Multi-element hybrid monitoring method based on ACAS

Abstract

The invention discloses a multi-element hybrid monitoring method based on ACAS, which acquires target source information by actively sending C-mode inquiry, dynamically inquires and tracks an S-mode target in a hybrid monitoring mode, and passively receives and acquires ADS-B (Automatic Dependent Surveillance-Broadcast) information and ADS-R (Automatic Dependent Surveillance-Response) information in an airspace at the same time. Carrying out mixed monitoring management of multi-information, carrying out dynamic multi-track management on each monitored target, and carrying out relevant removal processing on tracks of the targets; according to the method, track correlation fusion processing is carried out on a plurality of targets, an optimization strategy is designed to select an optimal track in real time, a reliable tracking target is provided for an anti-collision algorithm, the utilization rate of multiple data sources in an airspace can be improved, occupation of inquiry frequency resources is reduced, and the tracking efficiency is improved. And when the quality of a certain type of target data source is reduced under the condition that the external electromagnetic environment is complex, the track selection type can be switched in time, the continuity of the target is ensured, and the target tracking quality is improved.

Description

Technical Field

[0001] The invention relates to the technical field of airborne collision avoidance, and in particular to a multi-element hybrid monitoring method based on ACAS. Background Art

[0002] The airborne ACAS system includes monitoring, collision avoidance, response, and ADS-BOUT functions. First, by passively detecting the intermittent oscillation signals and extended intermittent oscillation signals of other S-mode transponders in the airspace, the presence of surrounding ACAS equipment is sensed. The monitoring function module actively initiates periodic C-mode and S-mode inquiries in accordance with the DO-185B standard to detect the distribution of the target's position, altitude, direction, and other characteristics, and track the target's movement status; the collision avoidance function module further completes the logical calculation of air collision avoidance through the collision avoidance logic algorithm, and promptly gives traffic warnings or decision warnings (warning display strips, warning voice); the response function module promptly responds to the RF inquiry data in accordance with the DO-181E standard; the ADS-BOUT function module broadcasts periodic information according to the current real-time data of the carrier aircraft and the DO-260B standard; the collision avoidance system provides pilots with reliable and efficient target situation awareness and threat warnings to avoid flight collision accidents, and has an irreplaceable position in improving flight safety.

[0003] With the innovation of secondary radar technology and standards, the means and methods of monitoring L-band targets in the airspace are becoming more and more diverse, the proportion of spectrum resource occupation is increasing year by year, and frequency resources are becoming scarce and tight. In particular, the popularization of the S-mode interrogation scheduling strategy of secondary radar will aggravate the resource occupation of the 1030MHz / 1090MHz frequency in the air, and will also increase the response failure rate of the transponder, which will indirectly affect the target tracking quality of the ACAS system. How to reasonably and fully use the existing diversified data sources, which will not increase the occupation of interrogation frequency resources, but also improve the target tracking quality, and reduce the waste of interrogation scheduling resources to a certain extent, is a difficult problem that needs to be solved urgently. Although the existing ACAS system adopts certain hybrid monitoring means, the use of data is not sufficient. For example, the effective ADS-R data forwarded from the ground station in the airspace is not used. In terms of target management, a single target corresponds to a single track, and the target track source is single. There is a lack of fusion processing and refined management of diversified external sensor data. Once the quality of the external data source decreases, it will directly lead to a decrease in target tracking quality. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the track selection type cannot be switched in time, and the target tracking quality is poor. The purpose is to provide a multi-element hybrid monitoring method based on ACAS, which obtains target source information by actively issuing C-mode inquiries, and dynamically inquires and tracks S-mode targets by adopting a hybrid monitoring method. At the same time, it also passively receives and obtains automatic dependent surveillance-broadcast ADS-B information and ADS-R information in the airspace, and performs hybrid monitoring management of multi-element information. Dynamic multi-track management is performed on each monitored target, and the track of the target is de-correlated; track correlation fusion processing is performed on multiple targets, and an optimization strategy is designed to select the optimal track in real time, providing a reliable tracking target for the anti-collision algorithm. It can not only improve the utilization rate of multiple data sources in the airspace and reduce the occupation of inquiry frequency resources, but also when the quality of a certain type of target data source decreases under complex external electromagnetic environment, the track selection type can be switched in time to ensure the continuity of the target and improve the target tracking quality.

[0005] The present invention is achieved through the following technical solutions:

[0006] The first aspect of the present invention provides a multivariate hybrid monitoring method based on ACAS, comprising the following specific steps:

[0007] Use hybrid surveillance to interrogate multiple targets and obtain track data of multiple targets;

[0008] Among the track data of the multiple targets, a decorrelation operation is performed on the multiple track data of each target respectively;

[0009] Perform fusion operation on the track data after decorrelation operation;

[0010] The optimal track is selected based on the fused track data.

[0011] Furthermore, the hybrid monitoring method specifically includes:

[0012] Monitor the ADS-B signal strength. When the ADS-B signal strength is less than the set threshold and the ADS-B signal quality is greater than the signal quality set threshold, do not actively query the S-mode target and maintain the ADS-B track.

[0013] When the strength of the ADS-B signal is less than the set threshold, and the ADS-B track signal quality is less than the signal quality set threshold, then switch to hybrid surveillance: When it is determined that the ADS-B track does not meet the requirements for active surveillance in terms of distance and altitude, reset the confirmation inquiry interval according to the distance and altitude thresholds, and conduct confirmation inquiries on the S-mode track according to the reset intervals. If the confirmation is successful, maintain hybrid surveillance. If the confirmation fails, switch to active surveillance and actively inquire about the S-mode target; When it is determined that the ADS-B track meets the requirements for active surveillance in terms of distance and altitude, switch to active surveillance and actively inquire about the S-mode target;

[0014] When the strength of the ADS-B signal is greater than or equal to the threshold, and / or the ADS-B signal quality is less than the signal quality setting threshold, the S-mode target is actively interrogated;

[0015] When it is determined that the S-mode track meets the requirements of mixed surveillance, it will switch to mixed surveillance, reset the confirmation inquiry interval according to the distance and altitude thresholds, and conduct confirmation inquiries on the S-mode track according to the reset intervals;

[0016] When a Mode S track is in mixed surveillance and the ADS-B track quality of the same Mode S address is high, it will switch to extended mixed surveillance and will not actively interrogate the Mode S target.

[0017] Furthermore, before decorrelation operation is performed on the track data, multiple types of tracks of each target are maintained according to the track data of multiple targets, specifically including:

[0018] Actively detect C-mode targets and use C-mode replies to create and maintain C-mode tracks;

[0019] Actively detect Mode S targets and use Mode S replies to create and maintain Mode S tracks;

[0020] Passively receive ADS-B IN information, and use ADS-B messages to create and maintain ADS-B tracks;

[0021] Passively receive ADS-R information, and use ADS-R messages to create and maintain ADS-R tracks.

[0022] Further, the decorrelation operation is performed on the multiple track data of each target in the track data of the multiple targets, specifically including:

[0023] Select a main track;

[0024] Select a possible non-relevant track for the target, where all the target's Mode C tracks and ADS-R tracks of NON-ICAO addresses are possible non-relevant tracks;

[0025] The possible non-correlated tracks of the target are decorrelated with the main track of the target.

[0026] Furthermore, the selection priority of the main track is: S mode track, ADS-B track, non-false C mode track, the first false C mode track, and ADS-R track.

[0027] Further, the decorrelation operation of the possible non-correlated tracks of the target with the main track of the target specifically includes:

[0028] Get possible non-related track types and main track types:

[0029] If the possible non-relevant track is a false C-mode track, and the type of the main track is not a C-mode track, then the C-mode track is deleted from the target, a new target is created, and the C-mode track is assigned to the target;

[0030] If the possible non-relevant track is a false C-mode track, and the type of the main track is a C-mode track, then the false C-mode track is deleted from the current target, a new target is created, and the C-mode track is assigned to the target;

[0031] If the possible non-related track is not related to the main track, the possible non-related track is deleted from the current target, a new target is created and the possible non-related track is assigned to the target.

[0032] Furthermore, the process of correlating and fusing multiple targets includes:

[0033] A main track is selected for each of the multiple targets according to the selection priority of the main track;

[0034] Compare all main tracks in pairs to determine the fused track and the non-fused track:

[0035] The fused target is obtained through the fused track, and the non-fused target is obtained through the non-fused track;

[0036] Perform fusion operations based on fusion targets and non-fusion targets.

[0037] Further, the determining of the fused track and the non-fused track specifically includes:

[0038] Get possibly non-relevant track types:

[0039] S421. If the types of the two main tracks are ADS-B, ADS-R or S-mode tracks, and the S-mode addresses of the two main tracks are ICAO addresses: for two targets with the same S-mode address, the track with a shorter track establishment time is marked as a fused track, and the track with a longer track establishment time is marked as a non-fused track;

[0040] S422. If the types of the two main tracks do not meet S421, and the track is related to the main track in distance and altitude, the track with a shorter track establishment time is marked as a fused track, and the track with a longer track establishment time is marked as a non-fused track.

[0041] Further, the performing the fusion operation according to the fusion target and the non-fusion target specifically includes:

[0042] If the fused target has no Mode S track and the non-fused target has a Mode S track, the Mode S track of the non-fused target is assigned to the fused target;

[0043] If the non-fused target has a C-mode track, all its C-mode tracks are assigned to the fused target;

[0044] If the fused target has no ADS-B track and the non-fused target has an ADS-B track, the ADS-B track of the non-fused target is assigned to the fused target;

[0045] If the fused target has no ADS-R track and the non-fused target has an ADS-R track, the ADS-R track of the non-fused target is assigned to the fused target.

[0046] Furthermore, the optimal track selection according to the fused track data specifically includes:

[0047] S51. If the target has an ADS-B track, and the ADS-B track is related to the S-mode track, the height of the ADS-B track is valid, and the quality of the ADS-B track is high, then select the ADS-B track; otherwise, enter S52;

[0048] S52, if the target has an S-mode track and the S-mode track distance is valid, select the S-mode track, otherwise enter S53;

[0049] S53, if the target has a C-mode track, and the C-mode track is not a false track, and the distance of the track is valid, then select the C-mode track, otherwise enter S54;

[0050] S54. If the target has an ADS-B track, the ADS-B track quality is high, and the S-mode track of the same S-mode address is under mixed surveillance, then select the ADS-B track, otherwise go to S55;

[0051] S55. If the target has an ADS-R track and the passive ADS-R track is of high quality, select the ADS-R track.

[0052] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0053] By actively sending out C-mode inquiries to obtain target source information, using a hybrid monitoring method to dynamically inquire and track S-mode targets, and also passively receiving and obtaining broadcast automatic dependent surveillance ADS-B information and ADS-R information in the airspace, hybrid monitoring management of multiple information is performed. Dynamic multi-track management is performed on each monitored target, and the target's track is de-correlated; track correlation fusion processing is performed on multiple targets, and an optimization strategy is designed to select the optimal track in real time, providing reliable tracking targets for the anti-collision algorithm. This can not only improve the utilization rate of multiple data sources in the airspace and reduce the occupation of inquiry frequency resources, but also when the quality of a certain type of target data source decreases due to a complex external electromagnetic environment, the track selection type can be switched in time to ensure the continuity of the target and improve the target tracking quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0055] Figure 1 is a flow chart of a multivariate hybrid monitoring method in an embodiment of the present invention;

[0056] Figure 2 Schematic diagram of hybrid monitoring switching in an embodiment of the present invention;

[0057] Figure 3 Schematic diagram of multi-track decorrelation processing in an embodiment of the present invention;

[0058] Figure 4 Schematic diagram of multi-target correlation fusion processing in an embodiment of the present invention. DETAILED DESCRIPTION

[0059] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0060] As a possible implementation, Figure 1As shown, this embodiment is a multi-element hybrid surveillance method based on ACAS, which specifically provides a hybrid surveillance management method for targets using data from multiple sensors in the ACAS system, including hybrid surveillance inquiry, independent track management of multiple data sources, multi-track decorrelation of targets, correlation fusion of multiple targets, and track optimization of targets. Use multiple external data sources to track targets, and each target can have multiple C-mode tracks, but at most one S-mode track, ADS-B track, and ADS-R track. Secondly, manage the multiple tracks in each target, remove irrelevant tracks, and maintain the removed tracks to the newly created target. Again, perform correlation fusion comparison on the multiple targets, and for multiple targets that meet the relevant conditions, retain one target, delete the redundant related targets, and fuse the tracks in the redundant related targets into the retained targets. Finally, for each target, select an optimal track according to the optimal selection strategy and send it to the anti-collision logic algorithm to complete the multi-element hybrid surveillance process.

[0061] S1. Mixed monitoring query, such as Figure 2 As shown, it is a specific schematic diagram of hybrid monitoring query. This embodiment reduces the query resource occupation through hybrid monitoring. The specific real-time method is as follows:

[0062] 1. When the strength of the ADS-B signal is less than the threshold and the ADS-B signal quality is greater than the signal quality setting threshold, the S-mode target will not be actively interrogated and the ADS-B track will be maintained.

[0063] 2. When the ADS-B track signal quality is less than the signal quality setting threshold, it will switch to hybrid surveillance, reset the confirmation inquiry interval according to the distance and altitude thresholds, and conduct confirmation inquiry of the S-mode track according to the reset interval. If the confirmation is successful, it will maintain hybrid surveillance. If the confirmation fails, it will switch to active surveillance and actively inquire about the S-mode target;

[0064] 3. When the ADS-B track meets the active surveillance requirements in terms of distance and altitude, it will switch to active surveillance and actively interrogate the S-mode target;

[0065] 4. When the strength of the ADS-B signal is greater than or equal to the threshold, or the ADS-B signal quality is less than the signal quality setting threshold, the S-mode target is actively interrogated;

[0066] 5. When the S-mode track meets the requirements of mixed surveillance, it will switch to mixed surveillance, reset the confirmation inquiry interval according to the distance and altitude thresholds, and conduct confirmation inquiries on the S-mode track according to the time interval;

[0067] 6. When a Mode S track is in mixed surveillance and the quality of the ADS-B track with the same Mode S address is good, it will switch to extended mixed surveillance and will not actively interrogate the Mode S target.

[0068] S2. Use multiple data sources to maintain multiple types of tracks for each target. The process is as follows:

[0069] 1. Actively detect C-mode targets and use C-mode replies to create and maintain C-mode tracks;

[0070] 2. Actively detect Mode S targets and use Mode S replies to create and maintain Mode S tracks;

[0071] 3. Passively receive ADS-B IN information, and use ADS-B messages to create and maintain ADS-B tracks;

[0072] 4. Passively receive ADS-R information and use ADS-R messages to create and maintain ADS-R tracks.

[0073] S3. Decorrelate multiple tracks of a single target, such as Figure 3 As shown, the specific process is as follows:

[0074] S31. First, a main track is selected for the target, with the priority being: Mode S track, ADS-B track, non-false Mode C track, first false Mode C track, ADS-R track;

[0075] S32. A possible non-relevant track is selected for the target, and all C-mode tracks and ADS-R tracks of the target with NON-ICAO addresses are possible non-relevant tracks;

[0076] S33. Decorrelate the possible non-correlated tracks of the target with the main track of the target:

[0077] S331. If the possible non-related track is a false C-mode track, and the type of the main track is not a C-mode track, delete the C-mode track from the target, create a new target and assign the C-mode track to the target;

[0078] S32. If the possible non-related track is a false C-mode track, and the type of the main track is a C-mode track, delete the false C-mode track from the current target, create a new target and assign the C-mode track to the target;

[0079] S33. In other cases, if the possible non-related track is not related to the main track, the possible non-related track is deleted from the current target, a new target is created and the possible non-related track is assigned to the target.

[0080] S4. Fusion of multiple targets, such as Figure 4 As shown, the specific process is as follows:

[0081] S41. First, select a main track for each target; the priority is: S-mode track, ADS-B track, non-false C-mode track, the first false C-mode track, ADS-R track;

[0082] S42. All main tracks are compared in pairs. When the tracks are related to the main tracks in distance, the fused tracks and non-fused tracks are determined as follows:

[0083] S421. If the types of the two main tracks are ADS-B, ADS-R or S-mode tracks, and the S-mode addresses of the main tracks are ICAO addresses: for two targets with the same S-mode address, mark the track with the smaller track establishment time as the fused track and the other as the non-fused track;

[0084] S422. When step S421 is not satisfied and the track is related to the main track in distance and altitude, the track with a smaller track establishment time needs to be marked as a fused track and the other as a non-fused track.

[0085] S43. Obtain fusion targets through fusion tracks, obtain non-fusion targets through non-fusion tracks, and perform fusion processing between targets:

[0086] S431. If the fused target has no Mode S track and the non-fused target has a Mode S track, the Mode S track of the non-fused target is assigned to the fused target;

[0087] S432. If the non-fused target has a C-mode track, all of its C-mode tracks are assigned to the fused target;

[0088] S433. If the fused target has no ADS-B track and the non-fused target has an ADS-B track, the ADS-B track of the non-fused target is assigned to the fused target;

[0089] S434. If the fused target has no ADS-R track and the non-fused target has an ADS-R track, the ADS-R track of the non-fused target is allocated to the fused target.

[0090] S5. Optimize the track of the fused target and send it to the anti-collision process. The process is as follows:

[0091] S51. If the target has an ADS-B track, and the ADS-B track is successfully associated with the S-mode track, and the height of the ADS-B track is valid, and the ADS-B track quality is high, then select the ADS-B track; otherwise, proceed to step S52;

[0092] S52. If the target has an S-mode track and the S-mode track distance is valid, select the S-mode track, otherwise proceed to step S53;

[0093] S53. If the target has a C-mode track, and the C-mode track is not a false track, and the distance of the track is valid, then select the C-mode track, otherwise go to step S54;

[0094] S54. If the target has an ADS-B track, and the ADS-B track quality is high, and the S-mode track of the same S-mode address is in mixed surveillance, then select the ADS-B track, otherwise proceed to step S55;

[0095] S55. If the target has an ADS-R track and the passive ADS-R track quality is high, select the ADS-R track.

[0096] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multivariate hybrid monitoring method based on ACAS, characterized in that: The specific steps include: Use hybrid surveillance to interrogate multiple targets and obtain track data of multiple targets; In the track data of the multiple targets, decorrelation operation is performed on the multiple track data of each target respectively; Perform fusion operation on the track data after decorrelation operation; The optimal track is selected based on the fused track data.

2. The multivariate hybrid monitoring method based on ACAS according to claim 1, characterized in that: The hybrid monitoring method specifically includes: Monitor the ADS-B signal strength. When the ADS-B signal strength is less than the set threshold and the ADS-B signal quality is greater than the signal quality set threshold, do not actively query the S-mode target and maintain the ADS-B track. When the strength of the ADS-B signal is less than the set threshold, and the ADS-B track signal quality is less than the signal quality set threshold, then switch to hybrid surveillance: When it is determined that the ADS-B track does not meet the requirements for active surveillance in terms of distance and altitude, reset the confirmation inquiry interval according to the distance and altitude thresholds, and conduct confirmation inquiries on the S-mode track according to the reset intervals. If the confirmation is successful, maintain hybrid surveillance. If the confirmation fails, switch to active surveillance and actively inquire about the S-mode target; When it is determined that the ADS-B track meets the requirements for active surveillance in terms of distance and altitude, switch to active surveillance and actively inquire about the S-mode target; When the strength of the ADS-B signal is greater than or equal to the threshold, and / or the ADS-B signal quality is less than the signal quality setting threshold, the S-mode target is actively interrogated; When it is determined that the S-mode track meets the requirements of mixed surveillance, it will switch to mixed surveillance, reset the confirmation inquiry interval according to the distance and altitude thresholds, and conduct confirmation inquiries on the S-mode track according to the reset intervals; When a Mode S track is in mixed surveillance and the ADS-B track quality of the same Mode S address is high, it will switch to extended mixed surveillance and will not actively interrogate the Mode S target.

3. The multivariate hybrid monitoring method based on ACAS according to claim 1, characterized in that: Before decorrelation operation is performed on the track data, multiple types of tracks of each target are maintained according to the track data of multiple targets, including: Actively detect C-mode targets and use C-mode replies to create and maintain C-mode tracks; Actively detect Mode S targets and use Mode S replies to create and maintain Mode S tracks; Passively receive ADS-B IN information, and use ADS-B messages to create and maintain ADS-B tracks; Passively receive ADS-R information, and use ADS-R messages to create and maintain ADS-R tracks.

4. The multivariate hybrid monitoring method based on ACAS according to claim 1, characterized in that: The decorrelation operation is performed on the track data of each target respectively in the track data of the multiple targets, specifically including: Select a main track; Select a possible non-relevant track for the target, where all the target's Mode C tracks and ADS-R tracks of NON-ICAO addresses are possible non-relevant tracks; The possible non-correlated tracks of the target are decorrelated with the main track of the target.

5. The multivariate hybrid monitoring method based on ACAS according to claim 4, characterized in that: The selection priority of the main track is: S mode track, ADS-B track, non-false C mode track, the first false C mode track, ADS-R track.

6. The multivariate hybrid monitoring method based on ACAS according to claim 5, characterized in that: The decorrelation operation of respectively performing decorrelation operation on the possible non-correlated tracks of the target and the main track of the target specifically includes: Get possible non-related track types and main track types: If the possible non-relevant track is a false C-mode track, and the type of the main track is not a C-mode track, then the C-mode track is deleted from the target, a new target is created, and the C-mode track is assigned to the target; If the possible non-relevant track is a false C-mode track, and the type of the main track is a C-mode track, then the false C-mode track is deleted from the current target, a new target is created, and the C-mode track is assigned to the target; If the possible non-related track is not related to the main track, the possible non-related track is deleted from the current target, a new target is created and the possible non-related track is assigned to the target.

7. The multivariate hybrid monitoring method based on ACAS according to claim 5, characterized in that: The process of fusing the track data after decorrelation operation includes: A main track is selected for each of the multiple targets according to the selection priority of the main track; Compare all main tracks in pairs to determine the fused track and the non-fused track: The fused target is obtained through the fused track, and the non-fused target is obtained through the non-fused track; Perform fusion operations based on fusion targets and non-fusion targets.

8. The multivariate hybrid monitoring method based on ACAS according to claim 7, characterized in that: The determining of the fused track and the non-fused track specifically includes: Get possibly non-relevant track types: S421. If the types of the two main tracks are ADS-B, ADS-R or S-mode tracks, and the S-mode addresses of the two main tracks are ICAO addresses: for two targets with the same S-mode address, the track with a shorter track establishment time is marked as a fused track, and the track with a longer track establishment time is marked as a non-fused track; S422. If the types of the two main tracks do not meet S421, and the track is related to the main track in distance and altitude, the track with a shorter track establishment time is marked as a fused track, and the track with a longer track establishment time is marked as a non-fused track.

9. The multivariate hybrid monitoring method based on ACAS according to claim 7, characterized in that: The fusion operation according to the fusion target and the non-fusion target specifically includes: If the fused target has no Mode S track and the non-fused target has a Mode S track, the Mode S track of the non-fused target is assigned to the fused target; If the non-fused target has a C-mode track, all its C-mode tracks are assigned to the fused target; If the fused target has no ADS-B track and the non-fused target has an ADS-B track, the ADS-B track of the non-fused target is assigned to the fused target; If the fused target has no ADS-R track and the non-fused target has an ADS-R track, the ADS-R track of the non-fused target is assigned to the fused target.

10. The multivariate hybrid monitoring method based on ACAS according to claim 1, characterized in that: The selecting the optimal track according to the fused track data specifically includes: S51. If the target has an ADS-B track, and the ADS-B track is related to the S-mode track, the height of the ADS-B track is valid, and the quality of the ADS-B track is high, then select the ADS-B track; otherwise, enter S52; S52, if the target has an S-mode track and the S-mode track distance is valid, select the S-mode track, otherwise enter S53; S53, if the target has a C-mode track, and the C-mode track is not a false track, and the distance of the track is valid, then select the C-mode track, otherwise enter S54; S54. If the target has an ADS-B track, the ADS-B track quality is high, and the S-mode track of the same S-mode address is under mixed surveillance, then select the ADS-B track, otherwise go to S55; S55. If the target has an ADS-R track and the passive ADS-R track is of high quality, select the ADS-R track.

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