JP2007263660A - Positioning device, control method for positioning device, and control program for positioning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positioning device and the like capable of using a positioning fundamental code of a very weak signal intensity, and allowing positioning at a speed and precision in response to a degree of weakness of the signal intensity. <P>SOLUTION: This positioning device 20 has an integration time setting means for setting the first integration time of an integration time for executing incoherence, the second integration time specified as an integration time longer than the first integration time, and the third integration time specified as an integration time longer than the second integration time, and a signal intensity threshold value setting means for setting the first signal intensity threshold value specified as a signal intensity threshold value capable of determining a phase of a positioning fundamental code, the second signal intensity threshold value specified as a signal intensity threshold value lower than the first signal intensity threshold value, and the third signal intensity threshold value specified as a signal intensity threshold value lower than the second signal intensity threshold value, and the integration time setting means sets the integration time, based on a drift error of a reference oscillator in the positioning device 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a positioning device that uses radio waves from a transmission source, a positioning device control method, and a positioning device control program.

Conventionally, a positioning system that measures the current position of a GPS receiver by using, for example, a GPS (Global Positioning System) that is a satellite navigation system has been put into practical use.
This GPS receiver uses radio waves from GPS satellites (hereinafter referred to as satellite radio waves) based on navigation messages (including approximate satellite orbit information: almanac, precision satellite orbit information: ephemeris, etc.) indicating the orbits of GPS satellites. A C / A (Clear and Acquisition or Coarse and Access) code, which is one of pseudo noise codes (hereinafter referred to as PN (Psuedo random noise code) codes), is received. The C / A code is a code that is the basis of positioning.
The GPS receiver specifies from which GPS satellite the C / A code is transmitted. For example, the distance (pseudo distance) between the GPS satellite and the GPS receiver is calculated based on the transmission time and reception time of the C / A code. The GPS receiver measures the position of the GPS receiver based on the pseudoranges of three or more GPS satellites and the position of each GPS satellite on the satellite orbit (Japanese Patent Laid-Open No. Hei 10-2010). No. 339772).
In order to receive a signal from a GPS satellite, it is necessary to match the phase of the received C / A code and the replica C / A code generated inside the GPS receiver.
In order to match the phase of the received C / A code and the phase of the replica C / A code generated inside the GPS receiver, correlation processing is performed while shifting the phase of the replica C / A code and the reception intermediate (IF) frequency. Yes.
This correlation processing is composed of coherent and incoherent.
Coherent is a process in which C / A codes received by a GPS receiver are integrated synchronously, and a correlation result between the integration result and a replica C / A code is obtained. An output value obtained by coherent processing is called a coherent value. For example, if the coherent time is 10 msec, the coherent value at a time of 10 msec is calculated. As a result of the coherent processing, a correlated phase and a coherent value are output.
Incoherent is a process of calculating an incoherent value by integrating the coherent values.
Since a large number of satellite sets can be generated by using C / A codes of many GPS satellites, for example, a small PDOP (Position Division Of Precise) satellite set can be selected to improve positioning accuracy. be able to.
Here, since the C / A code is modulated by the navigation message, for example, the polarity may be inverted every 20 milliseconds. This polarity inversion degrades the coherent value. In order to specify a reliable phase that can be used for positioning, the coherent value needs to be equal to or greater than a predetermined value, so the number of C / A codes that can specify the phase may decrease. .
On the other hand, a technique for improving sensitivity by performing correlation processing in anticipation of polarity inversion has been proposed (for example, Patent Document 1). In this specification, “sensitivity” is used to mean the ability to recognize a signal from a GPS satellite including a C / A code separately from noise.
JP 2004-340855 A

However, when the signal intensity from the GPS satellite is weak, there is a problem that the phase of the received C / A code may not be specified even if polarity inversion is predicted. As a result, there is a problem that a C / A code having a weak signal strength cannot be used for positioning, and the accuracy of the positioning position may not be improved.
In this specification, “signal strength” is used synonymously with “radio wave strength”.

  Therefore, the present invention can use a positioning basic code of weak signal strength, and can perform positioning at a speed and accuracy according to the degree of weakness of signal strength, and a control method of the positioning device An object of the present invention is to provide a control program for a positioning device.

  According to the first aspect of the present invention, there is provided a positioning device that receives a positioning basic code from a transmission source, performs a correlation process including coherent and incoherent, and measures a current position, wherein the incoherent A first integration time that is an integration time for performing the above, a second integration time that is defined as an integration time longer than the first integration time, and a third integration that is specified as an integration time longer than the second integration time. Integrated time setting means for setting time, a first signal strength threshold defined as a signal strength threshold capable of determining the phase of the positioning basic code, and a signal strength threshold lower than the first signal strength threshold A signal strength threshold setting means for setting a second signal strength threshold defined as: a third signal strength threshold defined as a signal strength threshold lower than the second signal strength threshold; And the integration time setting means, on the basis of the drift error of the reference oscillator of the positioning apparatus, is achieved by the positioning device, characterized in that it is configured for setting the integration time.

According to the configuration of the first invention, the positioning device can set the second integrated time defined as a time longer than the first integrated time, and is longer than the second integrated time. The third integrated time defined as time can be set.
The longer the integration time, the more clearly the positioning basic code can be distinguished from noise in the correlation processing. That is, the sensitivity can be improved as the integration time is longer. This is particularly effective when the signal strength is weak. However, when the drift error is large, the received frequency of the positioning basic code and the frequency on the positioning device side deviate from each other. Therefore, the degree of improvement in sensitivity when the integration time is lengthened becomes small.
In this regard, since the positioning device is configured to set the integration time based on the drift error of the reference oscillator of the positioning device, it is possible to reliably improve sensitivity by increasing the integration time. Can do.
Further, the positioning device can set the second signal strength threshold defined as a signal strength weaker than the first signal strength threshold, and further defined as a signal strength weaker than the second signal strength threshold. The third signal strength threshold to be set can be set.
For this reason, when the signal intensity is weak, positioning can be performed with high accuracy by setting the signal strength threshold high after setting the integration time long.
In addition, when the signal strength is weak, the current signal strength threshold may not reach the signal strength threshold, and the positioning position may not be calculated. Here, if the signal intensity threshold is set low, the position accuracy is degraded, but the possibility that the positioning position can be calculated increases.
In addition, when the signal strength is strong, the positioning device can perform quick and highly accurate positioning by using, for example, the first integration time and the first signal strength threshold.
As a result, a positioning basic code with weak signal strength can be used, and positioning can be performed at speed and accuracy according to the degree of weakness of signal strength.

  According to a second aspect of the present invention, there is provided the positioning apparatus according to the first aspect, wherein any one of the accumulated times and any one of the signal intensity thresholds are combined.

The longer the integration time is set, the better the sensitivity is, but it takes longer time to calculate the positioning position. On the other hand, as the signal strength threshold is set higher, the accuracy of the positioning position is improved, but the possibility that the positioning position cannot be calculated increases.
In this regard, according to the configuration of the second invention, for example, positioning is performed by appropriately combining each integration time and each signal intensity threshold according to the reception state of the positioning basic code or a request from the user. be able to.

  According to a third aspect of the present invention, in the configuration of the second aspect of the present invention, the signal strength threshold is configured to be changeable in a state where each of the integration times is set.

According to the configuration of the third aspect of the invention, the positioning device can calculate the positioning position by changing the signal strength threshold when the positioning position cannot be calculated in the state where each integration time is set. Can be.
In addition, since there are three types of signal strength thresholds, even if the signal strength is low level, if the signal strength level is a high low level, the positioning position can be secured while ensuring accuracy by setting the second signal threshold value. Can be calculated.
Furthermore, when the signal intensity is extremely low, setting the third signal threshold value can improve the possibility that the positioning position can be calculated although the accuracy is deteriorated.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, a change from the first integrated time to the second integrated time and a change from the first integrated time to the third integrated time. A change from the second integration time to the third integration time, a change from the second integration time to the first integration time, and a change from the third integration time to the second integration time. And a positioning device that can be changed from the third integrated time to the first integrated time.

  According to the structure of 4th invention, the said positioning apparatus can change the said integration time suitably according to the signal strength of the said positioning basic code, or a user's request | requirement.

  According to a fifth aspect of the invention, in the configuration of the first aspect of the invention, a normal mode for positioning using the first integration time and the first signal strength threshold, and the second integration time and the second signal strength threshold are used. Using the first high sensitivity mode for positioning, the second high sensitivity mode for positioning using the third integration time and the first signal strength threshold, the third integration time and the third signal strength threshold. Thus, the positioning device is configured to be capable of executing the third high sensitivity mode for positioning.

  According to a sixth aspect of the present invention, in the configuration of the fifth aspect of the present invention, the normal mode can be shifted to the first high sensitivity mode or the second high sensitivity mode. 3. A positioning device configured to be able to shift to a high sensitivity mode.

  According to the seventh aspect of the present invention, a positioning device that receives a positioning basic code from a transmission source, performs a correlation process consisting of coherent and incoherent, and positions a current position, starts positioning. A starting step; a drift calculating step in which the positioning device calculates a drift of a reference oscillator of the positioning device; a drift error calculating step in which the positioning device calculates a drift error that is an error of the drift; and the positioning device A drift error evaluation step for determining whether or not the drift error is within a predetermined error tolerance range, and the positioning device has the drift error within the error tolerance range in the drift error evaluation step. An integrated time extending step for extending the integrated time for performing the incoherent when the determination is made; and the positioning device A signal strength threshold changing step for lowering a signal strength threshold capable of determining a phase of the positioning basic code when positioning is not completed within a predetermined time specified in advance. Achieved by the control method.

  According to the configuration of the seventh aspect of the invention, it is possible to use a positioning basic code having a weak signal strength and to perform positioning at a speed and accuracy according to the degree of the weak signal strength.

  In the configuration of the eighth invention, the object is to provide a positioning device that receives a positioning basic code from a transmission source, performs a correlation process including coherent and incoherent, and measures a current position. A positioning start step to start; a drift calculating step in which the positioning device calculates a drift of a reference oscillator of the positioning device; and a drift error calculating step in which the positioning device calculates a drift error that is an error of the drift; A drift error evaluation step in which the positioning device determines whether or not the drift error is within a predetermined error allowable range; and the positioning device has the drift error within the error allowable range in the drift error evaluation step. If it is determined that the accumulated time for performing the incoherent is extended, And a signal strength threshold changing step for lowering a signal strength threshold that can determine the phase of the positioning basic code when the positioning device does not complete positioning within a predetermined time specified in advance. This is achieved by a control program for the positioning device.

  According to the configuration of the seventh aspect of the invention, it is possible to use a positioning basic code having a weak signal strength and to perform positioning at a speed and accuracy according to the degree of the weak signal strength.

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
The embodiments described below are preferred specific examples of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. Unless otherwise stated, the present invention is not limited to these embodiments.

FIG. 1 is a schematic diagram illustrating a terminal 20 and the like according to the embodiment of this invention.
As shown in FIG. 1, the terminal 20 can receive radio waves S1, S2, S3 and S4 from GPS satellites 12a, 12b, 12c and 12d which are positioning satellites. The GPS satellite 12a or the like is an example of a transmission source.
Various codes (codes) are carried on the radio wave S1 and the like. One of them is the C / A code Sca. The C / A code Sca is a signal having a bit rate of 1.023 Mbps and a bit length of 1,023 bits (= 1 msec). The C / A code Sca is composed of 1023 chips. The terminal 20 is an example of a positioning device that measures the current position, and performs positioning of the current position using the C / A code. This C / A code Sca is an example of a positioning basic code.

  Moreover, there are almanac Sal and ephemeris Seh as information put on the radio wave S1 and the like. Almanac Sal is information indicating general satellite orbits of all GPS satellites 12a and the like, and Ephemeris Seh is information indicating precise satellite orbits of the respective GPS satellites 12a and the like. Almanac Sal and Ephemeris Seh are collectively called navigation messages.

For example, the terminal 20 can receive C / A codes from three or more different GPS satellites 12a and the like, and can determine the current position.
First, the terminal 20 specifies to which GPS satellite the received C / A code corresponds. Next, by identifying the phase of the C / A code, the distance between each GPS satellite 12a and the like and the terminal 20 (hereinafter referred to as a pseudorange) is calculated. Subsequently, the current position is calculated based on the position of each GPS satellite 12a or the like on the satellite orbit at the current time and the pseudo distance described above.
The terminal 20 performs correlation processing described later in order to specify the phase of the above-described C / A code. This correlation process consists of coherent and incoherent.

The terminal 20 can communicate with other terminals via the communication base station 50. The communication base station 50 is, for example, a mobile phone communication base station.
Note that, unlike the present embodiment, the terminal 20 may perform positioning using radio waves from the communication base station 50, for example. Further, unlike the present embodiment, the terminal 20 may perform positioning by receiving radio waves from a LAN (Local Area Network).

(Main hardware configuration of terminal 20)
FIG. 2 is a schematic diagram showing a main hardware configuration of the terminal 20.
As shown in FIG. 2, the terminal 20 has a computer, and the computer has a bus 22. A CPU (Central Processing Unit) 24, a storage device 26, and the like are connected to the bus 22. The storage device 26 is, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), or the like.
In addition, an input device 28, a power supply device 30, a GPS device 32, a display device 34, a communication device 36, and a clock 38 are connected to the bus 22.

(About the configuration of the GPS device 32)
FIG. 3 is a schematic diagram showing the configuration of the GPS device 32.
As shown in FIG. 3, the GPS device 32 includes an RF unit 32a and a baseband unit 32b.
The RF unit 32a receives the radio wave S1 and the like with the antenna 33a. Then, the LNA 33b as an amplifier amplifies a signal such as a C / A code carried on the radio wave S1. Then, the mixer 33c down-converts the signal frequency. Then, the quadrature (IQ) detector 33d performs IQ separation on the signal. Subsequently, the A / D converters 33e1 and 33e2 are configured to convert the IQ-separated signals into digital signals, respectively.
The baseband unit 32b receives the signal converted into the digital signal from the RF unit 32a, samples and integrates each chip (not shown) of the signal, and the C / A code held by the baseband unit 32b It is comprised so that it may take a correlation with. The baseband unit 32b has, for example, 128 correlators (not shown) and accumulators (not shown), and can perform correlation processing at 128 phases simultaneously.
As described above, the correlation processing includes coherent and incoherent.
The correlator is configured to perform coherent processing. The accumulator is configured to perform incoherent processing.
Coherent is a process in which the baseband unit 32b correlates the received C / A code with the replica C / A code.
For example, if the coherent time is 10 msec, a correlation value between the C / A code and the replica C / A code synchronously integrated in the time of 10 msec is calculated. As a result of the coherent processing, a correlated phase and a correlation value are output.
Incoherent is a process of calculating an incoherent value by accumulating correlation values of coherent results.
Incoherent is a process of calculating an incoherent value by accumulating the correlation accumulated value of the coherent result.
As a result of the correlation processing, the phase output by the coherent processing and the incoherent value are output.

(About main software configuration of terminal 20)
FIG. 4 is a schematic diagram showing a main software configuration of the terminal 20.
As shown in FIG. 4, the terminal 20 includes a control unit 100 that controls each unit, a GPS unit 102 corresponding to the GPS device 32 in FIG. 2, a communication unit 104 corresponding to the communication device 36, and a time measuring unit 106 corresponding to the clock 38. Etc.
The terminal 20 also includes a first storage unit 110 that stores various programs and a second storage unit 150 that stores various information.

As illustrated in FIG. 4, the terminal 20 stores a navigation message 152 in the second storage unit 150. The navigation message 152 includes an almanac 152a and an ephemeris 152b.
The terminal 20 uses the almanac 152a and the ephemeris 152b for positioning.

  As illustrated in FIG. 4, the terminal 20 stores a positioning program 112 in the first storage unit 110.

5, 6, and 7 are explanatory diagrams of a positioning method based on the positioning program 112.
As shown in FIG. 5A, the control unit 100 calculates the estimated frequency A by adding the Doppler shift H2 and the drift DR to the transmission frequency H1 from the observable GPS satellite 12a or the like.
The control unit 100 refers to the almanac 152a to determine a GPS satellite 12a that can be observed from the current approximate position at the current time measured by the time measuring unit 106. As the current approximate position, the initial position Q0 shown in the initial position information 154 (see FIG. 4) is used. The initial position Q0 is, for example, the previous positioning position.
The transmission frequency H1 from the GPS satellite 12a or the like is known, for example, 1,575.42 MHz.
The Doppler shift H <b> 2 is caused by relative movement between each GPS satellite 12 a and the terminal 20. The control unit 100 calculates the line-of-sight speed (speed relative to the direction of the terminal 20) of each GPS satellite 12a and the like at the current time by the ephemeris 152b. Then, the Doppler shift H2 is calculated based on the line-of-sight speed.
The control unit 100 calculates an estimated frequency A for each GPS satellite 12a and the like.
The drift DR is a change in the oscillation frequency due to a temperature change of the clock (reference oscillator: not shown) of the terminal 20. This drift DR is set to, for example, 500 hertz (Hz), which is an average drift of the clock of the terminal 20 in advance.

As shown in FIG. 5B, the control unit 100 performs correlation processing by dividing one chip of the C / A code, for example, at equal intervals by the baseband unit 32b. One chip of the C / A code is divided into, for example, 32 equal parts. That is, the correlation processing is performed at the phase width (first phase width W1) interval of 1/32 chips. The phase of the first phase width W1 interval when the control unit 100 performs the correlation process is referred to as a first sampling phase SC1.
For example, the control unit 100 searches the first chip to the 1023th chip of the C / A code.
At this time, as shown in FIG. 5C, the control unit 100 searches for the radio wave S1 and the like at a frequency having a predetermined width with the estimated frequency A as the center. For example, the radio wave S1 and the like are searched for in a frequency step every 100 Hz in a frequency range from (A-100) Hz to (A + 100) Hz.

The correlation process is composed of coherent and incoherent.
Coherent is a process in which the baseband unit 32b correlates each chip of the received C / A code and replica C / A code.
For example, as shown in FIG. 6A, if the coherent time α is 10 msec, a correlation integrated value or the like at a time of 10 msec is calculated. As a result of the coherent processing, a correlated phase and a correlation integrated value are output.
Incoherent is a process of calculating an incoherent value by accumulating the correlation accumulated value of the coherent result in the incoherent time β. The incoherent time is 8 seconds (s) in the normal mode.
As a result of the correlation processing, the phase output by the coherent processing and the incoherent value are output. The correlation value P is an incoherent value.
As shown in FIG. 6B, the baseband unit 32b outputs a correlation value P corresponding to the phases C1 to C64 for two chips. Each of the phases C1 to C64 is the first sampling phase SC1.

  The control unit 100 specifies the first positioning phase CP1 that is the phase corresponding to the maximum correlation value Pmax. At this time, the first positioning phase CP1 is specified only when the reliability R exceeds a reliability threshold γ described later. This is because when the reliability R does not exceed the reliability threshold γ, the correlation result lacks reliability, and accurate positioning cannot be performed. As shown in FIG. 6B, the reliability R is calculated by dividing the difference between Pmax and Pnoise by Pmax.

After calculating the first positioning phase CP1 once, the control unit 100 performs a search around the first positioning phase CP1.
For example, the control unit 100 searches for a range of ± 256 chips around the already calculated first positioning phase CP1.
As for the frequency, a range of ± 1.0 kHz is searched in 100 Hz steps centering on the estimated frequency when the maximum correlation value Pmax is calculated.

As shown in FIG. 7, for example, it can be considered that n C / A codes are continuously arranged between the GPS satellite 12 a and the terminal 20. Since the distance between the GPS satellite 12a and the terminal 20 is not necessarily an integer multiple of the length of the C / A code, there is a code fraction C / Aa. That is, between the GPS satellite 12a and the terminal 20, there are a part that is an integral multiple of the C / A code and a fractional part. The total length of the integral multiple of the C / A code and the fractional part is the pseudorange. The terminal 20 performs positioning using this pseudo distance.
The position of the GPS satellite 12a in the orbit can be calculated using the ephemeris 152b. Then, by calculating the distance between the position of the GPS satellite 12a in the orbit and the initial position Q0, a portion that is an integral multiple of the C / A code can be specified.
Then, as shown in FIG. 7, the correlation process is performed while moving the phase of the replica C / A code in the direction of the arrow X1, for example.
The phase with the maximum correlation value is the code fraction C / Aa.

The control unit 100 calculates a pseudo distance between each GPS satellite 12a and the terminal 20 based on the code fraction C / Aa corresponding to three or more GPS satellites 12a and the like. The position of each GPS satellite 12a or the like in the orbit is calculated by the ephemeris 152b. Then, based on the positions of the three or more GPS satellites 12a or the like in the orbit and the pseudo distance, the current position is measured and the positioning position Q1 is calculated.
The control unit 100 stores positioning position information 156 indicating the positioning position Q1 in the second storage unit 150.

FIG. 8 is an explanatory diagram of the positioning program 112.
As shown in FIG. 8A, the coherent time α is set to 10 milliseconds (ms), for example.
As the incoherent time β, any one of 4 seconds (s), 24 seconds (s), and 64 seconds (s) can be set. The incoherent time β is an example of an accumulated time. 4 seconds (s) is an example of the first integration time. 24 seconds (s) is an example of the second accumulated time. 64 seconds (s) is an example of the third integration time.

  Further, any one of 0.7, 0.4, and 0.2 can be set as the reliability threshold γ. The reliability threshold γ is an example of a signal strength threshold. 0.7 is an example of a first signal strength threshold. 0.4 is an example of the second signal strength threshold. 0.2 is an example of a third signal strength threshold.

As shown in FIG. 8B, positioning performed by setting the incoherent time β to 4 seconds (s) and the reliability threshold value to 0.7 is referred to as a normal mode. In this normal mode, when the signal strength is sufficiently strong, the positioning position Q1 can be calculated quickly. Further, the positioning position Q1 with high accuracy can be calculated in the normal mode.
This normal mode is a suitable positioning mode, for example, when the signal intensity input to the antenna 33a (see FIG. 3) is minus (−) 154 dBm or more (strong signal intensity).

Positioning performed by setting the incoherent time β to 24 seconds (s) and the reliability threshold value to 0.4 is referred to as a first high sensitivity mode. In the first high sensitivity mode, the positioning position Q1 can be calculated relatively early when the signal intensity is slightly weak. In addition, the positioning position Q1 with relatively high accuracy can be calculated by the first high sensitivity mode.
This first high sensitivity mode is suitable, for example, in the case of a signal intensity (weak signal intensity) of minus (−) 156 dBm or more and less than minus (−) 154 dBm.

Positioning performed by setting the incoherent time β to 64 seconds (s) and the reliability threshold value to 0.7 is referred to as a second high sensitivity mode. By this second high sensitivity mode, the positioning position Q1 can be calculated when the signal intensity is weak. Further, the positioning position Q1 with high accuracy can be calculated by the second high sensitivity mode.
This second high sensitivity mode is suitable for a signal intensity (very weak signal intensity) of minus (−) 160 dBm or more and less than minus (−) 156 dBm.

Positioning performed by setting the incoherent time β to 64 seconds (s) and the reliability threshold value to 0.2 is referred to as a third high sensitivity mode. With this third high sensitivity mode, the positioning position Q1 can be calculated when the signal intensity is weak. In addition, although the accuracy is degraded by the third high sensitivity mode, the possibility that the positioning position Q1 can be calculated is improved.
This third high sensitivity mode is suitable when it is desired to increase the possibility that the positioning position Q1 can be calculated in a very weak signal usage.
The first high sensitivity mode, the second high sensitivity mode, and the third high sensitivity mode are collectively referred to as a high sensitivity mode.

As illustrated in FIG. 4, the terminal 20 stores a positioning position output program 114 in the first storage unit 110. The positioning position output program 114 displays the positioning position Q1 calculated by the control unit 100 in the normal mode, the first high sensitivity mode, the second high sensitivity mode, or the third high sensitivity mode on the display device 34 (see FIG. 2). It is a program for.
Note that the terminal 20 is initially set to start positioning in the normal mode.

  As illustrated in FIG. 4, the terminal 20 stores a drift calculation program 116 in the first storage unit 110.

FIG. 9 is an explanatory diagram of the drift calculation program 116.
As shown in FIG. 9, the control unit 100 first calculates a position Qg on the orbit of the GPS satellite 12a or the like at the current time with reference to the ephemeris 152b, for example.
Subsequently, radio waves S1 and the like from three or more GPS satellites 12a and the like are received, preliminary positioning is performed, and a positioning position Qpre is calculated. The terminal 20 can calculate the positioning position Qpre if it can receive the radio wave S1 having a strong signal intensity from at least three GPS satellites 12a. However, in positioning, by using a larger number of GPS satellites, it is possible to improve PDOP (Position Division Of Precision) and the like, and positioning accuracy is improved. Since the positioning position Qpre is not displayed on the display device 34, the position accuracy may not be good. For this reason, in the preliminary positioning, it is sufficient that the radio wave S1 having a strong signal intensity can be received from the three GPS satellites 12a and the like.
Subsequently, the Doppler shift H2 is calculated using the ephemeris 152b, the satellite position Qg, and the positioning position Qpre.
The reception frequency H3 is obtained by adding the Doppler shift H2 and the drift DR to the oscillation frequency H1 from the GPS satellite 12a or the like.
For this reason, drift DR is computable by Formula 2 of FIG. That is, the drift DR can be calculated by subtracting the oscillation frequency H1 and the Doppler shift H2 from the reception frequency H3.
The control unit 100 stores drift information 158 indicating the drift DR in the second storage unit 150.
This drift DR is a drift of a reference oscillator (not shown) of the terminal 20.
The drift calculation program 116 and the control unit 100 are an example of drift calculation means.

  As illustrated in FIG. 4, the terminal 10 stores a drift error calculation program 118 in the first storage unit 110.

FIG. 10 is an explanatory diagram of the drift error calculation program 118.
As illustrated in FIG. 10A, the control unit 100 calculates the drift error DRe according to Equation 3. That is, the drift error DRe is calculated by adding the position error dP to the time error dt and further adding the product of the elapsed time Δt and the elapsed time factor error bHz. The drift error calculation program 122b and the control unit 100 are an example of drift error calculation means.
The time error dt is a time error of the time measuring unit 106. For example, immediately after the positioning is completed, the time error of the time measuring unit 106 is calculated by the positioning calculation, and the time error can be corrected. Therefore, the time error dt is 1 millisecond (ms). For example, the time error dt increases as 10 milliseconds (ms), 1 second (s), and 10 seconds (s) as time elapses from the end of positioning. The time error dt is converted into a frequency error. For example, 1 millisecond (ms) corresponds to 5 hertz (Hz), 10 milliseconds (ms) corresponds to 10 hertz (Hz), and 1 second (s) corresponds to 15 hertz (Hz). 10 seconds (s) corresponds to 30 hertz (Hz).

  The position error dP is a positioning error of the positioning position Qpre in the preliminary positioning. When the signal intensity is small or when the PDOP (Position Dilution Of Precision) is large, the position error dP becomes large. The position error dP is converted into a frequency error. For example, 5 meters (m) corresponds to 5 hertz (Hz), 10 meters (m) corresponds to 10 hertz (Hz), and 30 meters (m) corresponds to 15 hertz (Hz).

The elapsed time factor error bHz is due to the expansion of the drift error due to factors other than the above-described time error dt and position error dP. According to the simulation, for example, the 1 Hz drift error Dre increases per second.
The elapsed time Δt is reset to 0 when the time error dt or the position error dP is updated.
As shown in FIG. 10B, the drift error Dre is an error of the drift DR.
When the control unit 100 can calculate a plurality of drift errors DRe by combining a plurality of signals S1, etc., the control unit 100 sets the average value as the drift error DRe. By using the average value as the drift error DRe, accuracy and reliability are higher than in the case of generating using a set of one GPS satellite.
The control unit 100 stores the drift error information 160 indicating the drift error DRe in the second storage unit 150.

  As illustrated in FIG. 4, the terminal 20 stores a drift error evaluation program 120 in the first storage unit 110. The drift error evaluation program 120 is a program for the control unit 100 to determine whether or not the drift error DRe is within ± 50 hertz (Hz), which is a predetermined range. A frequency range within ± 50 hertz (Hz) is an example of an allowable error range. The drift error evaluation program 120 and the control unit 100 are an example of drift error evaluation means.

As illustrated in FIG. 4, the terminal 20 stores an incoherent time setting program 122 in the first storage unit 110. The incoherent time setting program 122 is a program for the control unit 100 to set the incoherent time β (see FIG. 8). The incoherent time setting program 122 and the control unit 100 are examples of integrated time setting means.
The control unit 100 is configured to set the incoherent time β based on the evaluation result by the drift error evaluation program 120. This means that the control unit 100 is configured to set the incoherent time β based on the drift error DRe.
Specifically, if the drift error DRe is within ± 50 hertz (Hz), the control unit 100 sets the incoherent time β to 64 seconds (s). At this time, the incoherent time β is set to 64 seconds regardless of the elapsed time from the start of the normal mode. For this reason, it is possible to shift to the high sensitivity mode at an early stage.
On the other hand, when the drift error DRe is not within ± 50 hertz (Hz), the control unit 100 maintains the incoherent time β at the initial 8 seconds (s).

As illustrated in FIG. 4, the terminal 20 stores a reliability threshold setting program 124 in the first storage unit 110. The reliability threshold setting program 124 is a program for the control unit 100 to set the reliability threshold γ (see FIG. 8). The reliability threshold setting program 124 and the control unit 100 are an example of a signal strength threshold setting unit.
Specifically, the control unit 100 sets the reliability threshold value γ to be low when the positioning position Q1 is not calculated within a predetermined time.
For example, in the second high sensitivity mode in which the incoherent time β is set to 64 seconds and the reliability threshold γ is set to 0.7, if the positioning position Q1 cannot be calculated even after 128 seconds (s), the reliability The threshold value γ is changed to 0.2, and the mode shifts to the third high sensitivity mode. The transition from the second high sensitivity mode to the third high sensitivity mode means that the reliability threshold value γ is lowered in a state where the incoherent time β is set to 64 seconds.
That is, the above-mentioned incoherent time setting program 122 cannot calculate the positioning position Q1 within a predetermined time after shifting to the high sensitivity mode without waiting for a predetermined time while maintaining the reliability threshold γ. For the first time, the reliability threshold γ can be lowered.
Accordingly, it is possible to calculate the positioning position Q1 with high accuracy in the high sensitivity mode according to the reception state of the drift error DRe and the radio wave S1, and improve the possibility of calculating the positioning position Q1 with low accuracy. It can also be made.
Further, for example, in the normal mode, the positioning position Q1 is calculated even though 24 seconds (s) has elapsed or all the steps of incoherent for 4 seconds (see FIG. 5C) have been completed. If not, the reliability threshold γ is changed to 0.4. At this time, the control unit 100 sets the incoherent time β to 24 seconds based on the incoherent time setting program 122 described above. This means shifting from the normal mode to the first high sensitivity mode. Thereby, although the accuracy is relatively low, the possibility that the positioning position Q1 can be calculated is improved.

The terminal 20 is configured as described above.
The terminal 20 can set, as the incoherent time β, 24 seconds (s) defined as a time longer than the initial setting of 4 seconds (s), and more than 24 seconds (s). 64 seconds (s), which is defined as a long time, can be set.
The longer the incoherent time β, the clearer the C / A code can be distinguished from noise in the correlation process. This is particularly effective when the signal strength is weak. Here, when the drift error DRe is large, the frequency of the received C / A code and the frequency of the replica C / A code are different from each other. Therefore, the degree of improvement in sensitivity when the incoherent time β is increased is small.
In this respect, since the terminal 20 is configured to set the incoherent time β based on the drift error DRe of the reference oscillator of the terminal 20, the sensitivity is surely improved by increasing the incoherent time β. be able to.
Further, the terminal 20 can set 0.4, which is defined as a signal strength threshold lower than 0.7, which is the initial setting, as the reliability threshold γ, and a signal lower than 0.4. 0.2 defined as the intensity threshold can be set.
When the signal intensity is weak, positioning can be performed with high accuracy by setting the incoherent time β long and setting the signal intensity threshold γ high.
Further, when the signal strength is weak, the current signal strength threshold γ may not reach the signal strength threshold γ, and the positioning position Q1 may not be calculated. Here, if the signal strength threshold γ is set low, the position accuracy is degraded, but the possibility that the positioning position Q1 can be calculated is improved.
In addition, when the signal strength is strong, the terminal 20 performs quick and accurate positioning by using, for example, 4 seconds as the incoherent time β and 0.7 as the signal strength threshold γ. Can do.
As described above, since the terminal 20 can change or set the incoherent time β and the signal strength threshold γ separately, the terminal 20 can perform positioning at a speed and accuracy according to the drift error Dre and the signal strength. .
As a result, a positioning basic code with weak signal strength can be used, and positioning can be performed at a speed and accuracy according to the degree of weakness of signal strength.

As described above, the longer the incoherent time β is set, the more the sensitivity is improved, but it takes a longer time to calculate the positioning position Q1. On the other hand, as the signal strength threshold γ is set higher, the accuracy of the positioning position Q1 is improved, but the possibility that the positioning position Q1 cannot be calculated increases.
In this regard, the terminal 20 can perform positioning by combining the incoherent time β and the signal strength threshold γ as appropriate in accordance with, for example, the reception state of the C / A code or a request from the user.

Further, the terminal 20 is configured to be able to change the signal strength threshold γ in a state where the incoherent time β is set to a predetermined time.
For this reason, in a state where the incoherent time β is set to a predetermined time and the positioning position Q1 cannot be calculated, the terminal 20 reduces the signal strength threshold γ stepwise to ensure accuracy, It is possible to calculate the positioning position Q1.
Hereinafter, an operation example of the terminal 20 will be described with reference to FIG.

FIG. 11 is a schematic flowchart illustrating an operation example of the terminal 20.
First, the terminal 20 starts a normal mode (step ST1 in FIG. 11). This step ST1 is an example of a positioning start step.
Subsequently, the terminal 20 calculates the drift DR (step ST2). This step ST2 is an example of a drift calculation step.

Subsequently, the terminal 20 calculates a drift error (step ST3). This step ST3 is an example of a drift error calculating step.
Subsequently, the terminal 20 determines whether or not the drift error DRe is within ± 50 hertz (Hz) (step ST4). This step ST4 is an example of a drift error evaluation step.

  When determining that the drift error DRe is within ± 50 hertz (Hz) in step ST4, the terminal 20 changes the incoherent time β to 64 seconds (s) (step 5). This step ST5 is an example of an integration time extension step.

Subsequently, the terminal 20 determines whether 128 seconds (s) have elapsed (step ST6).
If it is determined in step ST6 that the terminal 20 has passed 128 seconds (s), it is determined whether or not the positioning position Q1 has been calculated (step ST7). In step ST7, it is determined whether or not the positioning position Q1 has been calculated between the change of the incoherent time β to 64 seconds (s) and the current time.

When determining that the positioning position Q1 is calculated in step ST7, the terminal 20 repeats step ST6 and subsequent steps again.
On the other hand, when determining that the positioning position Q1 is not calculated in step ST7, the terminal 20 changes the reliability threshold value γ to 0.2 (step ST8). This step ST8 is an example of a signal strength threshold value changing step.

Subsequently, the terminal 20 determines whether or not the normal mode transition condition is satisfied that the number of GPS satellites being tracked is 3 or more and the average signal strength is −154 dBm or more (step ST9).
If the terminal 20 determines in step ST9 that the normal mode transition condition is not satisfied, step ST6 and subsequent steps are repeated. In step ST6 after the second time, the terminal 20 determines an elapsed time since the previous positioning position Q1 was calculated.
On the other hand, if the terminal 20 determines in step ST9 that the normal mode transition condition is satisfied, step ST1 and the subsequent steps are repeated.

  When the terminal 20 determines that the drift error DRe is not within ± 50 hertz (Hz) in step ST4 described above, the normal mode is continued (step ST5A).

Subsequently, the terminal 20 determines whether 24 seconds (s) has elapsed or whether all the steps of 4-second integration (incoherent) (see FIG. 5C) have been completed (step ST6A). . Here, since the correlation process takes the correlation between the C / A code and the replica C / A code for each frequency step (see FIG. 5C) around the estimated frequency A, the first time If the reliability threshold value γ is exceeded in this step, positioning is completed in the first 4 seconds. On the other hand, even if all the steps after the sixth time are completed, the reliability threshold γ may not be exceeded.
If it is determined in step ST6A that the terminal 20 has passed 24 seconds (s) or all steps of 4-second integration have been completed, it is determined whether or not the positioning position Q1 has been calculated (step ST7A). In step ST7A, it is determined whether or not the positioning position Q1 has been calculated from the start of the normal mode to the current time.

When determining that the positioning position Q1 is calculated in step ST7A, the terminal 20 repeats step ST6A and subsequent steps again. In the second step ST6A, the terminal 20 determines whether the elapsed time since the previous positioning position Q1 was calculated and whether all the steps of 4-second integration have been completed.
On the other hand, when determining in step ST7A that the positioning position Q1 has not been calculated, the terminal 20 changes the incoherent time β to 24 seconds (s) and changes the reliability threshold γ to 0.4. (Step ST8A).

Subsequently, terminal 20 determines whether or not the normal mode transition condition is satisfied that the number of GPS satellites being tracked is three or more and the average signal strength is −154 dBm or more (step ST9A).
In Step ST9A, when the terminal 20 determines that the normal mode transition condition is not satisfied, Step ST6A and the subsequent steps are repeated.
On the other hand, when the terminal 20 determines in step ST9A that the normal mode transition condition is satisfied, step ST1 and the subsequent steps are repeated.

  By the above-described steps, a positioning basic code having a weak signal strength can be used, and positioning can be performed at a speed and accuracy according to the degree of weakness of the signal strength.

(Modification)
The terminal 20 may calculate the drift DR by the method shown in FIG.
For example, a timing signal TM1 with a high-accuracy 1-second pulse is received from the communication base station, a timing difference with the 1-second pulse timing signal TM2 generated by the terminal 20 is calculated, and this timing difference may be used as the drift DR. . For example, if the timing signal TM1 is maintained as a 1-second pulse signal having an accuracy equivalent to the time accuracy of the GPS satellite 12a using the radio wave S1 from the GPS satellite 12a, the timing signal TM1 is used as a reference. The drift DR of the timing signal TM2 of the terminal 20 can be calculated.
Further, as shown in step ST41 of FIG. 13, the terminal 20 may determine whether the number of GPS satellites is 3 or more and the signal strength is −154 dBm or more after step ST4.
In step ST41, when the terminal 20 determines that the number of GPS satellites is 3 or more and the signal intensity is −154 dBm or more, the normal mode is continued without extending the incoherent time β ( Step ST5A in FIG. 13).
On the other hand, in step ST41, when the terminal 20 determines that the number of GPS satellites is 3 or more and the signal strength is not -154 dBm or more, the incoherent time β is extended (step ST5). .

  Thus, even if the drift error Dre is in the range of ± 50 hertz (Hz), if the number of GPS satellites is 3 or more and the signal strength is -154 dBm or more, the positioning position Q1 is set in the normal mode. Since there is a high possibility of being able to calculate, it is possible to maintain the normal mode in which the highly accurate positioning position Q1 can be calculated quickly.

The present invention is not limited to the embodiments described above. Furthermore, the above-described embodiments may be combined with each other.
For example, the incoherent time β is changed from 4 seconds (s) to 24 seconds, changed from 24 seconds to 64 seconds, changed from 24 seconds to 4 seconds, and changed from 64 seconds to 24 seconds. It may be possible to change from 64 seconds to 4 seconds. Thereby, the receiving state of the signal S1 and the like, and the positioning speed and positioning accuracy according to the user's request can be realized.

It is the schematic which shows the terminal etc. of embodiment of this invention. It is the schematic which shows the main hardware constitutions of a terminal. It is the schematic which shows the structure of a GPS apparatus. It is the schematic which shows the main software structures of a terminal. It is explanatory drawing of a positioning method. It is explanatory drawing of a positioning method. It is explanatory drawing of a positioning method. It is explanatory drawing of a positioning program. It is explanatory drawing of a drift calculation program. It is explanatory drawing of a drift error calculation program. It is a schematic flowchart which shows the operation example of a terminal. It is a figure which shows an example of the calculation method of a drift. It is a schematic flowchart which shows the operation example of a terminal.

Explanation of symbols

  12a, 12b, 12c, 12d ... GPS satellite, 20 ... terminal, 32 ... GPS device, 50 ... communication base station, 112 ... positioning program, 114 ... positioning position output program, 116 ... Drift calculation program, 118 ... Drift error calculation program, 120 ... Drift error evaluation program, 122 ... Incoherent time setting program, 124 ... Reliability threshold setting program

Claims (8)

A positioning device that receives a positioning basic code from a transmission source, performs a correlation process including coherent and incoherent, and positions a current position,
A first accumulated time which is an accumulated time for performing the incoherent;
A second accumulated time defined as an accumulated time longer than the first accumulated time;
A third integrated time defined as an integrated time longer than the second integrated time;
Integration time setting means for setting
A first signal strength threshold defined as a signal strength threshold capable of determining a phase of the positioning base code;
A second signal strength threshold defined as a signal strength threshold lower than the first signal strength threshold;
A third signal strength threshold defined as a signal strength threshold lower than the second signal strength threshold;
A signal strength threshold setting means for setting
Have
The positioning device, wherein the integrated time setting means sets the integrated time based on a drift error of a reference oscillator of the positioning device.   The positioning device according to claim 1, wherein any one of the accumulated times and any one of the signal intensity thresholds are combined.   The positioning device according to claim 1, wherein the signal intensity threshold is changeable in a state in which each integrated time is set.   A change from the first integration time to the second integration time; a change from the first integration time to the third integration time; a change from the second integration time to the third integration time; It is possible to change from 2 accumulated time to the first accumulated time, change from the 3rd accumulated time to the second accumulated time, and change from the 3rd accumulated time to the first accumulated time. The positioning device according to any one of claims 1 to 3, wherein the positioning device is provided. A normal mode for positioning using the first integration time and the first signal strength threshold;
A first high sensitivity mode for positioning using the second integration time and the second signal strength threshold;
A second high sensitivity mode for positioning using the third integration time and the first signal strength threshold;
A third high sensitivity mode for positioning using the third integration time and the third signal strength threshold;
The positioning device according to claim 1, wherein the positioning device is configured to be executable. The normal mode is configured to be able to shift to the first high sensitivity mode or the second high sensitivity mode,
The positioning device according to claim 5, wherein the positioning device is configured to be able to shift from the second high sensitivity mode to the third high sensitivity mode. A positioning device that receives a positioning basic code from a transmission source, performs a correlation process including coherent and incoherent, and positions a current position, a positioning start step for starting positioning,
A drift calculating step in which the positioning device calculates a drift of a reference oscillator of the positioning device;
A drift error calculating step in which the positioning device calculates a drift error that is an error of the drift; and
A drift error evaluation step in which the positioning device determines whether the drift error is within a predefined error tolerance; and
In the drift error evaluation step, when the positioning apparatus determines that the drift error is within the allowable error range, an integration time extension step of extending an integration time for performing the incoherence;
A signal strength threshold value changing step for lowering a signal strength threshold value that can determine the phase of the positioning basic code when the positioning device does not complete positioning within a prescribed time defined in advance;
A method for controlling a positioning device, comprising: On the computer,
A positioning device that receives a positioning basic code from a transmission source, performs a correlation process including coherent and incoherent, and positions a current position, a positioning start step for starting positioning,
A drift calculating step in which the positioning device calculates a drift of a reference oscillator of the positioning device;
A drift error calculating step in which the positioning device calculates a drift error that is an error of the drift; and
A drift error evaluation step in which the positioning device determines whether the drift error is within a predefined error tolerance; and
In the drift error evaluation step, when the positioning apparatus determines that the drift error is within the allowable error range, an integration time extension step of extending an integration time for performing the incoherence;
A signal strength threshold value changing step for lowering a signal strength threshold value that can determine the phase of the positioning basic code when the positioning device does not complete positioning within a prescribed time defined in advance;
A control program for a positioning device, characterized in that

Images