ADS-B height updating method based on air pressure and geometry height compatibility

Abstract

The invention provides an ADS-B (Automatic Dependent Surveillance-Broadcast) height updating method based on compatibility of air pressure and geometric height, which belongs to the technical field of air traffic surveillance and specifically comprises the following steps: judging the track information of a local aircraft and the effectiveness of geometric height and air pressure height in the track information of a target aircraft; calculating the relative barometric altitude by using the calculated value of the barometric altitude of the target aircraft at the moment T1 and the barometric altitude calculated value of the local aircraft at the moment t; obtaining a predicted value of the track data of the target aircraft at the T1 moment; performing correlation judgment on the observed value and the predicted value of the track information of the target aircraft at the T1 moment to obtain a final output track; and outputting the relative height of the target aircraft and the local aircraft according to the final output flight path middle height data, the local aircraft height data and the effectiveness of the local aircraft pressure height. Through the processing scheme provided by the invention, the reliability of ADS-B track monitoring is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of air traffic surveillance, in particular to an ADS-B height updating method based on compatibility of barometric height and geometric height. BACKGROUND

[0002] With the improvement of the complexity of the aircraft system and the wide application of multi-source navigation equipment, the situation related to height in ADS-B becomes increasingly complex. There are cases of abnormal local barometric height data and cases of target aircraft providing only one of the geometric height and the barometric height. In the application of multi-aircraft cooperation, conflict detection, flight spacing maintenance and other applications that rely on high-reliability relative height calculation, abnormal processing failure or vertical conflict misjudgment may be caused. The Chinese interpretation of ADS-B is Automatic Dependent Surveillance-Broadcast, and the full name in English is Automatic Dependent Surveillance-Broadcast.

[0003] Therefore, an ADS-B track height data processing method compatible with barometric height and geometric height, with height type identification and substitution logic, is needed. In the case of local barometric height failure or target providing only geometric height, the method can automatically switch to using geometric height for relative height calculation, improving the adaptability and robustness of the ADS-B system in a diversified equipment environment. In the prior art, in the case that the ADS-B system may only receive barometric height, the geometric height is updated using an approximate formula: The formula is based on the assumption of a spherical earth, and the error is small at low altitudes, but the difference between barometric height and geometric height may increase significantly at high altitudes or under non-standard atmospheric conditions, resulting in cumulative track calculation errors and affecting the reliability of the surveillance system. In ADS-B track processing, if the target aircraft provides only geometric height and the local aircraft uses barometric height for relative height calculation, significant vertical spacing errors will occur due to the different measurement principles and inconsistent references of the two types of height.

[0004] The existing track processing method lacks a processing mechanism under abnormal conditions. When the local geometric height data is invalid or the barometric height data is invalid, fault isolation and degradation processing cannot be achieved, resulting in logical confusion of the output relative height. SUMMARY

[0005] Therefore, the present application provides an ADS-B height updating method based on compatibility of barometric height and geometric height, which solves the problems in the prior art and improves the reliability of ADS-B track surveillance.

[0006] The ADS-B height updating method based on compatibility of barometric height and geometric height provided by the present application adopts the following technical solution: An ADS-B height updating method based on compatibility of barometric height and geometric height comprises: Step 1, obtain the current time t the current time T the current time T 1 the observed value of the target aircraft's track information Step 2, determine the current time t the current time T the current time T 1 the validity of the geometric altitude and the barometric altitude in the target aircraft's track information, if the geometric altitude is valid, the valid geometric altitude is taken as the calculated value, if the geometric altitude is invalid, the geometric altitude value is calculated according to the valid barometric altitude using an approximate formula as the calculated value, if the barometric altitude is valid, the valid barometric altitude value is taken as the calculated value, if the barometric altitude is invalid, the barometric altitude value calculated according to the valid geometric altitude using an approximate formula is taken as the calculated value, the calculated value of the target aircraft's barometric altitude at the time t1 and T the calculated value of the barometric altitude of the host aircraft at the time t0 t the relative barometric altitude is calculated; Step 3, the geometric altitude calculated value of the target aircraft's track information at the time t0 is extrapolated to the time t1 to obtain the predicted value of the target aircraft's track data at the time t1 T T T T Step 4, the observed value and the predicted value of the target aircraft's track information at the time t1 are determined for correlation, and the relative barometric altitude is added to the calculated value of the barometric altitude of the host aircraft at the time t0 to obtain the barometric altitude of the target aircraft at the time t1 T t T T T Step 5, the difference between the current time of the host aircraft's track and the current time of the target aircraft's track is calculated, and the time difference is determined, if the time difference < 0.2s, the preliminary track information of the target aircraft at the time t1 is directly used as the final output track, if the time difference ≥ 0.2s, the target aircraft's track at the time t1 is linearly extrapolated to obtain the target aircraft's track at the time t0, and the extrapolation result is taken as the final output track t T T T t ​​​​​​​​​​​​​​Step 6, output the relative height between the target aircraft and the local according to the validity of the height data in the final output track, the local height data and the local barometric height.

[0007] Optionally, in step 2, the specific steps of judging the validity of the geometric height and the barometric height in the track information of the target aircraft at the last time T 0 and the track information of the target aircraft at the latest time T 1 include: When the encoding value of the "type" field of the air position message of the target aircraft is in the range of 9-18, the encoding value of the "height" field of the air position message is the barometric height , the difference between the geometric height and the barometric height is obtained through the decoding value of the "difference from barometric height" field in the air speed message , the geometric height of the aircraft , and the valid bit of the geometric height of the target aircraft and the valid bit of the barometric height are set to 1; When the encoding value of the "type" field of the air position message of the target aircraft is in the range of 20-22, the encoding value of the "height" field of the air position message is the geometric height , the difference between the geometric height and the barometric height is obtained through the decoding value of the "difference from barometric height" field in the air speed message , the barometric height of the aircraft , and the valid bit of the geometric height of the target aircraft and the valid bit of the barometric height are set to 1; When the "difference from barometric height" field in the air speed message is invalid, the valid bit of the geometric height of the target aircraft or the valid bit of the barometric height is set to 0.

[0008] Optionally, the specific steps of step 3 include: First, convert the track information of the target aircraft at time T 0 from the WGS84 coordinate system to the ENU coordinate system, and then extrapolate the track information at time T 0 to time T 1 from the three dimensions (x, y, z) of the EUN coordinate system respectively through Kalman filtering, to obtain the predicted value of the track data of the target aircraft in the ENU coordinate system at time T 1.

[0009] Optionally, the step of converting the track information of the target aircraft at time T 0 from the WGS84 coordinate system to the ENU coordinate system includes: T0Target aircraft longitude, latitude and altitude are converted from WGS84 coordinate system to ECEF coordinate system, and then converted to ENU coordinate system through a rotation transformation matrix with the local position as the reference, to obtain T 0Position data of the target aircraft at the moment.

[0010] Optionally, in step 4, the specific steps of converting the position data in the predicted value to generate the position data in WGS84 coordinates include: The position of the target aircraft in the ENU coordinate system is converted to ECEF coordinates through coordinate rotation and reference point translation, and then the corresponding position data in WGS84 coordinates is obtained by inverse solution using the geometry of the Earth ellipsoid.

[0011] Optionally, in step 4, the specific steps of converting the position data in the predicted value to generate the position data in WGS84 coordinates include: The position of the target aircraft in the ENU coordinate system is converted to ECEF coordinates through coordinate rotation and reference point translation, and then the corresponding position data in WGS84 coordinates is obtained by inverse solution using the geometry of the Earth ellipsoid.

[0012] Optionally, in step 6, if the local geometric height is invalid and the barometric height is valid, the relative height is the relative barometric height; If the local geometric height is valid and the barometric height is valid, the relative height is the relative barometric height; If the local geometric height is valid and the barometric height is invalid, the relative height is the relative geometric height.

[0013] In summary, the present application includes the following beneficial technical effects: The calculation of relative height in the method of the present application is compatible with both barometric height and geometric height, which has higher data reliability than the track updating method with single height source; The method of the present application designs a height conversion logic, which does not use the standard formula to calculate the geometric height when the local geometric height and traffic geometric height data are valid, effectively reducing the problem of large error between barometric height and geometric height in high altitude or non-standard atmospheric conditions, and improving the reliability of height data.

[0014] The method of the present application can also output accurate ADS-B height data when the barometric height of the target aircraft is invalid or the geometric height is invalid; The method of the present application increases the processing mechanism under abnormal conditions and designs a relative height calculation logic when the local barometric height is invalid or the geometric height is invalid, which can correctly calculate the relative height of the target aircraft and the local machine. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings described below only illustrate some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0016] Figure 1 The flowchart for updating the ADS-B track height data in the embodiments of the present application is shown in the figure. Figure 2 The flowchart for converting the WGS84 coordinate system track to the ENU coordinate system track in the embodiments of the present application is shown in the figure. Figure 3 The flowchart for converting the ENU coordinate system track to the WGS84 coordinate system track in the embodiments of the present application is shown in the figure. DETAILED DESCRIPTION

[0017] The embodiments of the present application will be described in detail below with reference to the drawings.

[0018] The embodiments of the present application are described below through specific concrete examples, and those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in the specification. Obviously, the described embodiments are only some of the embodiments of the present application, not all. The present application can also be implemented or applied by other different specific embodiments, and the details in the specification can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0019] It should be noted that the various aspects of the embodiments described below are within the scope of the appended claims. It should be apparent that the aspects described herein can be embodied in a wide variety of forms and that any specific structure and / or function described herein is merely illustrative. Based on the present application, those skilled in the art should understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, an apparatus and / or a method can be implemented using any number of the aspects set forth herein. In addition, this apparatus and / or method can be implemented using other structures and / or functionalities in addition to or other than those set forth herein.

[0020] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The illustrations only show the components related to this application and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0021] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0022] This application provides an ADS-B altitude update method based on air pressure and geometric altitude compatibility.

[0023] An ADS-B altitude update method based on barometric and geometrical altitude compatibility includes: Step 1, obtain the current time t The aircraft's flight path information, the target aircraft's previous moment T Flight track information for 0, latest time. T 1. Observed values ​​of the target aircraft's trajectory information.

[0024] Step 2, determine the current time. t The aircraft's flight path information, the target aircraft's previous moment T 0's flight track information and latest time T 1. The validity of geometric altitude and barometric altitude in the target aircraft's trajectory information. If the geometric altitude is valid, it is used as the calculated value. If the geometric altitude is invalid, the geometric altitude value is calculated using an approximate formula based on the valid barometric altitude, and the barometric altitude value is used as the calculated value. If the barometric altitude is valid, it is used as the calculated value. If the barometric altitude is invalid, the barometric altitude value is calculated using an approximate formula based on the valid geometric altitude, and the barometric altitude value is used as the calculated value. T The relative air pressure altitude is calculated by taking the target aircraft's air pressure altitude at time 1 and the aircraft's air pressure altitude at time t.

[0025] Determine the target aircraft at the previous moment T 0's flight track information and latest time T The specific steps for ensuring the validity of the geometric altitude and barometric altitude in the target aircraft's trajectory information include: When the "Type" field of the target aircraft's air position message is coded in the range of 9-18, the "Altitude" field of the air position message is coded as barometric altitude. The decoded value of the "barometric altitude difference" field in the "air speed message" The difference between geometric altitude and barometric altitude is obtained, which gives the aircraft's geometric altitude. and the effective position of the target aircraft's geometric altitude Effective position of barometric altitude Set to 1; When the "Type" field of the target aircraft's air position message is encoded in the range of 20-22, the "Altitude" field of the air position message is encoded as geometric altitude. The decoded value of the "barometric altitude difference" field in the "air speed message" The difference between geometric altitude and barometric altitude is obtained; this gives the aircraft's barometric altitude. and the effective position of the target aircraft's geometric altitude and effective position of air pressure altitude Set to 1; When the "barometric altitude difference" field in the airspeed message is invalid, the target aircraft's geometric altitude will be valid. or effective barometric altitude Set to 0.

[0026] Step 3, utilize the target aircraft's previous moment T The geometric altitude calculation value of the 0 track information will be T Extrapolation of 0 track data to T At time 1, the target aircraft was obtained. T The predicted value of the trajectory data at time 1; specifically, firstly, the predicted value of the trajectory data at time 1; T The target aircraft trajectory information at time 0 is transformed from the WGS84 coordinate system to the ENU coordinate system, and then processed using Kalman filtering from the three dimensions (x, y, z) of the ENU coordinate system. T Extrapolation of flight track information at time 0 to T At moment 1, we obtain T The predicted flight data of the target aircraft in the ENU coordinate system at time 1. WGS84 stands for World Geodetic System 1984; ENU stands for East-North-Up.

[0027] Will T The steps to convert the target aircraft trajectory information at time 0 from the WGS84 coordinate system to the ENU coordinate system include: T The longitude, latitude, and altitude of the target aircraft are transformed from the WGS84 coordinate system to the ECEF coordinate system, and then the ECEF coordinates are converted to the ENU coordinate system using a rotation transformation matrix with the aircraft's position as a reference. T Position data of the target aircraft at time 0. ECEF stands for Earth-Centered, Earth-Fixed.

[0028] Step 4, the correlation between the observation value and the prediction value of the target aircraft trajectory information at time t1 is determined, and the T 1time target aircraft flight path information is obtained by adding the relative barometric altitude to the local barometric altitude calculated value at time t1 t T 1time target aircraft barometric altitude, using the prediction value and T 1time target aircraft barometric altitude as T 1time target aircraft preliminary trajectory information, wherein the position data in the prediction value is the position data of the WGS84 coordinate generated by conversion; the specific steps of converting the position data in the prediction value into the position data of the WGS84 coordinate include: converting the position of the target aircraft in the ENU coordinate system into the ECEF coordinate through coordinate rotation and reference point translation transformation, and then inversely solving the corresponding WGS84 coordinate position data by using the geometric relationship of the earth ellipsoid.

[0029] Step 5, calculate the current time t of the local trajectory and the current time T 1of the target aircraft trajectory, and judge the time difference, if the time difference <0.2s, directly use T 1time target aircraft preliminary trajectory information as the final output trajectory, if the time difference ≥0.2s, linearly extrapolate the trajectory of T 1time target aircraft to obtain the trajectory of the target aircraft at t time, and take the extrapolation result as the final output trajectory.

[0030] wherein, the specific steps of linearly extrapolating the trajectory of T 1time target aircraft include: convert the target aircraft trajectory in the WGS84 coordinate system into the trajectory in the ENU coordinate system; update the three-dimensional coordinates of the target aircraft on the ENU coordinate system x , y and z axis with time and the east-west speed, north-south speed and vertical speed of the target aircraft: ; ; ; wherein, wherein, are the target aircraft ENU three-dimensional coordinates at time t2 after extrapolation, t are the target aircraft three-dimensional coordinates at time t1, are the target aircraft three-dimensional coordinates at time t1, T are the target aircraft three-dimensional coordinates at time t1, are the target aircraft three-dimensional coordinates at time t1, T ​Target aircraft three-dimensional velocity at time 1.

[0031] Re-convert the extrapolated target aircraft position data in ENU coordinate system into position data in WGS84 coordinate system, and combine the target aircraft position data in WGS84 coordinate system in step 3 T 1 Velocity information of the predicted value of the track data at time 1 and the latest time T 1 Time information and quality parameters in the observation value of the track information of the target aircraft to generate the latest aircraft track.

[0032] Step 6, output the relative height of the target aircraft and the host according to the effectiveness of the height data in the final output track, the local height data and the local barometric height.

[0033] As shown in Figure 1 , Figure 2 and Figure 3 , the embodiment of the present application provides a detailed step of an ADS-B height updating method based on the compatibility of barometric height and geometric height, which is specifically as follows Step 1: obtain and store the track information of the host at the current time t , including the position information, velocity information, time information and quality parameters of the host, and the position information is longitude and latitude and height. For the height data of the host, it is necessary to determine whether the geometric height from GPS and the barometric height from ADC are valid according to the effectiveness of the avionics data. If valid, store the barometric height and geometric height at the current time and use them for subsequent processing; if the barometric height or the geometric height is invalid, set the corresponding height and height validity to 0. Wherein, ADC is the full name of Analog-to-Digital Converter, and the Chinese name is Analog / Digital Converter.

[0034] Step 2, parse and store the track data of the aircraft at the current T 1, including the position information, velocity information, time information and quality parameters of the target aircraft. Among them, the height data includes the barometric height and the geometric height of the target aircraft, and the storage steps of the height data are as follows: When the "type" field coding value of the air position message of the aircraft is in the range of 9-18, the "height" field coding value of the air position message is the barometric height ; At this time, the difference between the geometric height and the barometric height can be obtained through the decoding value of the "barometric height difference" field in the "air speed message" , and then the geometric height of the aircraft is calculated by the following formula (1) , and the valid bit of the aircraft geometric height and the effective bits of the geometric altitude are set to 1. (1). When the "type" field of the air position message of the aircraft is encoded as a value in the range of 20-22, the "altitude" field of the air position message is encoded as the geometric altitude ; at this time, the difference between the geometric altitude and the barometric altitude can be obtained through the decoded value of the "difference from barometric altitude" field in the "air speed message" , and the barometric altitude of the aircraft is calculated by the following formula (2) , and the effective bits of the geometric altitude and the effective bits of the barometric altitude of the aircraft are set to 1. (2). When the "difference from barometric altitude" field in the air speed message is invalid, the geometric altitude or the barometric altitude of the aircraft is calculated, and the effective bits of the geometric altitude or the effective bits of the barometric altitude of the aircraft are set to 0.

[0035] Step 3: read the track data of the previous T 0 moment of the current aircraft in the track database, and generate a corresponding track state vector. The track state vector includes position information, speed information, time information, mass parameters, etc. Among them, the position information of the track state vector is expressed in the ENU east-north-up coordinate system, so it is necessary to convert the stored longitude, latitude and altitude of the aircraft from the WGS84 coordinate system to the three-dimensional coordinates of x, y and z in the ENU coordinate system. In the coordinate conversion, first, the validity of the geometric altitude and the barometric altitude of the local machine and the aircraft is judged, and then the assignment is made according to the judgment result, and the relative barometric altitude and the relative geometric altitude of the local machine and the aircraft are output at the same time, and the coordinate conversion process is as shown in Figure 2 .

[0036] Step 3.1: judge the validity of the local machine geometric altitude. If the local machine geometric altitude is valid and the barometric altitude is valid, the local machine geometric altitude and the barometric altitude are directly stored. If the local machine geometric altitude is valid and the barometric altitude is invalid, the local machine geometric altitude information is directly stored, and the local machine barometric altitude is calculated according to the following formula (3) (3). wherein, is the effective geometric altitude of the local machine, R is the radius of the earth.

[0037] If the local geometric altitude is invalid, and the barometric altitude is valid, then the local barometric altitude is stored directly, and the local geometric altitude is calculated according to the following formula 4) (4); wherein, is the local valid geometric altitude, R is the earth radius.

[0038] Step 3.2 Using the same logic as steps 3.1, the geometric altitude T and the barometric altitude of the aircraft at time 0 are updated.

[0039] Step 3.3 First, the target aircraft longitude, latitude and altitude are converted from the WGS84 coordinate system to the ECEF coordinate system, and then the ECEF coordinates are converted to the ENU coordinate system through a rotation transformation matrix with the local position as the reference, to obtain T the position data of the target aircraft at time 1.

[0040] According to the following formula (5), the aircraft track in the WGS84 coordinate system and the local track are converted to the ECEF coordinate system: (5); wherein, = semi-major axis = 6378137.0 m; represents the square of the first eccentricity = 6.69437999 014x10 3 ; = ground latitude / radian; = ground longitude / radian; = geometric altitude of the local or aircraft; .

[0041] When h in formula (5) is the geometric altitude of the aircraft, , , indicate the ECEF position of the aircraft track; when h in formula (5) is the geometric altitude of the local, , , indicate the ECEF position of the aircraft track.

[0042] Step 3.4 According to the aircraft track and the local track in the ECEF coordinate system, the aircraft ENU track in the ENU coordinate system is derived: (6); wherein, = ground latitude / radian of the local,​ = Local longitude / latitude, , , represents the ECEF position of the aircraft, , , represents the ECEF position of the track.

[0043] Step 4: Convert the position data reported by the aircraft at time T 1 from the WGS84 coordinate system to the ENU coordinate system, and output the relative pressure altitude of the aircraft at time T 1 in the WGS84 coordinate system : (7); Step 5: Extrapolate the track state vector at time T 0 to time T 1, and combine the observed position data of the aircraft at time T 1 to generate the predicted value at time T 1 using Kalman filtering. Taking the position data in the x-axis direction as an example, Kalman filtering and track extrapolation are performed: First, the track state is linearly extrapolated to the applicable time of the current report: (8); (9); wherein are the position and velocity of the aircraft track, and the position and velocity of the extrapolated track, dt represents the time difference between the current report and the last track update, i.e. dt = T 1- T 0.

[0044] After extrapolating the track covariance matrix, first obtain the covariance matrix of the aircraft track by data quality: : (10); wherein: represents the standard deviation of the estimated position uncertainty, which is derived from NACp; represents the standard deviation of the horizontal velocity uncertainty, which is derived from NACv. NACP stands for Navigation Accuracy Category for Position, and NACv stands for Navigation Accuracy Category for Velocity.

[0045] The extrapolation of the track covariance matrix is then performed by the following equation: (11); (12); (13); where Q is the process noise variance (m / s 2 , and here Q is 6.003.

[0046] Finally, the position state vector is generated by taking the position update as an example. First, the residual variance is calculated by extrapolating the track position variance and the estimated measurement position variance : (14); where represents the extrapolated track position variance in the x direction, and EPU / 1.96 represents the estimated measurement position variance.

[0047] Then, the gain vector and are calculated from the extrapolated track variance and the residual variance: (15) The state and are then generated according to the following equations (16) and (17): (16); (17); where represents the measurement position in the ENU coordinate system.

[0048] The calculation method of the state covariance matrix is as follows: (18); (19); (20).

[0049] Step 6: After obtaining the predicted value at the extrapolation time in the x, y, and z axis directions using the Kalman filter algorithm respectively, the predicted value is sent into the relevant window, the distance and height difference between the track predicted value and the track observed value are calculated, and compared with the distance threshold and the height threshold. If the threshold determination passes, the track is updated using the track predicted value. The distance threshold and the height threshold are respectively: (21); (22); wherein: is calculated by NACp, For the barometric height dominant, it is a fixed value as defined in the foregoing, 31.11 m, for the geometric height dominant, it is calculated by NACp or by GVA. Wherein, the full name of GVA should be Geometric Viability Assay, the Chinese interpretation is geometric viability assay.

[0050] Step 7: Perform a preliminary track update on the position state vector or velocity state vector passed by the relevant window judgment. Take the position update as an example. As shown in Figure 3 , first, the position of the target aircraft in the ENU coordinate system is converted into the ECEF coordinate system through coordinate rotation and reference point translation, and then the corresponding WGS84 coordinate position data is obtained by inverse solution of the earth ellipsoid geometry.

[0051] Step 7.1 Store the local geometric height and barometric height.

[0052] Step 7.2 Convert the generated position data in the ENU coordinate system to the state vector in the ECEF coordinate system according to the following formula (23); (23); wherein: denotes the ground latitude of the local aircraft, denotes the ground longitude of the local aircraft, denotes the ECEF coordinates of the local aircraft, denotes the position of the aircraft in the ENU coordinate system.

[0053] Step 7.3, convert the generated state vector in the ECEF coordinate system to the state vector in the WGS84 coordinate system according to the following formula (24);

[0054] wherein: a denotes the semi-major axis of the earth = 6378137.0 m, b denotes the semi-minor axis of the earth = 6356752.3142 m, denotes the square of the first eccentricity = 6.69437999 014 10 -3 , denotes the square of the second eccentricity = 6.73949674 228x10 -3 , denotes the ground latitude / radian, denotes the ground longitude / radian, represents the ground geometric height of the aircraft.

[0055] Finally, the current position state vector in WGS84 coordinate system is used to update the current flight path in the flight path database. T 1 of the aircraft, wherein the geometric height is obtained through the coordinate conversion process directly assigned, the barometric height then the relative height calculated according to formula (6) is assigned: (25); Step 8: Calculate the difference between the local flight path applicable time and the aircraft flight path applicable time ; (26).

[0056] Step 9: Judge the time difference, if the time difference , then directly use T 1 of the aircraft as the final output flight path, and skip step 10; if the time difference is greater than or equal to 0.2s, then enter step 10.

[0057] Step 10: Linearly extrapolate the flight path of T 1 of the aircraft.

[0058] According to formula (3) to formula (7), the aircraft flight path in WGS84 coordinate system is converted into the flight path in ENU coordinate system.

[0059] According to formula (27) to formula (29), the time difference obtained in step 8 and the east-west speed, north-south speed and vertical speed of the aircraft are updated to the three-dimensional coordinates on the x, y and z axes of the ENU coordinate system; (27); (28); (29); wherein, are the aircraft ENU three-dimensional coordinates at t , respectively, are the aircraft three-dimensional coordinates at T 1, are the aircraft three-dimensional velocities at T 1.

[0060] According to formula (23) to formula (25), the extrapolated aircraft position data in the ENU coordinate system is re-converted into position data in the WGS84 coordinate system, and combined with the updated speed information in step 5 and the time information, quality parameters and other data analyzed in step 2 to generate the latest aircraft track. At this time, the applicable time of the track is consistent with the local machine.

[0061] Step 11: According to the local track and the aircraft track output in step 9 or step 10, the relative height of the local machine and the aircraft is calculated, and the final ADS-B track is output.

[0062] If the local geometric height is invalid and the barometric height is valid, the relative height is the relative barometric height; If the local geometric height is valid and the barometric height is valid, the relative height is the relative barometric height; If the local geometric height is valid and the barometric height is invalid, the relative height is the relative geometric height.

[0063] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for updating ADS-B height based on air pressure and geometric height compatibility, characterized in that, Comprising: Step 1, acquire current time t local track information, target aircraft last time T 0 track information, latest time T 1 observation value of track information of target aircraft; Step 2, judging the current time t the track information of the local aircraft, the track information of the target aircraft at the last time T 0 the track information of the local aircraft, the track information of the target aircraft at the last time T 1 the validity of the geometric height and the barometric height in the track information of the target aircraft, if the geometric height is valid, the valid geometric height is taken as the calculation value, if the geometric height is invalid, the geometric height value calculated according to the valid barometric height by using an approximate formula is taken as the calculation value, if the barometric height is valid, the valid barometric height value is taken as the calculation value, if the barometric height is invalid, the barometric height value calculated according to the valid geometric height by using an approximate formula is taken as the calculation value, and T 1 the calculation value of the barometric height of the target aircraft at the time and t the calculation value of the barometric height of the local aircraft at the time to calculate the relative barometric height Step 3, utilize the target aircraft's previous moment T The geometric altitude calculation value of the 0 track information will be T Extrapolation of 0's trajectory data to T At time 1, the target aircraft was obtained. T Predicted values ​​of track data at time 1; Step 4, the correlation between the observation value and the prediction value of the target aircraft trajectory information at time T1 is determined, and the correlation is added to the relative barometric altitude to obtain the barometric altitude of the target aircraft at time T1 T 1 the correlation between the observation value and the prediction value of the target aircraft trajectory information at time T1 is determined, and the correlation is added to the relative barometric altitude to obtain the barometric altitude of the target aircraft at time T1 t 1 the barometric altitude of the target aircraft at time T1 is calculated by adding the local barometric altitude at time T1 to the relative barometric altitude T 1 the barometric altitude of the target aircraft at time T1 is calculated by adding the local barometric altitude at time T1 to the relative barometric altitude T 1 the barometric altitude of the target aircraft at time T1 is calculated by adding the local barometric altitude at time T1 to the relative barometric altitude T 1 the barometric altitude of the target aircraft at time T1 is calculated by adding the local barometric altitude at time T1 to the relative barometric altitude Step 5, calculate the current time of the local track t the current time of the target aircraft track T 1, judge the time difference, if the time difference <0.2s, directly use T 1 time target aircraft preliminary track information as the final output track, if the time difference ≥0.2s, to T 1 time target aircraft track linear extrapolation of the track, get the target aircraft track at t time, extrapolation results as the final output track; Step 6, output the relative height of the target aircraft and the local according to the validity of the height data in the final output track, the local height data and the local barometric height.

2. The barometric and geometric height compatible ADS-B height updating method according to claim 1, wherein, In step 2, the validity of the geometric height and the barometric height in the track information of the target aircraft at the last time point and the track information of the target aircraft at the current time point are determined. T 0the track information of the target aircraft at the last time point T 1the track information of the target aircraft at the current time point When the "Type" field of the airborne position message of the target aircraft is encoded with a value in the range 9-18, the "Altitude" field of the airborne position message is encoded as pressure altitude The difference between geometric altitude and pressure altitude is obtained from the decoded value of the "Difference from pressure altitude" field in the "Airborne velocity message" The geometric altitude of the aircraft and the target aircraft geometric altitude valid bit and the pressure altitude valid bit are set to 1. when the "type" field of the air position message of the target aircraft is coded with a value in the range 20-22, the "altitude" field of the air position message is coded with the geometric altitude , the difference between the geometric altitude and the barometric altitude is obtained from the decoded value of the "difference from barometric altitude" field in the air speed message , the barometric altitude of the aircraft , and the target aircraft geometric altitude significant bits and the barometric altitude significant bits are set to 1 When the "Difference from Baro Altitude" field in the "Over-the-Air Speed Message" is not valid, the geometric altitude valid bit for the target aircraft is set to 0. or the baro altitude valid bit is set to 0. ​ 3. The barometric and geometric height compatible ADS-B height updating method according to claim 1, wherein, The specific steps of step 3 include: First of all T The target aircraft trajectory information at time 0 is transformed from the WGS84 coordinate system to the ENU coordinate system, and then processed using Kalman filtering from the three dimensions (x, y, z) of the ENU coordinate system. T Extrapolation of flight track information at time 0 to T At moment 1, we obtain T Predicted flight data of the target aircraft in the ENU coordinate system at time 1.

4. The barometric and geometric height compatible ADS-B height updating method according to claim 3, wherein, Will T The steps to convert the target aircraft trajectory information at time 0 from the WGS84 coordinate system to the ENU coordinate system include: T The longitude, latitude, and altitude of the target aircraft are transformed from the WGS84 coordinate system to the ECEF coordinate system, and then the ECEF coordinates are converted to the ENU coordinate system using a rotation transformation matrix with the aircraft's position as a reference. T Position data of the target aircraft at time 0.

5. The barometric and geometric height compatible ADS-B height updating method according to claim 3, wherein, In step 4, the specific steps of converting the position data in the predicted value to generate the position data of WGS84 coordinates include: The position of the target aircraft in the ENU coordinate system is converted into ECEF coordinates through coordinate rotation and reference point translation transformation, and then the corresponding position data of WGS84 coordinates is obtained by inverse solution using the geometry of the earth ellipsoid.

6. The barometric and geometric height compatible ADS-B height updating method according to claim 1, wherein, In step 6, if the local geometric height is invalid, the barometric height is valid, then the relative height is the relative barometric height; If the local geometric height is valid, the barometric height is valid, then the relative height is the relative barometric height; If the local geometric height is valid, the barometric height is invalid, then the relative height is the relative geometric height.

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