JP3178293B2 - Positioning device using global positioning system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position locating apparatus using a differential global positioning system (DGPS), and more particularly to a measure against multipath.

[0002]

2. Description of the Related Art In recent years, GPS has been used which receives radio waves from a plurality of artificial satellites arranged in orbit around the earth and detects the receiving position. From each satellite, its orbit data and the like are multiplied by a pseudo-random (PRN) code to spread the spectrum, a signal obtained by phase-modulating the carrier with the spread signal is transmitted, and a signal from the i satellite is received on the earth. , The distance between the i satellite and the receiving point can be calculated from the difference T between the reception time of the PRN code and the transmission time of the PRN code and the propagation speed C of the radio wave. However, since the time error E of the GPS receiver is actually included, the distance CT is a pseudo distance. The unknown is the receiving point (X,
Y, Z) and the time error, these values can be known by receiving radio waves from four satellites.

When positioning is performed using a CRN code that is generally released as a PRN code, it is said that a distance error of about 100 m occurs due to the time resolution of the PRN code and an artificial error. ing.

Therefore, conventionally, an error of a positioning value by a GPS at a fixed point whose true position is known or a correction value thereof is notified to a moving point, and the positioning value is corrected at the moving point based on the correction data. GPS that improves accuracy by using
(DGPS) has been proposed.

[0005]

However, in general, GPS
When a satellite radio wave is received by a GPS antenna, the direction of reflection by a reflecting surface such as a metal surface or a water surface is GP in a receiving environment.
In the case of the direction of the S antenna, the GPS antenna locks erroneously in the reflection direction, and an error occurs in the pseudo distance to be detected due to the longer propagation path compared to the direct wave. This error is generally called a multipath error, and since the original error is about 100 m as described above (may be 150 m or more depending on the arrangement of the GPS satellites) in the single positioning without DGPS, as described above. Although there is no significant effect, especially in the case of DGPS, since the original error has a high accuracy of about several meters to 10 m, a multipath error has a considerable adverse effect.

Of course, a technique for removing such a multipath error has been proposed in the past. For example, Japanese Unexamined Patent Publication No. Hei 6-281721 discloses a technique in which a tall building such as an urban area runs along a road. G when the vehicle runs
When receiving signals from PS satellites and performing positioning calculations, positioning calculations are performed using only signals from high-elevation GPS satellites, thereby avoiding the effects of multipath caused by buildings and accurately determining the current position of the traveling vehicle. A desired navigation system is disclosed. However, even when using satellite radio waves within such a limited range, the received waves may be all affected depending on the state of the sky (such as the ionosphere) in that range. There is a problem that varies.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object a GPS and, in particular, a DG.
An object of the present invention is to provide a position locating device capable of reliably detecting the occurrence of a multipath error in positioning by PS and preventing the occurrence of a positioning error.

[0008]

According to another aspect of the present invention, there is provided a position locating device using a GPS according to the first aspect of the present invention, wherein the position locating device is arranged to be separated by a predetermined distance and receives a signal from the same artificial satellite. A first and a second GPS antenna,
A first calculating a first radio path distance (first pseudo distance) to the artificial satellite based on a signal received by a GPS antenna;
Pseudo distance calculating means; second pseudo distance calculating means for calculating a second radio path distance (second pseudo distance) to the artificial satellite based on a signal received by the second GPS antenna;
When the difference between the first radio path distance and the second radio path distance is equal to or larger than a predetermined value, the apparatus further comprises a determination unit that determines that the signal from the artificial satellite is in a multipath state.

According to another aspect of the present invention, there is provided a position locating apparatus using a GPS, further comprising: receiving means for receiving correction data from a reference station; A correcting means for correcting the first radio path distance or the second radio path distance;
While performing GPS, the determination unit determines that a difference between the first radio path distance and the second radio path distance is equal to or greater than a predetermined value, and that a change amount of correction data transmitted from the reference station is equal to or less than a predetermined value. In this case, it is determined that the signal from the artificial satellite is in a multipath state.

According to a third aspect of the present invention, there is provided a position locating apparatus using a GPS, wherein the positioning means further includes the immediately preceding positioning data when the determination means determines that the apparatus is in a multipath state. Characterized in that it has output control means for outputting positioning data having a smaller change amount.

[0011]

In the position locating apparatus using GPS according to the first aspect, the first radio path distance (first pseudo distance) and the second radio path distance (second pseudo distance) for the same artificial satellite are compared. When the multipath does not occur, the two distances have substantially the same value. If there is a difference equal to or more than the predetermined value, it can be determined that a multipath error has occurred.

According to a second aspect of the present invention, there is provided a position locating apparatus using GPS, wherein a system for performing DGPS for correcting a pseudo distance based on correction data from a reference station utilizes a change amount of the correction data to reduce a multipath error. The presence or absence is more reliably determined.

That is, in general, if there is a large difference between the two pseudoranges, a multipath error has occurred. However, even if the signal from the artificial satellite itself has a problem and the multipath error does not occur, the multipath error does not occur. A large difference may occur between the two pseudo distances. Therefore, the correction data transmitted from the reference station is monitored by DGPS, and when the change amount is less than a predetermined value and there is no large change, the signal itself from the artificial satellite has no abnormality, and therefore, two pseudo distances Can be determined to be due to a multipath error.

In the position locating apparatus using GPS according to the third aspect, when a multipath error is detected, positioning data based on a pseudo distance is not output, but more reliable positioning data is output.

The more reliable positioning data is positioning data having a smaller change from the immediately preceding positioning data. For example, GPS (or DGPS) positioning data and position data based on autonomous navigation (calculated based on vehicle speed and direction) Out of the calculated position data) is output.

Thus, for example, when a multipath error is detected, the positioning data is not output,
There is no fear of the user.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of this embodiment. The vehicle is equipped with two GPS antennas 1 and 2. It is preferable to install these GPS antennas 1 and 2 before and after the vehicle roof such as a vehicle instrument panel and a rear package tray as shown in FIG. Thus, two GPS antennas 1 sandwich the vehicle roof,
When 2 is arranged, the direction of arrival of the radio wave by the multipath is different from that of the direct wave, and the arrival of the multipath to each antenna can be made different from the antenna directivity due to the shielding of the vehicle roof. Also, two GPS antennas 1,
By placing 2 apart (about 1 to 2 m),
The effect on each antenna is likely to be different for various types of multipath occurrence factors.

The GPS signals received by the GPS antennas 1 and 2 are output to high frequency amplifiers RF3 and RF4 and amplified. The amplified 1.575 GHz signal is then output to mixers MIX5 and MIX6, and the temperature compensated crystal oscillator TC
It is mixed with the signal from XO13. Mixers MIX5, MIX6
Are output to intermediate frequency amplifiers IF7 and IF8,
Amplification of approximately 100-120 dB is performed. In this embodiment, the IF is one stage, but a plurality of stages can be provided as needed. The signals from IFs 7 and 8 are converted to digital signals by A / D converters 9 and 10 and output to spectrum despreaders SS11 and SS12. SS11,12
Then, a C / A code corresponding to the GPS signal is generated by using a clock signal of 1.023 MHz C / A code correlation obtained by dividing the clock signal from the TCXO 13 by the PLL 14, and spectrum despreading is performed. Search and lock the maximum point of code correlation by shifting the phase. In the correlation processing, the correlation calculation is performed in consideration of the Doppler effect of the GPS satellite and the like. In addition, these SS
Numerals 11 and 12 have a multi-channel configuration, which can be individually locked to signal codes of four GPS satellites, respectively, and can be simultaneously locked to the same GPS satellite. In the present embodiment, first, a search is made with the codes of eight GPS satellites, and four satellites having a high-accuracy satellite arrangement are selected from the locked satellites. This allows channels A and B
Both receive signals from the same satellite. SS
The GPS signals despread in 11 and 12 are
15 is output. The CPU 15 calculates a pseudo distance using signals from the SSs 11 and 12 according to a calculation program stored in the ROM 16. The calculated pseudo distance is R
It is stored in the AM 17 and is used for a difference calculation described later.

On the other hand, D transmitted from the reference station by FM multiplexing
The GPS correction data is received by the FM antenna 18,
The signal is converted into an FM composite signal by the receiver 19. F
The signal from the M receiver 19 is output to the decoder 20,
Only the DGPS correction data portion is cut out from the FM composite signal. Then, the extracted DGPS data is output to the CPU 15 via the interface 21. Note that there are several types of DGPS correction data transmission methods. In this embodiment, the error of the pseudorange of each GPS satellite is measured by a reference station, and the correction value of the pseudorange for each GPS satellite is transmitted. US RTCM (Radio
Technical Committeefor Ma
(SC.104 standard) defined by the SC-104 standard. The CPU 15 that has input such correction data corrects the calculated pseudo distance for each satellite (pseudo distance to four GPS satellites) with this correction value, and improves the normal position accuracy to several meters to 10 meters. Let it.

The configuration of this embodiment is as described above.
When the pseudo distance is corrected using the GPS correction data, the accuracy of the DGPS positioning data decreases if a multipath error occurs. Therefore, the presence or absence of a multipath error is detected as follows.

That is, the pseudo distances to four identical GPS satellites are calculated for channels A and B, so that the values of the pseudo distances for channels A and B are substantially equal unless a multipath error occurs. On the other hand, when a multipath error has occurred, a difference larger than the noise of each pseudo distance measurement system occurs in the pseudo distance between the two channels. Normal,
Since the noise of each pseudo distance measurement system is 1 m or less, the difference between the pseudo distances of the two channels with respect to the same GPS satellite is calculated. If the difference is several meters or more, the CPU 15 determines that a multipath error has occurred. Can be determined. Although the case of DGPS is shown in this embodiment, it is apparent that a multipath error can be detected by the same processing as needed in the case of normal GPS.

However, if there is a defect in the signal itself from the GPS satellite, the pseudo distance between the two channels may be different even if no multipath error occurs.
In the case of GPS, it is more reliable to determine whether the DGPS correction data has not changed significantly (whether the amount of change is within a range of, for example, 10 m) and determine whether there is a multipath error. Become.

FIG. 2 is a timing chart showing an example of the multipath error detection processing described above. FIG.
FIG. 2A shows a temporal change of one of pseudo distances for four GPS satellites calculated on channel A, and FIG.
(B) is a change over time of the pseudo distance for the same GPS satellite calculated on channel B. FIG. 2C shows the time change of DGPS correction data for the same GPS satellite transmitted by FM multiplex from the reference station. Time t1 to t2
In the above, the pseudo distance of the channel A and the pseudo distance of the channel B are largely different from each other, and the difference is equal to or more than a predetermined value, and the change amount of the DGPS correction data at that time is not largely changed and is equal to or less than a predetermined value (10 m). In this case, it can be determined that a multipath error has occurred.

In this manner, the presence or absence of a multipath error can be determined. However, if it is determined that a multipath error has occurred, the CPU 15 does not output the positioning data and prevents the position display from "jumping". Can be. Instead of outputting the positioning data, the CPU 15 monitors a change in the vehicle speed, and when the vehicle speed is equal to or less than a predetermined value as shown in FIG. 2D, the pseudo distance (or the distance corrected using the DGPS correction data) is calculated. The smaller change (channel A in the example of FIG. 2)
) Can be output as positioning data and a flag indicating that a multipath error has occurred can be output. Alternatively, the amount of position change estimated based on the detection signals of the direction sensor and the vehicle speed sensor can be used. It is also possible to compare the magnitude of the position change amount obtained by correction with the DGPS correction data, and to output the smaller change amount as the positioning data.

If the positioning data is not output, the driver of the vehicle suddenly disappears from the display screen, causing anxiety. However, by outputting such more reliable positioning data, It is possible to prevent the driver from feeling uneasy.

[0027]

As described above, according to the position locating apparatus using GPS according to any one of claims 1 to 3, it is possible to detect the occurrence of a multipath error and prevent the positioning error.

In particular, in the position locating apparatus using the GPS according to the second aspect, the occurrence of the multipath error can be reliably detected in the DGPS system, and the influence of the multipath error on the highly accurate positioning data of the DGPS. Can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of an embodiment of the present invention.

FIG. 2 is a timing chart of the embodiment.

FIG. 3 is an explanatory diagram of a GPS antenna installation location of the embodiment.

[Explanation of symbols]

1, 2 GPS antenna, 15 CPU, 18 FM antenna, 19 FM receiver, 20 decoder.

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01C 21/00-21/36 G01C 23/00-25/00 G01S 5/00-5/14 G08G 1 / 00-9/02 H04B 7/24-7/26 H04Q 7/00-7/38

Claims (3)

(57) [Claims] 1. A position locating device using a global positioning system, comprising: first and second GPS antennas arranged to be separated by a predetermined distance and receiving signals from the same artificial satellite; and signals received by the first GPS antenna. A first pseudo-range calculating means for calculating a first radio path distance to the artificial satellite based on the first and second antennas; and a second pseudo distance calculating means for calculating a second radio path distance to the artificial satellite based on a signal received by the second GPS antenna. Pseudo distance calculating means, and determining means for determining that a signal from the artificial satellite is in a multipath state when a difference between the first radio path distance and the second radio path distance is equal to or greater than a predetermined value. A position locating device using a differential global positioning system. 2. The position locating apparatus using the global positioning system according to claim 1, further comprising: a receiving unit for receiving correction data from a reference station; and at least the first radio path distance using the received correction data. Or a correction unit for correcting the second radio path distance, wherein the determination unit determines that a difference between the first radio path distance and the second radio path distance is equal to or more than a predetermined value, and is transmitted from a reference station. When the change amount of the corrected data is equal to or less than a predetermined value,
A position locating apparatus using a global positioning system, wherein it is determined that a signal from the artificial satellite is in a multipath state. 3. The position locating apparatus using the global positioning system according to claim 1, further comprising: a step of determining whether the multi-path state is determined by the determining means. A position locating apparatus using a global positioning system, comprising: output control means for outputting positioning data having a smaller change amount.