JP2007263659A - Positioning device, control method for positioning device, control program for positioning device, and computer-readable recording medium recorded with control program for positioning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positioning device and the like capable of enhancing sensitivity and capable of calculating a positioning position, even when a drift is generated and even when a signal intensity is very weak. <P>SOLUTION: This positioning device 20 for positioning a current position, by receiving a positioning fundamental code from a transmission source 12a or the like and by carrying out correlation processing comprising a coherence and an incoherence, is constituted to set the first integration time of a time for executing the incoherence, the second integration time specified as a time longer than the first integration time, and the third integration time specified as a time longer than the second integration time. <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, a positioning device control program, and a computer-readable recording medium that records the 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 of synchronously integrating the C / A codes received by the GPS receiver and correlating the integration result with the replica C / A code. 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 the C / A code is modulated by the navigation message, the polarity may be reversed every 20 milliseconds. This polarity inversion degrades the coherent value. As a result, the incoherent value is also deteriorated.
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, since the reference oscillator of the GPS receiver undergoes a frequency change due to temperature (hereinafter referred to as “drift”), there is a discrepancy between the frequency of the C / A code and the frequency of the replica C / A code. For this reason, in particular, when the signal strength from the GPS satellite is weak, there is a problem that the sensitivity may not be improved even if the polarity inversion is predicted. As a result, there is a problem that the positioning position cannot be calculated (positioning calculation does not converge).
In this specification, “signal strength” is used synonymously with “radio wave strength”.

Therefore, the present invention, even when drift occurs and the signal strength is weak,
It is an object to provide a positioning device capable of improving the sensitivity and calculating the positioning position, a positioning device control method, a positioning device control program, and a computer-readable recording medium recording the positioning device control program. .

  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 integrated time that is a time for performing the above, a second integrated time that is defined as a time longer than the first integrated time, a third integrated time that is specified as a time longer than the second integrated time, Is achieved by a positioning device characterized by being configured to be settable.

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 sensitivity can be improved as the integration time is longer. This is the same even when drift occurs and the signal intensity is weak.
For this reason, according to the configuration of the first invention, even when drift occurs and the signal strength is weak, the sensitivity can be improved and the positioning position can be calculated.
Further, as described above, the positioning device can set not only the first integrated time and the third integrated time but also the second integrated time. This means that even if the signal intensity is weak, the second integrated time or the third integrated time can be set according to the level of the weakness. For this reason, for example, the third integrated time is set when the signal strength is extremely weak, but the second integrated time is set when the signal strength is slightly weaker than the normal signal strength. can do. If the positioning position can be calculated in the second integration time, the positioning position can be calculated earlier than when the third integration time is used. Therefore, the positioning device can calculate the positioning position at an early stage according to the degree of weakness of the signal intensity.

  According to a second invention, in the configuration of the first invention, a first signal strength threshold defined as a signal strength capable of determining a phase of the positioning basic code, and a signal strength weaker than the first signal strength threshold And a third signal strength threshold that is defined as a signal strength that is weaker than the second signal strength threshold. .

According to the configuration of the second invention, the positioning device can set a second signal strength threshold defined as a signal strength that is weaker than the first signal strength threshold, and further, from the second signal strength threshold A third signal strength threshold defined as a weak signal strength can be set.
When the signal strength is weak, if the signal strength that can determine the phase of the positioning basic code is set high, the signal strength may not be reached and the positioning position may not be calculated. Here, if the signal strength capable of determining the phase of the positioning basic code is set weak, the positioning accuracy can be calculated, but the positioning position can be calculated.
For this reason, according to the configuration of the second invention, the positioning position can be calculated even when the signal strength is weak.
Further, as described above, the positioning device can set not only the first signal strength threshold and the third signal strength threshold but also the second signal strength threshold. This means that even if the signal strength is weak, the second signal strength threshold or the third signal strength threshold can be set according to the degree of the weakness. Therefore, for example, the third signal strength threshold is set when the signal strength is extremely weak, but the second signal strength threshold is set when the signal strength is slightly weaker than the normal signal strength. Can be set. If the positioning position can be calculated using the second signal strength threshold, it is possible to calculate a positioning position with higher accuracy than when the third signal strength threshold is used. For this reason, the positioning device can accurately calculate the positioning position according to the degree of weakness of the signal intensity.

  According to a third invention, in the configuration of the second invention, normal positioning means for performing a normal mode which is positioning using the first integrated time and the first signal strength threshold, the second integrated time and the second A first high-sensitivity positioning unit that performs a first high-sensitivity mode that is positioning using a signal strength threshold; and a first high-sensitivity mode that performs positioning using the third integration time and the third signal strength threshold. 2 high-sensitivity positioning means, allowable time lapse determining means for determining whether or not a predetermined allowable time has elapsed since the start of the normal mode, and when the allowable time has elapsed, the first And a high sensitivity mode starting means for starting the high sensitivity mode or the second high sensitivity mode.

According to the configuration of the third aspect of the invention, since the positioning device has the high sensitivity mode starting means, the first high sensitivity mode or the second high sensitivity mode is started when the allowable time has elapsed. be able to.
Since the normal positioning means performs positioning in the first integration time, the positioning result can be output quickly. Further, since the normal positioning means performs positioning using the first signal strength threshold, the accuracy of the positioning result is high. However, when the signal strength is weak, the first signal strength threshold may not be exceeded in the first integration time. As a result, the positioning position may not be calculated.
In this regard, since the positioning device can start the first high sensitivity mode or the second high sensitivity mode when the allowable time has elapsed, positioning is possible even when the signal strength is weaker. The position can be calculated.

  According to a fourth aspect of the present invention, there is provided the drift calculating means for calculating the drift of the reference oscillator of the positioning device and the drift for calculating the drift error as the drift error in the configuration of the second aspect or the third aspect. An error calculating means; a drift error evaluating means for determining whether or not the drift error is within a predetermined allowable error range; and the first high sensitivity mode or the second based on an evaluation result of the drift error evaluating means. And a high-sensitivity mode selection means for starting one of the high-sensitivity modes.

According to the configuration of the fourth invention, since the positioning device has the high sensitivity mode selection means, the first high sensitivity mode or the second high sensitivity mode is selected based on the evaluation result of the drift error evaluation means. Can start.
As the drift error is smaller, the positioning device can generate a reception frequency that matches the frequency of the positioning basic code. For this reason, a sensitivity improves. This means that when the drift error is small, the accuracy of the positioning position can be ensured even if the third signal strength threshold is used.
In this regard, for example, when the drift error is not within the allowable error range, the positioning device starts the first high sensitivity mode, and the drift error is within the allowable error range and is sufficiently small. In this case, since the second high sensitivity mode is started, the accuracy of the positioning position can be ensured according to the drift error even if the signal intensity is weak.

  According to the fifth 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 in the first integration time. A normal mode start step for starting a normal mode for performing positioning; an allowable time elapse determination step for determining whether or not a predetermined allowable time has elapsed since the positioning device started the normal mode; The positioning device calculates a drift of a reference oscillator of the positioning device, a drift calculation step where the positioning device calculates a drift error, and the positioning device predefines the drift error. A drift error evaluation step for determining whether or not it is within the allowable error range, and positioning is performed in a second integration time longer than the first integration time. And a high sensitivity mode start step for starting a second high sensitivity mode in which positioning is performed in the first high sensitivity mode or in a third integration time longer than the second integration time. Achieved by:

  According to the configuration of the fifth invention, even when drift occurs and the signal intensity is weak, the sensitivity can be improved and the positioning position can be calculated.

  According to the sixth aspect of the present invention, there is provided a positioning apparatus that receives a positioning basic code from a transmission source, performs a correlation process including coherent and incoherent, and determines a current position. A normal mode start step for starting a normal mode for positioning in the accumulated time, and an allowable time elapse determination for determining whether or not a predetermined allowable time has elapsed since the positioning device started the normal mode. 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 an error in the drift, and the positioning device in the drift error Drift error evaluation step for determining whether or not is within a predetermined allowable error range, and a second accumulated time longer than the first accumulated time And a high sensitivity mode start step of starting a second high sensitivity mode for performing positioning in a third integrated time longer than the second integrated time. This is achieved by a positioning device control program.

  According to the seventh aspect of the present invention, there is provided a positioning apparatus that receives a positioning basic code from a transmission source, performs correlation processing including coherent and incoherent, and determines a current position in a computer. A normal mode start step for starting a normal mode for positioning in the accumulated time, and an allowable time elapse determination for determining whether or not a predetermined allowable time has elapsed since the positioning device started the normal mode. 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 an error in the drift, and the positioning device in the drift error Drift error evaluation step for determining whether or not is within a predetermined allowable error range, and a second accumulated time longer than the first accumulated time And a high sensitivity mode start step of starting a second high sensitivity mode for performing positioning in a third integrated time longer than the second integrated time. This is achieved by a computer-readable recording medium that records a control program for the positioning device.

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.
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 normal mode program 112 in the first storage unit 110.

FIG. 5 is an explanatory diagram of the normal mode program 112.
As shown in FIG. 5, in the normal mode program 112, the coherent time α1 is set to 10 milliseconds (ms), the incoherent time β1 is set to 8 seconds (s), and the reliability threshold value γ1 is set to 0.7. The incoherent time β1 is an example of a first integration time. The reliability threshold γ1 is an example of a first signal strength threshold. The reliability threshold γ1 is defined as a signal strength that can specify the code phase of the C / A code with a predetermined accuracy. Here, the predetermined accuracy is an error range in which the positioning position error is within 5 meters, for example, in the positioning result using the code phase.
The normal mode program 112 is a program for the control unit 100 to perform positioning using the incoherent time β1 and the reliability threshold value γ1. That is, the normal mode program 112 and the control unit 100 are examples of normal positioning means.
Positioning based on the normal mode program 112 is referred to as a normal mode.

6 to 8 are explanatory diagrams of the positioning method.
As shown in FIG. 6A, 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 the GPS satellites 12a and the like that can be observed at the current time measured by the time measuring unit 106. 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. 6B, 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.
As shown in FIG. 5B, the baseband unit 32b outputs correlation values P corresponding to the phases C1 to C64 for two chips. Each of the phases C1 to C64 is the 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, for this reason, the control unit 100 searches for the radio wave S1 and the like at a frequency having a predetermined width around the estimated frequency A. For example, the radio wave S1 and the like are searched for in a frequency range of (A-100) Hz to a frequency of (A + 100) Hz at a frequency of 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. 7A, 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.
A graph (hereinafter referred to as “correlation graph”) showing the phases C1 to C64 and the correlation value P subjected to the correlation processing is as shown in FIG.

  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 the reliability threshold value α1. This is because when the reliability R does not exceed the reliability threshold value α1, the correlation result lacks reliability, and accurate positioning cannot be performed. As shown in FIG. 7B, 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, the range of ± 1.0 kHz is searched in units of 100 Hz with the estimated frequency A as the center.

As shown in FIG. 8, 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 part 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, it is possible to specify an integer multiple of the C / A code.
Then, as shown in FIG. 8, 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. Then, the position of each GPS satellite 12a or the like in the orbit is calculated by the epheris 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.

  As illustrated in FIG. 4, the terminal 20 stores a first high sensitivity mode program 114 in the first storage unit 110.

FIG. 9 is an explanatory diagram of the first high sensitivity mode program 114.
As shown in FIG. 9, in the first high sensitivity mode program 114, the coherent time α2 is set to 10 milliseconds (ms), the incoherent time β2 is set to 24 seconds (s), and the reliability threshold value γ2 is set to 0.4. ing. The incoherent time β2 is defined as a time longer than the incoherent time β1 described above. This incoherent time β2 is an example of a second accumulated time. The reliability threshold γ2 is defined as a signal strength weaker than the reliability threshold γ1. The reliability threshold γ2 is an example of a second signal strength threshold.
The first high sensitivity mode program 114 is a program for the control unit 100 to perform positioning in the incoherent time β2 and the reliability threshold value γ2. The first high sensitivity mode program 114 and the control unit 100 are an example of first high sensitivity positioning means.
Positioning based on the first high sensitivity mode program 114 is referred to as a first high sensitivity mode.
The positioning method is the same as that of the normal mode program 112 described above.
However, since the incoherent time β2 is longer than the incoherent time β1, the positioning by the first high sensitivity mode program 114 is more sensitive than the positioning by the normal mode program 112. Further, since the reliability threshold γ2 is lower than the reliability threshold γ1, there is a high possibility that the positioning position Q1 can be calculated.

  As illustrated in FIG. 4, the terminal 20 stores a second high sensitivity mode program 116 in the first storage unit 110.

FIG. 10 is an explanatory diagram of the second high sensitivity mode program 116.
As shown in FIG. 10, in the second high sensitivity mode program 116, the coherent time α3 is set to 10 milliseconds (ms), the incoherent time β3 is set to 64 seconds (s), and the reliability threshold value γ3 is set to 0.2. ing. The incoherent time β3 is defined as a time longer than the incoherent time β2. This incoherent time β3 is an example of a third integration time. The reliability threshold γ3 is defined as a signal strength weaker than the reliability threshold γ2. The reliability threshold γ3 is an example of a second signal strength threshold.
The second high sensitivity mode program 116 is a program for the control unit 100 to perform positioning in the incoherent time β3 and the reliability threshold value γ3. The second high sensitivity mode program 116 and the control unit 100 are an example of second high sensitivity positioning means.
Positioning based on the second high sensitivity mode program 116 is referred to as a second high sensitivity mode.
The positioning method is the same as that of the normal mode program 112 described above.
However, since the incoherent time β3 is longer than the incoherent time β2, the positioning by the second high sensitivity mode program 116 is more sensitive than the positioning by the first high sensitivity mode program 114. Further, since the reliability threshold γ3 is lower than the reliability threshold γ2, there is a high possibility that the positioning position Q1 can be calculated.

The above-described normal mode is a positioning mode in which the positioning position Q1 can be calculated, for example, when the signal intensity input to the antenna 33a (see FIG. 3) is minus (−) 154 dBm or more.
The first high sensitivity mode is, for example, a positioning mode in which the positioning position Q1 can be calculated at a signal intensity of minus (−) 156 dBm or more. The first high sensitivity mode is suitable for a signal intensity of minus (−) 156 dBm or more and less than minus (−) 154 dBm.
The second high sensitivity mode is, for example, a positioning mode in which the positioning position Q1 can be calculated at a signal intensity of minus (−) 160 dBm or more. The second high sensitivity mode is suitable for a signal intensity of minus (−) 160 dBm or more and less than minus (−) 156 dBm.

  As illustrated in FIG. 4, the terminal 20 stores a positioning position output program 118 in the first storage unit 110. The positioning position output program 118 is a program for the control unit 100 to display the positioning position Q1 calculated by the normal mode program 112, the first high sensitivity mode or the second high sensitivity mode on the display device 34 (see FIG. 2). is there.

  As illustrated in FIG. 4, the terminal 20 stores a high sensitivity transition determination program 120 in the first storage unit 110. The high sensitivity transition determination program 120 is a program for determining whether, for example, 24 seconds (s), which is a predetermined time, has elapsed since the control unit 100 started the normal mode. 24 seconds is defined as the time at which the incoherent time β1 ends a predetermined number of times. For example, if the incoherent time β1 is 8 seconds, 24 seconds is defined as the time to end three times. This 24 seconds is an example of an allowable time.

As illustrated in FIG. 4, the terminal 20 stores a high sensitivity mode selection program 122 in the first storage unit 110. The high sensitivity mode selection program 122 is a program for starting the first high sensitivity mode or the second high sensitivity mode when 24 seconds have elapsed since the control unit 100 started the normal mode. The high sensitivity mode selection program 122 and the control unit 100 are an example of high sensitivity mode starting means.
The high sensitivity mode selection program 122 includes a drift calculation program 122a, a drift error calculation program 122b, and a drift error evaluation program 122c.

FIG. 11 is an explanatory diagram of the drift calculation program 122a.
As illustrated in FIG. 11, the control unit 100 first calculates a position Qg on the orbit of the GPS satellite 12a and 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, the drift DR can be calculated by Equation 1. 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 122a and the control unit 100 are an example of drift calculation means.

FIG. 12 is an explanatory diagram of the drift error calculation program 122b.
As illustrated in FIG. 12A, the control unit 100 calculates the drift error DRe using 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.
The drift error Dre is an error of the drift DR as shown in FIG.
The control unit 100 stores the drift error information 160 indicating the drift error DRe in the second storage unit 150.

  The drift error evaluation program 122c 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 122c and the control unit 100 are an example of drift error evaluation means.

  Based on the high sensitivity mode selection program 122, the control unit 100 starts the first high sensitivity mode when the drift error DRe is not within ± 50 hertz (Hz). On the other hand, the control unit 100 starts the second high sensitivity mode when the drift error DRe is within ± 50 hertz (Hz). The high sensitivity mode selection program 122 and the control unit 100 are also examples of high sensitivity mode selection means.

  As illustrated in FIG. 4, the terminal 20 stores a normal mode transition determination program 124 in the first storage unit 110. The normal mode transition determination program 124 determines whether or not the normal mode transition condition B for shifting to the normal mode is satisfied while the control unit 100 is performing the first high sensitivity mode or the second high sensitivity mode. It is a program to do.

FIG. 13 is an explanatory diagram of the normal mode transition determination program 124.
As shown in FIG. 13, the normal mode transition condition B is, for example, that the signal intensity SP is −154 dBm or more and that there are six or more GPS satellites being tracked.
The signal strength SP can be calculated based on the reliability R.
When the control unit 100 determines that the normal mode shift condition B is satisfied, the control unit 100 shifts to the normal mode.

The terminal 20 is configured as described above.
The terminal 20 can set an incoherent time β2 defined as a time longer than the incoherent time β1, and can further set an incoherent time β3 defined as a time longer than the incoherent time β2. it can.
The longer the incoherent time, the clearer the C / A code can be distinguished from noise in the correlation process. This is the same even when drift occurs and the signal intensity is weak.
For this reason, the terminal 20 can improve the sensitivity and calculate the positioning position even when drift occurs and the signal intensity is weak.
Furthermore, the terminal 20 can set not only the incoherent times β1 and β3 but also β2 as described above. This means that even if the signal strength is weak, the incoherent time β2 or β3 can be set according to the degree of the weakness. For this reason, for example, the incoherent time β3 is set when the signal strength is extremely weak, but the incoherent time β2 is set when the signal strength is slightly weaker than the normal signal strength. Can do. If the positioning position can be calculated in the incoherent time β2, the positioning position can be calculated earlier than when the incoherent time β3 is used. For this reason, the terminal 20 can calculate a positioning position at an early stage according to the degree of weakness of the signal intensity.
The “normal signal strength” is, for example, a signal strength at which the signal strength input to the antenna 33a (see FIG. 3) is minus (−) 154 dBm or more. The “weak signal strength that is slightly weaker than the normal signal strength” means, for example, that it is minus (−) 156 dBm or more and less than minus (−) 154 dBm. The “extremely weak signal strength” means that it is minus (−) 160 dBm or more and less than minus (−) 156 dBm.

Further, the terminal 20 can set a reliability threshold γ2 defined as a signal strength weaker than the reliability threshold γ1, and further sets a reliability threshold γ3 defined as a signal strength weaker than the reliability threshold γ2. Can be set.
When the signal strength is weak, if the signal strength that can determine the phase of the C / A code is set to be strong, the signal strength may not be reached and the positioning position may not be calculated. Here, if the signal intensity capable of determining the phase of the C / A code is set to be weak, the positioning accuracy can be calculated, but the positioning position can be calculated.
For this reason, the terminal 20 can calculate the positioning position Q1 even when the signal strength is weak.
In addition, as described above, the terminal 20 can set not only the reliability threshold values γ1 and γ3 but also the reliability threshold value γ2. This means that even if the signal intensity is weak, the reliability threshold value γ2 or the reliability threshold value γ3 can be set according to the level of the weakness. For this reason, for example, the reliability threshold value γ3 is set when the signal strength is extremely weak, but the reliability threshold value γ2 is set when the signal strength is slightly weaker than the normal signal strength. Can do. If the positioning position can be calculated with the reliability threshold γ2, it is possible to calculate a positioning position with higher accuracy than when the reliability threshold γ3 is used. For this reason, the terminal 20 can calculate the positioning position with high accuracy according to the degree of weakness of the signal intensity.

Further, the terminal 20 can start the first high sensitivity mode or the second high sensitivity mode when 24 seconds (s) have elapsed since the start of the normal mode.
In the normal mode, since positioning is performed at the incoherent time β1, the positioning result can be output quickly. In the normal mode, since the positioning is performed with the reliability threshold γ1, the accuracy of the positioning position is high. However, when the signal strength is weak, the reliability threshold γ1 may not be exceeded in the incoherent time β1. As a result, the positioning position may not be calculated.
In this regard, since the terminal 20 can start the first high sensitivity mode or the second high sensitivity mode when 24 seconds have elapsed, the terminal 20 calculates the positioning position even when the signal strength is weaker. be able to.

Further, the terminal 20 can start the first high sensitivity mode or the second high sensitivity mode in accordance with the drift error DRe.
As the drift error DRe is smaller, the terminal 20 can generate a reception frequency that matches the frequency of the C / A code. For this reason, a sensitivity improves.
In this regard, the terminal 20 starts the first high sensitivity mode when the drift error DRe is not within ± 50 hertz, and the second high when the drift error DRe is within ± 50 hertz and is sufficiently small. Since the sensitivity mode is started, the accuracy of the positioning position can be ensured according to the drift error DRe even if the signal intensity is weak.
Hereinafter, the operation of the terminal 20 will be described in summary with reference to FIG.

FIG. 14 is a schematic flowchart illustrating an operation example of the terminal 20.
First, the terminal 20 starts a normal mode (step ST1 in FIG. 14). This step ST1 is an example of a normal mode start step.
Subsequently, the terminal 20 determines whether or not 24 seconds have elapsed (step ST2). This step ST2 is an example of an allowable time passage determination step.
When determining that 24 seconds have elapsed in step ST2, the terminal 20 determines whether or not the positioning position Q1 has been calculated (step ST3). In step ST3, it is determined whether or not the positioning position Q1 has been calculated in 24 seconds from the start of operation in the normal mode. In step ST3, if the terminal 20 determines that the positioning position Q1 has been calculated, the normal mode is continued, and step ST2 and subsequent steps are repeated.

On the other hand, if the terminal 20 determines in step ST3 that the positioning position has not been calculated, the drift DR is calculated (step ST4). This step ST4 is an example of a drift calculation step.
Subsequently, the terminal 20 calculates a drift error DRe (step ST5). This step ST5 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 ST6). This step ST6 is an example of a drift error evaluation step.

If the terminal 20 determines in step ST6 that the drift error DRe is not within ± 50 hertz (Hz), it starts the first high sensitivity mode (step ST7). This step ST7 is an example of a high sensitivity mode start step.
Subsequently, the terminal 20 determines whether or not 48 seconds (s) have elapsed (step ST8).
If it is determined in step ST8 that the terminal 20 has passed 48 seconds (s), it is determined whether or not the positioning position Q1 has been calculated (step ST9). In step ST9, it is determined whether or not the positioning position Q1 has been calculated between the start of the operation in the first high sensitivity mode and the current time.

If the terminal 20 determines in step ST9 that the positioning position Q1 has not been calculated, the terminal 20 repeats step ST4 and subsequent steps again.
On the other hand, when determining that the positioning position Q1 is calculated in step ST9, the terminal 20 determines whether or not the normal mode transition condition B is satisfied (step ST10).
If the terminal 20 determines in step ST10 that the normal mode transition condition B is not satisfied, the terminal 20 repeats step ST4 and subsequent steps again.
On the other hand, if it is determined in step ST10 that the normal mode transition condition B is satisfied, steps ST1 and after are repeated.

When determining that the drift error DRe is within ± 50 hertz (Hz) in step ST6 described above, the terminal 20 starts the second high sensitivity mode (step ST7A). This step ST7A is also an example of the high sensitivity mode start step.
Subsequently, the terminal 20 determines whether 128 seconds (s) have elapsed (step ST8A).
If it is determined in step ST8A that the terminal 20 has passed 48 seconds (s), it is determined whether or not the positioning position has been calculated (step ST9). In step ST9, it is determined whether or not the positioning position Q1 has been calculated between the start of the operation in the second high sensitivity mode and the current time.

  Through the above-described steps, the terminal 20 can improve the sensitivity even when drift occurs and the signal strength is extremely weak.

(Modification)
The terminal 20 may calculate the drift DR by the method shown in FIG.
For example, a highly accurate 1-second pulse timing signal TM1 may be received from a communication base station, a timing difference from the 1-second pulse timing signal TM2 generated by the terminal 20 may be calculated, and the 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 or the like using the radio wave S1 or the like from the GPS satellite 12a or the like, the timing signal TM1 is used as a reference. The drift DR of the timing signal TM2 of the terminal 20 can be calculated.

The present invention is not limited to the embodiments described above. Furthermore, the above-described embodiments may be combined with each other.
Further, for example, a high sensitivity mode other than the first high sensitivity mode and the second high sensitivity mode may be implemented by appropriately combining the incoherent time β1 and the like and the reliability threshold value γ1 and the like.

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 normal mode program. 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 1st high sensitivity mode program. It is explanatory drawing of a 2nd high sensitivity mode program. It is explanatory drawing of a drift calculation program. It is explanatory drawing of a drift error calculation program. It is explanatory drawing of a normal mode transfer judgment 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.

Explanation of symbols

  12a, 12b, 12c, 12d ... GPS satellite, 20 ... terminal, 32 ... GPS device, 50 ... communication base station, 112 ... normal mode program, 114 ... first high sensitivity Mode program 116 second high sensitivity mode program 118 positioning position output program 120 high sensitivity transition determination program 122 high sensitivity mode selection program 122 a drift calculation program 122b ... Drift error calculation program, 122c ... Drift error evaluation program, 124 ... Normal mode transition judgment program

Claims (7)

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 that is a time for performing the incoherent;
A second cumulative time defined as a time longer than the first cumulative time;
A third cumulative time defined as a time longer than the second cumulative time;
It is comprised so that setting is possible, The positioning apparatus characterized by the above-mentioned. A first signal strength threshold defined as a signal strength capable of determining the phase of the positioning base code;
A second signal strength threshold defined as a signal strength weaker than the first signal strength threshold;
A third signal strength threshold defined as a signal strength weaker than the second signal strength threshold;
The positioning device according to claim 1, wherein the positioning device is configured to be settable. Normal positioning means for performing a normal mode that is positioning using the first integration time and the first signal strength threshold;
First high-sensitivity positioning means for performing a first high-sensitivity mode, which is positioning using the second integration time and the second signal strength threshold;
Second high-sensitivity positioning means for performing a second high-sensitivity mode, which is positioning using the third integration time and the third signal strength threshold;
An allowable time elapse determining means for determining whether or not a predetermined allowable time has elapsed since the start of the normal mode;
High sensitivity mode starting means for starting the first high sensitivity mode or the second high sensitivity mode when the allowable time has elapsed;
The positioning device according to claim 2, further comprising: Drift calculating means for calculating a drift of a reference oscillator of the positioning device;
Drift error calculating means for calculating a drift error that is an error of the drift;
Drift error evaluation means for determining whether the drift error is within a predetermined allowable error range;
High sensitivity mode selection means for starting either the first high sensitivity mode or the second high sensitivity mode based on the evaluation result of the drift error evaluation means;
The positioning device according to claim 2, wherein the positioning device includes: A normal mode start step in which 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 starts a normal mode in which positioning is performed in the first integration time. When,
An allowable time elapsed determination step for determining whether or not a predetermined allowable time has elapsed since the positioning device started the normal mode;
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 an error of the drift; and
A drift error evaluation step in which the positioning device determines whether the drift error is within a predetermined allowable error range; and
A high sensitivity mode for starting a first high sensitivity mode in which positioning is performed in a second integration time longer than the first integration time or a second high sensitivity mode in which positioning is performed in a third integration time longer than the second integration time. A starting step;
A method for controlling a positioning device, comprising: On the computer,
A normal mode start step in which 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 starts a normal mode in which positioning is performed in the first integration time. When,
An allowable time elapsed determination step for determining whether or not a predetermined allowable time has elapsed since the positioning device started the normal mode;
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 an error of the drift; and
A drift error evaluation step in which the positioning device determines whether the drift error is within a predetermined allowable error range; and
A high sensitivity mode for starting a first high sensitivity mode in which positioning is performed in a second integration time longer than the first integration time or a second high sensitivity mode in which positioning is performed in a third integration time longer than the second integration time. A starting step;
A control program for a positioning device, characterized in that On the computer,
A normal mode start step in which 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 starts a normal mode in which positioning is performed in the first integration time. When,
An allowable time elapsed determination step for determining whether or not a predetermined allowable time has elapsed since the positioning device started the normal mode;
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 an error of the drift; and
A drift error evaluation step in which the positioning device determines whether the drift error is within a predetermined allowable error range; and
A high sensitivity mode for starting a first high sensitivity mode in which positioning is performed in a second integration time longer than the first integration time or a second high sensitivity mode in which positioning is performed in a third integration time longer than the second integration time. A starting step;
The computer-readable recording medium which recorded the control program of the positioning apparatus characterized by performing these.

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