JP2022181484A - Aircraft position measurement system, positioning processing device, aircraft position measurement method and program - Google Patents

Abstract

To provide an aircraft position measurement system that enhances resistance to deterioration of a system performance caused by a change in external environment.SOLUTION: In an aircraft position measurement system 100, a plural signal reception station 2d is configured to receive a first signal including identification information from an aircraft 1 of a monitor object, a second signal (ADS-B signal) including identification information and position information from a second aircraft 4, a reference signal from a reference station 3 and a positioning signal from a positioning satellite 5. Each of a plurality of reception stations 2a to 2c and 2e to 2i is configured to receive at least one of the first signal, second signal, reference signal and positioning signal. A positioning processing device 8 is configured to calculate an amount of offset between the plural signal reception station 2d and the plurality of reception stations 2a to 2c receiving the second signal, and calculate a time difference as of reception of the first signal at the different reception station on the basis of the amount of offset. The positioning processing device 8 is configured to measure a position of the first aircraft 1 on the basis of the calculated time difference at the reception time of the first signal and a position of the reception station.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present disclosure relates to an aircraft positioning system, a positioning processing device, an aircraft positioning method, and a program.

Typical methods for realizing time synchronization between receiving stations, which is necessary for aircraft position measurement, are the reference station synchronization method based on the reference signal received from the reference station, and the positioning signal with time information received from one or more positioning satellites. GNSS (Global Navigation Satellite System) synchronization schemes are known. Time synchronization means that the difference between the times measured by the clock device of the receiving station is equal to or less than a predetermined upper limit value. The clock device also includes a clock counter whose counter value increases at a determined cycle.

For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2013-200282) discloses that a combination of a GPS (Global Positioning System) synchronization method, which is one of the GNSS synchronization methods, and a reference station synchronization method enables flexible arrangement of receiving stations. and proposes a system for measuring the position of an aircraft with resistance to jamming. FIG. 3 of the same patent document shows a configuration example of a receiving station.

In addition, Patent Document 2 (International Publication No. 2017/212636) proposes a system for measuring an aircraft position with high accuracy using a GPS synchronization method. FIG. 2 of the same patent document shows an example of the overall configuration of the aircraft position measurement system.

Japanese Unexamined Patent Application Publication No. 2013-200282 WO2017/212636

The reference station synchronization method and the GNSS synchronization method are typical time synchronization methods used in aircraft positioning systems, but both have the vulnerability of easily degrading system performance due to changes in the external environment.

In the reference station system, it is necessary to have a line of sight between the reference station and the receiving station. An example of the vulnerability of the reference station synchronization method is the influence of radio wave shielding due to the construction of a new building in the airport field. This is because a newly constructed building may prevent the transmission radio wave from the reference station from reaching the receiving station. In addition, when the multipath wave mixture temporarily increases due to changes in the airport environment or the like, an error occurs in the arrival time of the reference signal, which may degrade the time synchronization accuracy of the aircraft position measurement system.

Examples of vulnerabilities in the GNSS synchronization system include the influence of interference waves mixed by mobile LTE (Long Term Evolution) signals, etc., and the influence of disturbance due to hostile signal jamming and false signals. These interfering waves or jamming waves may affect the accuracy of GNSS signals (also called positioning signals) from positioning satellites, degrading the time synchronization accuracy of the aircraft positioning system.

Therefore, it is conceivable that sufficient time synchronization accuracy cannot be ensured by simply combining the reference station synchronization method and the GNSS synchronization method as in Patent Document 1. One of the purposes of the present disclosure is to propose a time synchronization method different from the conventional one, and combine this new time synchronization method with the conventional time synchronization method to improve resistance to deterioration of system performance due to changes in the external environment. to provide an aircraft positioning system that

An aircraft positioning system according to the present disclosure combines a first signal including identification information of a first aircraft transmitted from a first aircraft to be monitored and identification information and location information of a second aircraft transmitted from a second aircraft. a second signal receiving station having a clock counter; a reference signal receiving station receiving the first signal and a reference signal transmitted from the reference station; having a clock counter; a positioning signal receiving station that receives a positioning signal transmitted from a positioning satellite, generates a time signal based on the positioning signal, and has a clock counter; and at least two of the second signal, the reference signal, and the positioning signal. wherein each of the three types of signals, the second signal, the reference signal and the positioning signal, is received by any one of the multiple signal receiving stations It is possible to communicate with each of the first signal receiving station and the multiple signal receiving stations that are either the second signal receiving station, the reference signal receiving station, or the positioning signal receiving station. and a positioning processor for determining the position of the first aircraft.
Each of the first signal receiving station and the multiple signal receiving station that received any one of the first signal, the second signal and the reference signal or generated the time signal receives or generates the type of signal and the first signal. When two signals are received, the position information of the second aircraft included in the second signal, the counter value of the clock counter at the time the signal was received or generated, and each of the first signal receiving station and multiple signal receiving stations to the positioning processing device.
The positioning processing device stores a receiving unit that receives time counter information transmitted from each of the first signal receiving station and the multiple signal receiving stations, and the positions of each of the reference station, the first signal receiving station, and the multiple signal receiving stations. A position information storage unit, a counter value included in time counter information transmitted by each of a second signal receiving station and a plurality of signal receiving stations that received the same second signal, position information of a second aircraft, and a second signal receiving station and the positions of the multiple signal receiving stations, representing the difference between the counter values of the second signal receiving station and the clock counters of each of the multiple signal receiving stations at the time when the second aircraft transmitted the second signal. A second signal receiving station offset amount calculating unit that calculates an offset amount, a counter value included in time counter information transmitted by each of a reference signal receiving station and a plurality of signal receiving stations that have received the same reference signal, a reference station, a reference A reference signal for calculating, based on the positions of the signal receiving station and the multiple signal receiving station, the amount of offset between the clock counters of each of the reference signal receiving station and the multiple signal receiving station at the time the reference station transmits the reference signal. Based on the counter value included in the time counter information transmitted by each of the positioning signal receiving station and the multiple signal receiving station that generated the same time signal, the inter-receiving station offset calculation unit and the positioning signal receiving station and the multiple signal receiving stations Positioning signal receiving station offset calculation unit for calculating the offset amount at the time of generating the time signal between the respective clock counters, and two different first signal receiving stations receiving the same first signal. For each pair, based on the counter value included in the time counter information transmitted by the first signal receiving station when the first signal is received and the offset amount between the clock counters of the two first signal receiving stations , a time difference calculator for calculating, for a predetermined number of sets, a time difference, which is a difference between the times at which the two first signal receiving stations receive the same first signal; an aircraft position determination unit for calculating the position of the first aircraft based on the position;

According to the present disclosure, it is possible to provide an aircraft position measurement system that is more resistant to system performance degradation due to changes in the external environment than when only the reference station time synchronization method and the GNSS time synchronization method are used.

1 is a diagram showing a configuration example of an aircraft position measurement system according to Embodiment 1; FIG. FIG. 2 is a block diagram showing a functional configuration example of each receiving station and positioning processing device in FIG. 1; FIG. 2 is a diagram for explaining the ADS-B synchronization system; FIG. FIG. 5 is a timing chart for explaining an example of time difference calculation processing; 4 is a flow chart showing an example of a position measurement process for an aircraft; It is a block diagram which shows an example of the hardware constitutions of a positioning processing apparatus.

Hereinafter, embodiments will be described in detail with reference to the drawings. In addition, the same reference numerals may be given to the same or corresponding parts, and the description thereof may not be repeated.

Embodiment 1.
[Overall configuration example of aircraft positioning system]
FIG. 1 is a diagram showing a configuration example of an aircraft positioning system according to Embodiment 1. FIG. The aircraft positioning system 100 of FIG. Receiving stations (AI) 2a-2i receive signals from at least one of reference station 3, aircraft 4, and positioning satellites 5. FIG. Although one reference station 3, one aircraft 4, and one positioning satellite 5 are described as representatives, there may be more than one. When collectively referring to the receiving stations 2a to 2i or when referring to any one station, the receiving station 2 is used. An aircraft 1 to be monitored moves on a runway or a taxiway in the order 1a, 1b, 1c. There are usually a plurality of aircraft 1 present in the airport. Here, one aircraft 1 will be described as an example. Aircraft 4 is an aircraft in flight and transmits ADS-B (Automatic Dependent Surveillance-Broadcast) signals. An ADS-B signal is a signal in which an aircraft 4 voluntarily broadcasts a signal containing its own identification information, location information, and the like.

Each of the reference station 3 and the receiving station 2 is assigned a unique number or character string. A station is identified by a number or character string assigned to each station. Each of the reference station 3 and the receiving station 2 communicates with other stations and the like by including information identifying itself in the transmitted signal. Each of the aircraft 1, 4 and the positioning satellites 5 also includes information identifying itself in the signals it transmits.

The aircraft positioning system 100 is a multi-rate system that measures the position of the aircraft 1 from the difference in reception times by receiving mode S signals including identification information of itself transmitted from the aircraft 1 at a plurality of receiving stations 2a to 2i. ration system. When measuring the position of an aircraft 1 on an airport surface such as a runway or a taxiway, it is necessary for a total of three or more receiving stations 2 to receive the mode S signal of the aircraft 1, and the altitude of the aircraft 1 is determined by In total, four or more receiving stations 2 need to receive the Mode S signal of the aircraft 1 when measuring the position including. In order to measure the position of the aircraft 1 with high accuracy, time synchronization is performed between the different receiving stations 2 based on any of the ADS-B signals, reference signals, and GNSS signals received by each of the receiving stations 2a to 2i. is carried out. Aircraft 1 is the first aircraft to be monitored. A Mode S signal is the first signal containing the identity of the aircraft 1 . A GNSS signal is also called a positioning signal.

Specifically, the receiving stations 2a to 2c cannot receive the reference signal from the reference station 3 due to the influence of the shielding object 7, but can receive the ADS-B signal from the aircraft 4. FIG. The receiving stations 2a to 2c use the ADS-B signal received from the aircraft 4 to perform time synchronization. Details of time synchronization based on the ADS-B signal will be described later with reference to FIG.

The receiving stations 2e to 2g cannot receive the ADS-B signal from the aircraft 4 due to the interference wave/interference wave 6a, but can receive the reference signal from the reference station 3. A reference signal is a signal that contains its own identification information. The receiving stations 2e to 2g use the reference signal received from the reference station 3 to perform time synchronization.

Receiving stations 2 h and 2 i cannot receive ADS-B signals from aircraft 4 and reference signals from reference station 3 , but can receive GNSS signals from positioning satellites 5 . Also, the receiving station 2d can receive any of the ADS-B signal from the aircraft 4, the reference signal from the reference station 3, and the GNSS signal from the positioning satellite 5. By receiving the GNSS signal from the positioning satellite 5, the clock devices of the receiving stations 2h, 2i, and 2d are time-synchronized with the clock device of the positioning satellite 5. FIG. Aircraft 4 is the second aircraft. The ADS-B signal is a second signal transmitted from the second aircraft containing the identification and location information of the second aircraft.

As described above, in the aircraft positioning system 100, each receiving station 2 can receive at least one of a reference signal, a GNSS signal, and an ADS-B signal, and at least one receiving station 2 ( In that case, the receiving station 2d) is configured to receive all of the reference signal, the GNSS signal and the ADS-B signal. This makes it possible to increase resistance to deterioration of system performance due to changes in the external environment. For example, the receiving station 2d may receive the reference signal and the GNSS signal, and the receiving station 2h may receive the GNSS signal and the ADS-B signal. A receiving station 2 that receives at least two types of signals among the reference signal, the GNSS signal and the ADS-B signal is called a multi-signal receiving station. Receiving stations 2d and 2h become multi-signal receiving stations. One or more multi-signal receiving stations need only be able to receive three types of signals: reference signals, GNSS signals (positioning signals), and ADS-B signals (second signals). It is sufficient that the types of signals received by the multiple signal receiving stations are determined so that any of the three types of signals, ie, the GNSS signal and the ADS-B signal, can be received by any one of the multiple signal receiving stations. A multi-signal receiving station may not be able to receive the Mode S signal (the first signal).

Receiving stations 2a-2d are second signal receiving stations that receive a first signal and a second signal containing identification and location information of a second aircraft transmitted from a second aircraft and have a clock counter. The receiving stations 2d to 2g are reference signal receiving stations that receive the first signal and the reference signal transmitted from the reference station and have clock counters. Receiving stations 2d, 2h, and 2i are positioning signal receiving stations that receive the first signal and positioning signals transmitted from positioning satellites, generate time signals based on the positioning signals, and have clock counters. Any one of the second signal receiving station, the reference signal receiving station and the positioning signal receiving station is called the first signal receiving station.

[Example of functional configuration of each receiving station and positioning processing device]
FIG. 2 is a block diagram showing a functional configuration example of each receiving station and positioning processing device in FIG. As shown in FIG. 2, each receiving station 2 includes a GNSS receiver 10, a local clock 11, a downconverter 12, a reception processor 13, a transmitter 14, a GNSS antenna 15, and an antenna 16. Prepare. The positioning processing device 8 includes a receiving unit 17 , a hybrid TDOA (Time Difference of Arrival) processing unit 18 , a positioning tracking processing unit 19 and a storage unit 20 . Note that the receiving stations 2e to 2g that cannot receive GNSS signals may not have the GNSS receiving section 10. FIG.

First, the function of each component provided in each receiving station 2 will be described. The GNSS receiver 10 receives GNSS signals transmitted from positioning satellites via a GNSS antenna 15 . The GNSS receiver 10 generates a 1PPS (Pulse Per Second) signal every second. The GNSS receiver 10 performs decoding processing on the received GNSS signal to grasp the reception time point of the GNSS signal and to grasp the error between the clock device of the receiving station 2 and the clock device of the positioning satellite. By receiving the GNSS signal and performing synchronization processing, the clock device of the receiving station 2 is time-synchronized with the clock device of the positioning satellite. The 1PPS signal is a time signal based on the GNSS signal, which is generated each time one second elapses in the clock device of the receiving station 2 .

The local clock unit 11 has a clock counter 21 that increases by 1 at a predetermined cycle (eg, 500 MHz) and a mechanism that acquires the counter value of the clock counter 21 at specified timing. The local clock unit 11 receives the 1PPS signal generated by the GNSS receiving unit 10 and holds the counter value of the local clock at the time of receiving the 1PPS signal. Hereinafter, the time corresponding to the clock counter value is called fine time. The fine time can be considered as a value obtained by multiplying the clock counter value by the time per clock counter (for example, 2 nsec for a 500 MHz period). The clock counter value returns to 1 when it reaches the maximum counter value determined by the number of bits representing the clock counter value.

Downconverter 12 receives the reference signal transmitted from reference station 3 , the ADS-B signal transmitted from aircraft 4 and the Mode S signal transmitted from aircraft 1 via antenna 16 . The down-converter 12 down-converts the received reference signal, ADS-B signal, and Mode S signal, and outputs them to the reception processing unit 13 .

The reception processing unit 13 A/D (Analog to Digital) converts the down-converted reference signal, ADS-B signal, and Mode S signal input from the down converter 12, and then performs decoding processing. Further, the reception processing unit 13 detects rising edges of the reference signal, the ADS-B signal, and the mode S signal, and holds the local clock counter value (that is, fine time) at the time of detection.

The transmission unit 14 generates a fine time indicating the generation time of the 1PPS signal detected by the local clock unit 11, and a fine time indicating the reception time of the reference signal, the ADS-B signal, and the mode S signal detected by the reception processing unit 13. The time is transmitted to the positioning processing device 8.

Next, the function of each component of the positioning processing device 8 will be described. The receiving unit 17 receives time counter information including the fine time detected by the local clock unit 11 and the fine time detected by the reception processing unit 13 from each receiving station 2 . The positioning processing device 8 can communicate with all receiving stations 2 . The positioning processing device 8 measures the position of the aircraft 1 to be monitored.

The hybrid TDOA processing unit 18 calculates the fine time difference representing the reception time between two different receiving stations for the same signal. The fine time difference between two different receiving stations for the same signal is called TDOA (Time of Difference of Arrival). Specifically, in the case of FIG. 1, the hybrid TDOA processing unit 18 calculates the fine time difference indicating the point in time when the same ADS-B signal is received from the aircraft 4 by the receiving stations 2a to 2c. Compute for all possible pairs of stations. Further, the hybrid TDOA processing unit 18 calculates the fine time difference indicating the point in time when the same reference signal is received from the reference station 3 by the receiving stations 2e to 2f for all possible pairs of two stations among the receiving stations 2e to 2f. calculate. The hybrid TDOA processing unit 18 calculates the fine time difference representing the generation time of the 1PPS signal most recently generated in the receiving stations 2d, 2h, and 2i by all possible two stations among the receiving stations 2d, 2h, and 2i. Compute for a set.

The positioning tracking processing unit 19 receives the same 1PPS signal input from the hybrid TDOA processing unit 18 and generates the same 1PPS signal from each receiving station 2 at the time when the same 1PPS signal is generated from the TDOA, which is the fine time difference between the receiving stations 2. Calculate the fine time offset amount in . The offset amount is an amount representing a difference between counter values (fine time) representing the same time of different clock counters (held by each receiving station 2). By subtracting the offset amount from the fine time, the fine times of different clock counters can be converted to values with respect to the same reference. By subtracting the offset amount difference from the fine time difference, the time difference can be calculated from the fine time difference.

The positioning and tracking processing unit 19 receives the same reference signal from the hybrid TDOA processing unit 18, and from the TDOA, which is the fine time difference representing the time point at which each receiving station 2 receives the same reference signal, Calculate the fine time offset amount. The positioning and tracking processing unit 19 receives the same ADS-B signal from the TDOA, which is the fine time difference representing the time point at which each receiving station 2 receives the same ADS-B signal input from the hybrid TDOA processing unit 18. A fine time offset amount in the receiving station 2 is calculated. Such processing enables time synchronization between different receiving stations. Based on the offset amount of the fine time calculated, the positioning and tracking processing unit 19 calculates, from the fine time representing the point in time when the Mode S signal is received at each receiving station 2 that receives the Mode S signal transmitted by the aircraft 1 to be monitored, The time difference between the reception times of the Mode S signals received by each receiving station that receives the Mode S signals transmitted by the aircraft 1 is calculated.

When the number of receiving stations 2 receiving Mode S signals transmitted by the aircraft 1 is large, the positioning and tracking processing unit 19 performs Mode S A time difference, which is the difference between the times when the signals are received, is calculated. By using a predetermined number of sets, it is possible to prevent a decrease in positioning accuracy due to the use of receiving stations with low accuracy. The positioning tracking processing unit 19 prioritizes the reference signal receiving station over the positioning signal receiving station and the positioning signal receiving station over the second signal receiving station with respect to the set of the receiving stations 2 for calculating the time difference. Calculate the time difference of the number of pairs. The reason for determining the priority in this way is that the accuracy of time synchronization is higher in the order of the reference station synchronization method, the GNSS synchronization method, and the ADS-B synchronization method. Priority is given to a receiving station with high accuracy of time synchronization, and the time difference between the reception times of the mode S signal is calculated. By using the calculated time difference to measure the position of the aircraft 1, can improve the accuracy of measuring

More specifically, the order of priority of the set of two receiving stations 2 for calculating the time difference is as follows. The previous ones have higher priority. A receiving station that is both a reference signal receiving station and a positioning signal receiving station is referred to as a reference signal receiving station. A receiving station that is both a reference signal receiving station and a second signal receiving station is referred to as a reference signal receiving station. A receiving station that is both a positioning signal receiving station and a second signal receiving station is assumed to be a positioning signal receiving station.
(Priority order of selection of pair of receiving station 2)
1: Both stations are reference signal receiving stations.
2: 1 station is a reference signal receiving station and 1 station is a positioning signal receiving station.
3: 1 station is the reference signal receiving station and 1 station is the second signal receiving station.
4: Both stations are positioning signal receiving stations.
5: 1 station is a positioning signal receiving station, and 1 station is a second signal receiving station.
6: Both stations are second signal receiving stations.

The positioning and tracking processing unit 19 receives the same second signal, and the counter value and the position information of the second aircraft included in the time counter information transmitted by each of the second signal receiving station and the multiple signal receiving stations. Based on the positions of the station and the multiple signal receiving station, the difference in the counter value between the clock counters of each of the second signal receiving station and the multiple signal receiving station at the time when the second aircraft transmitted the second signal is calculated. It is a second signal receiving station offset amount calculation unit that calculates the offset amount to represent.

The positioning and tracking processing unit 19 transmits from the second aircraft based on the position information of the second aircraft included in the second signal and the positions of the second signal receiving station and the multiple signal receiving stations stored in the storage unit 20. The arrival time, which is the time until the second signal is received by each of the second signal receiving station or the plurality of signal receiving stations, is calculated for each of the second signal receiving station or the plurality of signal receiving stations and included in the time counter information. An offset amount is calculated based on the difference between the counter values and the arrival time.

The positioning tracking processing unit 19 calculates the counter value included in the time counter information transmitted by each of the reference signal receiving station and the multiple signal receiving stations that received the same reference signal, and the positions of the reference station, the reference signal receiving station, and the multiple signal receiving stations. and a reference signal receiving station offset calculation unit that calculates the offset amount between the clock counters of each of the reference signal receiving station and the multiple signal receiving stations at the time when the reference station transmits the reference signal.

Based on the counter value included in the time counter information transmitted by each of the positioning signal receiving station and the multiple signal receiving stations that generated the same time signal, the positioning tracking processing unit 19 determines whether each of the positioning signal receiving station and the multiple signal receiving stations A positioning signal receiving station offset amount calculation unit that calculates an offset amount between the clock counters provided at the time when the time signal is generated.

The positioning tracking processing unit 19 is included in the time counter information transmitted by the first signal receiving station when the first signal is received, for each set of two different first signal receiving stations that have received the same first signal. Based on the counter value and the amount of offset between the clock counters possessed by the two first signal receiving stations, a time difference, which is the difference between the times when the two first signal receiving stations receive the same first signal, is determined. It is a time difference calculation unit that calculates for the number of pairs obtained.

The positioning and tracking processing unit 19 measures the position of the aircraft 1 based on the calculated time difference between the reception times of the Mode S signals of each receiving station. Specifically, the positioning and tracking processing unit 19 converts the time difference between the reception times of the Mode S signals into the distance difference from the aircraft 1 and obtains a hyperbola under the condition that the distance difference is constant based on the position of each receiving station 2 . The position of the aircraft 1 is calculated by finding the intersection points of a plurality of hyperbolas.

The positioning and tracking processing unit 19 is an aircraft position measurement unit that calculates the position of the first aircraft based on the time difference and the position of the first signal receiving station.

The storage unit 20 stores in advance the position information of the reference station 3, the position information of each receiving station 2, and the propagation speed information of the Mode S signal and the ADS-B signal. Furthermore, the storage unit 20 stores a fine time indicating the point in time when each receiving station 2 that can receive the GNSS signal generated the 1PPS signal most recently, and each receiving station 2 that can receive the ADS-B signal most recently generated the ADS-B signal. A fine time indicating the point of time of reception and a fine time indicating the point of time when each receiving station 2 capable of receiving the reference signal most recently received the reference signal are stored. These information are necessary for time synchronization and aircraft positioning.

The storage unit 20 is a position information storage unit that stores the positions of the reference station, the first signal receiving station, and the multiple signal receiving stations.

[ADS-B synchronization method]
Next, the ADS-B synchronization method, which is one of the features of the present disclosure, will be described. FIG. 3 is a diagram for explaining the ADS-B synchronization method. As shown in FIG. 3, aircraft 4 broadcast ADS-B signals containing their position information.

The receiving stations 2a, 2b, 2c, and 2d receive the ADS-B signal transmitted from the aircraft 4, detect the rise of the waveform of the ADS-B signal, and hold the clock counter value (fine time) at the time of detection of the rise. . Further, the receiving stations 2a, 2b, 2c and 2d decode the received ADS-B signals and extract the position information of the aircraft 4 from the decoded ADS-B signals. The receiving stations 2 a , 2 b , 2 c , 2 d transmit time counter information including fine time and position information of the aircraft 4 to the positioning processing device 8 .

The positioning processing device 8 receives the fine time and the position information of the aircraft 4 from the receiving stations 2a, 2b, 2c and 2d. The positioning processing device 8 receives the position information ( _xa , _ya , _za ) of the receiving station 2a, the position information ( _xb , _yb , _zb ) of the receiving station 2b, the position information ( _xc , y _c , z _c ) and the position information (x _d , y _d , z _d ) of the receiving station 2d are known, and these position information and the position information of the aircraft 4 (x _r , y _r , z _r ) and the distances d _a , d _b , d _c , d _d between the aircraft 4 and each receiving station 2a, 2b, 2c, 2d are calculated by geometrical calculations. The distances d _a , d _b , d _c , and d _d are represented by the following formulas (1A), (1B), (1C), and (1D).

From the calculated distances between the aircraft 4 and the respective receiving stations 2a, 2b, 2c, 2d, arrival times τ _a , τ _b , τ _c and τ _d [nsec] can be obtained as shown in the following equation (2). However, in equation (2), the propagation speed of the ADS-B signal is c.

The arrival time of the ADS-B signal is the time until the ADS-B signal transmitted from the aircraft 4 is received by each receiving station that receives the ADS-B signal.

The arrival time τa of the ADS-B signal from the aircraft 4 is obtained from the fine times T _a , T _b , T _c , and T _d [nsec] indicating the reception times of the ADS-B signals at the receiving stations 2a, 2b, 2c, and 2d _. , τ _b , τ _c , and τ _d are subtracted to obtain the fine times of the receiving stations 2a, 2b, 2c, and 2d at the time when the aircraft 4 transmitted the ADS-B signal. The offset amount is calculated based on the fine times output by the clock counters of the different receiving stations 2 at the same time. Let Δt _a , Δt _b , Δt _c , and Δt _d be the offset amounts at the receiving stations 2a, 2b, 2c, and 2d. Therefore, as shown in the following equation (3), at the transmission time of the ADS-B signal, the offset amount can be calculated from the relationship that the value obtained by subtracting the offset amount from the fine time is equal, and the offset amount is subtracted from the fine time. This enables time synchronization among the receiving stations 2a, 2b, and 2c.

Equation (3) has three equations for four variables, and one variable has a degree of freedom. Here, Δt _d =0 based on the fine time of the receiving station 2d that receives all kinds of signals. Note that the offset amount Δt _j,k between the two receiving stations 2 _j and 2 _k may also be used. If Δt _j,k is used, then j<k if j,k is a number, and if j,k is alphabetic, then j is the one that precedes k in alphabetical order.

The reference station synchronization method is also basically the same as above. In the case of the reference station synchronization method, the position information of the reference station 3 is used instead of the position information of the aircraft 4, and the reference signal is used instead of the ADS-B signal.

[Specific example of time difference calculation process]
Hereinafter, the process of calculating the time difference between the reception times of the Mode S signals from the aircraft 1 to be monitored will be described using a specific example. FIG. 4 is a timing chart for explaining an example of time difference calculation processing. FIG. 4 shows the case where the receiving stations 2c, 2d, 2e and 2h of FIG. 1 receive Mode S signals from the same aircraft 1. In FIG. In FIG. 4, white squares indicate that each receiving station produced a 1PPS signal. A white circle indicates that an ADS-B signal was received at each receiving station. A black dot indicates that the reference signal was received at each receiving station. A double circle indicates that each receiving station has received a Mode S signal. t1, etc. in time t1, etc. are variables representing time points. Time such as t1 is not measured. Fine times T1 and T2 are measured at time t1.

At time t1, the receiving stations 2d and 2h receive GNSS signals from four or more positioning satellites 5. FIG. It is desirable that the number of positioning satellites 5 from which GNSS signals are received in common by the receiving stations 2d and 2h is large. Receiving stations 2d and 2h generate 1PPS signals that are time-synchronized with the clock device of positioning satellite 5. FIG. Since the receiving stations 2d and 2h are time-synchronized, they generate a 1PPS signal at the same time t1. The receiving stations 2d and 2h transmit to the positioning processor 8 fine times T1 and T2 and time counter information (described later) including information for identifying the 1PPS signal. The positioning processing device 8 calculates the offset amount _Δth of the clock counter of the receiving station 2h from the fine times T1 and T2 included in the received time counter information using the following formula. Note that Δt _d =0.
Δt _h =T2-T1 (4)

An ADS-B signal is transmitted from the aircraft 4 at time t2. Receiving stations 2c and 2d receive the ADS-B signal at times t3 and t4, respectively. The fine times indicating the reception times of the ADS-B signals detected by the receiving stations 2c and 2d are T3 and T4, respectively. The receiving station 2c creates fine time T3, time counter information including identification information and position information of the aircraft 4, and transmits the created time counter information to the positioning processing device 8. FIG. The receiving station 2 d creates fine time T 4 , time counter information including identification information and position information of the aircraft 4 , and transmits the created time counter information to the positioning processing device 8 . The positioning processing device 8 receives the time counter information from the receiving stations 2c and 2d, and based on the position information of the aircraft 4 and the position information of the receiving stations 2c and 2d included in the time counter information, the ADS from the aircraft 4 to the receiving station 2c. - Calculate the arrival time τ3 of the B signal and the arrival time τ4 of the ADS-B signal from the aircraft 4 to the receiving station 2d. The positioning processing device 8 further calculates the offset amount Δtc of the clock counter of the receiving station 2c using the following formula.
Δt _c =T3-τ3-(T4-τ4) (5)

A reference signal is transmitted from the reference station 3 at time t5. Receiving stations 2e and 2d receive the reference signal at times t6 and t7, respectively. Fine times indicating reception times of the reference signals detected by the receiving stations 2e and 2d are T5 and T6, respectively. The receiving station 2 e creates fine time T5 and time counter information including information for identifying the reference signal, and transmits the created time counter information to the positioning processing device 8 . The receiving station 2 d creates fine time T 6 and time counter information including information for identifying the reference signal, and transmits it to the positioning processing device 8 . The positioning processing device 8 that has received the time counter information from the receiving stations 2e and 2d determines the arrival time τ5 of the reference signal from the reference station 3 to the receiving station 2e and , and the arrival time τ6 of the reference signal from the reference station 3 to the receiving station 2d. The positioning processing device 8 further calculates the offset amount Δte of the clock counter of the receiving station 2e using the following formula.
Δt _e =T5−τ5−(T6−τ6) (6)

Receiving stations 2c, 2d, 2h and 2e receive Mode S signals from the monitored aircraft 1 at times t8, t9, t10 and t11, respectively. The fine times indicating the reception times of the Mode S signals detected by the receiving stations 2c, 2d, 2h and 2e are T7, T8, T9 and T10, respectively. The receiving station 2c creates fine time T7 and time counter information including information for identifying the mode S signal of the aircraft 1, and transmits the created time counter information to the positioning processing device 8. FIG. The receiving station 2d creates fine time T8 and time counter information including information for identifying the mode S signal of the aircraft 1, and transmits the created time counter information to the positioning processing device 8. FIG. The receiving station 2h creates fine time T9 and time counter information including information for identifying the Mode S signal of the aircraft 1, and transmits the time counter information to the positioning processing device 8. FIG. The receiving station 2e creates fine time T8 and time counter information including information for identifying the Mode S signal of the aircraft 1, and transmits the created time counter information to the positioning processing device 8. FIG.

The time counter information is obtained by each of the first signal receiving station and the multiple signal receiving stations that received any one of the Mode S signal, ADS-B signal, and reference signal, or received the positioning signal and generated the 1PPS signal. , is information to be generated and transmitted to the positioning processing device 8 . The time counter information includes the type of signal received or generated, the aircraft position information included in the ADS-B signal if an ADS-B signal is received, and the counter value of the clock counter at the time the signal was received or generated. and information identifying each of the first signal receiving station and the plurality of signal receiving stations.

In the case of the above example, the positioning processing device 8 calculates the time difference δ3 between the reception times of the Mode S signals by the receiving stations 2c and 2d using the following formula. Note that Δt _d =0.
δ3=(T7−Δt _c )−(T8−Δt _d ) (7)
By substituting equation (5) into equation (7), the following equation is obtained.
δ3=(T7-T3+τ3)-(T8-T4+τ4) (8)
The fine time indicating the reception time of the mode S signal is corrected by the fine time indicating the reception time of the ADS-B signal and the offset amount calculated from the position information of the aircraft 4 included in the ADS-B signal.

The positioning processing device 8 calculates the time difference δ4 between the reception times of the Mode S signals by the receiving stations 2h and 2d using the following formula.
δ4=(T9−Δt _h )−(T8−Δt _d ) (9)
By substituting equation (4) into equation (9), the following equation is obtained.
δ4=(T9-T2)-(T8-T1) (10)
The fine time indicating the reception time of the mode S signal is corrected by the offset amount calculated from the fine time when the 1PPS signal was generated.

A time difference δ5 between the reception times of the Mode S signals by the receiving stations 2e and 2d is calculated by the following formula.
δ5=(T10−Δt _e )−(T8−Δt _d ) (11)
By substituting equation (6) into equation (11), the following equation is obtained.
δ5=(T10-T5+τ5)-(T8-T6+τ5) (12)
The fine time indicating the reception time of the mode S signal is corrected by the offset amount calculated from the fine time indicating the reception time of the reference signal and the position information of the reference station 3 .

[An example of aircraft position measurement processing]
FIG. 5 is a flow chart showing an example of aircraft position measurement processing. Below, with reference to FIG. 5, the description so far of the process of measuring the position of the aircraft 1 to be monitored will be summarized.

In step S11, the positioning processing device 8 obtains the fine time at which each receiving station 2 most recently received the ADS-B signal and the time counter information including the position information of the aircraft 4 included in the ADS-B signal, Based on the time counter information including the fine time at which the reference signal was most recently received, the time counter information including the fine time at which each receiving station generated the 1PPS signal most recently, and the position information of the reference station 3 and each receiving station 2, The offset amount of the clock counter that each receiving station 2 has is calculated.

In step S12, when the positioning processing device 8 receives the time counter information including the fine time at which the mode S signal of the aircraft 1 was received from each receiving station 2 (YES in step S11), the process proceeds to step S13.

In step S13, the positioning processing device 8 selects three or more receiving stations based on the time counter information including the fine time when each receiving station 2 received the Mode S signal and the offset amount of the clock counter possessed by each receiving station 2. 2, the time difference between the reception times of the Mode S signals received from aircraft 1 is calculated.

In the next step S14, the positioning processing device 8 measures the position of the aircraft 1 based on the calculated time difference between the reception times of the Mode S signals and the position information of each receiving station 2. FIG. This completes the position measurement process for the aircraft 1 .

[Example of hardware configuration of positioning processing device]
FIG. 6 is a block diagram showing an example of the hardware configuration of the positioning processing device. Referring to FIG. 6 , positioning processing device 8 includes control unit 31 , main storage unit 32 , external storage unit 33 , operation unit 34 , display unit 35 and transmission/reception unit 36 . The main storage unit 32 , the external storage unit 33 , the operation unit 34 , the display unit 35 and the transmission/reception unit 36 are connected to the control unit 31 via the internal bus 30 .

The control unit 31 is composed of a CPU (Central Processing Unit) or the like, and operates according to a control program 39 stored in the external storage unit 33 to control each of the hybrid TDOA processing unit 18 and the positioning and tracking processing unit 19 shown in FIG. Execute the process. The control program 39 may be provided via a computer-readable storage medium or via a network.

The main storage unit 32 is composed of a RAM (Random Access Memory) or the like. The main storage unit 32 is used as a work area for the control unit 31 by loading the control program 39 stored in the external storage unit 33 .

The external storage unit 33 is composed of a non-volatile memory such as a flash memory or a hard disk, and stores programs and data for causing the control unit 31 to perform processing of the positioning processing device 8 . The storage unit 20 in FIG. 2 corresponds to the external storage unit 33 .

The operation unit 34 is used for user input operations to the positioning processing device 8 . Operation unit 34 includes, for example, a keyboard and a pointing device such as a mouse.

The display unit 35 is used to display information to the user, for example measurement information indicating the position of the aircraft 1 is displayed. The display unit 35 is configured by an LCD (Liquid Crystal Display), an organic EL display, or the like.

The transceiver 36 includes a wired or wireless communication device for connecting to a network. The transmitting/receiving section 36 is connected to each receiving station 2 via a network. The receiver 17 in FIG. 2 corresponds to the transmitter/receiver 36 .

[effect]
The effects of the present disclosure are summarized below. The reference station synchronization method and the GNSS synchronization method are typical time synchronization methods used in aircraft positioning systems, but they have the vulnerability that system performance tends to deteriorate due to changes in the external environment.

On the other hand, in the ADS-B synchronization method of the present disclosure, by using the position information of the aircraft included in the ADS-B signal from the aircraft, the arrival of the ADS-B signal from the aircraft to each receiving station ask for time. The ADS-B synchronization method of the present disclosure detects the difference in the clock counter value for each receiving station based on the arrival time of the ADS-B signal and the clock counter value indicating the reception time of the ADS-B signal at each receiving station. By grasping, time synchronization is performed. Furthermore, by combining the ADS-B synchronization method with the conventional GNSS synchronization method and reference station synchronization method, it is possible to increase the resistance to the vulnerability of the aircraft positioning system, which is prone to performance deterioration due to changes in the external environment. can be done.

The embodiments disclosed this time should be considered as examples and not restrictive in all respects. The scope of this application is indicated by the scope of claims rather than the above description, and is intended to include all changes within the meaning and scope of equivalence to the scope of claims.

1, 4 aircraft, 2, 2a to 2i receiving stations, 3 reference stations, 5 positioning satellites, 6a, 6b interference waves/interference waves, etc., 7 shields, etc., 8 positioning processing device, 10 GNSS receiving unit, 11 local clock unit, 12 down converter, 13 reception processing unit, 14 transmission unit, 15, 16 antennas, 17 reception unit, 18 hybrid TDOA processing unit, 19 positioning tracking processing unit, 20 storage unit, 21 clock counter, 30 internal bus, 31 control unit, 32 main storage unit, 33 external storage unit, 34 operation unit, 35 display unit, 36 transmission/reception unit, 39 control program, 100 aircraft position measurement system.

Claims (8)

receiving a first signal transmitted from a first aircraft to be monitored containing identification information of said first aircraft and a second signal transmitted from a second aircraft containing identification information and location information of said second aircraft; , a second signal receiving station having a clock counter;
a reference signal receiving station that receives the first signal and a reference signal transmitted from a reference station and has the clock counter;
a positioning signal receiving station that receives the first signal and a positioning signal transmitted from a positioning satellite, generates a time signal based on the positioning signal, and has the clock counter;
one or more multi-signal receiving stations that receive at least two kinds of signals among the second signal, the reference signal and the positioning signal, wherein the second signal, the reference signal and the positioning signal are received; a plurality of signal receiving stations in which types of signals to be received are determined such that each of three types of signals is received by any one of the plurality of signal receiving stations;
capable of communicating with each of the first signal receiving station, which is one of the second signal receiving station, the reference signal receiving station, and the positioning signal receiving station, and the plurality of signal receiving stations, and measuring the position of the first aircraft; and a positioning processing device for
Each of the first signal receiving station and the plurality of signal receiving stations that received any one of the first signal, the second signal, and the reference signal or generated the time signal received or generated the type of the signal; the position information of the second aircraft included in the second signal when the second signal is received; the counter value of the clock counter at the time the signal was received or generated; transmitting time counter information including information identifying each of the signal receiving station and the plurality of signal receiving stations to the positioning processing device;
The positioning processing device is
a receiver that receives the time counter information transmitted from each of the first signal receiving station and the plurality of signal receiving stations;
a position information storage unit that stores positions of each of the reference station, the first signal receiving station, and the plurality of signal receiving stations;
the counter value and position information of the second aircraft included in the time counter information transmitted by each of the second signal receiving station and the plurality of signal receiving stations that have received the same second signal; and the reception of the second signal. station and the positions of the multiple signal receiving stations, between the clock counters of each of the second signal receiving station and the multiple signal receiving stations at the time the second aircraft transmits the second signal. A second signal receiving inter-station offset amount calculating unit that calculates an offset amount representing the difference between the counter values of
the counter value included in the time counter information transmitted by each of the reference signal receiving station and the plurality of signal receiving stations that have received the same reference signal; between the reference signal receiving stations for calculating the offset amount between the clock counters of each of the reference signal receiving station and the plurality of signal receiving stations at the time when the reference station transmits the reference signal, based on the positions of the reference signal receiving stations. an offset amount calculator;
Based on the counter value included in the time counter information transmitted by each of the positioning signal receiving station and the plurality of signal receiving stations that generated the same time signal, each of the positioning signal receiving station and the plurality of signal receiving stations a positioning signal receiving station offset calculation unit that calculates the offset between the clock counters at the time of generating the time signal;
The counter included in the time counter information transmitted by the first signal receiving station when receiving the first signal for each set of two different first signal receiving stations that received the same first signal. and the offset amount between the clock counters of the two first signal receiving stations, the difference between the times when the two first signal receiving stations receive the same first signal. a time difference calculator that calculates the time difference for a predetermined number of sets;
an aircraft position determination component that calculates the position of the first aircraft based on the time difference and the position of the first signal receiving station. the second signal is an ADS-B signal;
The second signal receiving station regards the point of time when the rising edge of the ADS-B signal is detected as the point of time when the second signal is received,
The second signal receiving station offset amount calculating unit calculates the position information of the second aircraft included in the second signal, the second signal receiving station stored in the position information storage unit, and the multiple signal receiving station. a time of arrival of said second signal, which is the time it takes for said second signal transmitted from said second aircraft to be received at each of said second signal receiving station or said plurality of signal receiving stations, based on the location of said second signal; 2. The aircraft positioning system according to claim 1, wherein said offset amount is calculated for each receiving station or said plurality of signal receiving stations, and based on the difference between said counter values included in said time counter information and said arrival time. The time difference calculator calculates a predetermined number of sets of the time differences, giving priority to the reference signal receiving station over the positioning signal receiving station and giving priority to the positioning signal receiving station over the second signal receiving station. 3. An aircraft positioning system according to claim 1 or claim 2, wherein receiving a first signal transmitted from a first aircraft to be monitored containing identification information of said first aircraft and a second signal transmitted from a second aircraft containing identification information and location information of said second aircraft; a second signal receiving station having a clock counter; receiving the first signal and a reference signal transmitted from a reference station; a reference signal receiving station having the clock counter; and transmitting the first signal and the positioning satellite. a first signal receiving station which is any one of positioning signal receiving stations which receives a positioning signal, generates a time signal based on the positioning signal, and has the clock counter; and the second signal, the reference signal and One or more multiple signal receiving stations that receive at least two types of signals among the positioning signals, wherein each of the three types of signals of the second signal, the reference signal and the positioning signal is a positioning processing device capable of communicating with each of said plurality of signal receiving stations in which the types of signals to be received by said plurality of signal receiving stations are determined to be received by said plurality of signal receiving stations, and measuring the position of said first aircraft, ,
each of the first signal receiving station and the plurality of signal receiving stations that received any one of the first signal, the second signal, and the reference signal or generated the time signal transmits, receives, or the type of the generated signal; the positional information of the second aircraft included in the second signal when the second signal is received; the counter value of the clock counter at the time the signal was received or generated; a receiver for receiving time counter information including information identifying each of the first signal receiving station and the plurality of signal receiving stations;
a position information storage unit that stores positions of each of the reference station, the first signal receiving station, and the plurality of signal receiving stations;
the counter value and position information of the second aircraft included in the time counter information transmitted by each of the second signal receiving station and the plurality of signal receiving stations that have received the same second signal; and the reception of the second signal. station and the positions of the multiple signal receiving stations, between the clock counters of each of the second signal receiving station and the multiple signal receiving stations at the time the second aircraft transmits the second signal. A second signal receiving inter-station offset amount calculating unit that calculates an offset amount representing the difference between the counter values of
the counter value included in the time counter information transmitted by each of the reference signal receiving station and the plurality of signal receiving stations that have received the same reference signal; between the reference signal receiving stations for calculating the offset amount between the clock counters of each of the reference signal receiving station and the plurality of signal receiving stations at the time when the reference station transmits the reference signal, based on the positions of the reference signal receiving stations. an offset amount calculator;
Based on the counter value included in the time counter information transmitted by each of the positioning signal receiving station and the plurality of signal receiving stations that generated the same time signal, each of the positioning signal receiving station and the plurality of signal receiving stations a positioning signal receiving station offset calculation unit that calculates the offset between the clock counters at the time of generating the time signal;
The counter included in the time counter information transmitted by the first signal receiving station when receiving the first signal for each set of two different first signal receiving stations that received the same first signal. and the offset amount between the clock counters of the two first signal receiving stations, the difference between the times when the two first signal receiving stations receive the same first signal. a time difference calculator that calculates the time difference for a predetermined number of sets;
an aircraft position determination unit that calculates the position of the first aircraft based on the time difference and the position of the first signal receiving station. the second signal is an ADS-B signal;
The second signal receiving station regards the point of time when the rising edge of the ADS-B signal is detected as the point of time when the second signal is received,
The second signal receiving station offset amount calculating unit calculates the position information of the second aircraft included in the second signal, the second signal receiving station stored in the position information storage unit, and the multiple signal receiving station. a time of arrival, which is the time it takes for the second signal transmitted from the second aircraft to be received at the second signal receiving station or the plurality of signal receiving stations, based on the location of the second signal receiving station; 5. The positioning processing apparatus according to claim 4, wherein said offset amount is calculated for each of said plurality of signal receiving stations, and said offset amount is calculated based on said arrival time and the difference between said counter values included in said time counter information. The time difference calculator calculates a predetermined number of sets of the time differences, giving priority to the reference signal receiving station over the positioning signal receiving station and giving priority to the positioning signal receiving station over the second signal receiving station. The positioning processing device according to claim 4 or 5, wherein receiving a first signal transmitted from a first aircraft to be monitored containing identification information of said first aircraft and a second signal transmitted from a second aircraft containing identification information and location information of said second aircraft; a second signal receiving station having a clock counter; receiving the first signal and a reference signal transmitted from a reference station; a reference signal receiving station having the clock counter; a positioning signal receiving station that receives a positioning signal from the positioning signal, generates a time signal based on the positioning signal, and has the clock counter; and at least two signals among the second signal, the reference signal, and the positioning signal. wherein each of the three types of signals, the second signal, the reference signal and the positioning signal, is received by any of the multiple signal receiving stations storing the locations of the plurality of signal receiving stations whose types of signals to be received are determined in
receiving the second signal by the second signal receiving station and the multiple signal receiving stations receiving the second signal;
Each of the second signal receiving station that received the second signal and the plurality of signal receiving stations received the type of signal representing the second signal, location information of the second aircraft, and the second signal. Time counter information including the counter value of the clock counter at the time and information identifying each of the second signal receiving station and the plurality of signal receiving stations is sent to a positioning processing device for measuring the position of the first aircraft. a step of sending;
a step in which the positioning processing device receives the time counter information transmitted by each of the second signal receiving station and the plurality of signal receiving stations that have received the second signal;
the counter value and position information of the second aircraft included in the time counter information transmitted by each of the second signal receiving station and the plurality of signal receiving stations that have received the same second signal; and the reception of the second signal. station and the position of the multiple signal receiving station, between the clock counters of each of the second signal receiving station and the multiple signal receiving station at the time the second aircraft transmits the second signal. calculating an offset amount representing the difference between the counter values;
receiving the reference signal by the reference signal receiving station and the multiple signal receiving stations receiving the reference signal;
Each of the reference signal receiving station that has received the reference signal and the plurality of signal receiving stations has the type of signal representing the reference signal, the counter value at the time of receiving the reference signal, and the reference signal receiving station. and information identifying each of the plurality of signal receiving stations to the positioning processing device;
a step in which the positioning processing device receives the time counter information transmitted by the reference signal receiving station that received the reference signal and the multiple signal receiving station;
the counter value included in the time counter information transmitted by each of the reference signal receiving station and the plurality of signal receiving stations that have received the same reference signal; calculating the offset between the clock counters of each of the reference signal receiving station and the plurality of signal receiving stations at the time when the reference station transmits the reference signal, based on the position;
a step in which the positioning signal receiving station and the plurality of signal receiving stations that receive the positioning signals receive the positioning signals from the positioning satellites and generate the time signals;
Each of the positioning signal receiving station that generated the time signal and the plurality of signal receiving stations has the type of signal representing the time signal, the counter value at the time of receiving the time signal, and the positioning signal receiving station. and information identifying each of the plurality of signal receiving stations to the positioning processing device;
Based on the counter value included in the time counter information transmitted by each of the positioning signal receiving station and the plurality of signal receiving stations that generated the same time signal, each of the positioning signal receiving station and the plurality of signal receiving stations calculating the offset between the clock counters at the time of generating the time signal;
Among a plurality of first signal receiving stations, each of which is one of the second signal receiving station, the reference signal receiving station, and the positioning signal receiving station, two different first signal receiving stations receiving the same first signal For each set of signal receiving stations, the counter value included in the time counter information transmitted by the first signal receiving station when receiving the first signal, and the counter value possessed by the two first signal receiving stations calculating a time difference, which is the difference between the times when two said first signal receiving stations received the same first signal, for a determined number of sets, based on said offset amount between clock counters; ,
calculating the position of the first aircraft based on the time difference and the position of the first signal receiving station. receiving a first signal transmitted from a first aircraft to be monitored containing identification information of said first aircraft and a second signal transmitted from a second aircraft containing identification information and location information of said second aircraft; a second signal receiving station having a clock counter; receiving the first signal and a reference signal transmitted from a reference station; a reference signal receiving station having the clock counter; and transmitting the first signal and the positioning satellite. a first signal receiving station which is any one of positioning signal receiving stations which receives a positioning signal, generates a time signal based on the positioning signal, and has the clock counter; and the second signal, the reference signal and One or more multiple signal receiving stations that receive at least two types of signals among the positioning signals, wherein each of the three types of signals of the second signal, the reference signal and the positioning signal is a computer capable of communicating with each of said plurality of signal receiving stations in which the types of signals to be received are determined to be received by said plurality of signal receiving stations of
each of the first signal receiving station and the plurality of signal receiving stations that received any one of the first signal, the second signal, and the reference signal or generated the time signal transmits, receives, or the type of the generated signal; the positional information of the second aircraft included in the second signal when the second signal is received; the counter value of the clock counter at the time the signal was received or generated; a receiver for receiving time counter information including information identifying each of the first signal receiving station and the plurality of signal receiving stations;
a position information storage unit that stores positions of each of the reference station, the first signal receiving station, and the plurality of signal receiving stations;
the counter value and position information of the second aircraft included in the time counter information transmitted by each of the second signal receiving station and the plurality of signal receiving stations that have received the same second signal; and the reception of the second signal. station and the positions of the multiple signal receiving stations, between the clock counters of each of the second signal receiving station and the multiple signal receiving stations at the time the second aircraft transmits the second signal. A second signal receiving inter-station offset amount calculation unit that calculates an offset amount representing the difference between the counter values of
the counter value included in the time counter information transmitted by each of the reference signal receiving station and the plurality of signal receiving stations that have received the same reference signal; between the reference signal receiving stations for calculating the offset amount between the clock counters of each of the reference signal receiving station and the plurality of signal receiving stations at the time when the reference station transmits the reference signal, based on the positions of the reference signal receiving stations. an offset amount calculator,
Based on the counter value included in the time counter information transmitted by each of the positioning signal receiving station and the plurality of signal receiving stations that generated the same time signal, each of the positioning signal receiving station and the plurality of signal receiving stations a positioning signal receiving station offset amount calculation unit that calculates the offset amount between the clock counters at the time the time signal is generated;
The counter included in the time counter information transmitted by the first signal receiving station when receiving the first signal for each set of two different first signal receiving stations that received the same first signal. and the offset amount between the clock counters of the two first signal receiving stations, the difference between the times when the two first signal receiving stations receive the same first signal. a time difference calculator that calculates the time difference for a predetermined number of pairs;
an aircraft position measuring unit that calculates the position of the first aircraft based on the time difference and the position of the first signal receiving station;
A program that functions as

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