JP2008045896A - Program, positioning circuit, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize positioning having higher accuracy in consideration of a positioning error in a multipath environment. <P>SOLUTION: Satellite combinations which are combinations of four correction satellites are extracted based on a captured GPS signal, and each present position when using each satellite combination is measured relative to each satellite combination. A satellite combination determined to be the most suitable combination among the extracted satellite combinations is selected as a selected combination, and a measurement result in the selected combination is output to a map matching processing part. Then, a satellite combination having a measurement result most similar to a map matching result is determined as the most suitable combination of this time based on each measurement result in the extracted satellite combinations and position information which is the map matching result input from the map matching processing part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a program, a positioning circuit, and an electronic device.

As a positioning system using an artificial satellite, a GPS system is well known and is used in a car navigation system or the like. However, since positioning by the GPS system has many error factors and it is difficult to avoid the occurrence of positioning errors, various techniques for compensating for the positioning errors have been devised.

As an example thereof, Patent Document 1 discloses a technique for correcting an error in positioning (other positioning) by a GPS receiver by autonomous positioning based on a moving distance of a car in a car navigation system.

Further, in Patent Document 2, when the displacement between the previous determined position and the current predicted positioning position exceeds a predetermined range, a position obtained by adding the predetermined predicted displacement to the previous determined position is set as the current determined position. Technology is disclosed.
Japanese Patent Laid-Open No. 5-18768 JP-A-8-313278

However, in the techniques disclosed in Patent Document 1 and Patent Document 2, for example, a GPS receiver is located in a valley of a building, and a GPS signal from a GPS satellite does not reach the GPS receiver directly and is reflected on the building. It was not related to positioning in consideration of the so-called multipath environment that would be reached from.

That is, the techniques of Patent Document 1 and Patent Document 2 are techniques for determining whether or not to use the position of the positioning result as it is, and regarding the usage of the positioning result performed by the GPS receiver. It was not a technology related to GPS receiver positioning that considered errors in a multipath environment.

This will be specifically described with reference to the drawings. Compared to the case where the GPS receiver is located in a place where the field of view is open without any obstruction in the horizon direction, for example, as shown in FIG. 12, when located in a place surrounded by buildings such as the city center, The range in which GPS satellites can be directly observed (hereinafter referred to as “directly observable range”) is narrow. In FIG. 12, if there is no obstruction such as a building, the GPS satellite S1
Although all of S5 can be directly observed, only GPS satellites S2 to S4 can be directly observed by a shield such as a building.

However, the GPS receiver cannot grasp such a situation. That is, the GPS receiver cannot distinguish which GPS signal among the plurality of received GPS signals is a GPS signal that can be directly received without being reflected by a building or the like. Further, the directly observable range varies with the movement of the GPS receiver, and a large difference may occur between the number of satellites that can be directly observed at the previous positioning and the number of satellites that can be directly observed at the current positioning.

Under such circumstances, the conventional technique for improving the positioning error in the multipath environment is not the improvement of the positioning itself performed by the GPS receiver, but as disclosed in Patent Document 1 and Patent Document 2. The main point is how to use and process the positioning results obtained by the GPS receiver to reduce the influence of positioning errors.

The present invention has been made in view of the above-described problems, and an object of the present invention is to realize higher-accuracy positioning in consideration of positioning errors in a multipath environment.

A first invention for solving the above-described problem is a program for causing a program-executable processor to repeatedly execute measurement of the current position based on a plurality of received satellite signals, and from the received satellite signals, An extraction step for extracting a combination of satellite signals that can be used for measurement of the current position, a measurement step for measuring the current position for each combination of the extracted satellite signals, and the extracted satellite signal A map that allows data exchange with the processor of the selection step for selecting the combination determined to be the most suitable combination as the selection combination, and the measurement result of the measurement step for the selected selection combination. An output step for outputting to the matching processing unit, and the measurement step for each of the combinations of the extracted satellite signals. A determination step of determining the optimum combination of the extracted satellite signals from the combination of the extracted satellite signals based on the measurement result in the map and the position information that is the processing result from the map matching processing unit for the output; Is a program for causing the processor to repeatedly execute a series of processes including:

According to an eleventh aspect of the invention, there is provided a positioning circuit that repeatedly executes current position measurement based on a plurality of received satellite signals, and extracts a combination of satellite signals that can be used for current position measurement from the received satellite signals. For each combination of the extracted satellite signals, a measuring means for measuring a current position when the combination is used, and a combination determined to be the previous optimal combination among the combinations of the extracted satellite signals A combination of the extracted satellite signals, a selection unit that selects a selected combination, an output unit that outputs a measurement result of the selected combination to the map matching processing unit capable of data transmission and reception Position information which is a measurement result at each measurement step and a processing result from the map matching processing unit for the output. Based on the bets, determining means for determining this optimum combination from among the combinations of the extracted satellite signal may constitute a positioning circuit comprising a.

According to the first invention and the like, combinations of satellite signals that can be used for measurement of the current position are extracted, and for each of the extracted combinations of satellite signals, the current position when the combination is used is measured. Of the extracted combinations of satellite signals, the combination determined to be the optimal combination last time is selected as the selected combination, and the measurement result for the selected combination is output to the map matching processing unit that can exchange data. Then, based on the measurement result of each of the extracted satellite signal combinations and the position information input from the map matching processing unit, the current optimal combination is determined from the extracted satellite signal combinations.

This series of processing is repeatedly performed at a predetermined measurement interval (for example, every second). For example, if it is determined that the combination of the satellite signals with respect to the measurement result closest to the position of the map matching result is the optimum combination, this optimum combination has little positioning error, that is, among the extracted combinations, the multiple It is inferred that the combination has the least influence of positioning error in the path environment. Inductively, for example, it is rare that the reception environment, that is, the multipath environment changes suddenly during a measurement interval of 1 second, for example, and the number of satellites that can directly receive satellite signals varies greatly.
Therefore, if the combination of the satellite signals determined to be the optimal combination last time can be extracted this time, the measurement based on the combination is considered optimal. Therefore, it is possible to realize highly accurate positioning taking into account the multipath environment.

According to a second aspect of the present invention, there is provided a program for causing a program-executable processor to repeatedly execute a current position measurement based on a plurality of received satellite signals, and used to measure the current position from the received satellite signals. An extraction step for extracting possible satellite signal combinations;
For each of the extracted satellite signal combinations, a measurement step for measuring the current position when the combination is used, and a selection that selects a combination that has been determined to be the optimal combination last time among the extracted satellite signal combinations as a selection combination A map matching processing step for performing a predetermined map matching process based on a measurement result in the measurement step for the selected selection combination and correcting a current position, and the measurement of each of the combinations of the extracted satellite signals. A determination step of determining an optimum combination of the extracted satellite signals from the extracted combination of satellite signals based on the measurement result in step and the current position corrected by the map matching process. A program for repeatedly executing the program may be configured.

According to a twelfth aspect of the invention, there is provided a positioning circuit that repeatedly executes measurement of a current position based on a plurality of received satellite signals, and extracts a combination of satellite signals that can be used for measuring the current position from the received satellite signals. For each combination of the extracted satellite signals, a measuring means for measuring a current position when the combination is used, and a combination determined to be the previous optimal combination among the combinations of the extracted satellite signals Selecting means for selecting a selected combination, map matching processing means for performing a predetermined map matching process based on a measurement result of the measuring means for the selected selection combination, and correcting the current position, and the extracted Result of measurement by the measuring means for each combination of satellite signals and current position corrected by the map matching process Based on a determination means for determining this optimum combination from among the combinations of the extracted satellite signal may constitute a positioning circuit comprising a.

According to the second invention and the like, combinations of satellite signals that can be used for measurement of the current position are extracted, and for each of the extracted combinations of satellite signals, the current position when the combination is used is measured. Then, among the extracted satellite signal combinations, the combination determined to be the optimal combination last time is selected as the selected combination, and a predetermined map matching process is performed based on the measurement result for the selected combination, and the current position is corrected. The Then, based on the measurement result of each of the extracted satellite signal combinations and the corrected current position, the present optimum combination is determined from the extracted satellite signal combinations.

In this case as well, as in the first invention, it is possible to realize highly accurate positioning in consideration of the multipath environment by repeatedly executing a series of processes. In addition, it is not necessary to provide a map matching processing unit separately, and high-accuracy positioning can be realized by processing by one processor.

Further, as a third invention, in the program of the first or second invention, a determination step for determining whether or not the selection combination selected in the selection step satisfies a predetermined reset condition, and the determination step When it is determined that the selected combination is satisfied, the processor further includes a change step of changing the selected combination to a combination that is alternatively selected from the combinations extracted in the extraction step. A program may be configured.

According to the third aspect of the invention, when it is determined that the selected combination satisfies the predetermined reset condition, the selected combination is changed to a combination that is alternatively selected from the extracted combinations.
Therefore, it is possible to obtain an effect of effectively preventing accumulation of errors while repeatedly executing a series of processes.

As a fourth invention, there is provided a program according to the third invention, wherein the determination step includes:
) Based on at least one of the sky arrangement of the respective satellites that have generated each satellite signal of the selected combination selected in the selection step, 2) the signal strength of each satellite signal, and 3) the SN ratio of each satellite signal. Thus, a program that is a step of determining whether or not the selected combination satisfies a predetermined reset condition may be configured.

According to the fourth aspect of the present invention, at least one of the sky arrangement of the respective satellites emitting the respective satellite signals of the selected selected combination, the signal intensity of each of the satellite signals, and the SN ratio of each of the satellite signals is set. Based on this, it is determined whether or not the selected combination satisfies a predetermined reset condition. Therefore, for example, when the sky arrangement of the satellites is not good, when the signal strength of each satellite signal is small, or when the SN ratio of each satellite signal is large, the selected combination is changed.

Further, as a fifth invention, in the program of the third or fourth invention, the determination step includes at least a previous measurement result of the previous selection combination and a current measurement result of the current selection combination. A program that is a step for determining whether or not the currently selected combination satisfies a predetermined reset condition based on the change may be configured.

According to the fifth aspect of the invention, based on at least the change between the previous measurement result of the previous selection combination and the current measurement result of the current selection combination, whether the current selection combination satisfies a predetermined reset condition. It is determined whether or not.

Further, as a sixth invention, the program according to the third or fourth invention, wherein the measurement step is a step of measuring a current position and a traveling direction, and the determination step includes at least a previous selected combination. A step of determining whether or not the currently selected combination satisfies a predetermined reset condition based on a change between the advancing direction included in the previous measurement result and the advancing direction included in the current measurement result of the current selected combination. A program may be configured.

According to the sixth invention, the current position and the traveling direction are measured, and at least the traveling direction included in the previous measurement result of the previous selected combination and the traveling direction included in the current measured result of the current selected combination. Based on the change, it is determined whether or not the currently selected combination satisfies a predetermined reset condition. Therefore, for example, when the traveling direction changes suddenly, the selected combination is changed.

According to a seventh invention, there is provided the program according to any one of the third to sixth inventions, wherein the changing step generates a) each satellite signal of the combination for each combination extracted in the extraction step. B) Signal strength of each satellite signal of the combination, c)
Based on at least one of the signal-to-noise ratios of the satellite signals of the combination, a program that is a step for changing the selected combination this time to an alternative selected from the extracted combinations is configured. Also good.

According to the seventh aspect of the present invention, each of the extracted combinations, the sky arrangement of the satellites that emitted the satellite signals of the combination, the signal strength of the satellite signals of the combination, the SN of each satellite signal of the combination Based on at least one of the ratios, the currently selected combination is changed to a combination that is alternatively selected from the extracted combinations. Therefore, for example, a combination with a good satellite sky arrangement, a combination with a high signal intensity of each satellite signal, a combination with a good S / N ratio of each satellite signal, and the like are selected as selection combinations.

Further, as an eighth invention, there is provided the program according to any one of the third to seventh inventions, wherein the change step includes at least the previous measurement result of the previous selection combination and the combination extracted in the extraction step. Based on the current measurement results for each,
You may comprise the program which is a step which changes to the combination selected alternatively from the extracted combination.

According to the eighth invention, at least based on the previous measurement result of the previous selection combination and the current measurement result for each of the extracted combinations, the current selection combination is the extracted combination. It is changed to the combination selected alternatively.

Further, as a ninth invention, there is provided the program according to any one of the first to eighth inventions, wherein the selection step includes a combination determined to be the optimal combination last time in the combination extracted in the extraction step this time. If not, a) sky arrangement of each satellite that emitted each satellite signal of the combination, b) signal intensity of each satellite signal of the combination, c
) Based on at least one of the S / N ratios of the satellite signals of the combination, a program that is a step of selecting a combination to be selected this time from the extracted combinations may be configured.

According to the ninth aspect of the present invention, when the combination determined to be the optimal combination in the previous time is not included in the combination extracted this time, each of the extracted combinations that has generated each satellite signal of the combination. The combination selected as the current selected combination from the extracted combinations based on at least one of the sky arrangement of the satellites, the signal strength of each satellite signal of the combination, and the SN ratio of each satellite signal of the combination Is selected. Therefore, even when the extracted combination does not include the previous optimal combination, for example, a combination in which the satellite sky arrangement is favorable, a combination in which the signal strength of each satellite signal is high, and the SN ratio of each satellite signal By selecting a combination having a favorable value as a selected combination, it is possible to effectively prevent a decrease in positioning accuracy.

Further, as a tenth invention, there is provided the program according to any one of the first to ninth inventions, wherein the selection step includes at least a combination that has been determined to be the most suitable combination last time extracted in the extraction step this time. In the step of selecting the combination of satellite signals including the largest number of satellite signals emitted from the same satellite as the satellite that emitted each satellite signal of the combination determined to be the optimum combination last time as the selected combination. A certain program may be configured.

According to the tenth aspect of the present invention, each satellite signal of the combination determined to be the previous optimal combination is generated when at least the combination determined to be the previous optimal combination is not included in the combination extracted this time. A combination of satellite signals including the largest number of satellite signals emitted from the same satellite as the satellite is selected as the current selection combination. Therefore, even when the previous optimal combination is not included in the extracted combinations, the combination of satellite signals that approximates the previous optimal combination is selected as the selected combination, so that the positioning accuracy is effectively reduced. Is prevented.

Further, as a thirteenth invention, an electronic apparatus including the positioning circuit of the eleventh or twelfth invention may be configured.

Hereinafter, an embodiment in the case where the present invention is applied to a navigation device 1 will be described with reference to the drawings.

1. Principle First, the principle will be described.

The navigation device 1 includes a GPS receiver. The GPS receiver receives a GPS signal, which is a satellite signal transmitted from a GPS satellite, and based on the navigation message included in the received GPS signal, Calculate the position. Note that four GPS satellites are arranged on each of the six orbital planes, and in principle, four or more satellites are operated from anywhere on the earth so that they can always be observed in a geometric arrangement. Below, the received (captured) GP
The GPS satellite that has transmitted the S signal is referred to as a “capture satellite” in order to distinguish it from other GPS satellites.

In addition, the GPS receiver is a GP specified by a clock (quartz clock) provided in its own device.
Based on the reception time of the S signal and the transmission time of the GPS satellite included in the received GPS signal, the radio wave propagation time from the captured satellite to the own device is calculated.

Then, the GPS receiver calculates the distance from the captured satellite to itself by multiplying the calculated radio wave propagation time by the speed of light. However, the clock (quartz clock) provided in the GPS receiver
Is inferior in accuracy to a clock (atomic clock) provided in a GPS satellite, the radio wave propagation time includes a clock error. Therefore, the distance calculated here is a pseudo distance (pseudo distance) including an error.

The GPS receiver is based on information such as the position of the four captured satellites and the distance from each captured satellite to the own device based on the values of the four parameters of the three-dimensional coordinate value indicating the position of the own device and the clock error. Ask. Depending on the latitude of the positioning position, the positioning time, etc., there are usually four or more satellites that can be observed.
In the present embodiment, among the observable satellites, a combination of captured satellites consisting of four captured satellites (hereinafter referred to as “satellite combination”) is extracted, and the positioning result is considered to be most appropriate. By repeating a series of processes for determining satellite combinations (hereinafter referred to as “optimal combinations”), improvement in positioning accuracy in a multipath environment is realized.

The optimum combination is a position measured by each satellite combination (hereinafter referred to as “positioning position”).
And the position of the GPS receiver obtained as a result of the map matching process performed by the navigation device 1 (hereinafter referred to as “map matching result position”).

Here, the map matching process refers to a process of correcting the positioning position obtained by the GPS receiver to an appropriate position on the map. For example, it is assumed that the positioning position obtained by the GPS receiver is a position corresponding to the sea on the map. In this case, a process for correcting the positioning position, for example, on the coast road closest to the positioning position is performed. Since the process related to map matching is well known, detailed description is omitted.

FIG. 1 is a diagram for explaining the flow of processing for determining the optimum combination.
Hereinafter, a series of processing until satellite combinations are extracted and the optimum combination is determined from the extracted satellite combinations is referred to as “turn”, and the satellite combination determined to be the optimum combination in the turn is referred to as “current optimum combination”. The satellite combination determined to be the optimal combination in the immediately preceding turn is referred to as the “previous optimal combination”. However, here, in order to simplify the description, the satellite combinations extracted in each turn are described as four fixed “A” to “D”.

In addition to the current position, the GPS receiver simultaneously measures the current moving direction (traveling direction) and speed of the GPS receiver. In FIG. 1, the measured moving direction and speed are indicated as “movement vector”.
As an arrow. However, the direction of the arrow indicates the moving direction, and the length of the arrow indicates the speed. The moving direction and speed of the GPS receiver can be measured based on a change in frequency (Doppler shift) caused by a relative position change between the captured satellite and the GPS receiver.

In the first turn, the positioning position is measured based on each of the extracted satellite combinations “A” to “D”. Next, one satellite combination is selected from the satellite combinations “A” to “D” according to a predetermined selection method, and the selected satellite combination is set as a “selected combination”. As a selection method of the selected combination in the first turn, for example, selecting a satellite combination having the maximum sum of signal strengths of four captured satellites, or DOP (Dilution o) which is a measure of positioning accuracy based on the sky arrangement of captured satellites.
f Precision) (DOP includes HDOP, VDOP, PDOP, GDOP,
Hereinafter, it is collectively referred to as “DOP”. ) Is the smallest satellite combination. In FIG. 1, it is assumed that the satellite combination “C” is selected as the selected combination.

Next, map matching processing is performed based on the positioning result of the satellite combination “C” which is the selected combination. The obtained map matching result position and the satellite combinations “A” to “D”
”Is calculated, and the satellite combination corresponding to the positioning position where the calculated distance is the minimum is determined as the optimum combination this time. In FIG. 1, the smallest distance from the map matching result position is the positioning position by the satellite combination “C”, so the satellite combination “C” is the optimum combination this time. The first turn is now over.

In the second turn, the positioning position is measured based on each of the extracted satellite combinations “A” to “D”. Next, the satellite combination “C” that is the previous optimal combination (that is, the current optimal combination of the first turn) is selected as the selected combination, and the map matching process is performed based on the positioning result of the satellite combination “C”.

Then, the distance between the obtained map matching result position and each positioning position by the satellite combinations “A” to “D” is calculated, and the satellite combination corresponding to the positioning position where the calculated distance is the minimum is determined as the optimum combination this time. To do. In FIG. 1, the smallest distance from the map matching result position is the positioning position by the satellite combination “B”, so the satellite combination “B” is the optimum combination this time. This is the end of the second turn.

In the third turn, the positioning position is measured based on each of the extracted satellite combinations “A” to “D”. Next, the satellite combination “B” that is the previous optimal combination (that is, the current optimal combination of the second turn) is selected as the selected combination, and the map matching process is performed based on the positioning result of the satellite combination “B”.

Then, the distance between the obtained map matching result position and each of the positioning positions by the satellite combinations “A” to “D” is calculated, and the satellite combination corresponding to the positioning position where the calculated distance is the minimum is “current optimal combination”. Is determined. In FIG. 1, the smallest distance from the map matching result position is the positioning position by the satellite combination “A”, so the satellite combination “A” is the optimum combination this time. This is the end of the third turn. Thereafter, the turn is repeated in the same manner.

However, in the present embodiment, from the viewpoint of preventing accumulation of errors and the like, when each selected combination satisfies a predetermined reset condition in each turn, a process of changing the selected combination according to a predetermined selection method (hereinafter, referred to as “reset combination”) , Referred to as “reset”).

As a reset condition, for example, a predetermined time has passed since the last reset,
For example, the moving direction of the GPS receiver has changed greatly, the DOP value of the selected combination is large, and the like. Examples of the selection method include selecting a satellite combination having the maximum sum of signal intensities of the four captured satellites, selecting a satellite combination having the minimum DOP value, and the like. A specific example will be described in “2. Configuration”.

2. Configuration Next, the configuration will be described.

FIG. 2 is a block diagram showing a functional configuration of the navigation device 1 in the present embodiment. The navigation device 1 includes an antenna 10, a SAW 20, an LNA 30, an RF circuit unit 40, a baseband processing circuit unit 50, a map matching processing unit 60, an operation unit 70, and a display unit 80. The

In the navigation device 1, the GPS receiving unit 2 including the SAW 20, the LNA 30, the RF circuit unit 40, and the baseband processing circuit unit 50 corresponds to a GPS receiver. In addition, the RF circuit unit 40 and the baseband processing circuit unit 50 are respectively provided with different LSIs (Large Scals).
eIntegration) or as a single chip. Further, the entire GPS receiving unit 2 including the SAW 20 and the LNA 30 may be manufactured as one chip.

The antenna 10 is an antenna that receives an RF signal including a GPS signal transmitted from a GPS satellite, and outputs the received RF signal to the SAW 20.

SAW (Surface Acoustic Wave) 20 is a band-pass filter that allows only a predetermined frequency band component of the RF signal received by antenna 10 to pass.
Output to NA30.

An LNA (Low Noise Amplifier) 30 is a low noise amplifier that amplifies a signal that has passed through the SAW 20, and outputs the amplified signal to the RF circuit unit 40.

The RF circuit unit 40 multiplies the signal amplified by the LNA 30 and the oscillation signal of a predetermined frequency, and thereby the RF signal that has passed through the antenna 10, the SAW 20, and the LNA 30 is referred to as an intermediate frequency signal (hereinafter referred to as an “IF signal”). ) To downconvert. Then, after the IF signal is amplified, it is converted into a digital signal by an A / D converter and output to the baseband processing circuit unit 50.

The baseband processing circuit unit 50 performs correlation detection processing, etc., by performing an FFT operation or the like on the IF signal output from the RF circuit unit 40, captures and extracts a GPS signal, decodes the data, and navigation messages and time information Etc. are extracted, and pseudorange calculation and positioning calculation are performed. In addition, GP
The S signal is a spread spectrum modulated signal called C / A code (Clear and Acquisition or Coarse and Access).

The baseband processing circuit unit 50 includes a circuit that performs correlation detection processing, a circuit that generates a spread code for performing correlation detection, a circuit that decodes data, and each unit of the baseband processing circuit unit 50 through the RF circuit unit 40 And a central processing unit (CPU) 51 that performs various arithmetic processing including baseband processing, which will be described later, and a read only memory (ROM) 53.
And a RAM (Random Access Memory) 55.

3A and 3B show the ROM 53 and RA provided in the baseband processing circuit unit 50. FIG.
It is a figure which shows an example of the data stored in M55. The ROM 53 stores a baseband processing program 531 that is read by the CPU 51 and executed as baseband processing (see FIG. 10), and a reset condition table 533 in which reset conditions for the selected combination are defined.

In the baseband processing, the CPU 51 extracts a combination of four captured satellites based on the captured GPS signal, selects a selected combination from the satellite combinations, and maps the positioning result based on the selected combination. This is a process to be output to the processing unit 60. And C
The PU 51 receives the map matching result from the map matching processing unit 60, and determines the optimum combination based on the input map matching result and the positioning result of each of the previous satellite combinations. This baseband processing will be described later in detail using a flowchart.

FIG. 4 is a diagram illustrating a table configuration example of the reset condition table 533. In the reset condition table 533, data of a reset condition number 5331, a reset condition 5333, and a selection combination selection method 5335 are stored in association with each other.

Specifically, the reset condition 5333 with the number 5331 being “1” is “30 seconds have passed since the previous reset”. This is intended to periodically reset.
The reset condition 5333 whose number 5331 is “2” is “the change in the moving direction is greater than 90 °”. This is intended to perform resetting when the moving direction of the navigation device 1 changes abruptly. The reset condition 5333 whose number 5331 is “3” is “the DOP value of the selected combination is greater than 6”. This is intended to perform resetting when the sky arrangement of the captured satellites included in the selected combination is not good.

The reset condition 5333 whose number 5331 is “4” is “the average of the SN ratio (SNR) of GPS signals emitted by the acquisition satellites constituting the selected combination is greater than 10”. This is intended to perform resetting when a lot of noise is included in the GPS signal transmitted by the captured satellite included in the selected combination. The reset condition 5333 whose number 5331 is “5” is “the sum of the signal intensities of GPS signals emitted by the acquisition satellites constituting the selected combination is less than 8.” This is intended to perform resetting when the intensity of the GPS signal transmitted by the captured satellite included in the selected combination is small. By resetting according to these reset conditions 5333,
Accumulation of errors is effectively prevented. In addition, the value of each condition is an example and is a design item set appropriately.

As the selection combination selection method 5335, for example, “maximum signal strength” indicating “selecting a satellite combination having the maximum sum of signal strengths of GPS signals emitted from captured satellites” is set. As a result, the selected combination is changed to a satellite combination having a high signal strength and high positioning reliability.

In the baseband process, the CPU 51 refers to the reset condition table 533 and determines whether any of the reset conditions 5333 is satisfied. Then, the reset condition 533
3 is selected, a selected combination is selected from the extracted satellite combinations according to the selection combination selection method 5335 associated with the reset condition 5333. Note that the reset condition 5333 is determined in ascending order of the number 5331, and if it is determined that at least one of them is satisfied, the selected combination is selected according to the selection combination selecting method 5335.

The RAM 55 includes measurement data 551 that is data about measurement results, measurement history data 553 that is data about history of measurement results, optimum combination data 555 that is data about optimum combinations, and data about selected combinations. Certain selected combination data 557
And map matching data 559 which is data on the map matching result is stored.

FIG. 5 is a diagram illustrating a data configuration example of the measurement data 551. The measurement data 551 includes the number of captured satellites 5511 and the measurement result 5513 for each extracted satellite combination.
And the signal intensity 5515 which is the sum of the signal intensity of the captured satellites are stored in association with each other.

In the measurement result 5513, the measured positioning position, speed, and moving direction of the navigation device 1 (GPS receiver) are stored. The positioning position is represented by, for example, a three-dimensional coordinate value in the earth reference coordinate system. The moving direction is represented by 360 degrees, with true north as 0 degrees and true east as 90 degrees. In the baseband process, the CPU 51 updates the measurement data 551 as needed based on the measurement result for the extracted satellite combination.

FIG. 6 is a diagram illustrating a data configuration example of the measurement history data 553. Measurement history data 553
In this example, the data of the captured satellite numbers 5531, the measurement result 5533, and the map matching result position 5535 constituting the selected combination are associated with each other and stored for five records in the newest order. In the baseband process, the CPU 51 updates the measurement history data 553 as needed based on the measurement result for the selected combination and the map matching result input from the map matching processing unit 60.

The measurement history data 553 is used when the CPU 51 compares the measurement result for the immediately previous selected combination with the measurement result for the current selected combination. Specifically, when determining whether or not the reset condition 5333 is satisfied, for example, the movement direction included in the measurement result for the immediately previous selection combination and the movement direction included in the measurement result for the current selection combination To determine whether or not the change in the moving direction is greater than 90 °.

FIG. 7 is a diagram illustrating a data configuration example of the optimum combination data 555. Optimal combination data 5
55 stores the numbers of captured satellites constituting the optimum combination. In the baseband processing, the CPU 51 updates the optimal combination data 555 as needed based on the satellite combination determined to be the optimal combination this time.

FIG. 8 is a diagram illustrating a data configuration example of the selected combination data 557. Selection combination data 5
57 stores the numbers of captured satellites constituting the selected combination. In the baseband processing, the CPU 51 updates the selected combination data 557 as needed based on the satellite combination selected as the selected combination.

FIG. 9 is a diagram illustrating a data configuration example of the map matching data 559. The map matching data 559 stores a map matching result position represented by, for example, a three-dimensional coordinate value in the earth reference coordinate system. In the baseband process, the CPU 51 updates the map matching data 559 as needed based on the map matching result input from the map matching processing unit 60.

The map matching processing unit 60 is a functional unit that performs overall control of the navigation device 1 including the GPS receiving unit 2 and map matching processing, and includes a host CPU 61, a ROM 63,
A RAM 65 is provided.

The ROM 63 includes a map matching process in addition to various programs such as a system program for controlling the navigation apparatus 1, a map matching program for performing a map matching process, and an application program for displaying a navigation screen on the display unit 80. Geographic information, map information data, etc. are stored. Host C
The PU 61 performs various processes according to these programs and data while exchanging data with the CPU 51 of the baseband processing circuit unit 50.

The operation unit 70 is an input unit configured by, for example, a touch panel or a button switch, and outputs a pressed key or button signal to the host CPU 61. By operating the operation unit 70, various instructions such as destination input are input.

The display unit 80 is configured by an LCD (Liquid Crystal Display) or the like, and the host CPU 6
1 is a display device that performs various displays based on a display signal input from 1. The display unit 80 includes
A navigation screen or the like is displayed.

3. Process Flow Next, the process flow will be described.

In FIG. 10, the baseband processing program 531 stored in the ROM 53 is stored in the CPU 5.
2 is a flowchart showing a flow of baseband processing executed in the baseband processing circuit unit 50 by being read and executed by 1. Prior to the baseband processing, the GPS receiving unit 2 receives the RF signal by the antenna 10 and downconverts the IF signal to the IF signal by the RF circuit unit 40.
It is assumed that the signal is demodulated / decoded as needed.

In the baseband processing, first, the CPU 51 extracts a combination of captured satellites as a satellite combination based on the captured GPS signal (step A1). Then, the CPU 51 measures the current position, speed and moving direction of the navigation device 1 (GPS receiver) using each of the extracted satellite combinations (step A3), and updates the measurement data 551 in the RAM 55.

Next, the CPU 51 determines whether or not the measurement is the first time (step A5). If it is determined that the measurement is the first time (step A5; Yes), the satellite having the maximum signal strength 5515 stored in the measurement data 551. A combination is selected as a selected combination (step A7), and RA
The measurement history data 553 and selected combination data 557 of M55 are updated.

Next, the CPU 51 outputs the positioning result of the selected combination stored in the measurement data 551 to the host CPU 61 of the map matching processing unit 60 (step A9). And C
The PU 51 receives the map matching result from the host CPU 61 (step A11),
The measurement history data 553 and the map matching data 559 in the RAM 55 are updated.

Next, the CPU 51 performs an optimum combination determination process this time (step A13). Specifically, the distance between the map matching result position stored in the map matching data 559 and each positioning position stored in the measurement result 5513 of the measurement data 551 is calculated. Then, the satellite combination corresponding to the positioning position with the smallest calculated distance is determined as the optimum combination this time.

Next, the CPU 51 determines the optimum combination data 55 in the RAM 55 with the current optimum combination determined.
5 is updated (step A15). Then, the CPU 51 determines whether or not to end the process (step A17). If it is determined that the process has not ended yet (step A17; No), the CPU 51 returns to step A1. If it is determined that the process is to be terminated (step A17; Yes)
The CPU 51 ends the baseband process.

On the other hand, if it is determined in step A5 that the measurement was not the first time (step A
5) No), the CPU 51 checks the satellite combination stored in the measurement data 551 and the current (previous) optimum combination stored in the optimum combination data 555, thereby extracting the satellite combination extracted in step A1. It is determined whether or not there is an optimum combination (step A19).

If it is determined that there is no optimal combination (step A19; No), the CPU 51 refers to the measurement data 551 again, and determines whether there is a satellite combination including three or more captured satellites constituting the optimal combination. If it is determined that there is no satellite combination (step A21) (step A21; No), the process proceeds to step A7.

On the other hand, when it is determined in step A21 that there is a satellite combination including three or more captured satellites that constitute the optimum combination (step A21; Yes), the CPU 51 determines the satellite combination having the maximum signal intensity 5515 among the satellite combinations. As a selection combination (Step A2
3) The measurement history data 553 and the selection combination data 557 in the RAM 55 are updated. And CPU51 transfers a process to step A9. By performing such processing, the satellite combination that approximates the current (previous) optimum combination is selected as the selected combination even if the extracted (current) previous optimal combination is not included in the extracted satellite combination. Since it is selected, a decrease in positioning accuracy is effectively prevented.

If it is determined in step A19 that there is an optimum combination (step A19)
Yes), the CPU 51 selects the current (previous) optimum combination stored in the optimum combination data 555 as the selected combination (step A25), and the measurement history data 5 of the RAM 55
53 and selected combination data 557 are updated.

Next, the CPU 51 refers to the reset condition table 533 in the ROM 53 and determines whether any of the reset conditions 5333 is satisfied in the order of condition numbers 5331 (step A2).
7) When it is determined that none of the conditions is satisfied (step A27; No), the process proceeds to step A9.

On the other hand, if it is determined in step A27 that the reset condition 5333 is satisfied (
(Step A27; Yes), the CPU 51 selects a selection combination from the satellite combinations stored in the measurement data 551 according to the selection combination selection method 5335 corresponding to the reset condition 5333 (Step A29), and the measurement history in the RAM 55 Data 553 and selected combination data 557 are updated. And CPU51 transfers a process to step A9.

4). According to the present embodiment, a satellite combination that is a combination of four correction satellites is extracted based on the captured GPS signal, and the current position when the satellite combination is used is measured for each satellite combination. . Then, among the extracted satellite combinations, the satellite combination determined to be the optimum combination last time is selected as the selected combination, and the measurement result for the selected combination is output to the map matching processing unit 60. Then, based on the measurement result of each extracted satellite combination and the position information that is the map matching result input from the map matching processing unit 60, the satellite combination that is the measurement result closest to the map matching result is the current one. Judged as the optimal combination.

This series of processing is repeated. Basically, the processing interval (positioning interval) is 1 second as in the conventional GPS receiver. The optimal combination has the smallest positioning error because the positioning result is closest to the map matching result, that is, the extracted combination has the least influence of the positioning error in the multipath environment (for example, direct observation is possible) It is inferred that the number of acquired satellites included in the range is the largest). Inductively, it is rare that the reception environment, that is, the multipath environment changes rapidly during one second, and the number of captured satellites included in the directly observable range greatly differs. Therefore, if the four captured satellites determined to be the optimal combination last time can still be captured this time, positioning by the four captured satellites is considered optimal. According to the present embodiment, the navigation device 1 and G that have exactly realized this idea.
A PS receiver is realized, and high-accuracy positioning can be performed in consideration of a multipath environment.

5. Modified example 5-1. Application Example The present invention is not limited to a vehicle-mounted navigation device, but also a portable navigation device, a GPS
The present invention can be applied to an electronic device such as a portable phone having a function.

5-2. Map Matching Processing In the present embodiment, the map matching processing is described as being performed by the map matching processing unit 60, but may be performed by the baseband processing circuit unit 50. Specifically, the map matching program 532 is used as a subroutine of the baseband processing program 531.
Is stored in the ROM 53 (see FIG. 11). Then, the CPU 51 performs the map matching process by executing the map matching program 532 instead of steps A9 and A11 of FIG. 10 in the baseband process. It goes without saying that data such as geographic information and map information required in this case is stored in the ROM 53. Also in this case, it is possible to realize highly accurate positioning taking the multipath environment into consideration by repeatedly executing a series of processes. Further, it is not necessary to provide the map matching processing unit 60 individually, and high-accuracy positioning can be realized by processing by one processor (CPU 51).

5-3. Outputting positioning results In this embodiment, it has been described that only the positioning results for the satellite combination selected as the selected combination are output to the map matching processing unit 60. However, the positioning results for all the extracted satellite combinations are map-matched. The data may be output to the processing unit 60. In this case, the map matching processing unit 60 selects an optimal positioning result from all the input positioning results, and performs map matching processing based on the positioning results. As a standard for selecting the positioning result, the satellite combination with the smallest DOP value, the satellite combination with the largest sum of the intensity of the satellite signals, the satellite combination with the smallest average SN ratio of the satellite signals, the result of the previous map matching process A displacement from the position (position, traveling direction) can be considered.

5-4. Reset condition In this embodiment, it has been described that the selected combination is changed when any one of the reset conditions is satisfied. However, the selected combination is changed when two or more reset conditions are satisfied. good. Specifically, for example, in the reset condition table 533 of FIG. 4, two or more reset conditions 533 among the reset conditions 5333 having the numbers 5331 of “1” to “5”.
Only when 3 is established, the selected combination is changed according to the selected combination selection method 5335.

Further, the reset conditions are not limited to those shown in the reset condition table 533 of FIG. For example, the reset condition may be that the distance between the positioning position measured by the previous selection combination and the positioning position measured by the current selection combination is extremely large (distance> threshold).

5-5. Selection Combination Selection Method The selection combination selection method is not limited to that shown in the reset condition table 533 of FIG. For example, the satellite combination having the smallest DOP value may be selected, or the satellite combination having the smallest S / N ratio of the satellite signals may be selected.

Moreover, it is good also as a selection combination selection method combining several conditions. For example, selecting a satellite combination in which the DOP value is less than a predetermined value and the sum of the satellite signal strengths is greater than or equal to the predetermined value, or the sum of the satellite signal strengths is greater than or equal to the predetermined value and the satellite signal SN A satellite combination having an average ratio less than a predetermined value may be selected.

5-6. Selection of selection combination when the optimum combination is not included in the extracted satellite combination In this embodiment, when the optimum combination is not included in the extracted satellite combination, the selection combination is selected based on the magnitude of the signal strength. In this case as well, as described in “5-5. Selection Combination Selection Method”, a satellite combination having the smallest DOP value or a satellite signal having the smallest S / N ratio is selected. A combination may be selected. Moreover, you may decide to select a selection combination according to the selection method which combined these conditions. Thus, even if the extracted (or previous) optimum combination is not included in the extracted satellite combination, a combination in which the sky arrangement of GPS satellites is good, a satellite combination in which the signal strength of each GPS signal is large, A satellite combination having a good S / N ratio of each GPS signal is selected as the selected combination, so that a decrease in positioning accuracy is effectively prevented.

Explanatory drawing of optimal combination determination. The figure which shows the function structure of a navigation apparatus. FIG. 3A is a diagram showing a configuration of a ROM. FIG. 3B is a diagram showing a configuration of the RAM. The figure which shows the table structural example of a reset condition table. The figure which shows the data structural example of measurement data. The figure which shows the data structural example of measurement log | history data. The figure which shows the data structural example of optimal combination data. The figure which shows the data structural example of selection combination data. The figure which shows the data structural example of map matching data. The flowchart which shows the flow of a baseband process. The figure which shows the structure of ROM in a modification. Explanatory drawing of multipath.

Explanation of symbols

1 navigation device, 2 GPS receiver, 10 antenna, 20 SAW,
30 LNA, 40 RF circuit section, 50 baseband processing circuit section,
51 CPU, 53 ROM, 55 RAM, 60 Map matching processing unit,
61 host CPU, 63 ROM, 65 RAM, 70 operation unit,
80 display section

Claims (13)

A program for causing a program-executable processor to repeatedly measure the current position based on a plurality of received satellite signals,
An extraction step of extracting a combination of satellite signals that can be used to measure the current position from the received satellite signals;
For each combination of the extracted satellite signals, a measurement step for measuring the current position when using the combination;
A selection step of selecting a combination determined as the optimal combination last time among the combinations of the extracted satellite signals, as a selection combination;
An output step of outputting the measurement result in the measurement step for the selected selection combination to a map matching processing unit capable of exchanging data with the processor;
Based on the measurement result of each of the extracted satellite signal combinations in the measurement step and the position information which is the processing result from the map matching processing unit for the output, the current combination is selected from the extracted satellite signal combinations. A determination step of determining an optimal combination of:
A program for causing the processor to repeatedly execute a series of processes including: A program for causing a program-executable processor to repeatedly measure the current position based on a plurality of received satellite signals,
An extraction step of extracting a combination of satellite signals that can be used to measure the current position from the received satellite signals;
For each combination of the extracted satellite signals, a measurement step for measuring the current position when using the combination;
A selection step of selecting a combination determined as the optimal combination last time among the combinations of the extracted satellite signals, as a selection combination;
A map matching processing step for performing a predetermined map matching process based on a measurement result in the measurement step for the selected combination, and correcting a current position;
Judgment for determining the current optimum combination from among the extracted satellite signal combinations based on the measurement result in each measurement step of each of the extracted satellite signal combinations and the current position corrected by the map matching process Steps,
A program for causing the processor to repeatedly execute a series of processes including: A determination step for determining whether the selection combination selected in the selection step satisfies a predetermined reset condition;
A change step of changing the selected combination to a combination that is alternatively selected from the combinations extracted in the extraction step when it is determined to satisfy the determination step;
The program according to claim 1, wherein the processor is further included in the series of processes to be executed by the processor. The determination step includes 1) the sky arrangement of the satellites that have generated the satellite signals of the selected combination selected in the selection step, 2) the signal strength of each satellite signal, and 3) the S of each satellite signal.
The program according to claim 3, which is a step of determining whether or not the selected combination satisfies a predetermined reset condition based on at least one of the N ratios. The determination step determines whether or not the current selected combination satisfies a predetermined reset condition based on at least the change between the previous measured result of the previous selected combination and the current measured result of the current selected combination. The program according to claim 3 or 4, wherein the program is a step to perform. The measurement step is a step of measuring a current position and a traveling direction,
In the determination step, the current selection combination is predetermined based on at least a change in the traveling direction included in the previous measurement result of the previous selection combination and the traveling direction included in the current measurement result of the current selection combination. 4. A step of determining whether or not a reset condition is satisfied.
Or the program of 4. In the changing step, each of the combinations extracted in the extracting step includes a) a sky arrangement of the satellites that emit the satellite signals of the combination, b) the signal intensity of each satellite signal of the combination, and c) the combination of the combinations. 7. The step of changing the selected combination this time to an alternative selected from the extracted combinations based on at least one of the S / N ratios of the satellite signals. The program according to one item. The changing step is based on at least the previous measurement result of the previous selection combination and the current measurement result for each combination extracted in the extraction step, and the selected combination is selected from the extracted combinations. The program according to any one of claims 3 to 7, which is a step of changing to an alternatively selected combination. In the selection step, when the combination determined to be the optimum combination last time is not included in the combination extracted in the extraction step this time, each of the extracted combinations a) Each satellite signal of the combination is emitted B) Signal combination of each satellite signal of the combination, c) At least one of the S / N ratios of the satellite signals of the combination, and the combination selected this time among the extracted combinations The step of selecting a combination
9. The program according to any one of 8. The selection step is at least the same as the satellite that issued each satellite signal of the combination determined to be the previous optimal combination when the combination determined to be the previous optimal combination is not included in the combination extracted in the extraction step this time The program according to any one of claims 1 to 9, which is a step of selecting a combination of satellite signals including the largest number of satellite signals emitted by the satellite as the selected combination. A positioning circuit that repeatedly executes measurement of the current position based on a plurality of received satellite signals,
Extraction means for extracting a combination of satellite signals that can be used to measure the current position from the received satellite signals;
For each combination of the extracted satellite signals, measuring means for measuring the current position when using the combination,
Of the extracted satellite signal combinations, a selection means for selecting a combination determined as the optimal combination last time as a selection combination;
An output means for outputting a measurement result by the measurement means for the selected selection combination to a map matching processing unit capable of data exchange;
Based on the measurement result of each of the extracted satellite signal combinations by the measuring means and the position information which is the processing result from the map matching processing unit for the output, the combination of the extracted satellite signals A determination means for determining the optimum combination of this time;
Positioning circuit equipped with. A positioning circuit that repeatedly executes measurement of the current position based on a plurality of received satellite signals,
Extraction means for extracting a combination of satellite signals that can be used to measure the current position from the received satellite signals;
For each combination of the extracted satellite signals, measuring means for measuring the current position when using the combination,
Of the extracted satellite signal combinations, a selection means for selecting a combination determined as the optimal combination last time as a selection combination;
Map matching processing means for performing a predetermined map matching process based on a measurement result by the measurement means for the selected combination, and correcting a current position;
Judgment of determining the optimum combination of the extracted satellite signals from the combination of the extracted satellite signals based on the measurement result of the measurement means for each combination of the extracted satellite signals and the current position corrected by the map matching process Means,
Positioning circuit equipped with.   An electronic apparatus comprising the positioning circuit according to claim 11.

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