JP2008089309A - Positional information acquisition device, positional information acquisition method, and program for terminal device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an influence of an in-band noise to improve precision of a positioning solution. <P>SOLUTION: This positional information acquisition device is provided with a signal capturing and tracking means for capturing and tracking a signal satisfying the first condition as a GPS signal, a positional information calculating means for carrying out positioning using a captured and tracked track signal and for calculating positional information of a moving object, a moving object position determining means for determining whether the moving object is positioned in a prescribed place or not, based on the calculated positional information, and a capturing and tracking condition changing means for changing a condition for capturing and tracking the GPS signal, into the second condition different from the first condition, and the signal capturing and tracking means captures and tracks the signal, based on the second condition, during a period when determined to be positioned in the prescribed position by the moving object position determining means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a position information acquisition device that is mounted on a moving body and acquires position information of the moving body using a GPS signal from a GPS (Global Positioning System) satellite. The present invention also relates to a position information acquisition method for acquiring position information of a moving body using a GPS signal from a GPS satellite. The present invention also relates to a program for a terminal device that is executed by a control unit of a terminal device that acquires position information of a moving object using a GPS signal.

  GPS is a positioning system for acquiring position information using GPS signals transmitted from GPS satellites orbiting the earth. This GPS is used in a navigation system installed in a moving body such as a vehicle. Such a navigation system is equipped with a GPS receiver that captures and tracks a plurality of GPS satellites and performs position and velocity positioning using GPS signals obtained from these satellites.

  A spread spectrum communication system that is resistant to noise is adopted as a GPS modulation system. However, when the frequency of the noise is within the frequency band of the GPS signal (hereinafter referred to as “GPS band”), GPS is affected by the influence of the noise (hereinafter, such noise is referred to as “in-band noise”). The CN ratio of the signal can be reduced. Further, in the GPS receiver, synchronization with the frequency of the in-band noise having a high signal strength can be obtained, and PRN (Pseudo Random Noise) code correlation may be erroneously obtained. In this case, in-band noise is used for the positioning calculation. For this reason, the accuracy of the positioning solution is lowered.

  Here, in recent years, a lot of devices for realizing various functions are provided in the vehicle. And electromagnetic waves emitted by these devices may be a cause of reception failure as in-band noise, and may reduce the CN ratio of GPS signals. A GPS antenna for receiving a GPS signal is generally often installed in a vehicle and is easily affected by electromagnetic waves from the above-described devices. In the case of a navigation system incorporated during vehicle production, for example, a GPS antenna may be installed in a dashboard. In this case, the GPS receiver is greatly affected by unnecessary radiation noise in addition to the noise caused by the device.

  On the other hand, in order to avoid the influence of the noise by the said apparatus and unnecessary radiation noise, it is possible to install a GPS antenna outside a vehicle, for example. However, electromagnetic waves from mobile phones or the like having a frequency band close to the GPS band, for example, are flying outside the vehicle. Therefore, it can be said that it is difficult to avoid the influence of noise even if the GPS antenna is installed outside the vehicle.

  For example, if there is in-band noise (for example, noise with a frequency close to the Doppler frequency of the GPS signal that has been captured and tracked immediately before) when the vehicle enters a place where it is difficult to receive GPS signals (for example, a tunnel), GPS The receiver may erroneously capture and track the in-band noise as a GPS signal. As described above, in-band noise constantly exists in the reception environment surrounding the GPS receiver. Therefore, it can be said that such erroneous tracking is a phenomenon that is relatively easy to occur. When erroneous tracking occurs, the GPS receiver performs position and velocity positioning using in-band noise unless the GPS receiver receives a GPS signal and returns to a state where it can be captured and tracked. Therefore, a significant error may occur in the positioning solution. In addition, when there are many channels that have captured and tracked in-band noise among a plurality of channels of the GPS receiver, the number of channels that should be assigned to the original correct GPS signal is reduced. For this reason, not only the accuracy of the positioning solution is lowered, but also the number of tracking to the GPS signal does not reach the specified number, and there is a possibility that positioning is impossible. In addition, when mistracked in-band noise is used for positioning, a clock calculated by a control unit or the like may be shifted, which may make it difficult to capture and track a correct GPS signal.

For example, Patent Document 1 below discloses a system embedded in a tunnel that receives a GPS signal from a GPS satellite and transmits it to a space in the tunnel. According to the system described in Patent Document 1 below, it is possible for a vehicle located in a tunnel to receive a GPS signal satisfactorily.
JP-A-9-203777

  However, when constructing the system described in Patent Document 1, it is necessary to perform large-scale construction on tunnels throughout the country. Such construction is not preferable because it requires enormous costs and time. Therefore, for example, it is desired to improve the accuracy of the positioning solution by improving the performance on the GPS receiver side to reduce the influence of in-band noise in places where GPS signals such as tunnels are difficult to receive.

  In order to prevent the GPS receiver from capturing / tracking in-band noise, for example, it is conceivable to raise the reference of the GPS signal capturing / tracking condition (that is, lower the capturing / tracking sensitivity). However, if the standard of the acquisition / tracking conditions is increased, only GPS signals having a high signal level may be acquired / tracked. In other words, not only in-band noise but also GPS signals whose signal levels are not so high may not be captured and tracked. As a result, the number of GPS signals that can be captured and tracked decreases, and for example, the positioning rate decreases. From this point of view, it is not possible to improve the accuracy of the positioning solution simply by raising the reference of the acquisition / tracking conditions.

  Therefore, in view of the above circumstances, the present invention provides a position information acquisition device, a position information acquisition method, and a program for a terminal device that are suitable for reducing the influence of in-band noise and realizing improved accuracy of positioning solutions. The issue is to provide.

  A position information acquisition device mounted on a moving body according to an aspect of the present invention that solves the above-described problem relates to an apparatus that acquires position information of the moving body using a GPS signal from a GPS satellite. This position information acquisition device performs positioning using a signal acquisition and tracking means for acquiring and tracking a signal satisfying the first condition as a GPS signal, and the acquired tracking signal, and acquires the position information of the moving object. Position information calculating means for calculating, moving object position determining means for determining whether or not the moving object is located at a predetermined location based on the calculated position information, and the predetermined location by the moving object position determining means And a tracking condition changing means for changing the condition for capturing and tracking the GPS signal to a second condition different from the first condition when it is determined that the GPS signal is located in the position. The signal acquisition / tracking means performs signal acquisition / tracking based on the second condition during a period in which the moving body position determination means determines that the mobile body position determination means is located at the predetermined location.

  According to the position information acquisition apparatus configured as described above, conditions for capturing and tracking a GPS signal when the moving body enters a location such as a tunnel can be temporarily made severe. That is, since it becomes possible to set the capture / tracking conditions strictly in a place where the possibility of capturing / tracking the in-band noise is high, the possibility of erroneously capturing / tracking the in-band noise is reduced. In other places, it is possible to set the capture / tracking conditions relatively loosely. For example, it is possible to prevent a decrease in the positioning rate due to the stricter capture / tracking conditions. That is, according to the position information acquisition apparatus according to the present invention, the influence of in-band noise and the decrease in the positioning rate can be suitably reduced, so that the accuracy of the positioning solution can be improved.

  For example, the second condition may be stricter than the first condition.

  For example, when the tracking signal that satisfies the first condition that is captured and tracked by the signal capturing and tracking unit does not satisfy the second condition, the position information acquisition device converts the tracking signal into a noise component. Noise determination for determining whether or not the storage means for storing in a predetermined storage medium and the tracking signal captured and tracked by the signal acquisition and tracking means match the noise component stored in the predetermined storage medium It may be further provided with means. In this case, the signal acquisition and tracking unit may operate to stop acquisition and tracking of the tracking signal determined by the noise determination unit to match the noise component.

  In addition, the position information acquisition device, for example, when the tracking signal that satisfies the first condition that is captured and tracked by the signal capturing and tracking unit does not satisfy the second condition, A storage unit that stores the noise component in a predetermined storage medium and a tracking signal that is captured and tracked by the signal acquisition and tracking unit determines whether the noise component matches the noise component stored in the predetermined storage medium. Noise determining means and GPS signal determining means for determining whether or not the tracking signal determined to match the noise component based on the second condition is a GPS signal. May be. In this case, the signal acquisition and tracking unit may operate so as to stop acquisition and tracking of the tracking signal that is determined not to be a GPS signal by the GPS signal determination unit.

  In the position information acquisition apparatus, for example, the number of pieces of noise component information that can be stored in a predetermined storage medium by the storage unit may be limited to a predetermined number.

  Further, in the position information acquisition apparatus, for example, the process of confirming the presence or absence of a navigation message for the tracking signal captured and tracked by the signal capturing and tracking means is not performed under the first condition, and the second condition is not performed. Then, it may be executed.

  The position information acquisition device may further include map data corresponding to positioning using, for example, a GPS signal. In this case, the moving body position determination unit operates to compare the position information calculated by the position information calculation unit with the map data to determine whether or not the moving body is located at a predetermined location. Also good.

  In addition, a position information acquisition method according to one embodiment of the present invention that solves the above-described problem is a method for acquiring position information of a moving object using a GPS signal from a GPS satellite. In this position information acquisition method, a signal capturing and tracking step for capturing and tracking a signal satisfying the first condition as a GPS signal, positioning is performed using the captured and tracked tracking signal, and the position information of the moving object is obtained. A position information calculating step for calculating, and a moving body position determining step for determining whether or not the moving body is located at a predetermined location based on the calculated position information. In the signal acquisition and tracking step, signal acquisition and tracking are performed based on a second condition that is stricter than the first condition.

  A program for a terminal device according to an aspect of the present invention that solves the above problems includes a signal acquisition and tracking function that acquires and tracks a signal that satisfies the first condition as a GPS signal from a GPS satellite, and the acquisition and tracking Positioning is performed using the tracking signal thus obtained, a position information calculation function for calculating the position information of the moving body, and whether or not the moving body is located at a predetermined location based on the calculated position information When the mobile object position determination function and the mobile object position determination function determine that the vehicle is located at the predetermined location, the condition for capturing and tracking the GPS signal is changed to a second condition that is stricter than the first condition. A program for a terminal device for causing a control unit of a terminal device that acquires position information of a moving object using a GPS signal to execute a change function of a capture and tracking condition to be changed. During a period in which it is determined to be located, the signal acquisition and tracking functions, in which is characterized in that to perform signal acquisition and tracking based on said second criteria.

  According to the position information acquisition device, the position information acquisition method, and the terminal device program according to the present invention, the influence of in-band noise and the decrease in the positioning rate are preferably reduced, and the accuracy of the positioning solution is improved. Will come to be.

  The configuration and operation of the navigation system according to the embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a navigation system 200 according to the embodiment of the present invention. The navigation system 200 is a so-called car navigation device mounted on a vehicle (not shown). The navigation system 200 includes a GPS receiver 100, a gyro sensor 102, a vehicle speed sensor 104, an acceleration sensor 106, a CPU (Central Processing Unit) 108, an HDD (Hard Disk Drive) 110, a RAM (Random Access Memory) 112, a display unit 114, a speaker. 116 and an input unit 118. The CPU 108 performs overall control of the navigation system 200. Each component of the navigation system 200 realizes various functions under the control of the CPU 108.

  The GPS receiver 100 captures and tracks some of a plurality of GPS satellites that orbit the earth. Then, position measurement is performed using GPS signals from the captured and tracked GPS satellites to obtain current position information of the vehicle. Similarly, speed measurement using a GPS signal is performed to obtain information on the traveling speed of the vehicle. The GPS receiver 100 sends the obtained positioning result (hereinafter referred to as “GPS positioning” for convenience) to the CPU 108.

  The gyro sensor 102, the vehicle speed sensor 104, and the acceleration sensor 106 are sensors for known dead reckoning (hereinafter abbreviated as “DR”). The gyro sensor 102 measures the angular velocity related to the azimuth in the horizontal plane of the vehicle, and outputs the measurement result to the CPU 108. The vehicle speed sensor 104 detects the rotational speeds of the left and right drive wheels of the vehicle, generates a vehicle speed pulse signal corresponding to the average speed, and outputs it to the CPU 108. The acceleration sensor 106 measures information related to the gradient of the vehicle and outputs the measurement result to the CPU 108. For convenience of explanation, these sensor outputs are referred to as “DR sensor outputs”. The CPU 108 can perform well-known autonomous navigation based on these DR sensor outputs.

  The HDD 110 is a recording medium that stores various data such as a map database and a program. The RAM 112 is a memory in which, for example, data and programs stored in the HDD 110 are temporarily expanded. For example, the CPU 108 reads out a program stored in the HDD 110, expands it in a predetermined area of the RAM 112, and executes it. Thereby, for example, a navigation program operates to realize a navigation function.

  The display unit 114 is for displaying, for example, a navigation screen. The display unit 114 is a known touch panel such as a pressure-sensitive type or an electrostatic type, and also serves as an input unit. The input unit 118 is for performing a user operation, and is, for example, a mechanical input key installed on a front panel (not shown). For example, the power switch is one element constituting the input unit 118. When the display unit 114 or the input unit 118 is operated, a signal corresponding to the operation is input to the CPU 108. The CPU 108 controls each component so that processing corresponding to the user operation is executed. The speaker 116 outputs navigation sound such as notification of the direction of travel at a branch point.

  Here, the GPS receiver 100 will be described in detail. FIG. 2 is a block diagram showing the configuration of the GPS receiver 100 according to the embodiment of the present invention. As described above, the GPS receiver 100 captures and tracks a plurality of GPS satellites and performs GPS positioning calculation. The GPS receiver 100 is roughly divided into an RF (Radio Frequency) unit 1 and a digital processing unit 2. The RF unit 1 receives the GPS signal, down-converts it, and passes it to the digital processing unit 2. The digital processing unit 2 samples the signal received from the RF unit 1 to capture, track, and measure the position, and outputs a GPS positioning result to the CPU 108.

  The RF unit 1 includes a GPS antenna 10, an RF input unit 11, BPF (Band Pass Filter) 12 and 14, an LNA (Low Noise Amplifier) 13, a down converter 15, an AGC (Auto Gain Control) 16, a TCXO (Temperature Compensated Crystal Oscillator). ) 17 and a frequency synthesizer 18.

  When the GPS antenna 10 receives a GPS signal transmitted from a GPS satellite, the received signal is input to the BPF 12 via the RF input unit 11. Then, this signal passes through the BPF 12 and is limited to a predetermined band, and noise outside the GPS band is attenuated through the LNA 13 and the BPF 14 which are low noise amplifiers, and is input to the down converter 15.

  The TCXO 17 is a local oscillator that oscillates at a frequency lower than the frequency of the reception signal input to the down converter 15. The frequency synthesizer 18 generates a local oscillator signal based on the output from the TCXO 17 and outputs it to the down converter 15. The down converter 15 uses the local oscillator signal from the frequency synthesizer 18 and converts the received RF signal into an intermediate frequency (IF) signal that improves the stable operation and selection characteristics. The IF signal is gain-controlled by the AGC 16 and output to the digital processing unit 2.

  The digital processing unit 2 includes a demodulation unit 21, a positioning calculation unit 22, and an interface 23. The demodulator 21 includes an A / D converter 21a, a plurality of channels 21b, and an NCO (Number Controlled Oscillator) 21c.

  The A / D conversion unit 21a samples the IF signal from the RF unit 1, performs quadrature demodulation, and converts it into an I (In-phase) signal and a Q (Quadra-phase) signal. The I signal is an in-phase component in quadrature demodulation. The Q signal is a component that is orthogonal to the I signal. Hereinafter, for convenience of explanation, the I signal and the Q signal are collectively abbreviated as “IQ signal”.

  The A / D converter 21a outputs the converted IQ signal to the plurality of channels 21b. Here, the GPS receiver 100 needs to operate so as to simultaneously acquire and track at least three or four GPS signals in order to perform positioning calculation. In the GPS receiver 100, a plurality of channels 21b are provided so that processing for each GPS signal can be executed simultaneously. The IQ signal corresponding to each GPS signal is processed by a separate channel 21b.

  The NCO 21c is an oscillator that oscillates a numerically controlled frequency. In each channel 21b, Doppler elimination based on the output of the NCO 21c, code correlation detection by at least one correlator, and integration processing are executed on the input IQ signal. Then, the signal subjected to these processes is output to the positioning calculation unit 22. The positioning calculation unit 22 calculates a measurement value related to a signal from each channel 21b. A reference clock is input from the frequency synthesizer 18 to the NCO 21c. The NCO 21c executes NCO control related to the carrier, reference code generation of the PRN code, and NCO control related to the code.

  Here, a process for obtaining a desired measurement value based on a signal input to each channel 21b will be described. The range of the search frequency necessary for capturing the GPS signal is mainly due to deviations in the received frequency due to the Doppler effect and deviations such as variations (individual differences and aging) and variations (temperature characteristics and power supply variations) of the TCXO17. It is determined. First, the positioning calculation unit 22 estimates the search range of the Doppler frequency and code phase of the signal based on the navigation message that is the orbit information of the satellite, the previous positioning position, and the current time, and generates the set values thereof. , Output to the NCO 21c. Then, the search process executed in each channel 21b is controlled.

  Moreover, the positioning calculation part 22 designates the PRN code searched by each channel 21b for every channel 21b. Thereby, in each channel 21b, Doppler removal based on the set Doppler frequency is performed, and a correlation peak between the reference code of the designated PRN code and the input signal is detected within the set phase search range. Next, integration processing is executed, and when the level of the input signal exceeds a predetermined threshold, the input signal is captured as a GPS signal. Note that the longer the integration time is set, the higher the capture sensitivity. This integration time is also set by the positioning calculation unit 22.

  In each channel 21b, the tracking error in the GPS signal carrier and code captured via the tracking loop filter included in the positioning calculation unit 22 and the NCO 21c is corrected, and the tracking of the GPS signal is continued. If acquisition of the GPS signal fails, the positioning calculation unit 22 usually resets a wider search frequency range, code phase range, and higher sensitivity and outputs them to the NCO 21c. Then, the above processing is retried in the channel 21b under the control of the NCO 21c.

  The positioning calculation unit 22 acquires navigation messages included in a plurality of GPS signals necessary for positioning, and codes phase (pseudo distance), carrier frequency (pseudo distance rate), carrier phase (delta pseudo range), SN ratio, GPS The GPS time lag at the receiver 100 is calculated. And based on the measured value and data from these GPS signals, a position, speed, direction, and time are calculated (that is, positioning calculation). The calculated GPS positioning result is output to the CPU 108 via the interface 23. It is also possible to realize more adaptive and dynamic control for the navigation system 200 by inputting a set value to the GPS receiver 100 from the CPU 108 side.

  Here, the processing of the CPU 108 when receiving the GPS positioning result from the GPS receiver 100 and the DR sensor output from each sensor will be described.

  The CPU 108 performs DR positioning calculation based on the DR sensor output output by each sensor, and obtains the traveling direction and moving distance of the vehicle. Next, the CPU 108 compares the calculated DR positioning result and GPS positioning result with the error estimation value for each positioning result. Then, a positioning result determined to be highly accurate is selected based on the comparison result, and the selected positioning result is map-matched. Further, the CPU 108 searches the map database of the HDD 110 based on each positioning result, and extracts map image data around the current position. Next, a screen in which the vehicle position mark indicating the current position of the vehicle is superimposed on the extracted map image data is displayed on the display unit 114.

  Note that the map matching here refers to correcting an error such as a vehicle position mark being displayed at a position off the road in the map displayed on the display unit 114. By performing map matching, the vehicle position can be matched with the map, and the user can accurately grasp the current position of the vehicle. Map matching is always performed regardless of the execution of navigation.

  When a user operation is performed so that navigation is performed toward a certain destination, the CPU 108 reads a navigation program from the HDD 110 and develops it in, for example, the DRAM 112. Next, the map database of the HDD 110 is read, and the route search is executed by, for example, a known Dijkstra method with reference to the current position information based on the positioning result and the set destination information. Then, a route determined to be optimal is obtained as a search result. For example, the CPU 108 causes the display unit 114 to display the obtained route and various information related to the route. The user can grasp the route to the destination by referring to such navigation information.

  Next, with reference to the flowcharts shown in FIGS. 3 and 4, a process executed to acquire a highly accurate GPS positioning result in the present embodiment will be described. FIG. 3 is a flowchart showing the running state monitoring process executed by the CPU 108. FIG. 4 is a flowchart showing noise determination processing executed by the GPS receiver 100.

  First, the traveling state monitoring process shown in FIG. 3 will be described. The CPU 108 executes the driving state monitoring process each time map matching is performed (for example, once every second), for example, during a period from when the power of the navigation system 200 is turned on to when it is turned off. When executing the map matching, the CPU 108 determines whether or not the vehicle has entered a tunnel (or a predetermined area in which it is difficult to receive a GPS signal, such as an underground parking lot, a multi-story parking lot, and an underpass). Step 1, step is abbreviated as “S” in the following specification and drawings). Here, the CPU 108 knows where the vehicle is located on the map of the HDD 110 and its moving direction. When a vehicle enters the tunnel on the map of the HDD 110, it is considered that the vehicle has actually entered the tunnel.

  When it is determined that the vehicle has entered the tunnel based on the position and movement direction of the vehicle on the map of HDD 110 (S1: YES), the CPU 108 informs that fact (hereinafter referred to as “entry notification information”). Is output to the GPS receiver 100 (S2), and the process proceeds to S3. When it is determined that the vehicle has not entered the tunnel (S1: NO), the CPU 108 proceeds to the process of S3 without performing the process of S2. The approach notification information input to the GPS receiver 100 is held in, for example, an internal memory (not shown) of the positioning calculation unit 22. If the passage notification information is stored in the internal memory, the positioning calculation unit 22 overwrites and stores the entry notification information.

  In the process of S3, the CPU 108 refers to the position and moving direction of the vehicle on the map of the HDD 110, and determines whether or not the vehicle has exited the tunnel. When it is determined that the vehicle has exited the tunnel (S3: YES), the CPU 108 outputs information notifying that effect (hereinafter referred to as “pass-through notification information”) to the GPS receiver 100 (S4), FIG. The process of the flowchart in FIG. When it is determined that the vehicle has not exited the tunnel (S3: NO), the CPU 108 ends the process of the flowchart of FIG. 3 without performing the process of S4. The passing-through notification information input to the GPS receiver 100 is held in the internal memory of the positioning calculation unit 22, for example, similarly to the approach notification information. If the entry notification information is held in the internal memory, the positioning calculation unit 22 overwrites and stores the passing-through notification information.

  By this running state monitoring process, information indicating whether or not the vehicle is currently located in the tunnel (or a predetermined area where it is difficult to receive GPS signals) is held in the internal memory of the positioning calculation unit 22. become.

  Next, the noise determination process shown in FIG. 4 will be described. The GPS receiver 100 performs a noise determination process each time the above-described GPS positioning calculation is performed (for example, once every second), for example, during a period from when the power of the navigation system 200 is turned on to when it is turned off. When the GPS receiver 100 executes GPS positioning calculation and captures and tracks the GPS signal in each channel 21b, the current vehicle receives a tunnel (or GPS signal) by referring to the internal memory of the positioning calculation unit 22. It is determined whether or not it is located within a predetermined area that is difficult (S11).

  In the process of S11, when the entry notification information is held in the internal memory of the positioning calculation unit 22, the GPS receiver 100 determines that the vehicle is currently located at a place where it is difficult to receive GPS signals such as in a tunnel (S11: YES). Next, the reference of the capturing / tracking condition in the channel 21b capturing / tracking the GPS signal is changed (S12).

  Here, the navigation system 200 is mounted on a moving body, and the reception state of the GPS antenna 10 changes every moment. For this reason, it is likely that the waveform is disturbed due to the superposition of noise. Therefore, if the GPS signal acquisition / tracking condition standard is lowered (that is, the acquisition / tracking sensitivity is increased), for example, in-band noise can be easily acquired and tracked as a GPS signal, and the positioning accuracy may decrease. is there.

  In addition, since the reception state is changed every moment, reception of GPS signals may be intermittent or reception intensity may become unstable. Therefore, if the GPS signal acquisition / tracking condition standard is raised (that is, the acquisition / tracking sensitivity is lowered), for example, the number of GPS signals that can be acquired / tracked decreases. It may be less than the limit. As a result, for example, the positioning rate decreases, the real-time positioning is lost, the DOP (Dilution of Precision) increases, and the positioning accuracy decreases as a result.

  In order to avoid such a problem of deterioration in positioning accuracy, generally, acquisition and tracking conditions are optimized in consideration of a balance with positioning accuracy in the design stage. As an example of optimizing the acquisition / tracking conditions, it is known to set a threshold value used for determination of carrier synchronization or code correlation to an appropriate value. By setting these threshold values to appropriate values, it is difficult to cause a decrease in positioning accuracy due to the capture / tracking sensitivity.

  In addition, when the GPS receiver 100 executes initial positioning immediately after the navigation system 200 is turned on, in parallel with the noise determination processing of FIG. 4, the GPS receiver 100 measures the pseudorange, range rate, etc. while reading the contents of the navigation message in a long cycle. Based on the value, GPS positioning is performed once per second. This confirmation process of the navigation message is executed only for a limited period such as immediately after the navigation system 200 is turned on.

  The transmission speed of navigation messages is very slow (50 bps). For example, an ephemeris requires 6 seconds in one subframe. Therefore, the ephemeris cannot be obtained in real time for the measured value such as the pseudo distance used for positioning every second. The ephemeris is data transmitted at a cycle of 30 seconds, and the contents are not changed for 2 hours. From these viewpoints, it can be said that the navigation message confirmation process does not always have to be executed, and may be executed only during a limited period such as immediately after power-on. Further, when the navigation message confirmation process is always executed, the signal processing system is burdened by that amount, and the positioning rate may decrease, which is not preferable. For this reason, as an example of optimizing the capture / tracking conditions, the navigation message confirmation process is executed only for a limited period.

  Returning to the flowchart of FIG. The change of the criteria of the acquisition / tracking conditions in the processing of S12 includes increasing the threshold value used for determination of carrier synchronization, code correlation, etc., executing navigation message confirmation processing, and the like. That is, the GPS receiver 100 sets the conditions strictly by raising the reference of the capture / tracking conditions in the process of S12.

  The GPS receiver 100 determines whether or not the signal (hereinafter referred to as “tracking signal”) being captured / tracked in each channel 21b is a GPS signal based on the capture / tracking condition changed in the process of S12. Determine (S13). By increasing the threshold value in the process of S12, for example, the possibility that the code correlation with the in-band noise is erroneously taken can be reduced.

  In the process of S13, for example, the GPS receiver 100 determines that a tracking signal that has become uncorrelated due to a change in the acquisition / tracking condition, a tracking signal that has been revealed not to include a navigation message, or the like as noise. (S13: NO). Next, the positioning calculation unit 22 is controlled so as not to use the tracking signal determined to be noise (hereinafter referred to as “noise tracking signal”) for positioning (S14), and information such as the frequency and phase of the noise tracking signal ( In other words, the information of the measured value specified at the time of acquisition / tracking) is held in the internal memory of the measurement calculation unit 22 as interference wave information (S15). Then, the channel 21b that has captured and tracked the noise tracking signal is reset (that is, capturing and tracking of the noise tracking signal is stopped) (S16), and the flowchart of the noise determination processing in FIG. By resetting the channel 21b in this way, a new GPS satellite acquisition / tracking operation is executed in the next GPS positioning calculation. In this case, the GPS satellite acquisition / tracking operation is executed based on the acquisition / tracking conditions changed in the process of S12. Therefore, it is extremely unlikely that the noise tracking signal will be captured and tracked again by the channel 21b.

  In the processing of S11, when the notification information is stored in the internal memory of the positioning calculation unit 22 (or any information is not stored), the GPS receiver 100 indicates that the vehicle is currently out of the tunnel and the GPS signal (S11: NO). Next, the tracking signal of each channel 21 b is compared with the interference wave information held in the internal memory of the positioning calculation unit 22. Then, based on the comparison result, it is determined whether or not there is a tracking signal of each channel 21b whose frequency and phase match the interference wave information (S17). In the process of S17, if the frequency and phase difference between the tracking signal and the interference wave information are within predetermined values, they are regarded as “match”.

  In the process of S17, when a tracking signal having a frequency and phase that matches the interference wave information is detected (S17: YES), the GPS receiver 100 determines that the tracking signal may be a noise tracking signal. Proceed to Next, in the process of S12, the above-described processes after S13 are executed by raising the reference of the capture / tracking condition in the channel 21b.

  Further, in the process of S17, when a tracking signal having a frequency and phase that matches the interference wave information is not detected (S17: NO), the GPS receiver 100 determines that all tracking signals are GPS signals, The positioning calculation unit 22 is controlled to perform positioning using them (S18), and the flowchart of the noise determination process in FIG. 4 is ended. Note that when the interference wave information is not held in the internal memory of the positioning calculation unit 22, the GPS receiver 100 executes the process of S18 without executing the process of S17, and the flowchart of the noise determination process of FIG. finish. If it is determined in step S13 that there is no noise tracking signal (S13: YES), the GPS receiver 100 executes step S18 in the same manner as described above, and ends the flowchart of the noise determination process in FIG. To do.

  According to the present embodiment, it is possible to execute the positioning calculation using only the GPS signal without the noise tracking signal. In addition, by holding information such as in-band noise as jamming wave information, for example, a positioning calculation excluding noise tracking signals can be performed even in a location where GPS signals such as outside the tunnel can be satisfactorily received. Is possible. For this reason, it is possible to realize positioning using only the original GPS signal while optimizing the capture / tracking conditions in consideration of the balance with the positioning accuracy, and as a result, the accuracy of the positioning solution is improved.

  The above is the embodiment of the present invention. The present invention is not limited to these embodiments and can be modified in various ranges. For example, the running state monitoring process in FIG. 3 and the noise determination process in FIG. 4 are executed once per second in this embodiment, but may be executed in a cycle shorter than one second in another embodiment.

  For example, when the number of pieces of interference wave information is large, the determination criterion in the process of S13 becomes too high, and it takes time for re-acquisition / tracking and re-positioning. Therefore, it is desirable to set an upper limit on the number of pieces of interference wave information that can be held in the internal memory of the positioning calculation unit 22.

  When a signal in the same frequency band as the interference wave information is determined as a GPS signal in the process of S13, the interference wave information may be deleted from the internal memory of the positioning calculation unit 22.

  In another embodiment, the interference wave information or the like may be stored not in the internal memory of the positioning calculation unit 22 but in a memory (not shown) separately provided in the digital processing unit 2.

  In another embodiment, when a tracking signal having a frequency and phase that matches the interference wave information is detected in the process of S17, the tracking signal is determined to be a noise tracking signal without performing the processes in and after S12. Then, the acquisition and tracking may be stopped without using for positioning.

It is the block diagram which showed the structure of the navigation system of embodiment of this invention. The structure of the GPS receiver of embodiment of this invention is shown with a block diagram. It is the flowchart which showed the driving | running | working state monitoring process performed in embodiment of this invention. It is the flowchart which showed the noise determination process performed in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 RF part 2 Digital processing part 100 GPS receiver 102 Gyro sensor 104 Vehicle speed sensor 106 Acceleration sensor 108 CPU
110 HDD
112 RAM
114 Display unit 116 Speaker 118 Input unit 200 Navigation system

Claims (9)

In a position information acquisition device that is mounted on a moving body and acquires position information of the moving body using a GPS signal from a GPS (Global Positioning System) satellite,
Signal acquisition and tracking means for acquiring and tracking a signal satisfying the first condition as a GPS signal;
Position information calculating means for performing positioning using the acquired tracking signal and calculating the position information of the moving body;
Mobile body position determination means for determining whether or not the mobile body is located at a predetermined location based on the calculated position information;
Capture tracking condition changing means for changing a condition for capturing and tracking a GPS signal to a second condition different from the first condition when it is determined by the moving body position determining means to be located at the predetermined location; , And
The signal acquisition / tracking means performs signal acquisition / tracking based on the second condition during a period in which it is determined by the moving body position determination means to be located at the predetermined location. Acquisition device.   The position information acquisition apparatus according to claim 1, wherein the second condition is a stricter condition than the first condition. A predetermined storage medium;
A storage unit that stores the tracking signal as a noise component in the predetermined storage medium when the tracking signal that satisfies the first condition that is captured and tracked by the signal capturing and tracking unit does not satisfy the second condition;
Noise determining means for determining whether the tracking signal captured and tracked by the signal capturing and tracking means matches a noise component stored in the predetermined storage medium;
3. The signal acquisition / tracking means stops the acquisition / tracking of a tracking signal determined by the noise determination means to match the noise component. The position information acquisition device described in 1. A predetermined storage medium;
A storage unit that stores the tracking signal as a noise component in the predetermined storage medium when the tracking signal that satisfies the first condition that is captured and tracked by the signal capturing and tracking unit does not satisfy the second condition;
Noise determining means for determining whether or not a tracking signal captured and tracked by the signal capturing and tracking means matches a noise component stored in the predetermined storage medium;
GPS signal determination means for determining whether or not the tracking signal determined to match the noise component based on the second condition is a GPS signal,
The position information according to claim 1, wherein the signal acquisition and tracking unit stops acquisition and tracking of a tracking signal that is determined not to be a GPS signal by the GPS signal determination unit. Acquisition device.   5. The position information acquisition apparatus according to claim 3, wherein the number of pieces of noise component information that can be stored in the predetermined storage medium by the storage unit is limited to a predetermined number. 6. .   The process of confirming the presence or absence of a navigation message for the tracking signal captured and tracked by the signal capturing and tracking means is not performed under the first condition but is performed under the second condition. The position information acquisition apparatus according to any one of claims 1 to 5. Further comprising map data corresponding to positioning using GPS signals,
The moving body position determining means compares the position information calculated by the position information calculating means with the map data, and determines whether or not the moving body is located at a predetermined location. The position information acquisition apparatus according to any one of claims 1 to 6. In a position information acquisition method for acquiring position information of a moving body using a GPS signal from a GPS satellite,
A signal acquisition and tracking step of acquiring and tracking a signal satisfying the first condition as a GPS signal;
Positioning using the tracking signal that has been captured and tracked, a position information calculation step for calculating the position information of the moving body,
A moving body position determination step for determining whether or not the moving body is located at a predetermined location based on the calculated position information,
Position information that performs signal acquisition and tracking based on a second condition that is stricter than the first condition in the signal acquisition and tracking step when it is determined that the mobile object position is determined at the predetermined location in the moving body position determination step Acquisition method. A signal acquisition and tracking function for acquiring and tracking a signal satisfying the first condition as a GPS signal from a GPS satellite;
Positioning using the tracking signal that has been captured and tracked, a position information calculation function for calculating the position information of the moving body,
A moving body position determination function for determining whether or not the moving body is located at a predetermined location based on the calculated position information;
Capturing / tracking condition changing function for changing a condition for capturing / tracking a GPS signal to a second condition that is stricter than the first condition when it is determined by the moving body position determining function to be located at the predetermined location Is a program for a terminal device for causing the control unit of the terminal device to acquire the position information of the moving body using a GPS signal,
A terminal that causes the signal acquisition and tracking function to execute signal acquisition and tracking based on the second condition during a period in which it is determined to be located at the predetermined location by the moving body position determination function. Device program.

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