JP4650334B2 - Satellite positioning device - Google Patents

Description

  The present invention relates to a satellite positioning device that receives a signal from a satellite and calculates its own position.

  The satellite positioning device receives signals transmitted from a plurality of satellites orbiting the earth orbit and calculates its current position based on information included in the received signals (see, for example, Patent Document 1). .

A conventional satellite positioning device obtains satellite orbit information from signals transmitted from the satellite, and when the approximate measurement position and approximate time are known, the priority of the satellite with a high elevation angle is given as the order of searching for the satellite. The ranking is high.
Japanese Patent Laid-Open No. 3-108609

  By the way, when there are a plurality of satellites whose elevation angles are higher than the values set by the satellite positioning device (hereinafter referred to as visible satellites) and the acquisition priority of these satellites is high, the conventional satellite positioning is performed. The device captured all of those satellites.

  However, the positioning accuracy is almost the same between when all the satellites that are close to each other are captured and when only one of them is captured.

  In order to maintain good positioning accuracy, it is better to perform positioning using satellites that are dispersed as much as possible. However, if the number of reception channels of the satellite positioning device is small, if all of the multiple satellites that are close to each other are captured, other satellites cannot be captured due to the insufficient number of reception channels, and the positioning accuracy and positioning rate Has led to a decline.

  Thus, in order to capture satellites that are dispersed as much as possible, the number of reception channels is increased to cope with this problem, but there is a problem that the scale of hardware increases. In addition, there is a problem that power consumption increases accordingly.

  For example, in the case of a satellite positioning device that can be used in combination with a GPS compatible system, such as Galileo being developed in Europe and Japan's Quasi-Zenith Satellite, the number of satellites that can be used in the satellite positioning system increases. Only high-satellite satellites can be captured, and positioning accuracy may be reduced.

  The present invention has been made in view of the above, and an object of the present invention is to provide a satellite positioning device that can reduce the increase in hardware scale and the accompanying increase in power consumption.

  The satellite positioning device of the present invention is a satellite positioning device that performs positioning of the current position based on a signal received from a satellite, and capture means for capturing the satellite to obtain information for positioning from the signal transmitted by the satellite A C / N calculating means for calculating the C / N of a signal received from a captured satellite captured by the capturing means, and a plurality of visible areas that can be observed in the present apparatus based on azimuth and elevation angles. Based on which area of the area the classification means classifies the captured satellite, and when the number of captured satellites present in the area is the same among the plurality of areas, When the elevation angle of the area, the number of the acquired satellites, and the elevation angle of the area are the same, the minimum C / N value of the signal from the acquisition satellite existing in the area, the number of the acquisition satellites, the elevation angle of the area, and the C / When the minimum values of the two are the same, an exclusion target region is selected based on the priorities set in advance in the plurality of regions, and the signal C to be transmitted is selected from the captured satellites existing in the selected exclusion target region. An exclusion target selection unit that selects the captured satellite having the smallest / N as an exclusion target satellite, excludes the exclusion target satellite from the capture target, and captures a satellite that exists in the region where the capture satellite is not included among the plurality of regions. And a control means for controlling the capturing means.

  Since the satellite positioning device of the present invention selects and excludes the satellites to be excluded from the satellites that are being captured, and the satellites that exist in the area where there are no satellites to be captured are captured, the number of received channels is small. However, the satellite can be captured so as to maintain good positioning accuracy and positioning rate, and the increase in hardware scale and the accompanying increase in power consumption due to an increase in the number of reception channels can be reduced.

  The best mode for carrying out the satellite positioning device of the present invention will be described below with reference to the drawings. In the following, a GPS satellite will be described as an example of a satellite used for positioning.

  FIG. 1 is a block diagram showing a configuration of a satellite positioning device according to an embodiment of the present invention.

  As shown in FIG. 1, the satellite positioning device of this embodiment includes an antenna 1, a receiving unit 2 that receives a GPS signal transmitted by a GPS satellite through the antenna 1, and outputs a received signal, and reverses the received signal. Included in the received signal are despreading processing units 3a, 3b,..., 3n for spreading, C / N calculating units 4a, 4b,. Navigation data demodulation units 5a, 5b,..., 5n for demodulating the navigation data, a storage unit 6 for storing the navigation data and the like, a positioning calculation unit 7 for calculating the current position of the satellite positioning device from the navigation data, A classification unit 8 that groups the GPS satellites to be captured is provided, and a control unit 9 that controls each unit provided in the apparatus. The despreading processing units 3a, 3b, ..., 3n, the C / N calculation units 4a, 4b, ..., 4n, and the navigation data demodulation units 5a, 5b, ..., 5n each have a number n of received channels. The same number is provided, and signals from n GPS satellites can be processed simultaneously. In addition, the positioning calculation unit 7 includes a DOP calculation unit 71 that calculates PDOP and HDOP which are two accuracy reduction rates based on the navigation data.

  The GPS signal transmitted from the GPS satellite is spectrum-spread with a pseudo noise code composed of a synthesized wave of a C / A code for identifying the GPS satellite and navigation data such as orbit information and time information of the GPS satellite.

  When receiving the GPS signal transmitted from the GPS satellite via the antenna 1, the receiving unit 2 outputs the received signal to the despreading processing units 3a, 3b,.

  Each of the despreading processing units 3a, 3b,... Despreads the received signal using a PN code (pseudorandom code). Here, the PN code used for the despreading process takes a value determined for each GPS satellite, and by selecting this PN code, it is possible to select a GPS satellite that acquires data from the GPS signal. . This reception operation is generally referred to as acquisition of a GPS satellite because it searches for a GPS satellite and obtains data from the GPS satellite. The PN code corresponding to each satellite is stored in advance in the storage unit 6, and the GPS satellite to be captured can be selected based on control from the control unit 9.

  The C / N calculation units 4a, 4b,... Calculate the C / N of the despread received signal. Thereafter, the navigation data demodulation units 5a, 5b,... Can obtain navigation data such as almanac data and ephemeris data transmitted from GPS satellites by demodulating the received signals.

  Here, almanac data includes rough orbit information of all satellites, and ephemeris data includes satellite orbit information, clock correction information, and the like. The obtained navigation data is output to the positioning calculation unit 7 and stored in the storage unit 6.

  Then, the positioning calculation unit 7 calculates the current position of the satellite positioning device using the navigation data, and outputs the calculation result to the storage unit 6. In addition, the positioning calculation unit 7 outputs positioning dimension information indicating how many-dimensional position calculation has been performed in the calculation of the current position to the control unit 9.

  The signal transmitted from each GPS satellite includes the transmission time of the signal in addition to almanac data and ephemeris data. The distance (pseudo distance) between the GPS satellite and the satellite positioning device is calculated by multiplying the time difference between this transmission time and the time at which the satellite positioning device received the transmission signal from the GPS satellite by the speed of light. The position can be calculated by solving simultaneous equations with the position coordinates as unknowns using the pseudo distance.

  Here, when performing three-dimensional positioning, since there are three longitudes, latitudes, altitudes, and unknowns, it is necessary to capture at least three GPS satellites. Furthermore, since the clock of the satellite positioning device (not shown) is inaccurate as compared with the GPS satellite clock, one error correction amount of the clock is added as an unknown to eliminate the clock (time) error. It is necessary to solve an equation consisting of four unknowns. Therefore, when performing three-dimensional positioning, it is necessary to simultaneously capture four or more GPS satellites.

  In addition, the DOP calculation unit 71 calculates a precision reduction rate (DOP) due to the geometric arrangement of the GPS satellites to be captured based on the navigation data. Here, PDOP indicating the accuracy reduction rate in the horizontal and vertical directions and HDOP indicating the accuracy reduction rate in the horizontal direction are calculated. Then, the calculated PDOP and HDOP are output to the control unit 9.

  Here, with reference to the flowchart shown in FIG. 2, the procedure for replacing the GPS satellites to be captured in the satellite positioning apparatus according to the present embodiment will be described.

  First, in step S <b> 10, the control unit 9 determines whether three-dimensional positioning is performed based on the positioning dimension information from the positioning calculation unit 7. If three-dimensional positioning has been performed (YES), the process proceeds to step S20. If three-dimensional positioning has not been performed (NO), the process returns to step S10.

Next, in step S20, the control unit 9, PDOP determines whether a preset threshold value _{P 0} less. P ₀ smaller (YES), if the process proceeds to step S30, if not less than _{P 0} (NO) the flow returns to step S10.

Next, in step S30, the control unit 9, HDOP determines whether a preset threshold value _{H 0} is less than. H ₀ is less than (YES), if the process proceeds to step S40, if not less than _{H 0} (NO) the flow returns to step S10.

  PDOP and HDOP indicate that the smaller the value, the better the positioning accuracy. If the positioning accuracy is poor, the positioning itself may not be possible if the captured GPS satellites are excluded from the capture targets in the processing described later. Therefore, the processes of steps S20 and S30 are performed to confirm that the positioning is performed with a certain degree of accuracy.

Thereafter, in step S40, the control unit 9, using the navigation data, searching for visible satellites not in capturing object, and it calculates the number SV _1, determines whether the SV 1> _0. If SV ₁ > 0 (YES), the process proceeds to step S50. If SV ₁ > 0 is not satisfied (NO), the process returns to step S10.

  Next, in step S50, the control unit 9 controls the classification unit 8 to group the GPS satellites to be captured based on the azimuth angle and elevation angle. The classification unit 8 has, for example, an elevation angle of 90 to 60, 60 to 30, 30 to 15, 15 to 0 deg, and an azimuth angle of 0 to 60, 60 to 120, 120 to 180, 180 to 240, 240 to 300, 300 to The visible region (elevation angle 0 to 90 deg, azimuth angle 0 to 360 deg) that can be observed with this device is divided into a total of 24 areas, and the navigation satellite data is used to locate the GPS satellites to be captured. It is determined whether it is classified, and the classification result is output to the control unit 9.

Next, in step S60, the control unit 9 is a visible satellite that is not a capture target and is present in an area where there is no capture target GPS satellite based on the navigation data and the classification result from the classification unit 8. And the number SV ₂ is calculated, and it is determined whether SV ₂ > 0. When SV ₂ > 0 (YES), the process proceeds to step S70, and when SV ₂ > 0 is not satisfied (NO), the process returns to step S10.

  In step S70, the control unit 9 determines GPS satellite candidates to be excluded from the capture target. Candidates are determined by the following two procedures. First, as a first procedure, a candidate area is selected.

  Here, as the priority of area selection, the first is the order of the number of GPS satellites to be captured included in the area. This is because GPS satellites used for positioning are better distributed if they are distributed as much as possible, so that GPS satellites that are close to other GPS satellites are first excluded candidates. The second priority of area selection is the descending order of area elevation angle. This is because GPS satellites with a high elevation angle are often originally captured, so that the GPS satellites used for positioning are dispersed.

  The third priority of area selection is the order in which the minimum C / N of signals from the GPS satellites to be captured included in the area is small. This is because using a GPS satellite having a small C / N indicating the signal reception intensity for positioning is likely to cause an error. The fourth area selection priority is the priority order of the areas. The priority of the area is set in advance by the elevation angle and direction.

  Then, as the second procedure for determining the candidate GPS satellites to be excluded from the capture target, the smallest C / N among the capture target GPS satellites existing in the area selected in the first procedure above. Are determined as candidates for exclusion.

  Next, in step S80, the control unit 9 calculates PDOP and HDOP when the determined exclusion candidate GPS satellite is excluded from the capture target, and calculates change rates PR and HR from PDOP and HDOP when not excluded. The DOP calculation unit 71 is controlled to do so.

In step S90, the control unit 9 determines whether the threshold value PR ₀ is smaller than the rate of change PR is preset PDOP. If it is smaller than PR ₀ (YES), the process proceeds to step S90. If it is not smaller than PR ₀ (NO), the process returns to step S10.

Next, in step S100, the control unit 9 determines whether the threshold value HR ₀ is smaller than the rate of change HR is preset HDOP. If smaller than HR ₀ (YES), the process proceeds to step S110, and if not smaller than HR ₀ (NO), the process returns to step S10.

  In step S110, the control unit 9 excludes the exclusion candidate GPS satellites from the capture target, and despreads the GPS satellites searched in step S60 so that one GPS satellite is used as the capture target instead. The units 3a, 3b,... Are controlled.

If a plurality of GPS satellites are searched in step S60, they are first selected in descending order of elevation angle, and then selected in order of satellite number. Then, it returns to step S10 and repeats the subsequent processes.

  As described above, according to the present embodiment, the GPS satellites to be captured are classified by area, the GPS satellites to be excluded are selected and excluded from the captured GPS satellites, and instead captured and captured. Since GPS satellites selected from visible satellites that exist in areas where there are no GPS satellites are targeted for acquisition, channel allocation can be optimized, and positioning accuracy and positioning rate can be maintained well even with a small number of received channels GPS satellites can be captured. As a result, the increase in the hardware scale and the accompanying increase in power consumption and price due to an increase in the number of reception channels can be reduced.

  In addition, when a captured GPS satellite is excluded from the capture target and a free channel is created, this free channel can be used as a reception channel for a complementary system such as a WAAS (Wide Area Augmentation System). Thus, the positioning accuracy can be improved, and when a hybrid receiver with such a GPS compatible system is constructed, an increase in the number of reception channels can be suppressed, and power consumption and price can be suppressed.

It is a block diagram which shows the structure of the satellite positioning apparatus which concerns on one embodiment of this invention. 2 is a flowchart showing a procedure for replacing GPS satellites to be captured in the satellite positioning device shown in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 Receiving part 3a, 3b, ..., 3n Despreading processing part 4a, 4b, ..., 4n C / N calculation part 5a, 5b, ..., 5n Navigation data demodulation part 6 Storage part 7 Positioning Calculation unit 8 Classification unit 9 Control unit

Claims (1)

A satellite positioning device that measures the current position based on a signal received from a satellite,
Capture means for capturing the satellite to obtain information for positioning from the signal transmitted by the satellite;
C / N calculating means for calculating C / N of a signal received from a captured satellite captured by the capturing means;
Classification means for classifying the captured satellites based on which of a plurality of regions divided based on an azimuth angle and an elevation angle a visible region observable in the apparatus,
Among the plurality of regions, the number of the captured satellites existing in the region, the elevation angle of the region when the number of the captured satellites is the same, the number of the captured satellites, and the elevation angle of the region are the same when the number is the same. When the C / N minimum value of the signal from the acquired satellite, the number of acquired satellites, the elevation angle of the area, and the minimum value of the C / N are the same, the priority set in advance in the plurality of areas Based on this, an exclusion target region is selected, and from among the captured satellites present in the selected exclusion target region, the captured satellite having the smallest C / N of the signal to be transmitted is selected as the exclusion target satellite. When,
A satellite positioning system comprising: control means for excluding the exclusion target satellite from the acquisition target and controlling the acquisition means so as to acquire a satellite existing in an area where the acquisition satellite is not included among the plurality of areas. apparatus.

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