LU503768B1 - Methods and systems for apnt positioning and integrity monitoring in aviation navigation network - Google Patents

Abstract

Disclosed are methods and systems for Alternative Positioning, Navigation and Timing (APNT) positioning and integrity monitoring in an aviation navigation network. The methods includes: determining a positioning accuracy requirement in a goal-oriented scenario; determining the position of an aircraft by using an integrated positioning algorithm when the positioning accuracy requirement is high accuracy positioning, and performing integrity monitoring on integrated positioning by way of multi-solution separation; determining whether the aircraft is a high-altitude user when the positioning accuracy requirement is low accuracy positioning; and if not, determining the position of the aircraft by using an air-to-air positioning algorithm of high-altitude user and low- altitude user based on the L-band Digital Aeronautical Communications System (LDACS), and performing integrity monitoring on air-to-air positioning based on the least-square residual method.

Description

BL-5635

METHODS AND SYSTEMS FOR APNT POSITIONING AND INTEGRITY LUs03768

MONITORING IN AVIATION NAVIGATION NETWORK

TECHNICAL FIELD

[01] The present invention relates to the technical field of aviation navigation, and particularly relates to methods and systems for Alternative Positioning, Navigation and

Timing (APNT) positioning and integrity monitoring in aviation navigation network.

BACKGROUND ART

[02] Modernization of an aviation transportation system puts forward higher requirements on performance of an aviation navigation system. Global Navigation

Satellite System (GNSS) mainly includes Global Positioning System (GPS) of the US,

Global Navigation Satellite System (GLONASS) of Russia, Galileo Satellite Navigation

System of Europe and BeiDou Navigation Satellite System (BDS) of China. Dependent on its high accuracy and high availability, GNSS has become the primary system for providing Positioning, Navigation and Timing (PNT) services on a global range.

[03] However, due to low power and long propagation distance, GNSS signals are highly susceptible to radio-frequency interference in a propagation process and are thus interrupted. Only relying on the GNSS during the flight of an aircraft may cause loss of navigation information after the aircraft is interrupted by interference, and may cause flight accidents in serious case. As a frequently used navigation system second only to

GNSS, Inertial Navigation Systems (INS) is subject to certain limitations in time as errors thereof are accumulated over the time. Therefore, it is necessary to use an existing navigation aid system as a backup system. When the GNSS is unavailable, the navigation aid system provides the aircraft with APNT services, so as to construct an aviation navigation network, thereby guaranteeing flight continuity and integrity.

[04] The navigation aid system mainly includes Distance Measuring Equipment (DME), a Very High Frequency Omnidirectional Radio Range (VOR), an Instrument

Landing System (ILS), a barometric altimeter and other novel systems with navigation abilities such as L-band Digital Aeronautical Communication System (LDACS).

[05] At present, Next Generation Air Transportation System (Next Gen) of the US and

Single European Sky ATM Research (SESAR) of Europe conduct researches on APNT services and put forward some alternatives (for example, DME augmentation system,

LDACS, mode N based on SSR and eLoran). Further researches are still needed to determine how to select these alternatives in a sustainable manner without bringing risks to Dual-Frequency Multi-Constellation (DFMC) GNSS. SESAR conduct researches from short term, medium term and long term in terms of degree of sophistication of the APNT services. Short term researches achieve the APNT services mainly based on a DME/DME solution; medium term researches achieve the APNT services mainly based on a multi-

DME positioning algorithm with Receiver Autonomous Integrity Monitoring (RAIM); and a long term goal is to achieve the APNT services through advanced system structures of LDACS and eLORAN, is capable of providing better performance and supports

Performance Based Navigation (PBN)/ Required Navigation Performance (RNP) operations by using a substitute technology. Future APNT services are modularly 1

BL-5635 combined by means of existing navigation equipment and novel navigation techniques to LU503768 achieve a goal of RNPO.3 in a terminal moving region.

[06] Development of the APNT services is faced with many problems, where improvement of the positioning accuracy and integrity monitoring are the most urgent problems to be solved.

SUMMARY

[07] The objective of the present invention is to provide methods and systems for

Alternative Positioning, Navigation and Timing (APNT) positioning and integrity monitoring in aviation navigation network, which achieves integrity monitoring of ANPT services on the premise of improving the positioning accuracy.

[08] To achieve the above objective, the present invention provides the following solution:

[09] methods for APNT positioning and integrity monitoring in an aviation navigation network, including:

[10] determining a positioning accuracy requirement in a goal-oriented scenario;

[11] determining the position of an aircraft by using an integrated positioning algorithm when the positioning accuracy requirement is high accuracy positioning, and performing integrity monitoring on integrated positioning by way of multi-solution separation;

[12] determining whether the aircraft is a high-altitude user when the positioning accuracy requirement is low accuracy positioning; and

[13] if not, determining the position of the aircraft by using an air-to-air positioning algorithm of high-altitude user and low-altitude user based on the L-band Digital

Aeronautical Communications System (LDACS), and performing integrity monitoring on air-to-air positioning based on the least-square residual method.

[14] Optionally, the method further includes: determining the position of the aircraft by using a positioning algorithm based on Distance Measuring Equipment (DME)/DME when the aircraft is the high-altitude user, and performing the integrity monitoring on the positioning algorithm based on DME/DME.

[15] Optionally, the performing the integrity monitoring on the positioning algorithm based on DME/DME specifically includes:

[16] calculating the position of the aircraft which is not introduced to a new survey station and the position of the aircraft which is introduced to the new survey station;

[17] calculating the protection level of the positioning algorithm based on DME/DME based on the position of the aircraft which is not introduced to the new survey station and the position of the aircraft which is introduced to the new survey station; and

[18] comparing the protection level with a horizontal alerting limit required by an air route, so as to complete the integrity monitoring by the positioning algorithm based on

DME/DME.

[19] Optionally, the determining the position of the aircraft by using an air-to-air positioning algorithm of high-altitude user and low-altitude user based on the LDACS specifically includes:

[20] determining position information of the high-altitude user by using a Multi-DME 2

BL-5635 positioning algorithm; LU503768

[21] determining a measuring distance between the high-altitude user and the lower altitude user based on a two-way ranging function of the LDACS; and

[22] determining the position of the aircraft according to the measuring distance and the position information of the high-altitude user.

[23] Optionally, the performing integrity monitoring on air-to-air positioning based on the least-square residual method specifically includes:

[24] calculating a fault detection threshold through a false detection probability of a system;

[25] calculating the minimum detectable fault according to the detection threshold and a leak detection probability;

[26] calculating a horizontal accuracy factor of the system;

[27] calculating a horizontal protection level of the system through the minimum detectable fault and the horizontal accuracy factor; and

[28] completing the integrity monitoring on air-to-air positioning based on the horizontal protection level.

[29] Optionally, the determining the position of the aircraft by using an integrated positioning algorithm specifically includes:

[30] calculating ranging errors obtained by performing two-way ranging by ” DME stations and pseudo-range errors obtained by performing one-way measurement by ”

LDACS stations;

[31] constructing an observation equation of a ranging system based on the ranging errors and the pseudo-range errors;

[32] taking a barometric altitude as an observed quantity, and introducing a barometric altimeter into the system to obtain an altitude observation equation;

[33] constructing an observation model of the system based on the observation equation and the altitude observation equation; and

[34] solving the observation model by using the least square method to determine the position of the aircraft.

[35] Optionally, the performing integrity monitoring on integrated positioning by way of multi-solution separation specifically includes:

[36] calculating a master state estimation and a slave state estimation based on the observation model of the system;

[37] calculating a variance-covariance matrix based on the master state estimation and the slave state estimation;

[38] constructing horizontal position test statistic based on the variance-covariance matrix;

[39] calculating a fault detection threshold according to the false detection probability;

[40] determining whether there is a fault according to the test statistic and the detection threshold;

[41] if there is a fault, isolating the fault and calculating the protection level of the system;

[42] if there is no fault, calculating the protection level of the system directly; and

[43] completing the integrity monitoring on the integrated positioning according to the 3

BL-5635 protection level. LU503768

[44] An Alternative Positioning, Navigation and Timing (APNT) positioning and integrity monitoring system in an aviation navigation network, including:

[45] a requirement determination module, configured to determine a positioning accuracy requirement in a goal-oriented scenario;

[46] a first positioning and integrity monitoring module, configured to determine the position of an aircraft by using an integrated positioning algorithm when the positioning accuracy requirement is high accuracy positioning and to perform integrity monitoring on integrated positioning by way of multi-solution separation;

[47] a determination module, configured to determine whether the aircraft is a high- altitude user when the positioning accuracy requirement is low accuracy positioning; and

[48] a second positioning and integrity monitoring module, configured to, determine the position of the aircraft by using an air-to-air positioning algorithm of high-altitude user and low-altitude user based on the L-band Digital Aeronautical Communications

System (LDACS) when the aircraft is the high-altitude user, and to perform integrity monitoring on air-to-air positioning based on the least-square residual method.

[49] Optionally, the system further includes: a third positioning and integrity monitoring module, configured to determine the position of the aircraft by using a positioning algorithm based on Distance Measuring Equipment (DME)/DME when the aircraft is the high-altitude user, and to perform the integrity monitoring on the positioning algorithm based on DME/DME.

[50] Optionally, in the determining the position of the aircraft by using an air-to-air positioning algorithm of high-altitude user and low-altitude user based on the LDACS, the second positioning and integrity monitoring module specifically includes:

[51] a high-altitude user position information unit, configured to determine position information of the high-altitude user by using a Multi-DME positioning algorithm;

[52] a measuring distance determination unit, configured to determine a measuring distance between the high-altitude user and the lower altitude user based on a two-way ranging function of the LDACS; and

[53] a position determination unit, configured to determine the position of the aircraft according to the measuring distance and the position information of the high-altitude user.

[54] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[55] The present invention provides methods and systems for APNT positioning and integrity monitoring in an aviation navigation network, which provides an aircraft with various APNT alternatives according to different requirements of users on positioning accuracy and actual application conditions under the condition that the accuracy is reduced as aviation navigation based on GNSS is subject to interference and even the navigation is unavailable, and studies a fault detection algorithm for each alternative, so as to achieve the integrity monitoring of APNT services.

BRIEF DESCRIPTION OF DRAWINGS

[56] In order to describe the embodiments of the present invention or the technical scheme in the prior art more clearly, brief introduction on drawings needed to be used in 4

BL-5635 the embodiment will be made below. It is obvious that the drawings described below are LU503768 merely some embodiments ofthe present invention, and those skilled in the technical field can further obtain other drawings according to the drawings without creative efforts.

[57] FIG. 1 is a flow chart of methods for APNT positioning and integrity monitoring in an aviation navigation network provided by the present invention.

[58] FIG. 2 is an overall flow chart of the methods for APNT positioning and integrity monitoring in an aviation navigation network provided by the present invention.

[59] FIG. 3 is a hierarchical chart of a multi-solution separation method provided by the present invention.

[60] FIG. 4 is a flow chart of a multi-solution separation-based APNT integrity monitoring algorithm provided by the present invention.

[61] FIG. 5 is a schematic structural diagram of systems for APNT positioning and integrity monitoring in an aviation navigation network provided by the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[62] The technical solutions in the embodiments of the present invention are clearly and completely described below in combination with the drawings in the embodiments of the present invention. Apparently, the embodiments described are only some embodiments rather than all embodiments of the present invention. On a basis of the embodiments in the present invention, all other embodiments obtained by those skilled in the technical field without creative efforts fall into the scope of protection of the present invention.

[63] The most basic APNT method achieves positioning based on DME/DME.

However, this method requires a user to perform information transmission uninterruptedly with a certain quantity of DME stations during the flight. However, with respect to aircrafts flying at low altitudes, affected by terrain and urban environment, a part of ground DME ranging sources may be sheltered, which results in reduction of the positioning accuracy solved by the users. When the number of the ranging sources decreases to a certain extent, the APNT is even unavailable. To solve the problem, the present invention provides the low-altitude user with position information by taking the high-altitude user who acquires relatively high positioning accuracy through Multi-DME as an on-board ranging source, which is similar to achieve positioning through pseudo- range measurement in GNSS. The present invention achieves air-to-air cooperative positioning integrity monitoring based on the least-square residual algorithm and further calculates the protection level of the system by means of the minimum detectable fault.

However, with respect to users with higher positioning requirements, the positioning accuracy provided by this method is limited. To solve the problem, the present invention puts forward a positioning method by combining DEM, LDACS and the barometric altimeter, which achieves positioning through combined ranging, pseudo-range measurement and altitude measurement by means of the minimum residual algorithm.

This method is capable of providing the user with higher positioning accuracy.

[64] Another significant problem for the APNT is integrity monitoring. Required

Navigation Positioning (RNP) requires on-board equipment to have on-board performance monitoring and On-Board Performance Monitoring and Alerting (OPMA)

BL-5635 abilities, and DMF/DME positioning may not support the RNP navigation specifications. LU503768

Therefore, an On-Ground Performance Monitoring and Alerting (GPMA) concept which supports RNP is put forward, which is similar to a frequently used RAIM algorithm in

GNSS, thereby performing integrity monitoring for the DME/DME system. With respect to the positioning method by combining DEM, LDACS and the barometric altimeter, integrity monitoring is mainly performed through redundancy measurement. The present invention constructs the observation model of the system and achieves monitoring and separating of the APNT faults by way of multi-solution separation.

[65] In view of this, the present invention provides a navigation and Timing (APNT) positioning and integrity monitoring method and system in an aviation navigation network, which achieves integrity monitoring of ANPT services on the premise of improving the positioning accuracy.

[66] In order to make the above objectives, features and advantages of the present invention clearer and more comprehensible, the present invention will be further described in detail below in combination with the drawings and specific embodiments.

[67] The objective of the present invention is mainly achieved by the following technical solutions:

[68] 1. Accurate positioning and accuracy estimation for the high-altitude user are achieved through DME/DME.

[69] 2. The fault mode introduced in DME/DME positioning is determined, positional deviations corresponding to the DME are calculated, fault detection is achieved through the introduced novel survey stations, the protection level of the system is calculated, and meanwhile, the protection level is compared with the alerting limit to determine the availability of the system.

[70] 3. Positioning of the high-altitude user is achieved through Multi-DME, and air- to-air cooperative positioning between the high-altitude user and the low-altitude user is achieved based on the two-way ranging function of LDACS.

[71] 4. Positioning of the high-altitude user is achieved through Multi-DME, and air- to-air cooperative positioning between the high-altitude user and the low-altitude user is achieved based on the two-way ranging function of LDACS.

[72] 5. The fault model introduced in the air-to-air positioning is determined, and the fault detection algorithm is designed for its characteristics to model residual errors of positioning errors, so as to calculate the protection level of the system.

[73] ©. High accuracy positioning of the user is achieved through DME/LDACS/ barometric altimeter by utilizing the least square method.

[74] 7. Integrity monitoring of the integrated positioning is achieved by means of the multi-solution separation algorithm, positioning errors of a complete set and each corresponding sub set are calculated to achieve detection and exclusion of the APNT faults, and the protection level of the system is calculated to determine the availability of the system.

[75] Embodiment I

[76] As shown in FIG. 1 and FIG. 2, methods for APNT positioning and integrity monitoring in aviation navigation network provided in the embodiment include the following steps: 6

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[77] Step 101: a positioning accuracy requirement in a goal-oriented scenario is LU503768 determined, where the goal-oriented scenario is a scenario when GNSS is unavailable.

[78] Step 102: the position of an aircraft is determined by using an integrated positioning algorithm when the positioning accuracy requirement is high accuracy positioning, and integrity monitoring is performed on integrated positioning by way of multi-solution separation.

[79] Step 103: whether the aircraft is a high-altitude user is determined when the positioning accuracy requirement is low accuracy positioning; if not, Step 104 is executed; and if yes, Step 105 is executed.

[80] Step 104, the position of the aircraft is determined by using an air-to-air positioning algorithm of high-altitude user and low-altitude user based on the L-band

Digital Aeronautical Communications System (LDACS), and integrity monitoring is performed on air-to-air positioning based on the least-square residual method.

[81] Step 105: the position of the aircraft is determined by using a positioning algorithm based on Distance Measuring Equipment (DME)/DME when the aircraft is the high-altitude user, and the integrity monitoring is performed on the positioning algorithm based on DME/DME.

[82] The Step 105 specifically includes:

[83] 1. Positioning principle based on DME/DME

[84] DME which refers to a distance meter is distance measuring equipment widely applied to aviation navigation, which includes an on-board interrogator and an on-ground transponder. During work, the interrogator sends interrogating signals, and the transponder transmits responses in sync with the interrogating signals in order. In this way, the DME system can measure the slope distance between the aircraft and the earth station.

A single DME station cannot position the aircraft, and the position of the aircraft can be determined when two or more DEM station signals are received simultaneously.

[85] When positioning is performed based on the positioning principle of DMF/DME, the aircraft has to be located within a coverage area of the DME station and is capable of receiving input signals of at least two DME stations simultaneously. If only inputs of two

DME stations are received, the included angle between the aircraft and the connecting line of the two DME stations has to be within 30 degrees to 150 degrees. DME/DME is one of the primary modes that support Regional Area Navigation (RNAV), and its positioning accuracy is second to that of GNSS.

[86] 2. The integrity monitoring algorithm for DME/DME specifically includes: the position of the aircraft which is not introduced to the new survey station and the position of the aircraft which is introduced to the new survey station are calculated; the protection level of the positioning algorithm based on DME/DME is calculated based on the position of the aircraft which is not introduced to the new survey station and the position of the aircraft which is introduced to the new survey station, and the protection level is compared with the horizontal alerting limit required by the air route to complete the integrity monitoring of the positioning algorithm based on DME/DME. The detailed process is as follows:

[87] The DME signal may be susceptible to two threats in the propagation process.

On the one hand, the DME signal may be affected by terrain to generate the multipath 7

BL-5635

LL LL . . LU503768 effect, resulting in a ranging information error, and on the other hand, the DME signal may be susceptible to interference of other signals in the same channel, resulting in a receiving error ofthe DME signal. The former can be improved through change of signal waveform and echo suppression mechanism and the latter requires frequency assignment and compatibility research on the signal. The present invention integrates the two into a transponder fault which is reflected in position deviation of the DME station, making a non-zero mean value of DME error distribution.

[88] Assuming that the DME errors obey normal distribution, the mean value of fault- free transponders is zero and the mean value of fault transponders is equal to a station deviation: e, =N o o .

D (Alp, ’ D) (1); where Pi represents a standard deviation of a ranging [ 2 2

Lo. . On =4/0qc +O,, = deviation of the DME station, and © Sis ar Ogg 0.05NM ;

Ja = Max {0.085 NM,0.00125D,} and D, represent slant distances.

[89] The position is calculated based on two DME stations ’>J to obtain a horizontal position error: . ep + ep

DD, ; sin @,, a. . . 7 (2); where ” represents an included angle between the aircraft and pp, Co the two stations, and Y shall obey normal distribution: e, =N o

D, (App, >Opp, ) (3); where

Hp, + Hp,

Hon, = sina 27 @; 2 2

Jo +05,

Con, = sing, 7 (5);

[90] A single fault scenario is designed: assuming that the aircraft acquires an initial effective position through two fault-free DME stations, with change of the position of the aircraft, the initial two stations no longer satisfy geometrical conditions, and it needs to introduce a new station DME3 to replace one survey station in the initial stations. À Flight

Management System (FMS) compares the position of the aircraft which is not introduced to the new survey station with the position of the aircraft which is introduced to the new survey station to determine a potential ranging deviation and then to calculate the protection level of a solution of the position.

[91] Setting the ranging error Ry acquired by the two fault-free initial stations to 8

BL-5635

N(O LU503768

Oo . obey (©, DD) and the ranging error R; based on fault DME3 to obey

N(u,o CL . (44T ) a fault determination form is:

IR, —R, >T — failure (6);

R=R.-R Op = 4 lo} +0;

[92] test statistic “ "1275 is defined, where * PD2 P If the DME3 is free of fault, the test statistic © obeys N(0,07), and the fault detection threshold . “qe Py

T can be solved from the false detection probability : 2 2 pe + pal 7 ° "de = Fra

[93] if the DME3 has a fault, the test statistic À obeys N(44 op) , and the minimum detectable detection deviation “m is solved from the leak detection probability Lona and the detection threshold 7’: 1 T (X Un y

Pad = Nerd € ? dx 2x (8);

[94] assuming herein that the aircraft performs ranging by using the DME3 and the

DME], the Horizontal Protection Level (HPL) of the system is calculated through deviation detection:

H,,

HPL = pr, =

SIN &, 4 (9):

[95] the HPL is compared with the horizontal alerting limit required by the air route, and if the protection level is higher than the horizontal alerting limit, the system is unavailable.

[96] The determining the position of the aircraft by using an air-to-air positioning algorithm of high-altitude user and low-altitude user based on the LDACS specifically includes:

[97] position information of the high-altitude user is determined by using a Multi-

DME positioning algorithm; a measuring distance between the high-altitude user and the low-altitude user is determined based on the two-way ranging function of the LDACS; and the position of the aircraft is determined according to the measuring distance and the position information of the high-altitude user. A detailed process is as follows:

[98] (1) the air-to-air positioning algorithm of high-altitude user and low-altitude user based on the LDACS

[99] Affected by terrain masking, performance of the low-altitude user to transmit and 9

BL-5635 receive the navigation signal 1s limited, and it is hard to position. In comparison, the high- LU503768 altitude user can acquire ranging information and ranging error information from more ground ranging sources, for example, achieves accurate positioning through the Multi-

DME method, and broadcasts the position information and the covariance matrix of the high-altitude user as the on-board ranging source. Distance measurement between the high-altitude user and the lower altitude user is achieved in combination with air-to-air communication ability of the LDACS, and the lower altitude user can acquire own position. In view of a limited number of high-altitude ranging sources, two-dimensional positioning is performed only herein, and altitude measurement is performed in an assisted manner by utilizing the barometric altimeter.

[100] Air-to-air measurement is performed according to position measurement Va of the ranging source A of the high-altitude user, and its position error “4 obeys us N(OË) re 4 distribution . The distance between the lower altitude user and the on-board ranging source ” 1s: r= (x, a) TO MY Od” at) + (10); where u n Ne ; ; . (n) and x) represent positions of the aircraft and the ranging source, respectively, € 70) . M‘) represents a range error, represents a tropospheric delay, represents a . de” . dt multipath effect, represents a clock skew of the on-board ranging source, u represents a clock skew of a user receiver, and 16) represents a group of unit vectors in a connecting line direction of the user receiver and the ranging source, which is called as a Light of Sight (LoS) vector herein. . . (n)

[101] Under an underground of RNP operation, tropospheric delay T and influence M () of multipath can be neglected because they usually only cause a random error several orders of magnitudes less than Cr. Measurement of pseudorange between the on-board ranging source and the low-altitude user is achieved through the two-way ranging function of the LDACS:

Th _ r =c-\t —t oo . ( u n ) (11);where lu and # represent a transmitting time and a receiving time of the signal, respectively, and © represents a light speed.

[102] In the air-to-air positioning algorithm, the on-board ranging source is different from a satellite or the on-ground ranging source, and its position itself has non-negligible

BL-5635 . . . . . . . . LU503768 indeterminacy which can be regarded as an ephemeris error in the satellite and is obtained by adding noise Zr in distance measurement and the indeterminacy of the on-board ranging source along the LoS. The range error € m at the low-altitude user/ can be . 22020020400 NO,O, approximate to zero mean value Gaussian distribution ( J ) , where: 21 0,,=0,+ =. L| 12)

[103] >, represents an error covariance matrix for positioning according to the position of the ranging source and is relevant to the position indeterminacy of the ranging source itself, reflecting accuracy of a distance measurement value obtained by the ranging source signal. As the on-board ranging source achieves positioning through Multi-MDE, its positioning accuracy can be represented as:

T -1

O position = GDOP 0, = trace(H H) Op 1. (13);where H represents a direction cosine matrix between the ranging source and the plurality of DME stations thereof, so -1 >, =G Osten =G" (zrace(H”H) O5 Je (14);

[104] so, the variance of the range error is represented as: -1 ol=0+ (& (race (HH) 5; )e)-1, (15);

[105] the position is solved through the weighted minimum residual method by utilizing two equations (1) and (11):

T AT x = (G'wG) , 1 ox, G WG) G Wor, (16);where G represents a geometry matrix formed by the LoS unit vector and is relevant to the geometric position of the ranging source relative to the user, W represents a weighting matrix reflecting the range error caused 1

Te or by each ranging source, with a diagonal element On, “1 represents ranging . . ee Ix. —x|<e,e>0 ae obtained in an iterative process. When I'” ! , the user position is convergent to X and the positioning error obeys multivariate Gaussian distribution

NOX £=(G'w6a}" ©, ). the covariance matrix being ~~

[106] (2) the performing integrity monitoring on air-to-air cooperative positioning based on the least-square residual method specifically includes: 11

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[107] A fault detection threshold is calculated through a false detection probability of LU503768 the system; the minimum detectable fault is calculated according to the detection threshold and a leak detection probability; a horizontal accuracy factor of the system 1s calculated; a horizontal protection level of the system is calculated by the minimum detectable fault and the horizontal accuracy factor; and integrity monitoring on the air-to- air positioning is completed based on the horizontal protection level. The detailed process is as follows:

[108] Air-to-air cooperative positioning can achieve integrity monitoring through the least-square residual method.

[109] A linearized pseudorange observation equation is as follows:

Y=GX +g (17);

[110] Position estimation which makes the quadratic sum of the range error be the least is obtained through the least square method: oT ALT

X=(G'WG)'G’WY (19).

[111] a ranging residual vector is represented as: v=Y-GX =[W"-G(G'WG)"G"']WY = Q,WY (19); where Q represents a co-factor matrix of the ranging residual vector. Under a fault-free condition, the weighted norm of the residual 2 vector obeys centered distribution / with the degree of freedom being N-2: 2 _ _ ou? 2 m =|v| =v Wv~ yy, (20);

[112] the air-to-air cooperative positioning introduces a novel fault model, which may cause a novel potential integrity risk. Similar to an ephemeris fault in satellite navigation, in the air-to-air cooperative positioning, position broadcasting of the on-board ranging source may have a fault AX, which is reflected in the range error through the LoS vector: r= (x, = + 209) I c(t, ) +2 21);

[113] it is set that Ar = Ax A" so the ranging expression under the fault is:

A = (x, — x”) ) A Ar 4e (dé) — dt) + gl (22);

[114] when the fault occurs, an error Ar caused by the ranging fault makes the pseudorange ranging residual change, and the ranging error mean value corresponding to the failed ranging source position in the vector is no longer zero, so the norm of the 2 pseudorange residual vector obeys non-centered distribution 4 , non-centered 12

BL-5635

LU503768 parameter being Ar 2 2 yl 42 m = vi An aa (23);

[115] to evaluate the minimum detectable fault of the system, the leak detection probability is equal to the maximum probable fault at an appointed integrity risk. The fault detection threshold 7» is calculated first through the false detection probability

Pra of the system:

Pa=f f. (x)de=1-y} (12 a=, Fa Od os

[116] the minimum detectable fault E, is calculated according to the detection threshold and a leak detection probability:

Tp 2 2

Py=["f, Od 5 (TR) 0 Zy_ap2 wr (25);

[117] In an actual navigation process, even if there is no fault, there may still be a condition that the integrity monitoring algorithm is unavailable due to an unsatisfactory geometrical configuration of the visible ranging source. To determine the availability of the algorithm, it needs to calculate the horizontal protection level. A variation ÖHDOR of the horizontal accuracy factor is obtained through the horizontal accuracy factor

HDOP of the geometrical configuration of the on-board ranging source and the horizontal accuracy factor HDOR after the ‘ ranging source is removed:

A+ A

SHDOP = HDOP* — HDOP* = he

Qu (26);

[118] finally, the horizontal protection level of the system is calculated through the minimum detectable fault ©» and HDOP (the horizontal accuracy factor) of the system:

HPL = öHDOP x x0, XE, on,

[119] The determining the aircraft by using an integrated positioning algorithm specifically includes:

[120] the range error obtained by performing two-way ranging by ” DME and the pseudorange error obtained by performing one-way measurement by ” LDACS stations are calculated; an observation equation of the ranging system is constructed based on the range error and the pseudorange error, by taking barometric altitude as an observed 13

BL-5635 quantity, the barometric altimeter is introduced to the system to obtain an altitude LU503768 observation equation; an observation model of the system is constructed based on the observation equation and the altitude observation equation; and the observation model is solved by using the least square method to determine the position of the aircraft.

[121] (1) Integrated positioning algorithm

[122] Under the condition that GNSS is unavailable, the APNT algorithm based on

DMF/DME or LDACS can provide users in different air spaces with basic PNT function so as to provide the users with required navigation performance in combination with the above integrity monitoring algorithm.

[123] To further satisfy a higher requirement of a part of users on positioning accuracy and integrity, various positioning methods can be combined to improve redundancy measurement. For example, measurement by DME, LDACS and barometric altimeter are combined to position based on the minimum residual algorithm, with a block diagram of the algorithm shown in FIG. 3. The DME provides a two-way ranging quantity, the

LDACS provides a one-way ranging quantity, and the barometric altimeter provides altitude information by measuring the barometric pressure. Measurement information of the systems is combined to achieve higher accuracy positioning.

[124] First of all, the range error under positioning achieved by the DME and the

LDACS is calculated.

[125] The range error obtained by performing two-way ranging by ” DEM stations is:

Pr Is, - X| P1- Pi yp(x) = : = : —|s, —X —p

Pm | w | Pm = Pm (28); where Pi represents a distance measured by the /® DME station, Si represents the position of the /™ DME station, and X represents the user position.

[126] The pseudorange error obtained by performing one-way ranging by ” DEM stations is:

Pi (Is... - x] + dr) Pu - Pn y (x)= : = : —\[s,, — X|+ dt —p

Pin ( Ln | ) Pin = Pin (29);where Pi represents a pseudorange measured by the J®IDACS station, Sy represents the position of the J th DACS station, X represents the user position, and 9! represents a clock deviation.

[127] The two are combined to obtain the observation equation of the ranging system: 14

BL-5635

LU503768 qu a, a, 0 : : : : | Ax a, a, a, 0 |A £ y=Gx+e= ! 2 3 y «| | (30);where y

Aig Apis Gp, 1] Az Er : : : : | cdt

Aint Aina ins a 1 represents an observed quantity, i.e., a difference between a ranged quantity and an approximate calculated distance; G represents an observation matrix, with Us being a coefficient of the observation matrix; X represents a quantity of state to be estimated formed by three position errors (A > Ayı Az ) and the clock deviation 4 of the receiver under an earth coordinate system; £0 represents an” <1 order vector, ©. is an” x! order vector, which respectively represent the ranging deviation vectors caused by influence of propagating indeterminacy and noise of the receiver in the ranging processes of the DME and the LDACS, with standard deviations being °P and ©, respectively.

[128] To introduce the observation information of the barometric altimeter to the observation equation conveniently, it needs to project the state of quantity into the earth coordinate system, with coordinate transformation formulae as follows:

À = arctan (2)

X/ (IA),

Jx+y h==——N cos 4 (1B); -1

N a pom] E10 | N = =— + + J —e” si ry (31C); where les , a represents a major radius of a reference ellipsoid, and © represents flattening of ellipsoid.

[129] They are iterated herein to obtain the range error under the earth coordinate system, the range error being represented as:

Ad Ax

AA |= A| Ay

Ah Az . ; (32); where oA and 7 represent latitude, longitude and altitude, and À represents a transformation matrix of coordinates.

[130] By taking the barometric altitude as the observed quantity, the barometric

BL-5635 : a 1 : : : : Co LU503768 altimeter is introduced into the system to obtain the altitude observation equation:

H,-H=Ah+e, (33); where Hz represents the barometric altitude, # represents the user altitude estimated, and “= represents the measurement error of the barometric altimeter, which obeys zero mean value Gaussian distribution, with the standard deviation being “5.

[131] The above observed quantities are combined to obtain a novel observation equation:

PAP

Ad — £

Z 5 5 HX+V AG Ad ’ = — = + = +1€

Pri Pr 00 1 ol Ak L : Er x cdt

Pr1 7 Pin

H,-H

B (34); where Z represents the observation information, including the observed quantities of the DME, the

LDACS and the barometric altimeter; H represents the observation matrix; X represents the state of quantity, including the range error equivalent to three position errors and the clock deviation of the receiver under a geographic coordinate system; V represents a noise measurement matrix, with the mean value being 0 and the variance 2 onlin

R = oil, co? matrix being Bl. AG is the #X4 order matrix, representing an observation matrix of the navigation system obtained by subjecting the observation matrix G to coordinate transformation.

[132] According to the system model, a positioning solution thereof can be solved through the least square method. When there are more than three DME and LDACS stations, the equation (32) has a unique solution: Ad, AA, AM The solution is a Ah y superposed to an initial position to obtain a next approximate position, the position replaces the initial position and is substituted into the equation (32) for iteration till Ag. AA Ah, reaches the needed order of magnitude, so as to obtain the least square solution of the user position under the geographic coordinate system.

[133] (2) The performing integrity monitoring of APNT based on multi-solution 16

BL-5635 separation specifically includes: LU503768

[134] a master state estimation and a slave state estimation are calculated based on the observation model of the system; a variance-covariance matrix is calculated based on the master state estimation and the slave state estimation; horizontal position test statistic 1s constructed based on the variance-covariance matrix; a fault detection threshold 1s calculated according to the false detection probability, whether there is a fault is determined according to the test statistic and the detection threshold; if there is a fault, the fault is isolated and the protection level of the system is calculated; if there is no fault, the protection level of the system is calculated directly; and the integrity monitoring on the integrated positioning is completed according to the protection level.

[135] Fault detection

[136] Based on construction of the observation model of the combined system, integrity monitoring on APNT is achieved by the multi-solution separation method. Estimate obtained by utilizing all observed quantities is defined as the master estimation, and estimation obtained by excluding an observed quantity is the slave estimation. A fault threshold is set, and monitoring and isolating of the APNT fault are achieved by comparing the differences among different estimations and the amplitude of the set threshold.

[137] The master estimation of the state under full observed quantities can be obtained according to the observation equation: = = T -1 T — -1 “oe .

X,=Q,Z =(H'WH) H WZ (35); where W=R represents a positive definite weighting matrix, and Q represents a least square solution matrix under a full observation condition, with dimensionality being 4* (m+n+1) orders. The ! “distance observed quantity is removed, and the state is solved by utilizing residual observation information to obtain the slave estimation of the state:

NT 1 T “1yqT A _ '

X, =Q/Z,= (HW, H) H;WZ, (i=12,m +n) (36); where Q represents a 4 X (m + n) . . . . ... order least square solution matrix under an incomplete observation condition after the ‘ distance observed quantity is excluded. To facilitate subsequent calculation,

Qi is expanded toa ** (m+n+1) order matrix À by zeroizing the ‘th column:

X, =QZ (i=1,2---,m+n) (37);

[138] the variance-covariance matrix based on the master state estimation and the slave state estimation is: dP, = Ex, -X, (x, —X, y] 7 -£lQ,-e zz’ @,-0 7 = (Q, -Q,)R(Q, -Q,) (38); 17

BL-5635 d a a LU503768 2 ‚= 4/dP (1,1) + dP (2,2 . ©

[139] the test statistic ' (1) (22) of the horizontal position is constructed hereby, and the fault detection threshold {, is calculated according to the . 1 Pa. false detection probability X: dP, -1 Py

T = erf "|A 2(m+n) AP . CL (39); where represents the maximum characteristic . . . . _. . dP erf -1 value corresponding to the direction of the horizontal position in i, and (J erf(x)=—— |e di represents an inverse function of Vom >

[140] The fault is determined according to ”” +” group of test statistic and the fault detection threshold based on: . Ar . <T

[141] There is no fault Ho. all test statistic satisfies d, < L.

[142] There is a fault H,. at least one group of test statistic satisfies d, > I

[143] Fault separation

[144] After the fault is detected, it needs to position and identify the fault, so as to achievefault isolation. Through the slave estimation X, and the sub estimations Xi thereof, the processing course is similar to the fault detection process. It needs to calculate the test statistic di, and the detection threshold Li first, and then to perform determination. The ground to determine the fault of the 7 ranging source is as follows: if there is only one slave estimation X, and the test statistic Xi ofthe slave estimation and all the sub estimations all are less than the fault detection threshold, the 7" ranging source needs to be isolated.

[145] If the test statistic of all the slave estimations and the corresponding sub estimations is greater than the fault detection threshold, it illustrates that there are faults of the multiple ranging sources, and analogy of the method is needed for further analysis.

[146] The hierarchical chart of the multi-solution separation method is shown in FIG. 4.

[147] Protection level calculation

[148] After the integrity monitoring is performed, the availability strictly required by integrity shall be determined, and the horizontal protection level and the Vertical

Protection Level (VPL) of the aircraft are calculated.

[149] HPL Corresponding to each slave estimation X, includes two parts: one is a threshold disintegrating the slave estimation X, and the master estimation X, ie, the 18

BL-5635 p LU503768 fault detection threshold 1; obtained by calculating the false detection probability =, and the other is an error threshold “ of the horizontal position of the slave estimation itself:

HPL =T +a, (40):

[150] the error covariance matrix of the slave estimation X, is designed as: — T1ı1_ T

P, = E[0X,0X, ] - Q RQ, (41),

[151] X is set to be the maximum characteristic value corresponding to the direction of the horizontal position in P, , and with respect to the given leak detection probability

Lo , it can obtained:

Ir —1 a, =A erf (1-P,,) (42);

[152] the horizontal protection level of the multi-solution separation method is further calculated: 1153] HPL= max(HPL,)=max(T, +a,) (43):

[154] similarly, the vertical protection level of the multi-solution separation method can be calculated:

VPL =max(VPL,)=max(D, +a,) (44). where -1 P fa 1,= dR 3 3erf " (m+n) (45): a, = V P (8,3)erf” (1 Pa) (46).

[155] Embodiment IT

[156] As shown in FIG. 5, the embodiment provides systems for APNT positioning and integrity monitoring in an aviation navigation network, including:

[157] a requirement determination module 501, configured to determine a positioning accuracy requirement in a goal-oriented scenario;

[158] a first positioning and integrity monitoring module 502, configured to determine the position of an aircraft by using an integrated positioning algorithm when the positioning accuracy requirement is high accuracy positioning and to perform integrity monitoring on integrated positioning by way of multi-solution separation;

[159] a determination module 503, configured to determine whether the aircraft is a high-altitude user when the positioning accuracy requirement is low accuracy positioning;

[160] a second positioning and integrity monitoring module 504, configured to 19

BL-5635 determine the position of the aircraft by using an air-to-air positioning algorithm of high- LU503768 altitude user and low-altitude user based on the L-band Digital Aeronautical

Communications System (LDACS) when the aircraft is the high-altitude user, and to perform integrity monitoring on air-to-air positioning based on the least-square residual method; and

[161] a third positioning and integrity monitoring module 505, configured to determine the position of the aircraft by using a positioning algorithm based on Distance Measuring

Equipment (DME)/DME when the aircraft is the high-altitude user, and to perform the integrity monitoring on the positioning algorithm based on DME/DME.

[162] In the determining the position of the aircraft by using an air-to-air positioning algorithm of high-altitude user and low-altitude user based on the LDACS integrity monitoring module specifically includes:

[163] a high-altitude user position information unit, configured to determine position information of the high-altitude user by using a Multi-DME positioning algorithm;

[164] a measuring distance determination unit, configured to determine a measuring distance between the high-altitude user and the lower altitude user based on a two-way ranging function of the LDACS; and

[165] a position determination unit, configured to determine the position of the aircraft according to the measuring distance and the position information of the high-altitude user.

[166] Compared with the prior art, the present invention has the innovated parts as follows:

[167] The present invention provides the method for classification according to the requirement of the user on the positioning accuracy and the actual application conditions.

In view of characteristics in various conditions, three different APNT algorithms are provided;

[168] 1. The algorithm flow for realizing air-to-air relative cooperative positioning by utilizing the two-way ranging function of the LDACS is provided, and the position error

O position = GDOP-6, = Jirace(H"H) “Cp . . of the on-board ranging source for realizing positioning through Multi-DME and the range error 0; =0;+ (ce (race (11) où )c) . 1) for realizing positioning by the low-altitude user through the LDACS are given,

[169] 2. The special fault mode in the air-to-air cooperative positioning is analyzed, that is, the position information fault of the on-board ranging source itself, analogy thereof to the ephemeris fault in satellite navigation is performed, the ranging expression

A =(x, x) 10 +A (dl dt, +e" a in the fault mode is given, and fault detection by chi-square test and the solving method for the detection threshold are provided for the special fault;

[170] 3. The calculation method HPL=0HDOR, x0, x LE, for the horizontal protection level suitable for the air-to-air cooperative positioning algorithm based on the

BL-5635

LDACS 1s provided to determine the availability of the APNT system; LU503768

[171] 4. Range error expressions for realizing positioning by utilizing DME and

LDACS are given, respectively, and the observation equation a, a, a5 0 : : : : | Ax a, a, a, 0A € y=Gx+e= ! ? A y | " pig Ama Ama 1 | Az Er : : : : | edt

Duin Gonz mms 1 of the ranging system formed by combining ” two-way ranging quantity performed by DME and ” pseudorange measurement;

[172] 5. The novel integrated positioning method for realizing the APNT services by combining measurement information of DME/LDACS/barometric altimeter is provided,

[173] 6. The method of subjecting the observation equation obtained by combining

DME/LDACS to coordinate transformation to the geographic coordinate system and combining the observation equation with altitude measurement provided by the barometric altimeter to obtain the combined observation equation

Poi Pot a Ad — £ „ Pom Pon ax sv AG AA D = — = + = +1€

Pu Pi 0 0 1 ol Ah L : En ‘1 cdt

Pri 7 Pin

Hy—H is provided, and positioning is solved through the least square method;

[174] 7. The flow of integrity monitoring by using the multi-solution separation algorithm is given according to characteristics s of the DME/LDACS/barometric altimeter integrated positioning system; and the master estimation _ _ T “1yyT __

X, =Q,2=-(H WH) H WZ of the state and the slave estimation X, =QZ of the state are calculated according to the state equation, the novel horizontal position test statistic d, = AP, (1) + dP, (2,2) is constructed according to system characteristics, the dP, -1 Py

I= ef "Semen detection threshold (m+n) is calculated, and fault determination on the system is performed according to the test statistic and the fault detection threshold;

[175] 8. The flow of realizing fault isolation of the APNT ranging source by calculating the slave estimation X, of the state and the sub estimations x of the slave estimation 21

BL-5635 after the fault is detected is given; LU503768

[176] 9. The method for calculating the horizontal and vertical protection levels of the

APNT according to the covariance matrix of the difference between the master estimation and the slave estimation obtained by the DME/LDACS/barometric altimeter composite state equation and the false detection probability and the leak detection probability of the system.

[177] It can be seen from the solution provided by the present invention that the present invention has the following beneficial effects:

[178] I. The present invention provides the aircraft with various APNT alternatives, thereby providing a solution for positioning difficulty of the aircraft under the condition that GNSS is unavailable;

[179] II. The present invention provides the low-altitude users sheltered by terrain or buildings with a relative positioning method based on the two-way ranging function of the LDACS;

[180] III. The present invention provides the method for integrated positioning by utilizing DME/LDACS/barometric altimeter, thereby further improving the positioning accuracy of APNT,

[181] IV. To achieve the integrity monitoring of APNT, the present invention provides the fault detection algorithm suitable for each positioning algorithm, and the availability of the algorithm is proved by calculating the protection level; and

[182] V. The present invention is beneficial to improvement of degree of emphasis on

APNT at home, thereby promoting popularization and application of its algorithm.

[183] Each embodiment of the description is described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts between the embodiments may refer to each other. Since the system disclosed in the embodiments corresponds to the method disclosed in the embodiments, the description is simple, and reference can be made to the method description.

[184] Particular embodiments are used for illustrating the principles and implementations of the present invention herein, and the above description of the foregoing embodiments is used only to help illustrating the method of the present invention and the core principles thereof. In addition, those of ordinary skill in the art may make any modification in terms of particular implementations and scope of application in accordance with the ideas of the present invention. In conclusion, the content of the description should not be construed as limitations tothe present invention. 22

Claims (10)

BL-5635 CLAIMS LU503768

1. Methods for Alternative Positioning, Navigation and Timing (APNT) positioning and integrity monitoring in an aviation navigation network, comprising: determining a positioning accuracy requirement in a goal-oriented scenario; determining the position of an aircraft by using an integrated positioning algorithm when the positioning accuracy requirement 1s high accuracy positioning, and performing integrity monitoring on integrated positioning by way of multi-solution separation; determining whether the aircraft is a high-altitude user when the positioning accuracy requirement is low accuracy positioning; and if not, determining the position of the aircraft by using an air-to-air positioning algorithm of high-altitude user and low-altitude user based on the L-band Digital Aeronautical Communications System (LDACS), and performing integrity monitoring on air-to-air positioning based on the least-square residual method.

2. The methods for APNT positioning and integrity monitoring in an aviation navigation network according to claim 1, further comprising: determining the position of the aircraft by using a positioning algorithm based on Distance Measuring Equipment (DME)/DME when the aircraft is the high-altitude user, and performing the integrity monitoring on the positioning algorithm based on DME/DME.

3. The methods for APNT positioning and integrity monitoring in an aviation navigation network according to claim 2, wherein the performing the integrity monitoring on the positioning algorithm based on DME/DME specifically comprises: calculating the position of the aircraft which is not introduced to a new survey station and the position of the aircraft which is introduced to the new survey station; calculating the protection level of the positioning algorithm based on DME/DME based on the position of the aircraft which is not introduced to the new survey station and the position of the aircraft which is introduced to the new survey station; and comparing the protection level with a horizontal alerting limit required by an air route, so as to complete the integrity monitoring by the positioning algorithm based on DME/DME.

4. The methods for APNT positioning and integrity monitoring in an aviation navigation network according to claim 1, wherein the determining the position of the aircraft by using an air-to-air positioning algorithm of high-altitude user and low-altitude user based on the LDACS specifically comprises: determining position information of the high-altitude user by using a Multi-DME positioning algorithm; determining a measuring distance between the high-altitude user and the lower altitude user based on a two-way ranging function of the LDACS; and determining the position of the aircraft according to the measuring distance and the position information of the high-altitude user.

5. The methods for APNT positioning and integrity monitoring in an aviation navigation network according to claim 1, wherein the performing integrity monitoring on air-to-air positioning based on the least-square residual method specifically comprises: calculating a fault detection threshold through a false detection probability of a 23

BL-5635 system: LU503768 calculating the minimum detectable fault according to the detection threshold and a leak detection probability; calculating a horizontal accuracy factor of the system; calculating a horizontal protection level of the system through the minimum detectable fault and the horizontal accuracy factor; and completing the integrity monitoring on air-to-air positioning based on the horizontal protection level.

6. The methods for APNT positioning and integrity monitoring in an aviation navigation network according to claim 1, wherein the determining the position of the aircraft by using an integrated positioning algorithm specifically comprises: calculating ranging errors obtained by performing two-way ranging by ” DME stations and pseudo-range errors obtained by performing one-way measurement by ” LDACS stations; constructing an observation equation of a ranging system based on the ranging errors and the pseudo-range errors; taking a barometric altitude as an observed quantity, and introducing a barometric altimeter into the system to obtain an altitude observation equation; constructing an observation model of the system based on the observation equation and the altitude observation equation; and solving the observation model by using the least square method to determine the position of the aircraft.

7. The methods for APNT positioning and integrity monitoring in an aviation navigation network according to claim 6, wherein the performing integrity monitoring on integrated positioning by way of multi-solution separation specifically comprises: calculating a master state estimation and a slave state estimation based on the observation model of the system; calculating a variance-covariance matrix based on the master state estimation and the slave state estimation; constructing horizontal position test statistic based on the variance-covariance matrix; calculating a fault detection threshold according to the false detection probability; determining whether there is a fault according to the test statistic and the detection threshold; if there is a fault, isolating the fault and calculating the protection level of the system; if there is no fault, calculating the protection level of the system directly; and completing the integrity monitoring on the integrated positioning according to the protection level.

8. Systems for Alternative Positioning, Navigation and Timing (APNT) positioning and integrity monitoring in an aviation navigation network, comprising: a requirement determination module, configured to determine a positioning accuracy requirement in a goal-oriented scenario; a first positioning and integrity monitoring module, configured to determine the position of an aircraft by using an integrated positioning algorithm when the positioning 24

BL-5635 accuracy requirement is high accuracy positioning and to perform integrity monitoring LU503768 on integrated positioning by way of multi-solution separation; a determination module, configured to determine whether the aircraft is a high- altitude user when the positioning accuracy requirement 1s low accuracy positioning; and a second positioning and integrity monitoring module, configured to determine the position of the aircraft by using an air-to-air positioning algorithm of high-altitude user and low-altitude user based on the L-band Digital Aeronautical Communications System (LDACS) when the aircraft is the high-altitude user, and to perform integrity monitoring on air-to-air positioning based on the least-square residual method.

9. The systems for APNT positioning and integrity monitoring in an aviation navigation network according to claim 8, further comprising: a third positioning and integrity monitoring module, configured to determine the position of the aircraft by using a positioning algorithm based on Distance Measuring Equipment (DME)/DME when the aircraft is the high-altitude user and to perform the integrity monitoring on the positioning algorithm based on DME/DME.

10. The systems for APNT positioning and integrity monitoring in an aviation navigation network according to claim 8, wherein in the determining the position of the aircraft by using an air-to-air positioning algorithm of high-altitude user and low-altitude user based on the LDACS, the second positioning and integrity monitoring module specifically comprises: a high-altitude user position information unit, configured to determine position information of the high-altitude user by using a Multi-DME positioning algorithm; a measuring distance determination unit, configured to determine a measuring distance between the high-altitude user and the lower altitude user based on a two-way ranging function of the LDACS; and a position determination unit, configured to determine the position of the aircraft according to the measuring distance and the position information of the high-altitude user.