JPH0814919A - Navigation system - Google Patents

Abstract

PURPOSE:To provide a system with a high position-measurement accuracy using information on whether global positioning system GPS signal can be received or not and a reception signal level by enabling a navigation operation part to judge the condition of a building around a traveling body based on information from an output terminals. CONSTITUTION:A signal S9 is sent to an operation part 21 and it is judged that N synchronization state and PN non-synchronization state are discriminated when a level set by the amplitude of S9 is exceeded or not, respectively, and the result is outputted to a PN synchronization signal S13. Further, a signal 9 is sent to a vibration loop 19 and PN synchronization track signal S10 is outputted after processing by a dither signal S14 which is oscillated by a reference oscillator 22 and filtering at a filter frequency which is set by a reference signal S17. Then, the cut-off frequencies of low-pass filters 16, (a), and (b) are changed adaptably based on a signal S16 from an operation part 21, the filter constant of a vibration loop can be changed based on a signal S17 from an operation part 21, and then PN synchronization capturing signal S11 can be changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a navigation system using a received signal for receiving a signal from a NAVSTAR / GPS satellite.

[0002]

2. Description of the Related Art GPS (Global Positioning System) is a global radio navigation system using artificial satellites, which the US Department of Defense is constructing. The system consists of satellite system and ground system. A total of 24 satellites will be finally prepared, and if the system is completed, 2
4 hours, 3D positioning is possible all over the world.

A signal transmitted from a GPS satellite is a spread spectrum modulation signal which has an excellent capability of being less susceptible to interference and interference, having a high signal concealment capability, capable of distance measurement, time synchronization, and code division multiple access. is there.

The spread spectrum modulation is a pseudo noise code (Pseudo Noise code) which is a random code having a characteristic that an information data signal has a wider band than the frequency band of the information signal and has a high autocorrelation and low cross-correlation. PN
This is a method of transmitting by modulating with a code (this is called PN spreading). Therefore, the spread spectrum signal receiving apparatus is required to have the following functions. First, a PN code having the same pattern as the PN code used for spreading the information data on the transmitting side is generated inside the receiver, and the phase of the PN code and the PN of the received signal are generated.
This is a function of demodulating transmitted information data by matching and multiplying the phases of the codes and demodulating (this is called PN despreading).

Next, the operation will be described in detail.

After the receiver is started up, P of the signal to be received is
The phase of the PN code is changed until the phase of the N code and the phase of the PN code created inside the receiver match (phase synchronization), that is, a so-called PN search is performed until the desynchronization signal is obtained.

Next, since a lot of unnecessary noise signals are mixed in this despread signal, the center frequency of the despread signal and
The despread signal is filtered by matching the center frequencies of narrow band filters for removing unnecessary noise from the despread signal (frequency synchronization). By the above operation, unnecessary noise components are removed, the information signal is demodulated, and PN synchronization is established.

After the PN synchronization is established by the above operation, the phases of the PN codes are always matched (see, for example, Mitsuo Yokoyama, "Spread Spectrum Communication System", pp. 311--).
Control the PN code generator based on the signal from the seismic loop circuit (as shown at 325) (PN sync tracking), P
Track N. From the tracking state, the distance between three or more GPS satellites and the receiving organization is measured, and the self position is calculated.

In the GPS receiver, processes such as phase synchronization and frequency synchronization are indispensable and time-consuming until positioning is performed after the power is turned on. Therefore, conventionally, there is a method of changing the synchronous search speed and shortening the start-up time according to the method disclosed in Japanese Patent Laid-Open No. 58-191552.

[0010]

The signal level of the radio wave transmitted by the GPS satellite varies greatly depending on factors such as the elevation angle of the satellite and the deviation of the gain pattern of the antenna used in the receiving device with respect to the elevation angle.

Therefore, it is necessary to optimally select the optimum PN search speed according to the signal level, the bandwidth of the narrow band filter for removing unnecessary noise, and the parameters of the loop filter in the vibration loop circuit. However, (1) conventionally, since these parameters were made uniform regardless of the signal level, there was a problem that the time required for phase synchronization and frequency synchronization became long. Further, (2) there is a contradictory property between the time required for synchronization and the distance measurement accuracy, and it is difficult to satisfy both characteristics if these parameters are set uniformly. Further, in the vibration loop circuit, there is a problem that the accuracy of distance measurement deteriorates when the data is inverted. Furthermore, (3) whether or not the GPS signal can be received and the signal level are used only for changing the combination of satellites used for positioning.

It is an object of the present invention to realize a navigation system with high positioning accuracy by using information on whether GPS signals can be received or received signal levels.

[0013]

The above object is to notify the current position of a mobile unit by using a positioning satellite signal receiving apparatus for receiving a signal from a positioning satellite to determine the current position of the mobile unit and other sensor information. In the navigation system including a notification device, the positioning satellite signal receiving device includes storage means for storing the reception availability and the reception signal level, and an output terminal for outputting the stored information to a navigation calculation unit, and the navigation calculation unit is the This is achieved by providing means for judging the condition of the building around the moving body based on the information from the output terminal.

[0014]

[Operation] G for self-position measurement with the navigation system
When using the PS signal, it is checked whether there is an obstacle in the direction in which the GPS satellite can be seen, based on the GPS signal reception availability and the signal level. When you judge that there is an obstacle,
The map information and the position information output from the GPS receiver are matched. Furthermore, the map is checked to see if there is an obstacle in the direction in which the GPS satellites can be seen. Furthermore, the self-position is determined by map matching so as to be behind the obstacle.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows an example of the configuration of a GPS receiver to which the present invention is applied.

In FIG. 1, the spread spectrum signal having a center frequency of 1575.42 MHz transmitted from the GPS satellite is captured by the antenna 1 and transmitted to the high frequency section 23.

The high frequency section 23 amplifies this signal by the low noise amplifier 2 and outputs it to the reference oscillator 22 (for example, when the oscillation frequency is 6).
Carrier wave created by the first local oscillator 4 whose frequency is controlled at 5.472 MHz (for example, transmission frequency 1509.948)
(MHz) and down-converted by the mixer 3 to obtain the first intermediate frequency signal S1.

Further, an unnecessary noise signal is removed from the signal S1 by a band pass filter 5 (for example, a pass band width of about 2 MHz) and sent to the inverse spread spectrum unit 24.

In the inverse spread spectrum unit 24, the PN code NCO 8 and the PN code generator 7 are used to receive the GPS to be received.
P with the same pattern as the PN code of the satellite signal and in phase
The N code is used to despread the spread spectrum signal sent from the high frequency section 23 to obtain the second intermediate frequency signal S2.

The second intermediate frequency signal S2 is branched into two, mixed with two signals whose output phase difference of the reference oscillator 22 is 90 °, and frequency-converted (down-converted). Intermediate frequency signal S3. Obtain a and b (referred to as I signal and Q signal, respectively).

By separating the I and Q signals as described above, the processing can be performed at a low sampling frequency and the configuration of the digital signal processing unit is simplified.

Further, a low-pass filter provided before the A / D converter 12. a and b, the aliasing signal, which is a frequency component of 1/2 or more of the sampling frequency of the A / D converter, is removed, and the signal S4. Obtain a and b.

Here, the signal S3. a and b have a frequency fluctuation of about ± 4 KHz due to the Doppler effect, and considering the frequency fluctuation of the reference oscillator, the low-pass filter 12. a,
It is advisable to select the cutoff frequency of b to be about 5 to 7 KHz.

Further, the analog signal S4. a and b (for example, a sampling signal of 15.984375 MHz obtained by dividing the reference oscillator signal by 4096 by the frequency divider 11), a digital signal S5. It is converted into a and b and sent to the digital signal processing unit 25.

In the digital signal processing section 25, the carrier wave signal output from the third local oscillator 15 composed of a digital oscillator, the signal S5. a, b to mixer 14. a,
b mixed and down-converted signal S6.
Obtain a and b.

Further, a low pass filter 16.a, b capable of adaptively changing the signal cutoff frequency and changing the pass band by the signal S16 from the arithmetic unit 21 removes unnecessary noise from the signals S6.a, b. The carrier signals S7.a, b including the navigation data signal are obtained by removing them.

The data demodulator 17 is composed of, for example, a Costas demodulator or a TAN format demodulator, and the carrier signal S7. The carrier signal is reproduced from a and b, and the data signal S8 is demodulated by comparing this with the input signal and sent to the arithmetic unit 21.

Further, the detector 18 receives the input signals S7. a, b
The square root of the sum of squares of is calculated, and the amplitude information signal S of the input signal is calculated.
Get 9.

This signal S9 is sent to the calculation unit 21 and S9
If the amplitude of is equal to or higher than the set level, PN synchronization state, S
If the amplitude of 9 is less than or equal to the set level, the PN asynchronous state is determined, and the result is output as the PN synchronizing signal S13.

Further, the amplitude information signal S9 is the vibration loop 19
To the PN synchronization tracking signal S10 after being processed by the dither signal S14 transmitted from the reference oscillator 22 and filtered by the filter frequency set by the reference signal S17 from the arithmetic unit. In addition, the data inversion signal S15 is also input to the vibration loop 19 from the calculation unit 21 to control the input of the signal S9 from the detector 18 to the vibration loop 19. The switch 20 switches between the PN synchronization acquisition signal S11 and the PN synchronization tracking signal S10. If the PN synchronization signal S13 from the calculation unit 21 indicates the asynchronous state, it is switched to the PN synchronization acquisition signal S11 output from the calculation unit 21, and if it indicates the synchronization state, it is switched to the PN synchronization tracking signal S10.

The control signal S12 output from the switch 20 is input to the PN code NCO8 to control the phase of the PN code and create a PN synchronization state.

The GPS signal is demodulated and positioning is performed with the above configuration, but the point different from the conventional method is that the low pass filter 16. The cut-off frequency of a and b is the signal S1 from the calculation unit 21.
6, it is possible to adaptively change, the filter constant of the vibration loop can also be changed based on the control signal S17 from the calculation unit 21, and the PN synchronization acquisition signal S11
The speed at which the PN sync point can be searched for (search speed)
The point is that you can freely change. This PN search
It is realized by slightly changing the PN code chip rate frequency of the received wave and the chip rate frequency of the PN code created inside the receiver to equivalently change the phase of the PN code. For example, the chip rate frequency of the received wave PN code is 1.023 MHz, and the PN generated inside the receiver
If the code chip rate frequency is 1.0232 MHz, the search speed is 200 BIT / sec. Therefore, in order to speed up the search, it is sufficient to increase the chip rate frequency difference between them.

Next, the processing configuration of the arithmetic unit will be described with reference to FIG.

The navigation data analysis unit 44 demodulates the GP.
The navigation data is edited from the S satellite navigation data signal S8, and converted to Amarnac data (general position information of GPS satellites) and ephemeris data (detailed position information of GPS satellites) necessary for positioning and speed calculation. In addition, the data signal S8
Information regarding the amount of change in the Doppler frequency of the carrier wave is also transmitted to and transmitted.

The filter control calculation unit 45 uses a GP which will be described later.
The S / N ratio of the S signal is estimated and calculated, the bandwidth of the low pass filter is determined, and the filter signal S16 is output to the digital signal processing unit 24.

The synchronization judging section 46 monitors the amplitude information signal S9 of the input signal, and if the amplitude is above the set level, the PN synchronization state, and if the amplitude is below the set level, P
N Determined to be in an asynchronous state. Vibration loop control calculation unit 47
Is for optimizing a loop filter for preventing the positioning accuracy from deteriorating when data of an input signal is inverted, which will be described later, and for stable tracking at high speed. Therefore, the data inversion time is predicted and the data inversion signal S15 is output, and is changed by the control signal S17 of the multiplier constant of the loop filter.

The switch control signal section 48 outputs a PN synchronization signal S13 for switching between the synchronization acquisition mode and the synchronization tracking mode.

The Doppler fluctuation compensator 49 is provided with a carrier signal S
7. A third station oscillation control signal S24 is output to the third local oscillator to control so that the influence of Doppler fluctuation does not affect a and b.

The satellite selection unit 53 selects the combination of satellites that provides the highest positioning accuracy.

The positioning calculation 54 calculates its own three-dimensional position from the pseudo distance data signal S23 output from the distance measuring counter 44 and the position data of the GPS satellite.

The speed calculator 55 calculates its own speed and heading direction from pseudorange change rate data (this is obtained from the frequency change amount of the carrier), GPS satellite position data and the like. Next, the processing algorithm of the arithmetic unit 21 will be described with reference to FIG. After the power is turned on, the startup process 100 is performed, and the position and speed of the currently visible GPS satellite are obtained using the almanac data stored in the arithmetic unit 1
01.

From the combination of the geometrical positions, a combination of four HPS satellites capable of positioning the self position with the highest accuracy is determined (in the case of two-dimensional positioning, a combination of three satellites) 102.

Further, the Doppler shift frequency amount of the satellite signal is calculated 103 from the position and velocity of the GPS satellite.

After these basic calculations are completed, the digital signal processing section is set.

First, the constant of the loop filter of the vibration loop is set as a constant for rapid tracking 104.

Next, the carrier signal S7. To eliminate Doppler frequency fluctuations from a and b, the oscillation frequency of the third local oscillator 15 is set from the calculated Doppler shift amount 10
5. Further low pass filter 16. The bandwidths of a and b are set 106 by the method described later.

After the above settings are completed, the PN synchronous search is started. In the synchronization determination 107, the amplitude level of the GSP signal is monitored, and when it exceeds a certain level, it is determined that PN synchronization has been obtained, and positioning is started.

On the other hand, when the amplitude is below a certain level, P
The search is continued until the search for N1 cycles is completed, and if the PN synchronization is still not achieved, the oscillation frequency of the third local oscillator 15 is slightly changed and the PN synchronization search is performed again.
08.

When the PN synchronization is obtained, the switch control signal section 48 outputs the switch switching signal S13 and P
NNCO control signal S12 to PN search signal S11 to P
Synchronize by changing to N tracking signal S10 10
9. After the synchronization, the vibration loop control calculation 110 is performed to change the loop filter constant to a value that improves the pseudorange measurement accuracy, and then the calculation 111 is performed based on the Doppler frequency obtained from the data demodulator 17 to obtain a more accurate Doppler frequency. Low-pass filter 16 to remove fluctuations and improve pseudorange accuracy The band of a and b is narrowed 112. Also, the obtained navigation data is edited to obtain 113 almanac data, ephemeris data, and the like. Furthermore, the measured value of the pseudo distance or the pseudo distance change rate is input, and 114 is used to measure the self position 11
5, Speed and traveling direction 116 are calculated and output. Positioning is continued while synchronization is maintained, and if synchronization is lost, synchronization is regained and positioning is continued 117.

Next, the operation of each section will be described.

Data demodulator 17 of digital signal processing section
The navigation data signal S8 output from is edited / analyzed by the calculation unit 21 to obtain satellite time and position information (almanac data) of each GPS satellite. This almanac data (or previously collected almanac data)
Then, the elevation angle that each GPS satellite can see is calculated from the information on the time, the current position, and the current position.

Further, the gain G (dB) with respect to the elevation angle of the antenna 1 stored in the memory inside the calculation unit 21 is read out, and the amount L (dB) of the GPS signal at the elevation angle attenuated in the atmosphere is calculated. Here, the effective power of the GPS signal is calculated by P (dBm: 10logP (mW), and 0
dBm = 1 mW), the received GPS signal level S is calculated by the following equation.

S = P-L + G Further, if the noise level N (dBm) is approximated to the thermal noise level, the noise level N is calculated by the following equation.

N = kTB where k is the Boltzmann constant, T is the equivalent noise temperature, and B is the bandwidth of the receiver. The signal-to-noise ratio (S / N ratio) of the GPS satellite to be received can be calculated from the ratio between the GPS signal level S and the noise level N.

When this S / N ratio is high, the low pass filter 16. The cutoff frequencies of a and b are increased and the bandwidth is set to 1 (k
Hz). By thus widening the bandwidth, frequency synchronization becomes easier.

Further, the PN search speed is further increased so that phase synchronization can be obtained in a short time of 5 seconds or less.

When the S / N ratio is low, the low pass filter 16. Lower the cut-off frequency of a and b to 200
(Hz) narrow. By narrowing the bandwidth in this way, the S / N ratio is improved and the GPS signal can be captured.
Further, the PN search speed is slowed down so that phase synchronization can be obtained without error due to the influence of noise. Therefore, the phase synchronization time needs to be around 10 seconds.

The above is a method of changing each parameter according to the information of almanac data, time and current position, but there is also a method of changing each parameter based on the external data S18. Next, the operation will be described.

The arithmetic unit 21 outputs the almanac data to the external arithmetic device as the external data S18. In the arithmetic unit, a table of satellite elevation angles with respect to time is created from the approximate value of the current position and stored in a memory. If the orbital altitude of the GPS satellites is the same as it is now, the satellites will pass over the same ground every day, increasing in time by just over 4 minutes. Considering its effect,
The elevation angle of the GPS satellite is calculated from the current time and the satellite elevation angle table. The elevation value is sent to the calculation unit by the external data S18, and the low pass filter 16. The cutoff frequencies of a and b and the PN search speed are determined to achieve PN synchronization.
The operation of the external computing device can be stored and executed in the computing unit 21.

Still another method will be described.

First, the amplitude information signal S9 is taken into the arithmetic unit, and the S / N ratio of the GPS signal being received is measured. This is calculated from the difference in amplitude when no satellite is received and when a signal from a GPS satellite is received. The measured S / N ratio is compared with the S / N ratio calculated from the elevation angle of the satellite and the gain of the antenna, the calculated S / N ratio is corrected, and the correction value is stored. Further, the S / N ratio information is output as external data S18 to an external arithmetic unit (not shown). This external arithmetic unit stores S / N ratio information and time information in a memory. If positioning is performed at a later date, GPS
Considering the effect of the satellite passing over the same ground every day while being slightly faster than 4 minutes, the S of GPS signal at that time is taken into consideration.
The / N ratio is called from the memory and output to the arithmetic unit 21 as external data S18. With this information, the low pass filter 16. The cutoff frequencies of a and b and the PN search speed are determined to shorten the PN synchronization time. The operation of the external computing device can be stored and executed in the computing unit 21.

The processing method when there is no almanac data, time information, or current position information will be described below.
First, at the start of GPS signal reception, the low-pass filter 1
6. The cutoff frequencies of a and b are increased to widen the pass band width and the PN search is started. By thus widening the bandwidth, frequency synchronization becomes easier. However, if the bandwidth is widened in this way, the S / N ratio deteriorates, so that G having a low elevation angle is used.
In some cases, PS satellites cannot be captured. So GPS
When the signal cannot be captured, the low pass filter 16. Lower the cut-off frequencies of a and b, narrow the pass band width, perform another PN search, and
Establish N synchronization.

Although the acquisition of the GPS signal has been described above, positioning accuracy is another function desired by the GPS in addition to shortening the PN search time. To improve the positioning accuracy,
The PN code of the input GPS satellite signal and the P inside the receiver
The vibration loop 19 may be controlled so that the phases of the PN codes created by the N code generator 7 may be completely matched to increase the distance measurement accuracy.

Therefore, an example of the constitution of the vibration loop to which the present invention is applied is shown in FIG. 4, and its details will be described below.

The input amplitude information signal S9 is switched and held by the data inversion signal S15 and is switched by the switch 25.
Sent to In the switch 25, this signal is divided into a lead signal and a lag signal by the dither signal S14. Each of the lead signal and the lag signal passes through the loop filter, and the hold 26. Data is stored in a and b. Each output is input to the adder / subtractor 27,
The difference is taken and the PN synchronization tracking signal S10 is output.

Next, the operation will be described.

Amplitude information signal S9 input to the vibration loop
Has a feature as shown in FIG. FIG. 5A shows the navigation data signal S8, and the horizontal axis represents time.
That is, a phenomenon occurs in which the amplitude of S9 drops when the data is inverted. This occurs due to the influence of the filter used in the receiver and cannot be avoided. Further, such a sudden change in the amplitude level causes the loop filter 28. Passing a and b, PN
This adversely affects synchronization and deteriorates positioning performance.

Then, the data inversion time of the GPS navigation data signal S8 is calculated by the arithmetic unit 21 from the previous data inversion time and the data inversion cycle of 20 ms, and the signal level becomes 1 before and after the data inversion time. The data inversion signal S15 shown in (c) is output.

When the signal level in S15 is inverted from 0 to 1, the switch 23 is cut off to prevent the input from being applied, and at the same time, the data before the switch is cut off is stored in the hold 24.

On the contrary, when the signal level of S15 is inverted from 1 to 0, the switch 23 is connected and the hold 24 is disabled.

As a result, the amplitude information signal shown in FIG. 5 (b) is converted into the signal shown in FIG. 5 (d). In this way, the fluctuation of the amplitude level at the time of inversion of the information signal is reduced, so that the distance measurement accuracy and the positioning accuracy are improved. Further, the signal shown in FIG. 5 (d) is controlled by the switch 25 under the control of the dither signal S14 so that the advance signal S19 and the delay signal S2 are obtained.
Divided into 0.

The lead signal and the lag signal are sent to a loop filter and processed. The feature of the present invention is that this loop filter 28. A characteristic is that the multiplier constants inside a and b can be adaptively changed according to the processing process by the control signal S17 from the arithmetic unit.

When the PN search is performed to acquire the synchronization, it is necessary to surely acquire the synchronization and perform the tracking more rapidly. Therefore, the multiplier 29. Select a small value for the constant of a and set 1
Close to the characteristics of the next loop filter. Further, in the PN synchronization follow-up, in order to eliminate the tracking offset component and improve the positioning performance, the multiplier 29. A large value is selected for the constant of b and is used as the characteristic of the second-order loop filter.

Further, the multiplier 30. Values of the constants a and b are switched so that the positioning accuracy is improved. The signal output from the loop filter by the above method is held 2
6. sent to a and b. The signal switched by the switch 25 is the loop filter 28. In the case of outputting to the loop filter output signal just before the switch 25 is switched to the hold 26.a. Store in b.

Further, the loop filter 28. If the switch 25 is switched to output to the hold b. b holds the loop filter output signal immediately before the switch 25 is released and the switch 25 is switched. Store in a. The signals S21 and S22 obtained in this way
Is added and subtracted by the adder 27 to obtain the PN synchronization tracking signal.

Next, FIG. 6 shows an example in which the GPS receiver described above is incorporated into an automobile navigation system.

The system includes a sensor system, a display system, an information system,
It consists of a computing system.

The sensor has a GP for measuring its own absolute position.
An S receiver 31, an optical fiber gyro 39 for measuring a rotation angle, a steering angle sensor 37, a geomagnetic sensor 38 for detecting a bearing, and a vehicle speed sensor 36 for measuring a speed are used.

The display system is the LCD display 32, the information system is the road information receiver 34, and the operation system is C for storing the road map.
D-ROM 33, arithmetic unit 35 for obtaining self-position from sensor output and controlling map matching / display
Composed of.

The operation will be briefly described. The GPS receiver constantly measures its own position and displays the measurement result on the LCD display. However, if the GPS signal cannot be received due to the shadow of the building, the positioning cannot be performed. Therefore, while performing navigation using the optical fiber gyro, angle information output from the rudder sensor, angle information output from the vehicle speed sensor, and direction information output from the geomagnetic sensor,
It also uses map matching to improve positioning accuracy and displays the measurement results on the LCD display. With such a configuration, accurate navigation is always possible.
Further, it is also possible to constantly perform navigation by using sensor information such as an optical fiber gyro, a steering angle sensor, a speed sensor, a geomagnetic sensor, etc., and correct it by the positioning result of the GPS receiver.

Further, this GPS receiver can be applied to navigation systems for ships, airplanes, artificial satellites, etc.

Next, FIG. 7 shows an example in which the present GPS receiving device is incorporated into the automobile navigation system having the above-mentioned configuration to perform navigation.

Vehicle 4 running on the road in the figure
The traveling direction of 0 is represented by a vector 42, the building is represented by 41, and the direction vector in which the GPS satellite is viewed is represented by 43.

The positioning accuracy of the GPS system has an error of 30 m to 50 m depending on the visible arrangement of satellites. In order to correct the error, the map is compared with the positioning result, and the map is forcibly matched with the self-position on the road.

In the case of this figure, the running vector 42 of the automobile
From this, traveling on the road shown in the figure is selected. However, if you continue to drive in this state, the GP coming from the direction of vector 43
Since the S signal is blocked by the building 41, the GPS signal mounted on the automobile 40 cannot receive the GPS signal. This is determined by the fact that the signal level of the amplitude information signal S9 in FIG. 1 decreases and the PN synchronization is lost. Therefore this G
Map matching can be performed by using the information of the PS signal interruption. That is, the road map shown in FIG.
The information of the building 41 can be obtained from M33, and when the GPS signal is cut off, the accurate position can be known by performing map matching to the location on the road where the direction vector 43 of the GPS satellites intersects with the building 41. You can

[0087]

According to the present invention, it is possible to provide a navigation system with high positioning accuracy by using the information on whether or not GPS signals can be received and the receiving level.

[Brief description of drawings]

FIG. 1 is a block diagram of a GPS receiver.

FIG. 2 is a configuration diagram of an arithmetic processing unit.

FIG. 3 is a flowchart of processing of an arithmetic processing unit.

FIG. 4 is a detailed diagram of a vibration loop circuit.

FIG. 5 is a diagram showing signals input to and output from a vibration loop circuit.

FIG. 6 is an automobile navigation device using a GPS receiver.

FIG. 7 is map data used for map matching.

[Explanation of symbols]

20, 23, 25 ... Switch, 21 ... Arithmetic unit, 22 ... Reference oscillator, 24, 26.a, 26. b ... HOLD, 27 ...
Adder, 28. a, 28. b ... Loop filter, 29.
a, 29. b, 30. a, 30. b ... Multiplier, 31 ... G
PS receiver, 32 ... LCD display, 33 ... CD
-ROM, 34 ... Road information receiver, 35 ... Computing unit, 36
... vehicle speed sensor, 37 ... rudder angle sensor, 38 ... geomagnetic sensor, 39 ... optical fiber gyro, 40 ... automobile (navigator), 41 ... building, 42 ... running vector, 43 ... G
Direction vector in which PS satellite is visible, 44 ... Navigation data analysis unit, 45 ... Filter control calculation unit, 46 ... Synchronization determination unit, 4
7 ... Vibration loop control calculation unit, 48 ... Switch control signal unit, 49 ... Doppler fluctuation compensation unit, 50 ... Start-up processing unit, 51 ... Satellite position / speed calculation unit, 52 ... Doppler shift change amount calculation, 53 ... Satellite selection Part, 54 ... Positioning calculation part, 5
5 ... Speed calculation unit.

Claims (1)

[Claims] 1. A navigation system comprising a positioning satellite signal receiving device for receiving a signal from a positioning satellite to determine the current position of a mobile body and a notification device for notifying the current position of the mobile body using other sensor information. The positioning satellite signal receiving device includes storage means for storing whether or not reception is possible and a received signal level, and an output terminal for outputting the stored information to a navigation calculation section, and the navigation calculation section is based on the information from the output terminal. A navigation system comprising means for judging the condition of a building around the moving body.