS original satellite provides basic positioning and timing signals;

[0043] The high-precision GNSS reference station network collects GNSS original satellite navigation data in real time, performs error analysis and navigation enhancement data generation;

[0044] Low-Earth orbit satellites carry navigation enhancement payloads to receive navigation enhancement data uploaded from the ground and broadcast it within their coverage area via a broadcast link;

[0045] The user terminal receives raw GNSS satellite navigation data and navigation enhancement data transmitted by low-orbit satellites and performs fusion positioning calculations.

[0046] Specifically, a high-precision GNSS reference station network deployed on the ground acquires raw GNSS satellite navigation data, performs error analysis and generates navigation enhancement data, and broadcasts high-frequency, high-precision navigation enhancement data to low-altitude flight platforms as user terminals via low-orbit satellites, thereby achieving continuous, stable, and high-precision navigation services in the low-altitude airspace.

[0047] Its advantages lie in improving the availability and continuity of low-altitude navigation. By introducing multiple low-orbit satellites, these satellites form a densely covered and highly visible low-orbit satellite constellation, which significantly increases the number of visible navigation satellites and the signal quality in complex low-altitude environments, and reduces the positioning interruption or loss of lock caused by the obstruction of medium and high-orbit satellites.

[0048] To enhance navigation accuracy and reliability, the navigation enhancement payload carried by low-orbit satellites enables wide-area perception and real-time correction of GNSS positioning errors (including orbital errors, ionospheric delay, multipath errors, etc.), thereby improving positioning accuracy and stability in urban canyons, hilly areas, and other environments.

[0049] It provides high-timeliness navigation information services, utilizing the rapid revisit characteristics of low-orbit satellites and near-Earth communication links to achieve rapid updates and real-time broadcasts of navigation enhancement information, meeting the high-dynamic navigation needs of low-altitude dynamic flight platforms (such as UAVs, electric aircraft, etc.).

[0050] It reduces system deployment and usage costs, does not rely on a large-scale ground differential station network, can effectively reduce investment in ground infrastructure, and has cross-regional and large-scale navigation enhancement capabilities.

[0051] Example 2

[0052] like Figure 1 As shown, this embodiment provides a low-altitude satellite navigation signal enhancement method. The difference from Embodiment 1 is that the specific content of the error analysis includes collecting raw GNSS satellite navigation data from a high-precision GNSS reference station network and combining it with precise ephemeris, ionospheric models, and clock error models to separate and model the raw GNSS satellite orbit error, ionospheric delay, and multipath error. In step (I), the specific content of the navigation enhancement data generation includes generating navigation enhancement parameters covering different regions based on differential technology and spatial grid interpolation algorithms. The navigation enhancement parameters include satellite orbit correction, clock error correction, ionospheric delay correction, and residual estimation.

[0053] Error separation modeling includes,

[0054] Input: Multi-band pseudorange / carrier phase observations (L1 / L2 / L5),

[0055] Orbit error: computed by precise ephemeris and broadcast ephemeris difference,

[0056] Clock error: compensated based on atomic clock noise model (Allan variance) and satellite clock drift,

[0057] Ionosphere: grid model (2.5°x2.5°) is used to solve VTEC with dual-frequency observations,

[0058] Multipath: signal-to-noise ratio (C / N0) statistical analysis + elevation angle weighted filtering;

[0059] Space grid encoding compression, including

[0060] Divide the corrected parameters by latitude and longitude grid (patent example: 0.5°x0.5°),

[0061] Use delta-difference compression: only transmit the difference value of adjacent grid (data volume is reduced by 35%),

[0062] Time correlation coding: only send the change amount within 10 seconds for the same grid parameters;

[0063] Dynamic scheduling of the scheduling logic of the low earth orbit satellite:

[0064] if satellite coverage area == "urban canyon":

[0065] broadcast frequency = 2Hz # highest priority

[0066] elif satellite elevation angle > 30°:

[0067] broadcast frequency = 1Hz

[0068] else:

[0069] broadcast frequency = 0.5Hz # open area.

[0070] In this embodiment, an error modeling system composed of ground reference stations and data centers is established, and the orbit error, clock error, ionospheric error and other navigation error sources of GNSS satellites are dynamically perceived, and navigation enhancement data is generated through space interpolation and regional grid encoding technology.

[0071] Example 3

[0072] As Figure 2As shown, the embodiment provides a low-altitude satellite navigation signal enhancement method, which is different from the embodiment 1 in that, in step (III), the low-orbit satellite broadcasts navigation enhancement data to the ground user by using L-band or Ka-band navigation enhancement load; in step (IV), the integrated navigation solution algorithm selects a PPP-RTK hybrid solution algorithm; data fusion is performed through extended Kalman filter EKF or unscented Kalman filter UKF or deep learning auxiliary model to realize sub-meter level or even centimeter level precision navigation.

[0073] Among them, the fusion and solution specifically include,

[0074] Error compensation,

[0075] Orbit / clock difference: apply SSR format correction number (satellite coordinate offset δX, δY, δZ + clock difference δt)

[0076] Ionosphere: grid model interpolation (bilinear interpolation)

[0077] Multipath: satellite elevation angle-based weighting function Weight = 1 / (σ 2 _multipath)

[0078] The algorithm core of the fusion positioning engine:

[0079] % PPP-RTK hybrid solution pseudocode

[0080]

[0081] Output precision,

[0082] Static scenario: horizontal ≤ 0.1 m (95%)

[0083] Dynamic scenario: horizontal ≤ 0.5 m (95%).

[0084] In the embodiment, a multi-mode fusion algorithm is introduced at the terminal solution level, which fuses low-orbit enhancement data with traditional GNSS raw observation data, and is compatible with RTK, PPP, PPP-RTK and other solution modes. Especially under dynamic flight conditions, it can significantly improve the navigation accuracy and stability of low-altitude platforms.

[0085] The above embodiments only exemplarily illustrate the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical thought disclosed by the present application shall be covered by the claims of the present application.

Claims

1. A method of low-altitude satellite navigation signal augmentation, characterized by: Comprise the following contents, (I) Real-time acquisition of GNSS raw satellite navigation data by high-precision GNSS reference station network on the ground, error analysis and generation of navigation enhancement data; (II) After the navigation enhancement data is encoded and compressed, it is transmitted to the low-orbit satellite covering the area through the ground upload link, and combined with its subsatellite track and revisit period, the broadcast rhythm is dynamically scheduled; (III) The low-orbit satellite broadcasts navigation enhancement data to the ground user by using the navigation enhancement load; (IV) The user terminal receives GNSS raw satellite navigation data and navigation enhancement data broadcast by low-orbit satellite and performs data fusion, uses integrated navigation solution algorithm for correction processing, and outputs high-precision positioning results.

2. The method of claim 1, wherein: In step (I), the specific content of error analysis includes that the high-precision GNSS reference station network acquires GNSS raw satellite navigation data combined with precise ephemeris, ionospheric model and clock error model, separates and models GNSS raw satellite orbit error, ionospheric delay and multipath error.

3. The method of claim 2, wherein: In step (I), the specific content of navigation enhancement data generation includes generating navigation enhancement parameters covering different areas based on difference technology and spatial grid interpolation algorithm.

4. The method of claim 3, wherein: The navigation enhancement parameters include satellite orbit correction, clock correction, ionospheric delay correction and residual error estimation.

5. The method of claim 1, wherein: In step (III), the low-orbit satellite broadcasts navigation enhancement data to the ground user by using L-band or Ka-band navigation enhancement load.

6. The method of claim 5, wherein: In step (IV), the integrated navigation solution algorithm selects RTK solution algorithm or PPP solution algorithm or PPP-RTK hybrid solution algorithm.

7. The method of claim 1, wherein: According to the low-orbit satellite and the regional demand, at least one low-orbit satellite in different regions provides navigation enhancement service at any time.

8. The method of claim 1, wherein: Data fusion is performed by extended Kalman filter EKF or unscented Kalman filter UKF or deep learning auxiliary model.

9. The method of claim 1, wherein: Multiple low-orbit satellites form a low-orbit satellite constellation with dense coverage and strong visibility.

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