JP3524018B2 - Positioning system and positioning method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning system, and more particularly to a plurality of satellite range finding radio waves transmitted from a plurality of satellites orbiting the vicinity of the earth and relaying by range finding radio wave relay means mounted on those satellites. The present invention relates to a positioning system that receives a moving object distance measurement radio wave and determines the position of a positioning terminal.

[0002]

2. Description of the Related Art A satellite-based positioning system currently in operation receives one wave of a ranging radio wave transmitted from 5 or 6 satellites orbiting a low orbit at an altitude of about 1,000 km, and the Doppler NNS that calculates the two-dimensional position of a moving body by measuring the amount of temporal change in the range between satellites and mobile stations from the amount of frequency shift
S (Navy Navigation Satellite System) and altitude about 2
At least four ranging radio waves transmitted from more than 24 satellites that orbit the 10,000 km high altitude orbit are received, and four or more satellite-mobile pseudo ranges or 3 or more from the arrival times of those radio waves. GPS (Global Position) that calculates the three-dimensional position of a moving object by measuring the range difference between two or more satellites and mobile stations
ioning System).

In the NNSS, it is necessary to continuously receive ranging radio waves from one satellite for several minutes, so that it is impossible to obtain positioning information instantaneously and continuously. In addition, since it is difficult in principle to obtain highly accurate three-dimensional positioning information with the NNSS positioning method, it has been limited to two-dimensional positioning that also uses altitude information of the mobile body. Also,
Since the satellite altitude must be low in the positioning method using Doppler frequency shift, it was necessary to deploy many satellites in orbit to increase the frequency of positioning. For example,
Even if 5 or 6 satellites are deployed, the positioning frequency is about once per hour on average. Due to such performance drawbacks, N
NSS was mainly used for navigation of ships, and was hardly used for navigation of land vehicles and aircraft.

GPS is a globally available positioning system developed to solve the problem of NNSS all at once. Normally, not only is it possible to instantaneously and continuously obtain two-dimensional positioning information when the number of radio waves that can be received is three, and three-dimensional positioning information when there are four or more radio waves, but the accuracy is
Higher than SS. For this reason, the field of use of GPS has come to be widely used as a navigation means for not only ships but also aircraft and land vehicles. Particularly in the field of car navigation called car navigation, GPS terminals are growing into one of the huge industries as standard car equipment.

However, since it was necessary to deploy a large number of satellites to enable instantaneous and continuous positioning all over the world, the cost and period required for its development were enormous. The cost of maintaining a GPS is expected to be enormous, but it is only the GPS that will be developed and maintained.
Is a very important military and national facility that ignores profitability.

[0006] Since GPS is a positioning system that can easily obtain highly accurate and continuous positioning information simply by receiving distance measurement radio waves, GPS is extremely versatile, and its field of use and number of users will continue to increase. It must increase. However, GPS, which is a military facility that the United States provides its service free of charge as a national policy, uses Selectiv for its use.
e Availability (intentional management of positioning accuracy) and Anti-Spo
Restrictions due to ofing (conversion to secret code) are imposed. Further, as described above, the cost of maintaining the GPS is enormous, and there is no effective measure for collecting the usage fee from the user, so that privatization and commercialization of the positioning service is difficult. On the other hand, the privatization of positioning services is a natural consequence of the principle of a beneficiary-paid liberal economy, and its commercialization is a condition of its viability as an infrastructure.

In order to construct a positioning system that replaces GPS, it is essential to implement a new satellite positioning method suitable for privatization and commercialization. Further, at present, commercialization of mobile communication systems using a large number of low-altitude orbiting satellites is in progress at a rapid pace, and an era in which communication satellites are arranged everywhere in the sky is about to come. Considering such a situation, it is desired to provide a satellite positioning method using these communication satellites as positioning means. However, when a low altitude satellite is used as a ranging radio wave source, each satellite rapidly leaves the field of view of the positioning terminal, and thus it is difficult for the conventional positioning method to achieve stable positioning performance like GPS. In the NNSS positioning method, it is necessary to abandon instantaneous and continuous positioning.
This is because, in the S positioning system, the number of satellites that are always visible must normally be 4 or more, so that it becomes necessary to deploy several hundred satellites.

It is desired that positioning with higher accuracy be performed with a smaller number of satellites. In that case, it is preferable to effectively use a part of many satellites for positioning. Furthermore, the use of low earth orbit satellites is preferable.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a positioning system and a positioning method that can perform positioning with higher accuracy with a smaller number of satellites. Another object of the present invention is to provide a positioning system and a positioning method that can perform positioning with higher accuracy with a smaller number of satellites and can effectively use part of a large number of satellites for positioning. It is in. Still another object of the present invention is to perform more accurate positioning with a smaller number of satellites, and to effectively utilize a part of a larger number of satellites for positioning.
It is another object of the present invention to provide a positioning system and a positioning method that can use low-orbit satellites.

[0010]

Means for solving the problem Means for solving the problem are expressed as follows. In the expression, the technical matters corresponding to the claims are enclosed in parentheses (), and numbers, symbols, etc. are added. The number, symbol, etc. are at least one of the technical matters corresponding to the claim and a plurality of modes of implementation.
Although the correspondence and correspondence with the technical matters of the two forms are clarified, it is not intended to show that the technical matters of the claims are limited to the technical matters of the embodiments.

The positioning system according to the present invention transmits a distance measuring radio wave (3a) based on an individual time reference and receives a plurality of distance measuring radio waves (3b) based on the individual time reference.
Of the positioning terminal (10) having a function of detecting the arrival time of the satellite and decoding the positioning related information (55) superimposed on the distance measurement radio wave (3b) and the positioning related terminal based on the common time reference of the satellite (1i). Distance measurement radio waves (2i) with information (55) superimposed
And a plurality of satellites (1i: i) having a function of transmitting the distance measurement radio wave (3a) transmitted by the positioning terminal (10).
, 1, ..., N), a time difference Dc between the individual time reference and the common time reference and a plurality of satellites by communication between the positioning terminal (10) and the satellite (1i). The position Pi of the positioning terminal is determined by measuring the inter-positioning terminal distance Pi (i = 1, 2, ..., N).

By using the time common to a proper number of satellites in the satellite group, the time deviation of the self is accurately grasped and the position of the self is measured. Since any satellite can be used from the range-measurable satellites, the number of satellites used increases, and conversely, more accurate range-finding can be performed with fewer satellites. Linked with positioning, more concentrated data communication becomes possible. The data required for positioning can be superimposed on the ranging radio waves. The common time can be set with high accuracy by a known method described in detail in this specification.

The time deviation Dc can be measured only by using the radio relay means of one satellite, and for three-dimensional positioning of the positioning terminal, three groups including the satellite used for measuring the time deviation Dc are used. The number of satellites is sufficient, and two-dimensional positioning of the positioning terminal can be performed by two satellites including the satellite used for measuring the time deviation Dc. Therefore, it is possible to significantly reduce the frequency of non-positioning as compared with the case of GPS, and
In principle, positioning accuracy is improved. The method of obtaining the deviation Dc is a publicly known technique already published by the present inventor. The combination of this known technology and the technology that uses the common time of a plurality of satellites enables more accurate positioning with a smaller number of satellites.

The positioning terminal (10) receives n range-finding radio waves (2i) transmitted from a group of n rangeable satellites in which a communication link with the positioning terminal (10) is established in the satellite. Time difference D1i (= T) between the arrival time T1i at the positioning terminal (10) and the epoch time T0 generated based on the individual time reference.
1i-T0) is detected, and from the group of n positionable satellites, the reception condition of the ranging radio wave (2i) and the satellite sky placement condition are good in comparison, and the positioning terminal (10) A second step in which the i-th satellite (1i) capable of relaying the transmitted ranging radio wave and capable of receiving the relayed ranging radio wave (3a) by the positioning terminal (10) as a reference satellite; When the positioning terminal (10) transmits at the epoch time T0, the arrival time T of the distance measurement radio waves (3a, 3b) relayed by the reference satellite (i-th satellite)
2i and the epoch time T0, the time difference D2i (= T2i-
T0, the third step of detecting the radio wave round-trip propagation time between the reference satellite and the positioning terminal, and the time difference D2 from the reference satellite
i and the time difference D1i, the time deviation Dc is Dc = D2i /
The position vector Li of all the satellites included in the rangeable satellite group is calculated using the fourth step of calculating by the relational expression 2-D1i and the positioning related information broadcast by the rangeable satellite group or the ground wireless station. Step 5 and time difference D1i
By using the time difference D1i ′ obtained by correcting the propagation delay error depending on the radio wave propagation path included in, the distance Pi between all satellites / positioning terminals included in the rangeable satellite group is Pi = light speed × (D1i '+ Dc) The seventh calculated by the relational expression
Step and n distances Pi obtained from the sixth step
And the seventh step of determining the position vector R of the positioning terminal (10) from the n number of position vectors Li obtained from the fifth step and the position vector R0 of the positioning terminal (10) at the time of the previous update at a necessary frequency. It is equipped with a reception processing unit for execution.

Further, each satellite (1i) which constitutes the satellite group
Is an eighth step of updating a correction parameter for improving the time accuracy of the satellite-mounted clock that maintains the common time reference and broadcasting as positioning related information; and a ranging radio wave received by the positioning terminal (10) in the first step. A first step of generating and transmitting a distance measurement radio wave transmitted by the positioning terminal (10) that is received and processed in the third step and a first step of relaying the distance measurement radio wave.
A distance measurement radio wave generation relay unit that executes 0 steps at a required frequency is provided.

In the positioning calculation based on such steps, the positioning terminal can calculate the position vector every time the time deviation Dc and the distance Pi (i = 1, 2, ..., N) are measured. Depending on the deployment conditions of GPS, positioning information can be provided instantaneously and continuously as in GPS.
It is possible to solve the problem of the positioning performance of the SS. When calculating the time deviation Dc in the fifth step, the positioning terminal (10) sets Wi and Li as the orbital angular velocity vector and position vector of the satellite, and sets R and V as the position vector and speed vector of the positioning terminal (10). At this time, the correction value Ei of the error of the radio wave round-trip propagation time D2i caused by the movement of the satellite and the moving body during the propagation of the distance measurement radio wave is Ei = 2.
Wi · (R × Li) / C2 + Pi · V / C2 (C = speed of light), and when the correction value Ei is equal to or greater than the main positioning error, the time deviation is derived as The relational expression Dc = (D2i-Ei) / 2-D1i is applied. By performing such a correction on the time deviation Dc, it is possible to reduce the positioning error due to the time deviation error, and it is possible to achieve accuracy equal to or higher than that of GPS.

Further, the above-mentioned two steps: when the positioning terminal transmits at the epoch time T0, the reference satellite (i-th
Arrival time T2i of the ranging radio wave relayed by the satellite
Time difference between the epoch time T0 and the epoch time D0 (= T2i-T
0, the radio wave round-trip propagation time between the reference satellite and the positioning terminal (first repeating step), and from the time difference D2i and the time difference D1i with respect to the reference satellite, the time deviation Dc is Dc = D2i / 2-D1i. The time change rate B of the time deviation is estimated from the time series data of the time series data of the time deviation Dc, which is obtained by executing the calculation (second repeating step) at an appropriate frequency, and Even when the observation update of Dc is impossible due to the execution of the repeated steps, the current time deviation D is calculated by using the time deviation Dc0 at the time of the previous observation update and the elapsed time ΔTc from the previous observation update.
c is estimated and updated by Dc = Dc0 + B × ΔTc, and Pi
= The speed of light × (D1i ′ + Dc) is continuously calculated.

Even if the time deviation Dc cannot be updated, it is possible to suppress the divergence of the error of the time deviation Dc due to the clock drift of the positioning terminal and maintain the positioning accuracy by the above-mentioned steps. Become. Such effects can be further enhanced by applying a highly stable clock to the positioning terminal.

The satellite / positioning terminal distance Pi measured at irregular time intervals and the absolute value of the difference between the position vector Li of the satellite and the latest position vector R0 of the positioning terminal
The range deviation ΔZi is calculated from the latest calculated value P0i of the distance between the positioning terminals, the three-dimensional moving distance components ΔRx, ΔRy and ΔRz of the positioning terminal are calculated, the range deviation ΔZi, the moving distance. The standard deviation of the calculation errors of the components ΔRx, ΔRy, and ΔRz is obtained, and the standard deviation is divided by a specific reference standard deviation. The error proportional coefficient ki for the range deviation ΔZi and the moving distance components ΔRx, Δ The error proportionality coefficients kx, ky, and kz regarding Ry and ΔRz are determined, and the position vector R of the positioning terminal is irregularly timed using the least-squares observation matrix H configured using the error proportionality coefficients. It is added to update with.

With such a positioning algorithm, it is possible to provide stable optimum positioning information corresponding to the measurement conditions even when the measurement conditions change when a low altitude orbiting satellite is used. In particular, even if there is only one measurable range satellite, it is possible to estimate the moving distance component while maintaining appropriate accuracy, and if the time deviation Dc is updated with appropriate accuracy, appropriate accuracy is obtained. 2D positioning is possible.

The satellites constituting the satellite group receive the reference ranging radio wave generated and transmitted by a specific reference satellite or ground station and transmit it toward the ground, and the reference ranging radio wave is transmitted from the reference satellite or ground station. By measuring and transmitting the propagation time of the reference ranging radio wave before reaching the satellite, it is possible to provide an alternative radio wave of the ranging radio wave of the satellite that is transmitted based on the satellite common time reference. Normally, in order to maintain the common time reference of the satellite, the satellite needs a highly stable clock and a ranging radio wave generation relay unit that generates a ranging radio wave based on this clock, but most satellites have a ranging radio wave. Since it suffices to mount the relay means, not only the cost of the satellite can be reduced, but also the types of communication satellites that can be used as the ranging radio wave source are increased.

The positioning system according to the present invention comprises a plurality of satellites (1i) sharing a common reference time and a terminal (10), and the terminal (10) communicates with the satellite (1i) by transmitting and receiving a first ranging radio wave. A first detector for detecting the round-trip time between the terminals based on the individual reference time of the terminal, and a reception for receiving the second ranging radio wave transmitted by the satellite (1i) based on the common reference time of the satellite (1i) A second detector for detecting the time, the satellite (1i) has a superimposing device for superimposing satellite information on the second ranging radio wave, and the terminal (10) further has its round trip time and its round trip time. An offset calculator is provided for calculating the deviation between the common reference time and the individual reference time from the reception time by offsetting. By accurately knowing the deviation by such offset calculation, the distance is calculated in real time for positioning. By using the common time, the most appropriate satellite can be used, and its accuracy can be improved.

If the common time of a plurality of satellites in the satellite group consisting of satellite elements having a common time is used, the position of the terminal can be quickly calculated from the common time and the individual time of the terminal. Conversely, by using the common time of multiple ground stations in the ground station group consisting of ground station elements having a common time, the satellite position can be quickly calculated from the common time and the satellite's individual time. it can. Multiple times on multiple satellites can be shared in real time by the offset calculation described above. No strict high performance clock is required. Even if there is a special relativistic effect, that effect is canceled in real time by the principle of constant light velocity itself.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION In the embodiment of the positioning system according to the present invention, a satellite group is provided together with a plurality of terminals.
The satellite group corresponds to one of the positioning terminals 10 as shown in FIG. Satellite group is n
It is formed from the original satellite. The positioning terminal 10 includes satellites 1i (i = 1, 2, ..., N) of n satellites.
To receive a plurality of distance measurement radio waves 2i from them.

The difference D1i between the plurality of arrival times T1i of the plurality of distance measurement radio waves 2i and the epoch time T0 of the positioning terminal 10 is hereinafter referred to as a pseudo propagation time: D1i = T1i-T0. (1) From this, the pseudorange Si is defined: Si = cD1i. (2) Here, c is the propagation velocity of the propagating radio wave or light.

Although each satellite has a common time reference, the time reference of each positioning terminal is deviated from the common time reference. The difference between the common time and the time of each positioning terminal is represented by Dci. The deviation is hereinafter referred to as a clock offset. The difference between the positioning terminal 10 and the common time reference is represented by Dc. Pseudo propagation time D1
Clock offset D for the range measured based on i
A range deviation Q (= c · Dc) due to c occurs.
The relationship between the pseudo range Si and the real range Pi is expressed by the following formula: Pi = Si + Q. ... (3)

The actual range Pi is obtained by adding the range deviation Q caused by the estimated clock offset Dc to the pseudo range Si. It is assumed that the selected satellite is the i-th satellite. The round-trip time of the user distance measurement radio waves 3a and 3b propagating in the order of positioning terminal → i-th satellite → positioning terminal is:
It is represented by D2i. Pseudo propagation time D1i of selected satellite 1i
And the round-trip time D2i, the clock offset Dc is calculated by the following equation. Dc = D2i / 2-D1i. ... (4)

In such a measurement method, the propagation delay error caused by the ionosphere in the propagation path and the medium such as water vapor in the atmosphere is canceled. Due to the cancellation, the clock offset Dc is obtained as an accurate value. If the number of measurable satellites increases to three or more, the clock offset Dc can be estimated at the stage of positioning calculation like the positioning method by GPS, and the estimation backs up the measurement represented by the formula (4). The positioning function can be enhanced.

FIG. 6 is a time table illustrating how to obtain the equation (4). FIG. 6 shows the time advance A of the clock with higher accuracy managed by the satellite 1i (the value increases in the direction of the arrow).
And a time advance B of a clock with a lower precision managed by the terminal 10 (the value increases in the direction of the arrow).
The difference in accuracy between the two clocks does not substantially affect the accuracy of the deviation Dc because the measurement is performed in a short time. Therefore, it is assumed that both clocks have the same accuracy.

From the point of view of its accuracy, the difference in the time display between the satellite and the terminal at the same time point is extremely large, so that time adjustment (synchronization) is required. Since the time display difference is a relative time difference, it does not matter whether it is extremely large or extremely small. The deviation is represented by Dc as described above.

The first ranging radio wave K1 emitted from the satellite 1i at the satellite side time T1 arrives at the terminal 10 at the terminal side time T1 '. The satellite time T1 is carried on the radio wave and sent to the terminal 10 as a digital signal as an absolute value.
At the time T2 'unrelated to the reception time T1', the terminal 1
0 is the second distance measurement radio wave outgoing signal K2 (3 in FIG. 1) with respect to the satellite 1i.
Fire a). The second distance measurement radio wave K2 is sent back by the satellite 1i and returns to the terminal 10 at the terminal side time T3 ′ as the second distance measurement radio wave reconciliation K3 (3b in FIG. 1).

D2i = T3'-T2 '. This time D21
Is the same or absolute time for both clocks. Second
If the propagation time of the distance measurement radio wave outgoing component K2 and the propagation time of the second distance measurement radio signal component K3 are equal to each other, the deviation Dc is: Dc = (T3′−T2 ′) / 2− (T1′−T1) = D2i / 2-D1i. This equation matches equation (4).

FIG. 2 shows the operation of the embodiment of the positioning system according to the present invention, and shows the method of updating the position vector R of the positioning terminal 10. The positioning terminal 10 receives the ranging radio waves of the n rangeable satellite groups 1i and measures their pseudo propagation time D1i (step 41). Normally, the number of measurable range satellites n changes depending on the reception environment. If the satellites with poor reception are not excluded from the rangeable satellites,
It is preferable to increase the error proportionality coefficient shown in (1) to an appropriate value.

Next, a satellite having the best round-trip propagation time measurement condition is selected as the reference satellite from the n rangeable satellites (step 42). In general, satellites with higher elevation angles have better ranging accuracy. The satellite with the highest elevation angle is selected as the reference satellite. The i-th satellite is selected as the reference satellite. If the user position is generally known, the reference satellite-positioning terminal propagation time D2i can be detected regardless of whether the user ranging radio waves 3a and 3b are relayed by a plurality of satellites (step 43). Therefore, the pseudo propagation time D1i of the ranging radio wave 2i transmitted from the reference satellite
Using, the clock offset Dc, which is the difference between the individual time reference of the positioning terminal and the common time reference of the satellite, is calculated by equation (4) (step 44).

In this measuring method, both radio waves transmitted by the reference satellite and the positioning terminal pass through the same route,
The radio wave propagation delay error caused by the ionosphere and the atmosphere is canceled out, and the clock offset Dc can be accurately measured. Position vector Li of the distance-measurable satellite 1i whose origin is the center of the earth
Is obtained from the orbital elements broadcast from the satellite (step 45), and the distance Pi between the measurable satellite and the positioning terminal (hereinafter referred to as the measurement (actual) range) is calculated by the equation (3) (step 46). . The previously calculated user position vector is R
It is represented by 0. A deviation ΔPi between the measurement range Pi and the previous range Pi0 (= | Li−R0 |, which will be referred to as a calculation range hereinafter) obtained by calculation is obtained, and the deviation ΔR (= R0−R) of the user position vector R is It is given by the following equation (5) (step 47).

[Equation 1]

Here, the simplest positioning algorithm is adopted, and the observed values used for positioning calculation are the pseudo propagation time D1i and the round-trip propagation time D2 with respect to the reference satellite 2i.
Although only i, in step 47, as shown in FIG. 4 and described later, a positioning algorithm that considers the moving distance of the positioning terminal that can be estimated by the speed sensor and the direction sensor can be used.

FIG. 3 shows a ranging radio wave generation relay section 50 mounted on the satellite 1i. Distance measurement radio wave generation relay unit 50
Is provided with a data management means 51. The data management means 51 collects and processes satellite-related data 54 such as satellite orbital elements, clock data for calibrating the satellite onboard clock, and satellite tracker control information. Satellite-related data 5
4 is superimposed on the distance measurement radio wave 2i. The data management means 51 is connected to the satellite ranging radio wave generation means 52. The satellite-related data 54 is sent as broadcast information 55 from the data managing means 51 to the satellite ranging radio wave generating means 52.

The distance measurement radio wave generation means 52 performs spectrum spread of the radio wave so that precise distance measurement can be performed based on the common time reference, and broadcast information 55 is transmitted to the satellite distance measurement radio wave 2i.
Satellite ranging radio wave 2i superimposed on the broadcast information 55
Is broadcast to the terminal group. The ranging radio wave generation relay unit 50 is
Distance measuring radio wave relay means 53 is further provided. User distance measurement radio wave (outgoing) 3a transmitted from the user positioning terminal 10
Is received by the distance measurement radio wave relay means 53, and is immediately transmitted as a user distance measurement radio wave (reconstruction) 3b in the direction of reception.

The distance measurement radio wave relay means 53 is connected to the data management means 51. When the information required by the data management means 51 is superimposed on the user distance measurement radio wave 3a, the superimposed data is demodulated and reported to the data management means 51. The information required by the data management means 51 is data relating to positioning correction and clock correction.

FIG. 4 shows a method capable of coping with fluctuations in the number of measurement ranges (corresponding to the number of measurable satellites) measured by the positioning terminal 10. Range deviation Δ using the measurement range Pi and the previous user position vector R0 and satellite position vector Li
Calculate Zi (step 61).

[Equation 2]

Next, the moving distance components ΔRx, ΔRy and ΔRz of the positioning terminal are obtained from the speed sensor and the direction sensor, or the Doppler frequency shift amount of the distance measurement radio wave (step 6).
2). Furthermore, as shown in the following formulas (7-1 to 3),
The standard deviation of the error in which the range deviation and the moving distance are expected is defined, and the error proportional coefficients kx, ky, and kz, which are the ratios of these to the standard deviation of the standard (for example, the standard deviation of the typical distance measurement error) ( Step 63).

[Equation 3]

Here, XDOP, YDOP and ZDOP
Is the x-axis, y-axis and z determined in the previous positioning calculation
It is a positioning deterioration index related to the axis, and is a value obtained by dividing the standard deviation of the positioning error on the x-axis, the y-axis, and the z-axis by the reference standard deviation. Therefore, the error proportionality coefficients kx, ky, and kz appearing in the equations (7-1 to 3) are added with the standard deviation of the error represented as a function of the time t elapsed from the previous positioning calculation as a component. By applying the weighted least squares method, the user position vector R is updated by the positioning algorithm shown in equation (8).

[0043]

[Equation 4] Here, mi is a unit vector from the positioning terminal toward the i-th satellite, and mx, my, and mx are unit vectors (direction cosine vector) in the x-axis, y-axis, and z-axis directions of the positioning coordinate system. . Also, XDOP, YDOP and ZDO
P is a positioning deterioration index of the x-axis, the y-axis, and the z-axis, and is calculated by the following equations (9-1 to 3).

[Equation 5]

Such a coordinate system is a local horizontal coordinate system in which the x-axis of the positioning coordinate axis is vertical, the y-axis is east-west, and the z-axis is north-south. Considering the case where all the standard deviations are equal to the standard deviation of the standard, the observation matrix H of the expression (8) is expressed by the following expression (10).

[Equation 6]

Finally, the user position vector R is updated using the following equation (11) (step 64).

[Equation 7]

FIG. 5 shows another embodiment of the positioning system according to the present invention. The distance measurement radio wave 2i from the satellite is
It is a relay radio wave of the distance measurement radio wave 2i ′ generated by the parent satellite or the ground station 70. In this case, the distance measurement radio wave generation relay unit 50 mounted on the satellite shown in FIG. 1 is simplified, and the possibility of reducing the satellite cost is created. Only the time-based timing is transmitted from the parent satellite or ground station, and the satellite side generates radio waves for distance measurement.

The clock synchronization method used by the present invention is as follows.
The positioning terminal is the pseudo propagation time D1 of the distance measurement radio wave from the reference satellite.
i and the round-trip propagation time D2i of the user ranging radio wave that relays the satellite and returns to the positioning terminal are used. Therefore, high-precision clock synchronization is possible because the propagation delay error that occurs due to the propagation path is canceled, but in the world of radio navigation that requires clock synchronization technology with this level of precision, radio wave propagation is The clock offset estimation error due to the movement of satellites and positioning terminals in the past can no longer be ignored.

The equation (3) is a clock offset estimation error caused by the angular velocity of the satellite and the moving velocity of the positioning terminal, and is considered to be the error component included in the equation (4). Therefore, it is necessary to obtain the clock offset using the equation (4), but normally, by correcting this component, it is possible to remove an error exceeding several tens of meters in distance measurement error conversion. By statistically processing the temporal transition of the highly accurate clock offset estimated value obtained in this way, the time change rate B of the clock offset can be estimated, and even in an operating environment in which clock synchronization cannot be performed, Formula (12) below
The clock offset Dc can be updated by. Dc = Dc0 + B · ΔTc. ... (12) Dc
0: Time deviation ΔTc at the time of previous observation update: Elapsed time since the last observation update

[0049]

The positioning system and the positioning method according to the present invention can utilize a large number of communication satellites that orbit a low orbit as distance measuring means. Furthermore, it is easy to combine positioning and mobile communication services.

[Brief description of drawings]

FIG. 1 is a system block diagram showing an embodiment of a positioning system according to the present invention.

FIG. 2 is an operation flow showing an operation of the embodiment of the positioning system according to the present invention.

FIG. 3 is a circuit block diagram showing details of a distance measurement radio wave generation relay unit.

FIG. 4 is a flowchart showing another positioning algorithm.

FIG. 5 is a system block diagram showing another embodiment of the positioning system according to the present invention.

FIG. 6 is a time diagram showing a known synchronization method.

[Explanation of symbols]

10 ... Positioning terminal 1i ... i-th ranging satellite 1i ... ranging satellite serving as reference satellite 2i ... i-th satellite ranging radio wave 2i '... measurement transmitted from parent satellite / ground station to i-th satellite Distance radio waves 3a, 3b ... Forward / backward user distance measurement radio waves 50 ... Distance measurement radio wave generation / relay section 51 ... Data management means 52 ... Satellite distance measurement radio wave generation means 53 ... Distance measurement radio wave relay means 55 ... Positioning related information 70 ... Parent Satellite or ground station

─────────────────────────────────────────────────── --Continued from the front page (56) Reference JP-A 63-266375 (JP, A) JP-A 11-44749 (JP, A) JP-A 5-346459 (JP, A) JP-A 6- 102336 (JP, A) JP-A-6-102337 (JP, A) JP-A-54-70794 (JP, A) Patent 2795416 (JP, B2) Patent 2886290 (JP, B2) Patent 2915851 (JP, B2) (JP 58) Fields investigated (Int.Cl. ⁷ , DB name) G01S 5/00-5/14

Claims (7)

(57) [Claims] 1. A distance measurement radio wave transmitted based on an individual time reference, and arrival times of a plurality of distance measurement radio waves received based on the individual time reference are detected, and positioning-related radio waves superimposed on the distance measurement radio wave are detected. A positioning terminal having a function of decoding information, and a plurality of satellites having a function of transmitting a ranging radio wave on which the positioning related information is superimposed based on a common time reference and relaying the ranging radio wave transmitted by the positioning terminal And a plurality of satellite / positioning terminal distances Pi (i = 1, 2, ...) By the communication between the positioning terminals and the satellites, the time deviation Dc between the individual time reference and the common time reference is established. a positioning method for n) and measured by a using a positioning system for determining the position of the positioning terminal to determine the position of the positioning terminal, and the positioning terminal in a satellite constituting the constellation communication
Sent from n rangeable satellites with established links
The arrival time T1i of the n range finding radio waves at the positioning terminal
And the epoch time generated based on the individual time reference
The time difference D1i (= T1i-T0) from the time T0 is detected.
From the n rangeable satellite groups, and the reception conditions of the ranging radio wave and
The satellite sky placement conditions are good for comparison, and
It is possible to relay the range-finding radio waves transmitted by the mobile terminal, and
The distance measurement radio waves relayed can be received by the positioning terminal.
Selecting the enabled i-th satellite as the reference satellite, when the positioning terminal transmits at the epoch time T0
, The measurement relayed by the reference satellite (i-th satellite)
Time between arrival time T2i of distance radio wave and the epoch time T0
Graduation D2i (= T2i-T0, the reference satellite / the positioning)
Detecting the round trip propagation time between the terminals, the time difference D2i and the time difference D1i with respect to the reference satellite.
From the above, the time deviation Dc is calculated as Dc = D2i / 2-D1i
The positioning-related information broadcast by the measurable satellite group or terrestrial radio station
The position of all satellites included in the rangeable satellites
Calculating the position vector Li, the transmission dependent on the radio wave propagation path included in the time difference D1i.
Using the time difference D1i ′ obtained by correcting the seeding delay error
All satellites / positioning terminals included in the rangeable satellites
The inter-distance Pi is calculated by the formula: Pi = speed of light × (D1i ′ + Dc)
Calculating the n distances Pi and the n position vectors Li
From the position vector R0 of the positioning terminal at the time of update,
Determining a current position vector R of the positioning terminal . 2. The method according to claim 1 , wherein a correction parameter for improving time accuracy of a satellite-mounted clock that maintains the common time reference is updated and broadcast as positioning-related information from at least one of the satellite groups. A positioning method further comprising : generating and transmitting a ranging radio wave received by a terminal with the satellite, and relaying the ranging radio wave transmitted by the positioning terminal with at least one of the satellite group. 3. The measuring method according to claim 1 , wherein, when the time deviation Dc is calculated, the orbital angular velocity vector and position vector of the satellite are Wi and Li, and the position vector and velocity vector of the positioning terminal are R and V, respectively. Error Ei of the radio wave round-trip propagation time D2i caused by the movement of the satellite and the moving body during the propagation of the distance radio wave.
The following formula: Ei = 2Wi · (R × Li) / C2 + Pi
-Calculate by V / C2 (C = speed of light). When the error Ei becomes a main error of the positioning error, the following formula: Dc = D2i / 2- instead of the time deviation Dc.
A positioning method further comprising applying D1i-Ei. 4. The arrival time T2i of a ranging radio wave relayed by the reference satellite (i-th satellite) when the positioning terminal transmits at the epoch time T0, according to claim 1 . Detecting a time difference D2i from the epoch time T0 (= T2i-T0, radio wave round-trip propagation time between the reference satellite and the positioning terminal) (first repeating step), a time difference D2i with respect to the reference satellite, and the time. Difference D1i
From the above, the time deviation Dc is calculated as Dc = D2i / 2-D1i
The time deviation Dc obtained by executing the calculation (second repeating step) at an appropriate frequency.
Estimating the time change rate B of the time deviation from the time series data of, even when the observation update of the Dc by the execution of the first repeating step becomes impossible, the time deviation D at the time of the previous observation update
The method further includes estimating and updating the current time deviation Dc by using the following equation: Dc = Dc0 + B × ΔTc, using c0 and the elapsed time ΔTc from the previous observation update, and continuously executing the calculation of the distance Pi. <br/> Positioning method. 5. The satellite / positioning according to claim 1 , which is an absolute value of a difference between the Pi measured at irregular time intervals, a position vector Li of the satellite, and a latest position vector R0 of the positioning terminal. Calculating a range deviation ΔZi from the latest calculated value P0i of the inter-terminal distance, calculating three-dimensional moving distance components ΔRx, ΔRy and ΔRz of the positioning terminal, the range deviation ΔZi, the Moving distance component ΔRx, ΔR
The standard deviation of the calculation errors of y and ΔRz is calculated, and the standard deviation is divided by the standard deviation.
Error proportional coefficient ki concerning Zi and movement distance component ΔR
Error proportional coefficients kx, ky with respect to x, ΔRy and ΔRz
And kz , further comprising: updating the position vector R of the positioning terminal at irregular time intervals by using the least squares observation matrix H configured using the error proportionality coefficient. Method. 6. The satellite constituting the satellite group according to claim 1 , receives a reference ranging radio wave generated and transmitted by a specific reference satellite or a ground station, and transmits the radio wave toward the ground. Distance measurement of the satellite transmitted based on the satellite common time reference by measuring and broadcasting the propagation time of the reference distance measurement radio wave until the distance radio wave reaches the satellite from the reference satellite or the ground station. A positioning method further comprising providing an alternative radio wave of the radio wave. 7. A plurality of satellites sharing a common reference time and a terminal, wherein the terminal determines the round-trip time with the satellite by transmitting and receiving a first ranging radio wave based on the individual reference time of the terminal. A first detector for detecting, and a second detector for detecting a reception time of receiving a second ranging radio wave transmitted by the satellite based on a common reference time of the satellite
A detector, the satellite includes a superimposing device for superimposing satellite information on the second ranging radio wave, and the terminal further cancels the round-trip time and the reception time to obtain the common reference time. A positioning system comprising an offset calculator for calculating a deviation from the individual reference time.