JP2006126005A - Global positioning system receiving system and position measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a "GPS receiving system and a position measuring method" suppressing inconvenience in which positioning calculation is unavailable, and improving the positioning accuracy. <P>SOLUTION: There are provided: a theoretical receiving electric field intensity calculation part 4 calculating a theoretical receiving electric field intensity range for every plurality of GPS satellites; and a positioning calculation part 3 for calculating positions by using only signal of which the actual receiving electric field intensity detected with a receiving electric field intensity detection part 7 is within the theoretical receiving electric field intensity range, among signals from each GPS satellite which are actually received with a signal receiver 1. By excluding from the positioning calculation, only signal possibly abnormal in receiving electric field intensity and truely including an error component, the inconvenience in which positioning calculation is unavaible because the number of usable GPS signals is too small is suppressed. By the positioning calculation using signal from GPS satellites scattered in as wide range as possible, positioning error due to geometrical calculation is reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a GPS reception system and a position measurement method, and more particularly, to a GPS reception system that receives radio waves transmitted from a plurality of GPS satellites with a GPS receiver and measures an absolute position of a moving object by n-dimensional positioning processing. And suitable.

  Conventionally, as position detection means for detecting the position of a moving body such as a navigation device, inertial navigation (self-contained navigation) that measures the relative position of the moving body using a distance sensor and an angle sensor, and a plurality of GPS ( Global Positioning System) Satellite navigation (GPS navigation) has been put into practical use in which radio waves transmitted from satellites are received by a GPS receiver and the absolute position of a moving object is measured by n-dimensional positioning processing.

  Among these, a positioning system using self-contained navigation can measure the position of a moving body at a relatively low cost, but has a drawback that the position cannot be measured with high accuracy. On the other hand, a positioning system using GPS navigation can generally perform position measurement with higher accuracy than self-contained navigation. However, if radio waves sent from GPS satellites are affected by external noise, propagation path obstacles, or multipaths, positioning errors increase due to the inclusion of error components in the received signals of GPS receivers. There was a drawback that it would.

Conventionally, in order to avoid the disadvantage that the positioning error increases due to the influence of multipath, a technique has been proposed in which positioning calculation is performed only with a signal from a GPS satellite having a high elevation angle (for example, Patent Document 1).
JP-A-6-281721

  In the technique described in Patent Document 1, a signal received from a GPS satellite with a low elevation angle is affected by a multipath in a place where there are many tall buildings along the road such as an urban area. It is uniformly excluded as a thing. However, even if the elevation angle of the GPS satellite is low, there are also good signals that reach the GPS receiver without being affected by multipath. Nevertheless, if signals transmitted from GPS satellites with a low elevation angle are uniformly excluded during positioning calculation, the number of signals that can be used decreases, and positioning calculation itself may not be possible. there were.

  In addition, if positioning calculation is performed using only signals received from GPS satellites with a high elevation angle, only signals from GPS satellites that exist within a narrow range will be used for positioning calculations, and the Dop value will increase, resulting in geometric The error of the general calculation becomes large. Therefore, even if the influence of multipath can be reduced, there is a problem that the positioning error may increase.

  The present invention has been made to solve such problems, and by eliminating only signals that truly contain error components from the positioning calculation, the number of usable GPS signals is small and the positioning calculation is performed. It is an object of the present invention to be able to suppress the inconvenience of being unable to perform and improve the accuracy of position measurement using GPS navigation.

  In order to solve the above-described problems, in the present invention, a theoretical reception electric field strength range is calculated for each GPS satellite based on the distance between a plurality of GPS satellites and a GPS receiver, and is actually received by the GPS receiver. Among the signals from each GPS satellite, the positioning calculation is performed using only the signals whose received electric field strength is within the theoretical range of the received electric field strength.

  According to the present invention configured as described above, the received electric field strength of the signal from each GPS satellite received by the GPS receiver can be received if there is no influence from external noise, propagation path obstacles, multipaths, and the like. The received signal is excluded from the positioning calculation only when it falls outside the range of the theoretical electric field strength that would have been expected. Therefore, unlike the prior art that uniformly excludes a received signal from a GPS satellite having a low elevation angle from the positioning calculation, only a signal having an abnormal received electric field intensity and containing a true error component can be excluded from the positioning calculation.

  As a result, unnecessary GPS signals are not excluded, and it is possible to suppress the inconvenience that positioning calculation cannot be performed due to the small number of usable GPS signals. Also, even if the signal is sent from a GPS satellite with a low elevation angle, it is used for positioning calculation unless the received electric field strength at the GPS receiver is abnormal, so a wide range of GPS satellites are used for positioning calculation. As a result, the Dopp value becomes small, and the positioning error due to geometric calculation can be reduced to improve the accuracy of position measurement.

  Hereinafter, an embodiment of a GPS receiving system according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a functional configuration example of the GPS receiver 10 according to the present embodiment. FIG. 2 is a schematic diagram showing a positional relationship between the GPS receiver 10 according to the present embodiment and a plurality of GPS satellites S1 to S8. Currently, 24 GPS satellites are rotating around the earth, but for convenience of explanation, only eight GPS satellites S1 to S8 are illustrated in FIG. Of these, the number of satellites required for actual positioning is at least 3, usually 4 or more.

  In FIG. 2, a plurality of GPS satellites S <b> 1 to S <b> 8 travel around the earth while transmitting accurate time information and position information representing the place when the radio wave is emitted. The GPS receiver 10 of the present embodiment is mounted on, for example, an in-vehicle navigation device, and receives radio waves emitted from a plurality of GPS satellites S1 to S8 and measures its own position.

  In FIG. 1, reference numeral 1 denotes a signal receiving unit, which is a signal transmitted by radio waves from a plurality of GPS satellites (not shown in FIG. 1) (time information when the above-mentioned GPS satellites S1 to S8 emit radio waves). And the satellite position information) are received via the receiving antenna 2. Reference numeral 3 denotes a positioning calculation unit which calculates the absolute position and the absolute direction of the GPS receiver 10 by performing a three-dimensional positioning process or a two-dimensional positioning process (the absolute direction is the signal Doppler or the current absolute position and one sampling time). (Calculated from the difference from the absolute position before ΔT). This positioning calculation itself can employ a known method.

  Reference numeral 4 denotes a theoretical reception electric field strength calculation unit, which theoretically calculates the signals transmitted from the GPS satellites S1 to S8 based on the distances r1 to r8 between the GPS receiver 10 and the plurality of GPS satellites S1 to S8. A typical received electric field strength range is calculated. Hereinafter, this theoretical method for calculating the received electric field strength range will be described in detail. When calculating the theoretical reception field strength range, first, the distances r1 to r8 between the GPS receiver 10 and the plurality of GPS satellites S1 to S8 are obtained.

  The distances r1 to r8 are, for example, the position information of the GPS satellites S1 to S8 included in the GPS signal received by the signal receiver 1 and the GPS receiver 10 calculated by the positioning calculator 3. It can be obtained from the position information. In addition, when calculating the theoretical received electric field strength range, the signal having the actual received electric field strength deviating from the theoretical value has not yet been excluded, so that the GPS receiver 10 calculated by the positioning calculation unit 3 The position information may include a positioning error. However, this positioning error is about 100 m at most, and is extremely small compared to the distances r1 to r8 with the GPS satellites S1 to S8 which are more than 20,000 km. It can be ignored.

  The distances r1 to r8 between the GPS receiver 10 and the plurality of GPS satellites S1 to S8 are calculated by measuring the time until the radio waves emitted from the GPS satellites S1 to S8 reach the GPS receiver 10. Is also possible. That is, if the correct time when the GPS satellites S1 to S8 emit radio waves is known and the clock of the GPS receiver 10 is accurate, the difference between the time when the radio waves are emitted and the time when the radio waves are received and the speed of the radio waves are obtained. The distances r1 to r8 between the GPS receiver 10 and the respective GPS satellites S1 to S8 are obtained. When this method is applied, the GPS receiver 10 has a function for measuring the reception time of radio waves.

If the distances r1 to r8 between the GPS receiver 10 and each of the GPS satellites S1 to S8 are known, the theoretical reception electric field strength (external noise, propagation path obstacle, multipath, etc.) in the GPS receiver 10 is obtained from the following (Equation 1). If there is no such influence, the theoretical value of the electric field strength of the haze that can be received is obtained.
P _R = (λ / 4πd) ² · P _S (Formula 1)
Here, P _R is the theoretical received power, lambda is wavelength radio wave, d is the distance between the GPS receiver 10 and the GPS satellites S1 to S8 R1 to R8, P _S is the transmit power of each of the GPS satellites S1 to S8 (L1C / A rating is 480 watts).

  As described above, if the distances r1 to r8 between the GPS receiver 10 and each of the GPS satellites S1 to S8 are known, the theoretical received electric field strength can be obtained. However, in order to obtain a more accurate theoretical value, the attenuation rate of the signal intensity that attenuates when radio waves emitted from a plurality of GPS satellites S1 to S8 pass through the ionosphere or the atmosphere, and the directivity pattern of the receiving antenna 2 are used. The theoretical received electric field strength may be obtained in consideration of the antenna gain based on it. The configuration of FIG. 1 shows an example.

  Radio waves emitted from a plurality of GPS satellites S1 to S8 are attenuated when passing through the ionosphere and the atmosphere (ionosphere, stratosphere, troposphere existing in the thermosphere and mesosphere). The state of the atmosphere changes according to the season, time, and region, and the radio wave attenuation rate changes accordingly. Therefore, it is preferable to obtain the theoretical received electric field strength in consideration of the attenuation rate in the atmosphere.

The ionosphere / atmosphere model table information storage unit 5 stores a model-like attenuation rate using such an atmosphere state as a parameter as table information. When considering the influence of signal attenuation due to the atmosphere, the theoretical reception electric field intensity calculation unit 4 attenuates the signal intensity stored in the ionosphere / atmosphere model table information storage unit 5 as shown in the following (Equation 2). Multiply the rate to calculate the theoretical received field strength.
P _R = (λ / 4πd) ² · P _S · G ₁ G ₂ G ₃ (Expression 2)
Here, G ₁ is the attenuation factor in the ionosphere, G ₂ is the attenuation factor in the stratosphere, and G ₃ is the attenuation factor in the troposphere.

  That is, the theoretical reception electric field strength calculation unit 4 is based on the position information of the GPS receiver 10 calculated by the positioning calculation unit 3 and the date / time information measured by a clock (not shown), and the attenuation that matches the information. The rate (attenuation rate according to the season, time, and region) is read from the ionosphere / atmosphere model table information storage unit 5. Then, using the read attenuation rate, the theoretical received electric field strength is calculated according to (Equation 2).

  When the elevation angle of the GPS satellite is high, the distance that radio waves pass through the atmosphere is short. On the other hand, when the elevation angle of the GPS satellite is low, the distance that radio waves pass through the atmosphere becomes long. Therefore, the degree to which radio waves are affected when passing through the atmosphere varies depending on the elevation angle of the GPS satellite. Therefore, the ionosphere / atmosphere model table information storage unit 5 may store a model-like attenuation rate using the elevation angle information of the GPS satellite as a parameter in addition to position information and date / time information as table information.

  In this case, the theoretical reception electric field strength calculation unit 4 includes the position information of the GPS satellites S1 to S8 included in the signal received by the signal reception unit 1 and the GPS reception calculated by the positioning calculation unit 3. From the position information of the aircraft 10, the elevation angle and direction of each of the GPS satellites S1 to S8 are calculated. Then, based on the elevation angle / azimuth information of the GPS satellites S1 to S8 calculated in this way, the position information of the GPS receiver 10 calculated by the positioning calculation unit 3, and the date / time information measured by the clock, The attenuation rate that matches the information is read from the ionosphere / atmosphere model table information storage unit 5, and the theoretical received electric field strength is calculated according to (Equation 2) using the read attenuation rate.

  Further, the receiving antenna 2 has a directivity pattern specific to the antenna as shown in FIG. Therefore, the reception gain (antenna gain) varies depending on the direction from which the reception antenna 2 receives radio waves, that is, the elevation angle and azimuth angle of each of the GPS satellites S1 to S8 viewed from the reception antenna 2, and the reception electric field strength differs. Appears. Therefore, it is more preferable to obtain the theoretical received electric field strength in consideration of such an antenna gain.

  The antenna gain table information storage unit 6 stores, as table information, a model antenna gain using the directivity pattern of the receiving antenna 2 as shown in FIG. 3 and the elevation angle and azimuth angle of the GPS satellite as parameters. When considering the influence of the antenna gain, the theoretical reception electric field strength calculation unit 4 firstly calculates the position information of the GPS satellites S1 to S8 included in the signal received by the signal reception unit 1 and the positioning calculation. From the position information of the GPS receiver 10 calculated by the unit 3, the elevation angle and azimuth angle of each of the GPS satellites S1 to S8 are calculated.

Thereafter, the antenna gain corresponding to the directivity pattern of the receiving antenna 2 is read from the antenna gain table information storage unit 6 based on the obtained elevation angle and azimuth angle of each of the GPS satellites S1 to S8. Then, as shown in the following (Equation 3), the theoretical received electric field strength range is calculated by multiplying the read antenna gain.
P _R = (λ / 4πd) ² · P _S · G _R (Equation 3)
Here, G _R is the antenna gain.

When both the ionosphere / atmosphere attenuation factor and the antenna gain of the receiving antenna 2 are taken into account, the theoretical received electric field strength calculation unit 4 calculates the ionosphere / atmosphere model table as shown in the following (Equation 4). information calculated attenuation factor G ₁ G ₂ G ₃ of the signal intensity stored in the storage unit 5, the theoretical received field strength multiplied by the antenna gain G _R which is stored in the antenna gain table information storage section 6 To do.
P _R = (λ / 4πd) ² · P _S · G ₁ G ₂ G ₃ · G _R (Formula 4)

  Although the theoretical reception electric field strength for each GPS satellite is obtained by the above method, there is a model error considering the influence of the ionosphere and the atmosphere, individual variations in antenna directivity, and the like. Even when a GPS signal can be received under various circumstances, the actual received electric field strength at that time may not always match the calculated theoretical received electric field strength. In order to absorb this error, a predetermined allowable range is provided before and after the obtained theoretical value, and a predetermined range including the theoretical value is set as a theoretical received electric field strength range.

  FIG. 4 is a conceptual diagram showing an example of this theoretical reception field strength range. In FIG. 4, X1 to X8 indicate theoretical received electric field strengths obtained for the GPS satellites S1 to S8. In the example of FIG. 4, an allowable range of Y [dB] (for example, 2 [dB]) is set in the plus direction and the minus direction with the theoretical values X1 to X8 as the center, and the theoretical values X1 to X8 are the center. The 4 dB range is set as a theoretical received electric field strength range.

  Next, 7 is a received electric field strength detection unit, which detects the received electric field strength of the GPS signal actually received by the signal receiving unit 1 for each of the signals from the plurality of GPS satellites S1 to S8. Reference numeral 8 denotes a determination unit that determines whether or not the reception field strength detected by the reception field strength detection unit 7 is within the theoretical reception field strength range calculated by the theoretical reception field strength calculation unit 4. .

  After the theoretical reception field strength calculation unit 4 calculates the theoretical reception field strength range, the positioning calculation unit 3 receives a plurality of signals received by the signal reception unit 1 based on the determination result by the determination unit 8. Among the signals from the GPS satellites S1 to S8, the signal whose received field strength detected by the received field strength detector 7 is in the theoretical received field strength range calculated by the theoretical received field strength calculator 4 The absolute position of the moving body is measured by the n-dimensional positioning process.

  Next, the operation of the GPS receiver 10 configured as described above according to the present embodiment will be described. FIG. 5 is a flowchart showing the operation of the position measuring method using the GPS receiver 10 according to the present embodiment. In FIG. 5, the signal receiving unit 1 first receives signals transmitted by radio waves from a plurality of GPS satellites S1 to S8 (step P1).

  Next, the theoretical reception electric field strength calculation unit 4 is calculated by the positioning calculation unit 3 based on the position information of each of the GPS satellites S1 to S8 included in the signal received in step S1 and the signal, for example. The distances r1 to r8 between the GPS receiver 10 and the plurality of GPS satellites S1 to S8 are obtained based on the position information of the GPS receiver 10 and the GPS satellites S1 to S8 are further determined based on the distance information. A theoretical received electric field strength range in the GPS receiver 10 is calculated for each of the transmitted signals (step P2). At this time, the theoretical reception electric field intensity range may be obtained in consideration of the attenuation rate in the atmosphere of radio waves emitted from a plurality of GPS satellites S1 to S8 and the antenna gain based on the directivity pattern of the reception antenna 2.

  On the other hand, the received electric field strength detector 7 detects the received electric field strength of the GPS signal actually received by the signal receiver 1 for each of the signals from the plurality of GPS satellites S1 to S8 (step P3). Note that the process of step S2 and the process of step S3 may be performed simultaneously.

  When the theoretical reception field strength range and the actual reception field strength are obtained, the determination unit 8 determines whether or not the actual reception field strength is within the theoretical reception field strength range. A determination is made for each of the signals from S8 (step P4). Then, according to the determination result, the positioning calculation unit 3 has a theoretical received electric field strength range in which the actual received electric field strength is a theoretical signal among the GPS signals from the plurality of GPS satellites S1 to S8 received by the signal receiving unit 1. The absolute position of the moving body is measured by the n-dimensional positioning process using only the signal contained within (step P5). The processes in steps P1 to P5 as described above are repeatedly executed.

  As described above in detail, in the present embodiment, a theoretical reception electric field strength range is calculated for each of the plurality of GPS satellites S1 to S8, and the signal from the GPS satellites actually received by the signal receiving unit 1 Signals whose actual received field strength is out of the theoretical received field strength range are excluded from the positioning calculation because they may contain error components, and are within the theoretical received field strength range. Positioning is calculated using only signals.

  Therefore, unlike the conventional technology that uniformly excludes received signals from GPS satellites with low elevation angles from the positioning calculation, only signals that have an abnormal received electric field strength and that may truly contain error components are excluded from the positioning calculation. Can do. Accordingly, it is possible to suppress the inconvenience that the positioning calculation cannot be performed due to the small number of usable GPS signals. In addition, since the positioning calculation can be performed using signals from GPS satellites dispersed as widely as possible, the positioning error due to the geometric calculation can be reduced and the accuracy of the position measurement can be improved.

  In the above embodiment, the example in which the GPS receiver 10 has all the functional configurations shown in FIG. 1 has been described, but the present invention is not limited to this. For example, the GPS receiver includes only the signal receiver 1 and the receiving antenna 2, and the other configurations 3 to 8 are provided in a mobile body (for example, an in-vehicle navigation device) to which the GPS receiver is applied. The GPS reception system may be configured as follows.

In the above embodiment, as the atmosphere of the attenuation factor models, attenuation factor G ₁ in the _ionosphere, attenuation factor G ₂ in the _{stratosphere,} an example has been described to prepare separately attenuation factor G ₃ in the troposphere, these You may make it prepare in advance as one attenuation factor by multiplying beforehand.

  Moreover, although the said embodiment demonstrated the example which stores previously required information in the ionosphere / atmosphere model table information storage part 5 and the antenna gain table information storage part 6, this invention is not limited to this. For example, an ionosphere / atmosphere model table information storage unit 5 and an antenna gain table information storage unit 6 are provided in a server device or the like on the Internet, and when calculating a theoretical received electric field strength range from the server device via the Internet. Necessary information may be downloaded in real time.

  In the above embodiment, the condition that the actual received electric field strength detected by the received electric field strength detector 7 is in the theoretical received electric field strength range calculated by the theoretical received electric field strength calculator 4 is satisfied. Although the example of determining whether or not is described, the following conditions may be added. That is, a condition that a minimum value (for example, −130 [dBm]) necessary for the received electric field strength is set in advance, and the received electric field strength detected by the received electric field strength detection unit 7 must be equal to or higher than the minimum value. It is.

  In this case, the positioning calculation unit 3 has the lowest actual received electric field strength detected by the received electric field strength detection unit 7 among the GPS signals from the plurality of GPS satellites S1 to S8 received by the signal receiving unit 1. Using only the signals that are above and the received electric field strength detected by the received electric field strength detector 7 is in the theoretical received electric field strength range calculated by the theoretical received electric field strength calculator 4, n The absolute position of the moving object is measured by the dimension positioning process. In this way, a signal with a low S / N ratio can be excluded from the positioning calculation even within the theoretical received electric field strength range, and the positioning accuracy can be further improved.

  In addition, each of the above-described embodiments is merely an example of the embodiment for carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. In other words, the present invention can be implemented in various forms without departing from the spirit or main features thereof.

  The present invention is useful for a GPS receiving system that receives radio waves transmitted from a plurality of GPS satellites with a GPS receiver and measures the absolute position of a moving object by n-dimensional positioning processing.

It is a block diagram which shows the function structural example of the GPS receiver by this embodiment. It is a schematic diagram which shows the positional relationship of the GPS receiver by this embodiment, and several GPS satellites. It is a figure which shows the example of the directivity pattern of a receiving antenna. It is a conceptual diagram which shows the example of a theoretical receiving electric field strength range. It is a flowchart which shows the operation example of the position measuring method using the GPS receiver by this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Signal receiving part 2 Reception antenna 3 Positioning calculation part 4 Theoretical reception electric field strength calculation part 5 Ionosphere / atmosphere model table information storage part 6 Antenna gain table information storage part 7 Received electric field intensity detection part 8 Judgment part 10 GPS receiver

Claims (5)

A signal receiving unit that receives signals transmitted from a plurality of GPS satellites by radio waves;
A theoretical reception field strength calculation unit that calculates a theoretical reception field strength range for each of the signals transmitted from each GPS satellite based on the distance to the plurality of GPS satellites;
A received electric field strength detecting unit that detects a received electric field strength of a signal actually received by the signal receiving unit for each of the signals from the plurality of GPS satellites;
Theoretical reception in which the received electric field strength detected by the received electric field strength detector among the signals from the plurality of GPS satellites received by the signal receiver is calculated by the theoretical received electric field strength calculator. A GPS receiving system, comprising: a positioning calculation unit that measures an absolute position of a moving body by n-dimensional positioning processing using only a signal that falls within an electric field strength range. The theoretical received electric field strength calculating unit multiplies the signal received by radio waves from the plurality of GPS satellites by the attenuation factor of the signal strength that is attenuated when passing through the atmosphere. The GPS receiving system according to claim 1, wherein the GPS receiving system is calculated. The theoretical reception electric field strength calculation unit obtains an antenna gain according to a directivity pattern of a reception antenna included in the signal reception unit based on an elevation angle and an azimuth angle of the plurality of GPS satellites, and multiplies the antenna gain. The GPS reception system according to claim 1, wherein the theoretical reception electric field intensity range is calculated. The positioning calculation unit has a reception electric field strength detected by the reception electric field strength detection unit of the signals from the plurality of GPS satellites received by the signal reception unit that is a predetermined value or more, and the reception Using only the signals whose received field strength detected by the field strength detector is within the theoretical received field strength range calculated by the theoretical received field strength calculator, the absolute value of the moving object is obtained by n-dimensional positioning processing. The GPS receiving system according to any one of claims 1 to 3, wherein a position is measured. A first step of receiving at a GPS receiver signals transmitted by radio waves from a plurality of GPS satellites;
A second step of calculating a theoretical reception field strength range in the GPS receiver for each of the signals transmitted from each GPS satellite based on the distance between the plurality of GPS satellites and the GPS receiver;
A third step of detecting, for each of the signals from the plurality of GPS satellites, the received electric field strength of the signal actually received by the GPS receiver;
Of the signals from the plurality of GPS satellites received by the GPS receiver, the received electric field strength detected in the third step is within the theoretical received electric field strength range calculated in the second step. And a fourth step of measuring the absolute position of the moving body by an n-dimensional positioning process using only the input signal.

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