JPH06265624A - Position measuring apparatus - Google Patents

Abstract

(57) [Summary] [Objective] For example, positioning can be suitably performed even in a situation where the number of receivable satellites does not reach the number of satellites required for positioning by GPS alone or GLONASS alone. [Configuration] A first receiving unit 12 and a second receiving unit 14 are provided as receiving units that receive radio waves from satellites that respectively configure different satellite navigation systems. The timing generator 16 synchronizes the first and second receivers 12 and 14 to obtain a correction value and a pseudo distance at the same reception time. The calculated satellite position and pseudo distance are input to the calculation unit 18, and the calculation unit 18 executes positioning calculation. The current position of the user obtained by the positioning calculation is output by the output unit 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position measuring device which receives radio waves from a plurality of satellite navigation systems and measures the current position of a user.

[0002]

2. Description of the Related Art Conventionally, various satellite navigation systems have been operated and tried. Among these satellite navigation systems, GPS and CIS in USA (United States)
GLONASS in (former Soviet Union) together,
It is a system that receives radio waves from an artificial satellite existing in an orbit around the earth and measures the current position of a user, for example, a moving body such as an automobile or a ship.

FIG. 3 shows the principle of positioning (positioning) of a user in GPS and GLONASS.

In GPS and GLONASS, a predetermined number (target: 24) of satellites have been launched into orbit around the earth. Each GPS satellite transmits a radio wave phase-modulated by a unique pseudo noise (PN) code to a user. On the other hand, each GLONASS satellite transmits a radio wave, which is phase-modulated by a common PN code and has a carrier frequency unique to each satellite, to the user. The user receives this radio wave. The radio wave transmitted from each satellite includes orbit information related to the satellite as ephemeris data, for example. The user demodulates the data transmitted from each satellite and obtains the position of each satellite, that is, the satellite position. On the other hand, the user obtains the propagation time of radio waves from each satellite, and thus the distance between the satellite and the satellite involved in transmission, by capturing (phase-synchronizing) the PN code.
This distance includes an error of the clock mounted on the user, that is, a clock error, a clock error of each satellite with respect to the system time of the satellite navigation system, and an error related to propagation delay of radio waves. The user corrects the clock error of each satellite with respect to the system time of the satellite navigation system and the error related to the propagation delay of radio waves based on the correction data transmitted from the satellite. The error obtained in this way and including only the clock error of the user is called a pseudo distance.

The relationship between the satellite position and the pseudo range thus obtained and the current position of the user can be expressed by a known equation. As shown in this figure,
If the user's position is represented as a position vector in an X, Y, Z three-dimensional coordinate system having the origin O at the center of the earth, the distance between the satellite and the user is the position vector of each satellite minus the user's position vector. It is represented by the absolute value of the obtained vector. If there is no clock error on the user side, the equation expressing such a relation
The current position of the user can be determined by making simultaneous pieces and solving them. However, in practice, since the pseudo distance obtained by the above processing includes the user's clock error, the user's clock error must be treated as an unknown number to solve the simultaneous equations. As a result, the number of equations to be made simultaneous becomes four. In other words,
The user's current position cannot be three-dimensionally determined unless satellite positions and pseudoranges are obtained for at least four satellites (SV _{1 to} SV ₄ ).

Therefore, in the past, in order to determine the current position of the user three-dimensionally, it was necessary to be able to receive and demodulate radio waves from at least four satellites constituting the same satellite navigation system. When the height of the user viewed from the center of the earth can be regarded as constant (for example, when the user is a sea-moving body), the unknown number decreases by one, and it is sufficient to receive radio waves from three satellites.

[0007]

As described above, in the conventional satellite navigation system, radio waves are emitted from at least four satellites in the case of three-dimensional positioning and from at least three satellites in the case of two-dimensional positioning. I had to receive and determine the satellite position and pseudorange. Therefore, if the number of satellites that can receive radio waves is less than these numbers, the position of the user cannot be determined.

The present invention has been made to solve the above problems, and is suitable even when the number of satellites that can receive radio waves by the user is less than the number required for positioning. The purpose is to enable positioning.

[0009]

In order to achieve such an object, the position measuring device of the present invention receives radio waves from a plurality of satellites constituting the first satellite navigation system to detect the satellite position of the satellite. And the first to obtain the pseudo distance between the satellite and the user
A receiving unit, a second receiving unit that receives radio waves from a plurality of satellites forming the second satellite navigation system, and obtains a satellite position of the satellite and a pseudo distance between the satellite and a user; and first and second receiving units. The timing generator that outputs the satellite position and the pseudo-range at the same reception time by synchronizing the radio waves from the first and second receivers with a predetermined number or more of satellites in total of the first and second satellite navigation systems. A calculation unit that determines the current position of the user based on the satellite position and pseudo range output from the first and second reception units and the initial position or the previous position of the user when these satellites are received. , Are provided.

Further, according to the present invention, the calculation unit uses a first-order approximation formula in which a formula expressing the pseudo range by the satellite position, the current position of the user and the clock error is expanded around the initial position or the previous position of the user. , A clock error of the user relative to the current position of the user and the system time of each satellite navigation system is calculated.

According to the present invention, when the difference between the current position of the user calculated by the calculation and the initial position or the previous position of the user is large, the calculated current position of the user is set as the previous position of the user. It is characterized in that the clock error of the user with respect to the current position of the user and the system time of each satellite navigation system is calculated by substituting into the first-order approximation formula.

The present invention is characterized in that the first and second satellite navigation systems are GPS or GLONASS, respectively.

[0013]

In the position measuring system of the present invention, the radio waves from the plurality of satellites forming the first satellite navigation system are received by the first receiving section, and the radio waves from the satellites forming the second satellite navigation system are received. It is received by the second receiving unit.
In the first and second receivers, the satellite position of the satellite and the pseudo distance from the satellite are obtained based on the received radio waves, respectively. In the calculation unit, in addition to the initial position of the user input in the form of initial setting, the position of the user (previous position) obtained by the previous position measuring operation, and the first position
And the current position of the user is obtained based on the satellite position and the pseudo range obtained by the second receiving unit. At this time, an error occurs if the data is related to the reception time when the satellite position and the pseudo range given to the arithmetic unit are different. Therefore, the timing generation unit synchronizes the first and second reception units in advance. That is, the satellite position and the pseudo range at the same reception time are input from each reception unit to the calculation unit. By outputting the current position obtained by the calculation unit in the form of, for example, screen display or voice output, it is possible to supply the data regarding the current position to the operator or the like of the mounted moving body.

Therefore, according to the present invention, the position measurement can be preferably performed even when the position measurement cannot be executed by each satellite navigation system alone due to the small number of receivable satellites. For example, in the first satellite navigation system, it is assumed that the user needs to receive radio waves from four satellites in order to three-dimensionally measure the current position. Under such a situation, it is assumed that the number of satellites that can receive radio waves among the plurality of satellites forming the first satellite navigation system has decreased to two. In this case, the position measurement cannot be executed by the first satellite navigation system alone. On the other hand, in the present invention, radio waves are also received from the satellites constituting the second satellite navigation system, the satellite position and the pseudo range are obtained, and the satellite position and the pseudo range are calculated together with the satellite position and the pseudo range according to the first satellite navigation system. Since it is used for the position measurement calculation, it is possible to suitably determine the current position of the user even under such a situation.

As an equation used to obtain the current position of the user in the above-mentioned calculation unit, an equation expressing the pseudo range as a satellite position and the current position of the user as a clock error is used as an equation around the user's initial position or previous position. It is possible to use a first-order approximation formula that has been expanded to. In this case, the clock error of the user with respect to the current position of the user and the system time of each satellite navigation system is obtained by solving the first-order approximation formula. Further, when the difference between the current position of the user obtained by this calculation and the initial position or the previous position of the user is large, the obtained current position of the user is set as the previous position of the user and the first-order approximation formula is used. By substituting in, the clock error of the user with respect to the current position of the user and the system time of each satellite navigation system can be obtained more accurately.

As the first and second satellite navigation systems, any system capable of obtaining the satellite position and the pseudo range by reception is sufficient. Examples of such a system include GPS and GLONASS.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a position measuring device 10 according to an embodiment of the present invention. The position measuring device 10 shown in this figure includes a first receiving unit 12, a second receiving unit 14,
The timing generating unit 16, the calculating unit 18, and the output unit 20 are included.

The first receiving unit 12 is a circuit that receives radio waves from a satellite (SV) that constitutes a first satellite navigation system (for example, GPS) and demodulates the radio waves to obtain a satellite position and a pseudo range. The second receiving unit 14 is a circuit that receives a radio wave from a second satellite navigation system, for example, a satellite (SV) configuring GLONASS, demodulates the radio wave, and obtains a satellite position and a pseudo range. The timing generation unit 16 is a circuit that synchronizes both the first reception unit 12 and the second reception unit 14 so that the satellite position and the pseudo range related to the same reception time are obtained, and for example, from the TCXO and the frequency divider. Can be configured. The calculation unit 18 calculates the satellite position and the pseudo range obtained by the first and second reception units 12 and 14, the initial position of the user that is initially set, and the position of the user obtained by the previous positioning calculation (previous position). ), A predetermined positioning calculation is performed. The output unit 20 is means for outputting the current position of the user obtained by the positioning calculation of the calculation unit 18. When the position measuring device 10 shown in this figure is mounted on, for example, a ship or an automobile, the output unit 20 is a CRT,
It can be realized as a display device such as a liquid crystal display. Of course, it may be configured as a voice output device.

The feature of this embodiment is that a total of two first and second receivers 12 and 14 are provided as receivers to receive radio waves from satellites related to a plurality of satellite navigation systems such as GPS and GLONASS. There is a point that made it possible. The second feature is that the first and second receivers 12 and 14 are synchronized by the timing generator 16,
The satellite position and the pseudo range output from Nos. 14 and 14 are data at the same reception time. Further, the third feature is that the algorithm of the computing unit 18 uses an algorithm that can be used for positioning computation even with satellite positions and pseudoranges obtained from different satellite navigation systems (GPS, GLONASS, etc.). In point.

Next, the contents of the positioning calculation in the calculation unit 18 will be described.

First, the satellite position and pseudo range obtained by the first receiving section 12 and the satellite position and pseudo range obtained by the second receiving section 14 are represented as follows.

[0023]

[Equation 1] Furthermore, the initial position or the previous position of the user used for the positioning calculation in the calculation unit 18, the current position of the user to be obtained by the positioning calculation, and the clock error of each receiving unit 12 and 14 with respect to the system time of each satellite navigation system, It is defined as follows.

[0024]

[Equation 2] By defining each vector and scalar in this way, the pseudo distance ρ _i between the i-th satellite and the user can be expressed by the following equation.

[0025]

[Equation 3] The relationship shown in this figure can be conceptually expressed as shown in FIG. In this figure, the satellite position of each satellite, the user's initial position or previous position, and the user's current position can be expressed as a vector in an X, Y, Z three-dimensional coordinate system having an origin O at the center of the earth. . The distance between each satellite and the user can be expressed as the difference between each position vector. As mentioned above, the clocks of the first and second receivers 12 and 14 are offset with respect to the system time of the corresponding satellite navigation system, so that the clocks of the first and second receivers 12 and 14 are obtained. The obtained distance is a pseudo distance ρ _i including the clock error b _{j of the} user. The above formula is a formula expressing such a relationship.

Taylor expansion of this relational expression around the initial position or the previous position of the user gives the following expression.

[0027]

[Equation 4] In this equation, if the second or higher order term δ which is an error term is ignored and the first order approximation is performed, the following equation is obtained.

[0028]

[Equation 5] If this equation is made simultaneous with respect to i and expressed as a vector,
The formula is as follows.

[Equation 6] Expression obtained by modifying this expression

[Equation 7] Can be solved by the method of least squares when m + n is 5 or more. In other words, since the total number of unknowns is the total of the user's three-dimensional position and the clock error of each system, the total number of satellites that can be received by the first and second receivers 12 and 14 is 5 or more. Then, the above equation can be solved. Therefore, the first receiving unit 12 or the second receiving unit 1
Even if the number of receivable satellites by 4 alone is less than 4, the current position of the user can be obtained three-dimensionally.

Thus, according to this embodiment, for example, G
Even if the number of receivable satellites is less than the required number of satellites by PS or GLONASS alone, the current position of the user can be preferably obtained.

For example, in the case of performing three-dimensional positioning of a user, it was necessary to receive and demodulate radio waves from four satellites in positioning by GPS or GLONASS alone. On the other hand, in the case of the present embodiment, the number of satellites capable of receiving and demodulating radio waves is 3 for GPS,
In the case of two S's, the current position of the user can be obtained. Similarly, GPS that can receive and demodulate radio waves
Even when the number of satellites is 2 and the number of GLONASS satellites is 3, three-dimensional positioning can be performed. If two-dimensional positioning is allowed, the number of unknowns decreases, so m + n is 4 or more, and the number of satellites that can receive and demodulate radio waves is GP.
Two for each S and GLONASS.

In the above calculation, the relational expression relating to the pseudo-range with each satellite is Taylor-developed around the previous position or the initial position of the user to make a first approximation. Therefore,
If the difference between the user's initial position or previous position and the current position is large, a non-negligible error may occur.
In order to prevent such an error, the current position obtained by the calculation may be used as the previous position in the above equation and the result may be solved.

When performing two-dimensional positioning instead of three-dimensional positioning, the above equation is modified by using the relationship of X ² + Y ² + Z ² = H ² (H is the height from the center of the earth). Just do it.

Further, the current position of the user obtained by the calculation unit 18 may be output as it is by the output unit 20, but in reality, it is converted into a form such as latitude, longitude, and height. It is preferable to output it.

Further, the above explanation is related to GPS and GLON.
Although the ASS is used as an example, the satellite navigation system to which the present invention is applied only needs to be a system capable of obtaining the satellite position and the pseudo range by receiving and demodulating radio waves.
The GPS and GLONASS do not need to be limited. The present invention does not limit the number of satellite navigation systems that receive radio waves to two, and may be three or more.

[0035]

As described above, according to the present invention,
First and second synchronized by the timing generator
The satellite position and the pseudo range for the plurality of satellites that form the first and second satellite navigation systems,
Since the current position of the user is calculated using these, even if the number of receivable satellites does not reach the number required for positioning in each satellite navigation system alone, if the total number of satellites in each system is more than the specified number Therefore, it is possible to preferably obtain the current position of the user.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a position measuring device according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship of each vector in this embodiment.

FIG. 3 is a diagram showing a positioning principle in GPS and GLONASS.

[Explanation of symbols]

 10 Position Measuring Device 12 First Receiver 14 Second Receiver 16 Timing Generator 18 Arithmetic Unit 20 Output Unit

Claims (4)

[Claims] 1. A first satellite navigation system, which receives radio waves from a plurality of satellites constituting a first satellite navigation system to obtain a satellite position of the satellite and a pseudo distance between the satellite and a user, and a second satellite navigation system. A satellite at the same reception time by synchronizing the first and second receivers that receive radio waves from a plurality of satellites that make up the satellite to determine the satellite position of the satellite and the pseudo distance between the satellite and the user. A timing generator that outputs a position and a pseudorange, and when the first and second receivers receive radio waves from a predetermined number or more of satellites in total of the first and second satellite navigation systems, these satellites And a calculation unit for determining the current position of the user based on the satellite position and pseudo-range output from the first and second receiving units, and the initial position or the previous position of the user. Position measuring device. 2. The position measuring device according to claim 1, wherein the arithmetic unit develops a formula representing the pseudorange by the satellite position, the current position of the user and the clock error around the initial position or the previous position of the user. A position measuring device, which calculates a clock error of the user with respect to the current position of the user and the system time of each satellite navigation system by using the following approximation formula. 3. The position measuring device according to claim 2, wherein when there is a large difference between the user's current position calculated by calculation and the user's initial position or previous position, the calculated current position of the user. The position measuring device is characterized by calculating the clock error of the user with respect to the current position of the user and the system time of each satellite navigation system by substituting as the previous position of the user into the first-order approximation formula. 4. The position measuring device according to claim 1, wherein the first and second satellite navigation systems are GPS or GLONASS, respectively.