JPH09178870A - Method of extracting position measuring system time and position measuring system time extracting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely determine the time of a position measuring system by receiving the signals from a plurality of position measuring satellites to determine position information for receiving point, averaging it for a fixed time to determine the position of the receiving point, and using this, and the orbit information and time information for the satellites. SOLUTION: A signal processing part 101 receives signals from prescribed satellites, tracks them and demodulates navigation messages contained therein. A position measuring arithmetic processing part 102 determines the position of each satellite from orbit information and time information contained in the navigation message of each satellite, determines a pseudo distance from the satellite to the receiving point, and measures the position of the receiving point to determine the universal time coordinated. A position averaging processing part 103 averages the position information for the receiving point every fixed data number and transmits the result to an IPPS output processing part 106. When the position of the receiving point is determined, a position determination display part displays it. A serial data output processing part 105 outputs the universal time coordinated and the position of the receiving point from the outside, and the processing part 106 outputs a timing signal every second of a measuring system from the orbit information, time information and position information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning system for receiving a signal from a positioning satellite and determining the position of a receiving point,
The present invention relates to a method and apparatus for extracting the time of the positioning system.

[0002]

2. Description of the Related Art Conventionally, in a positioning system such as GPS, information for observing the distance from each positioning satellite to a receiving point and information for obtaining the position of each positioning satellite have been transmitted. , The receiver obtains the position of each positioning satellite and the distance from each positioning satellite to the receiving point by using the positioning signals from the positioning satellites required for three-dimensional positioning,
The position of the receiving point is obtained from the position of each positioning satellite and the distance from each positioning satellite to the receiving point.

In such a positioning system, a time system for unifying the time system in the system (GPS time in a GPS system) is set, and information for obtaining the time in the time system is transmitted from the satellite. Is included in the signal. Therefore, a receiver that receives such a signal
It has a function as a clock other than the purpose of positioning. In the GPS system, the clock on the satellite is an atomic clock, and the length of 1 second is almost the same as 1 second of the atomic time same as Coordinated Universal Time (hereinafter referred to as "UTC"). Therefore, by receiving the signal from the positioning satellite, it is possible to construct an extremely highly accurate electronic timepiece. A receiver for obtaining such accurate time information is a time comparison receiver (time transfe
A dedicated device is used as a receiver.

[0004]

In a conventional time comparison receiver that operates with a fixed reception point, at least one of the three-dimensional position information (latitude, longitude, height) of the reception point is input externally. When receiving a signal from a satellite, it outputs a pulse signal with high accuracy once per second in synchronization with UTC. This signal is hereinafter referred to as "1PPS". For example, as shown in FIG. 2, the position of the receiving point in X, Y, Z coordinates is (Xu, Yu,
Zu), the position of the positioning satellite obtained from the signal from the positioning satellite is (Xs, Ys, Zs), and the time of the clock held by the satellite is Ts, the received signal is (Xs,
Since Ys, Zs, Ts) are obtained, the known reception point position (Xu, Yu, Zu) and satellite position (Xs, Y)
(s, Zs), the distance R between the satellite and the receiving point is obtained from the positional relationship with the satellite, the radio wave delay time between them is calculated backward, and the time in the positioning system is obtained with high accuracy by correcting Ts by the radio wave propagation delay time. be able to.

However, in the conventional time comparison receiver that operates by fixing the receiving point, the information of the three-dimensional position of the receiving point must be externally input, and if the input is incorrect or its accuracy is high. If it is not, the correction for the delay time by R is not accurately performed, and the accuracy of 1PPS is also reduced.
In order to obtain the exact position of the receiving point, there are a method of reading from a map, a method of obtaining by a survey, a method of obtaining from a GPS receiver that performs independent positioning, and the like, but each method has the following problems. That is, in the method of (1), there are only a limited number of places where it is possible to know an accurate position within 30 m, and it is not possible to operate at any point. Method is costly and time consuming. The position of the receiving point can be relatively accurately measured at any point on the earth by the method of 1. However, in GPS, there is a variation of about 100 m in 2σ due to accuracy lowering factors such as SA (Selective Availability) mode. Therefore, the accuracy of 1PPS is limited according to the obtained positional accuracy of the receiving point.

An object of the present invention is to provide a method and apparatus for using only signals from positioning satellites and extracting the time of the positioning system with high accuracy.

[0007]

According to a first aspect of the present invention, there is provided a positioning system time extracting method according to claim 1, wherein only the signals from the positioning satellites are used and the positioning system time is extracted with high accuracy. , Receives signals containing orbital information and time information of each positioning satellite transmitted from multiple positioning satellites, obtains position information of the receiving point, and averages the position information of this receiving point over a predetermined time. To determine the position of the reception point, receive a signal transmitted from at least one positioning satellite and including orbit information and time information of the positioning satellite, and at least the orbit information and time information of this satellite and the determination. The time of the positioning system is obtained from the position information of the received point.

Further, the positioning system time extraction device of the present invention is
By automatically obtaining accurate position information of the receiving point,
In order to extract the time of the positioning system with high accuracy, as described in claim 2, a receiving means for receiving a signal transmitted from a plurality of positioning satellites and including orbit information and time information of each positioning satellite. A positioning means for obtaining the position information of the receiving point from the orbit information and time information of each positioning satellite received by the receiving means, and the position information of the receiving point is averaged over a predetermined time, and the receiving point is known. Positioning means for determining the position information of the receiving point, positioning based on the position information of the receiving point obtained by the receiving point position determining means, and at least orbit information and time information of at least one positioning satellite received by the receiving means. Positioning system time extracting means for obtaining the system time is provided.

In the positioning system time extraction method according to claim 1 and the positioning system time extraction device according to claim 2, the signals transmitted from a plurality of positioning satellites are received to obtain the position of the receiving point, and the reception thereof is performed. By averaging the position information of the points over a predetermined time, the position of the receiving point can be obtained with high accuracy. Then, the signal transmitted from at least one positioning satellite is received, and the time of the positioning system is obtained from at least the orbit information and the time information of the satellite and the position information of the receiving point. By thus averaging the position information of the receiving points obtained based on the signals from the satellites, variations in the positioning points due to various error factors are canceled out, and the positions of the receiving points are obtained with high accuracy, and Since the time of the positioning system is obtained based on the position information thus obtained, the time of the positioning system is obtained with high accuracy. For example, GPS
In this case, each GPS satellite goes around the earth in about 12 hours. Therefore, by averaging the positioning results over 12 hours or an integral multiple thereof, the error due to the satellite arrangement can be sufficiently suppressed. If the position of the receiving point is thus obtained with high accuracy, the position of the satellite is obtained from the orbit information and time information of the satellite as shown in FIG. 2, and the positional relationship between the position of the receiving point and the position of the satellite is obtained. The distance R between the satellite and the receiving point is calculated from the radio wave, the radio wave delay time between them is calculated backward, and the time in the positioning system can be calculated with high accuracy by correcting the time information acquired by reception by the radio wave delay time. When the radio wave propagation delay time is calculated by taking into account the ionosphere correction coefficient received from the satellite, it is possible to obtain a more accurate time with the influence of the ionospheric delay corrected.

[0010]

FIG. 1 is a block diagram showing a signal flow of a positioning system time extraction device of the present invention. In FIG. 1, a signal processing unit 101 receives a signal from a predetermined satellite by despreading a received signal with respect to a signal input from an antenna, tracks them, and demodulates a navigation message included in the received signal. In the positioning calculation processing unit 102, the position of each satellite is obtained from the orbit information and time information included in the navigation message of each satellite, the pseudo distance from the satellite to the receiving point is obtained, and the positioning of the receiving point is determined from these information. Perform and further determine UTC. The position averaging processing unit 103 averages the obtained position information of the receiving points for a fixed number of data (for example, for 24 hours or one week), and outputs the receiving point position information to the 1PPS output processing unit 1.
Give to 06. When the position of the reception point is determined by the averaging, the reception point position determined display unit 104 displays the state thereof. The serial data output processing unit 105 outputs the obtained UTC and the determined reception point position to the outside. The 1PPS output processing unit 106 outputs a timing signal 1PPS per second of the positioning system from the received orbit information and time information of the satellite and the determined position information of the receiving point.

Next, FIG. 3 is a block diagram showing the configuration of the positioning system time extraction device according to the embodiment of the present invention. FIG.
, The analog signal processing circuit 2a converts the signal from the GPS receiving antenna 1 into an intermediate frequency signal, and the AD converter 2
b converts the signal into digital data. The signal processing gate array 3 receives the digital data from the AD converter 2b, receives the C / A code pattern data, the C / A code phase data and the carrier phase data from the CPU 5, and generates the C / A code pattern and the C / A code pattern.
Performs correlation calculation with the A code. The signal processing gate array 3 has a free-run counter and 1PPS.
Is provided with a time counter that constitutes a circuit that outputs
The CPU 5 reads the value of the free-run counter at a predetermined timing. The clock circuit 4 includes a reference oscillator and divides the reference oscillation signal to measure the current time. However, the timing content of the clock circuit 4 is used only for predicting the satellites that can be captured immediately after the power is turned on, and the timing is not performed directly based on the signals from the satellites. The display interface 9 includes a display memory, generates a display signal according to the contents of the display memory, and outputs the display signal to the display unit 10. C
The PU 5 executes a program written in advance in the ROM 6 to read the correlation data from the signal processing gate array 3 and perform a predetermined loop filter calculation to the C / A code pattern data, C / A for the signal processing gate array 3.
The C / A code phase and the carrier phase are synchronized by giving the A code phase data and the carrier phase data, and the navigation message data is further extracted. Further, the CPU 5 uses the GPS included in the navigation message data.
From the information for determining the time and the UTC parameter, the UT
C is obtained, and data for displaying the value in the format of hour: minute: second is written in the display memory in the display interface 9. Further, the CPU 5 obtains the observation distance to each satellite, extracts each ephemeris (satellite orbit information), obtains the position of each satellite, calculates the position of the reception point, and further averages this to calculate the position of the reception point. To decide. Further CP
U5 outputs the determined reception point position information and UTC to the host device side via the data transmission interface 8. R
The AM 7 is used as a working area when executing these processes.

FIG. 4 is a block diagram showing the structure of the time counter in the signal processing gate array 3 shown in FIG. In FIG. 4, a free-run counter 31 is a free-run counter that counts a reference clock, and a latch circuit 33.
Is a circuit for holding the set value given from the CPU 5 shown in FIG. The comparison circuit 32 is a free-run counter 31
When the value of is equal to the value of the latch circuit 33, 1PPS
Is a circuit that outputs. Therefore, the generation timing of 1PPS changes depending on the set value set in the latch circuit 33. As will be described later, the CPU 5 shown in FIG. 3 calculates the value of the free-run counter 31 at the timing of 1PPS to be output next, and sets the same value in the latch circuit 33. As a result, the free-run counter 3
Corrected 1P without modifying the value of 1 itself
PS will be output.

FIG. 5 is a diagram showing the relationship between the GPS time possessed by the satellite side and the GPS time obtained by the receiver side. In FIG. 5, "satellite GPS system time" is the time indicated by the clock of the satellite and is the system time for counting 6 seconds of the subframe of the navigation message. "Receiver GPS system time" is the time obtained from the received signal on the receiver side, and is the time of a 6-second cycle in which the start position of the subframe is 0 second. Is delayed by the propagation delay time of the radio wave. Therefore, if the receiver GPS system time is corrected by the propagation delay time, the satellite GPS system time, that is, the accurate GPS time can be obtained. "Receiver time count" is shown in Fig. 4.
The contents of the free-run counter 31 shown in (1), and the difference between this value and the satellite GPS system time is obtained as a clock bias. Therefore, by adding the clock bias amount to the value of the free-run counter 31, the number of seconds synchronized with GPS can be obtained.

FIG. 6 is a flow chart showing a processing procedure for the independent positioning and the position determination of the receiving point of the positioning system time extraction device shown in FIG. When the power is turned on, first, it is determined whether or not the reception point position has already been obtained, and if it has not yet been obtained, the message "Please leave until the LED lights up" is displayed. After that, when at least one or more satellites are being tracked, satellite orbit information (ephemeris), ionospheric correction coefficient, time information, etc. are extracted from the navigation message obtained by demodulating the received signal. The time information includes Z count (a value obtained by counting the elapsed time from the GPS time reference time in 6-second units in a one-week cycle), the week number from the GPS time reference day, and the difference from UTC. (Cumulative leap second) and UTC parameter which is data for leap second adjustment. And 4
If the pseudo distance from one or more satellites to the receiving point is obtained, so-called four-satellite positioning using four satellites is performed,
If the pseudo distances from the three satellites to the receiving point are obtained, the so-called three-satellite positioning is performed using the final height information of the receiving point obtained at the time of the four-satellite positioning as it is. The position information of the reception points thus obtained is averaged for a certain period of time. For example, usually about 24 hours, a sufficient averaging effect can be obtained, but in order to further improve accuracy, for example, 1
Averaging for about a week. When the averaging of a certain number is completed in this way, the reception point position determination flag is set and the state is displayed by the LED or the like.
After that, when the difference between the determined reception point position obtained last time and backed up and the averaged reception point position this time is more than a predetermined distance, the reception point position averaged this time is updated as the determined reception point position. Then, the determined reception point position information is displayed. For example, if the average of 24 hours is taken, the position of the reception point can be obtained with an accuracy of about several meters, so that the position of the reception point averaged last time and the position of the reception point obtained by this averaging are calculated. If a difference exceeding a certain distance occurs between them, it is considered that the reception point has moved.

FIG. 7 is a flow chart showing a processing procedure performed every second. First, if the reception point position determination flag is in the set state and tracking of one or more satellites is performed,
Calculate GPS time (hereinafter referred to as GPSTIME). this is
GPSTIME = Week number * 604800 + Z count * 6 + Calculated by calculating clock bias. Then UTC = GPSTIME
-Calculate UTC as ΔUTC and output it. Here, ΔUTC is the UT obtained from the above-mentioned UTC parameter.
It is the number of seconds (cumulative leap second) of the difference between C and GPS time. After that, a set value for outputting accurate 1PPS is set in the latch circuit 33 shown in FIG. This setting is
It is obtained from the change per second of the clock bias obtained during the satellite tracking process, and the change in the clock bias occurs due to the error of the reference clock shown in FIG. By setting the set value in the latch circuit in this manner, 1PPS becomes a signal which is very accurately synchronized with the 1 second cycle of GPS, that is, the 1 second cycle of UTC.

Both UTC and 1PPS are output in a cycle of 1 second, but before the host device receives the signal of 1PPS, the next 1PPS received corresponds to what year, month, day, hour, minute and second. In order to know in advance whether there is a UT
It suffices to execute the processing shown in FIG. 7 so that C is output slightly ahead of 1PPS.

FIG. 8 is a flowchart showing a processing procedure for responding to a command given from the host device. If there is a command from the host device to request the position information of the reception point, the determined reception point position already obtained is transmitted to the host device.

The positioning system time extracting device described above can be used as a time server by connecting it to a workstation or the like. In this case, place the positioning system time extraction device on the roof of a building or in a place with an open field of view nearby, turn on the power, and then leave it until the LED indicating that the reception point position has been determined lights up, and then turn off the power. , Take it back to the room where you will actually operate it, connect it to the workstation, and install the antenna near the window. At the window of the building, only four satellites or three satellites can be in the field of view at the same time at least, but at least one satellite can be tracked, and its received signal and the determined reception point position already obtained. Can output an accurate 1PPS. In this example, the determined reception point position and the antenna position during actual operation are different, but if the difference is within 30 m, the error given to 1PPS will be 0.1 μs or less,
When used for the above-mentioned time server, there is practically no problem. When more strict accuracy is required depending on the purpose of use, the operation may be performed as it is at the determined reception point position.

[0019]

According to the present invention described in claims 1 and 2, the position of the reception point is obtained by receiving signals transmitted from a plurality of positioning satellites, and the position information of the reception point is obtained for a predetermined time. The position of the reception point can be obtained with high accuracy by averaging over. Therefore, the time of the positioning system is automatically obtained with high accuracy at an arbitrary point.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a processing flow of a positioning system time extraction device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a positioning system time extraction method.

FIG. 3 is a block diagram showing a configuration of a positioning system time extraction device according to an embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration example of a time counter in FIG.

FIG. 5 is a diagram showing a relationship between GPS time possessed by a satellite and GPS time obtained by a receiver.

FIG. 6 is a flowchart showing a processing procedure for positioning and determining a reception point position.

FIG. 7 is a flowchart showing a processing procedure performed every second.

FIG. 8 is a flowchart showing a procedure of command response processing.

[Explanation of symbols]

 1-antenna

Claims (2)

[Claims] 1. A position information of a receiving point is obtained by receiving a signal including orbit information and time information of each positioning satellite transmitted from a plurality of positioning satellites, and the position information of the receiving point is obtained for a predetermined time. The position of the reception point is determined by averaging over, and a signal including orbit information and time information of the positioning satellite transmitted from at least one positioning satellite is received, and at least the orbit information and time of this satellite are received. A positioning system time extraction method for obtaining a positioning system time from information and the position information of the determined receiving point. 2. Receiving means for receiving a signal including orbit information and time information of each positioning satellite transmitted from a plurality of positioning satellites, and orbit information of each positioning satellite received by the receiving means, and Positioning means for obtaining positional information of the receiving point from time information, receiving point position determining means for averaging the positional information of the receiving point over a predetermined time to obtain known positional information of the receiving point, and the receiving point position Positioning system time extraction means for determining the time of the positioning system from the position information of the receiving point obtained by the determining means and at least orbit information and time information of at least one positioning satellite received by the receiving means is provided. Characteristic positioning system time extraction device.