JP4985479B2 - Noise component removal apparatus and program - Google Patents

Description

  The present invention relates to a technique for removing a noise component from a carrier phase measurement value in a GPS (Global Positioning System) receiver or a Global Navigation Satellite System (GNSS) receiver.

  A GPS receiver or a Global Navigation Satellite System (GNSS) receiver (hereinafter collectively referred to as a GPS receiver) calculates a carrier phase measurement value from a frequency signal received from a satellite, and uses the calculated value to The position coordinates of the device are calculated. Although the carrier phase measurement value calculated in the GPS receiver is highly accurate, a reflected wave generated in the surrounding environment of the receiver is mixed as an indirect wave and is measured by the GPS receiver. Due to such a cause, an error occurs in the carrier phase measurement value, and the accuracy of the position estimation calculated from the measurement value is impaired.

  As a known technique for the above problem, by providing a specially designed receiving antenna in the GPS receiver, the intensity of the indirect wave can be suppressed to some extent with respect to the carrier phase measurement value calculated in the GPS receiver. A technique that can be used is provided (for example, Non-Patent Document 1).

  In addition, as another known technique for the above problem, the intensity of the indirect wave is suppressed to some extent with respect to the carrier phase measurement value calculated in the GPS receiver by specially designing the signal processing method of the GPS receiver. Technology that can be used.

Here, regarding the calculation method of the carrier phase measurement value of the GPS receiver, there is a wide range of methods for calculating the linear combination amount with respect to the carrier phase measurement value of the received signal of two frequencies and estimating the geometric distance term and the ionospheric delay term. Are known.
B. Hoffman-Wellenhof, H.H. Richteneger, J.A. Collins, “GPS Theory and Applications”, Springer Fairlark Tokyo Co., Ltd., March 31, 2005, p. 108-109, p. 120-123, p. 240-241

  As described above, conventionally, in order to remove the noise component due to the reflected wave from the carrier wave phase measurement value, it is necessary to provide a receiving antenna and a signal processing circuit. In order to reduce the manufacturing cost, it is not necessary to provide a special configuration, and it is preferable that the noise component can be estimated by a program or the like.

  An object of this invention is to provide the technique which can estimate the noise component contained in the carrier wave phase measured value of a GPS receiver with a simple structure.

In order to solve the above problems, the disclosed noise reduction program is for removing noise components from carrier phase measurement values measured in a global positioning system receiver or a global navigation satellite system (GNSS) receiver. A first linear combination including a geometric distance term for a received signal of two frequencies based on a carrier phase measurement value measured by the global positioning system receiver or the global navigation satellite system receiver. And a second linear combination including an ionospheric delay term, and first and second time variation components are extracted from the calculated first and second linear combinations, respectively, and the first and second time periods are extracted. A covariance matrix is calculated based on the extracted value of the fluctuation component, and the proportional coefficient value based on the calculated covariance matrix component and the first The computer is configured to execute a process of calculating a value obtained by estimating the term derived from the measurement noise included in the first linear combination using the two time fluctuation components.

  It is possible to calculate a variance for a time-varying component of the linear combination created from the carrier phase measurement value, and to estimate a noise component included in the measurement value in the position measurement calculation from the calculated variance.

  Furthermore, it is good also as a structure which makes a computer perform further the process which subtracts the value which estimated the said measurement noise origin term from said 1st linear combination. By removing the noise component included in the measurement value, the accuracy of position measurement is improved.

  According to the disclosed noise reduction apparatus, it is possible to estimate a noise component with respect to a carrier phase measurement value of a global positioning system receiver with a simple configuration.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram of a global positioning system including a GPS receiver according to the present embodiment. As shown in FIG. 1, the global positioning system includes a GPS satellite 10 and a GPS receiver 1.

  The GPS satellite 10 transmits data including time information and orbit information of the GPS satellite 10 itself on a signal and transmits it to the ground. The GPS receiver 1 calculates the position coordinates of its own device from the two frequency signals received from the GPS satellite 10.

The GPS receiver 1 according to the present embodiment includes a carrier phase measurement unit 2, a noise reduction unit 3, and a coordinate calculation unit 4.
The carrier wave phase measurement unit 2 of the GPS receiver 1 calculates a carrier wave phase measurement value from the two frequency signals received from the GPS satellite 10. The noise reduction unit 3 calculates a noise component included in the carrier phase measurement value and removes the obtained noise component. The coordinate calculation unit 4 calculates and outputs the position coordinates of the GPS receiver 1 using the carrier phase measurement value from which the noise component has been removed in the noise reduction unit 3.

  The GPS receiver 1 receives two frequency signals from a plurality of satellites 10 but is omitted from FIG. FIG. 1 shows only the configuration related to the process of calculating the position coordinates of the GPS receiver 1 from the carrier phase measurement value.

  In the GPS receiver 1 shown in FIG. 1, the noise reduction unit 3 estimates the noise component of the carrier phase measurement value and removes the noise component. Hereinafter, a method for estimating a noise component by the GPS receiver 1 according to the present embodiment will be specifically described.

  FIG. 2 is a configuration diagram of the noise reduction unit 3 in the GPS receiver 1 according to the present embodiment. 2 includes a linear combination amount calculation unit 11, a first time variation component extraction unit 12, a second time variation component extraction unit 13, a covariance matrix calculation unit 14, a correlation coefficient / proportional coefficient. An estimation unit 15, an update determination unit 16, an estimated proportional coefficient storage unit 17, an estimated noise calculation unit 18, and a noise removal unit 19 are included.

The linear combination amount calculation unit 11 calculates the linear combination amount from the carrier phase measurement value of the two-frequency GPS receiver 1 input from the carrier phase measurement unit 2.
The first time variation component extraction unit 12 and the second time variation component extraction unit 13 extract a time variation component (a component that varies rapidly) from the linear combination amount calculated by the linear combination amount calculation unit 11 and separates it. To do. Specifically, it is composed of a high-pass filter. Among these, the first time variation component extraction unit 12 separates the time variation component (first time variation component) from the linear combination including the geometric distance term ρ, and the second time variation component extraction unit 13 includes the ionosphere. A time variation component (second time variation component) is separated from the linear combination including the delay term I.

  The geometric distance term ρ is a term representing the geometric distance between the GPS satellite 10 and the GPS receiver 1, and the ionospheric delay term I is the ionospheric electron existing between the GPS satellite 10 and the GPS receiver 1. This is a term representing the delay caused by density.

The covariance matrix calculation unit 14 calculates a covariance matrix from the first and second time variation components obtained by extraction and separation by the first and second time variation component extraction units 12 and 13.
The correlation coefficient / proportional coefficient estimation unit 15 obtains a correlation coefficient and a proportional coefficient from the covariance matrix calculated by the covariance matrix calculation unit 14. Here, the proportionality coefficient means σ _αβ / σ _αα expressed in the equation (12) described later. The update determination unit 16 determines whether or not a predetermined condition is satisfied for the correlation coefficient calculated from the carrier phase measurement value at time t obtained by the correlation coefficient / proportional coefficient estimation unit 15. When the update determination unit 16 determines that the correlation coefficient satisfies the above-described predetermined condition and can be used for noise component estimation, the estimated proportional coefficient storage unit 17 uses the carrier phase measurement value at time t. The proportionality coefficient σ _αβ / σ _αα obtained from the calculated covariance matrix is stored. The stored value before that is updated (overwritten).

The estimated noise calculation unit 18 multiplies the estimated proportional coefficient storage unit 17 by the proportional coefficient stored at that time, and estimates the measurement noise-derived term from the linear combination including the geometric distance term ρ.
The noise removing unit 19 removes the noise component from the carrier phase measurement value using the noise component calculated by the estimated noise calculating unit 18 and outputs the result.

A method for estimating the measurement noise in the noise reduction unit 3 shown in FIG. 2 will be specifically described.
First, the carrier phase measurement value φ and the measurement noise δφ input to the linear combination amount calculation unit 11 are expressed by the following equations (1) and (2).

上記の式（１）及び式（２）のうち、ｋはＧＰＳ衛星１０、Ｌ１及びＬ２は２周波数信号、λはＧＰＳ信号波長、Ｉは電離圏遅延項、ρはＧＰＳ受信機１とＧＰＳ衛星１０との幾何距離、Ｎはバイアス項、κ（＝５９２９／３６００＝１．６４６９）は定数をそれぞれ表す。このうち、バイアス項Ｎについては、時間的に一定値である。

Of the above equations (1) and (2), k is a GPS satellite 10, L1 and L2 are two frequency signals, λ is a GPS signal wavelength, I is an ionospheric delay term, and ρ is a GPS receiver 1 and a GPS satellite. 10 is a geometric distance, N is a bias term, and κ (= 5929/3600 = 1.6469) is a constant. Among these, the bias term N is a constant value in time.

  The linear combination amount calculation unit 11 obtains the linear combination amounts represented by the following equations (3) to (6) from the above equations (1) and (2).

このうち、式（４）及び式（６）にそれぞれ含まれる測定雑音

Among these, the measurement noise included in each of the equations (4) and (6)

及び

as well as

の線形結合量については、以下の式（７）及び式（８）で表される。

The linear combination amount is expressed by the following equations (7) and (8).

式（３）及び式（４）においては、幾何距離項ρを含まず、電離層遅延項Ｉを含んでいる。一般的には電離層遅延項Ｉの時間変動は小さいため、時系列データに対するフィルタ処理の方法を用いて時間変動雑音

In the equations (3) and (4), the geometric distance term ρ is not included and the ionospheric delay term I is included. In general, since the time variation of the ionospheric delay term I is small, the time variation noise is calculated using a filtering method for time series data.

を分離することにより、測定雑音由来項、すなわち式（７）をほぼ正確に分離抽出することができる。

Can be separated and extracted almost accurately from the measurement noise-derived term, that is, the equation (7).

  On the other hand, in the equations (5) and (6), the ionospheric delay term I is not included, but the geometric distance term ρ is included. Since the coordinates of the GPS receiver 1 are reflected in the geometric distance term ρ, the components separated by performing the filtering process include not only measurement noise but also fluctuations in the coordinates of the GPS receiver 1. The impact of that. For this reason, the measurement noise shown in Expression (8) is not accurately separated.

Therefore, first, a time variation component is separated and extracted from the linear combination obtained from the carrier phase measurement value. Specifically, the filter processing is further performed on the expression (5) by the first time variation component extraction unit 12 in FIG.

を分離する。また、式（３）に対し、図２の第２の時間変動成分抽出部１３においてフィルタ処理を行い、時間変動雑音

Isolate. Further, the filter processing is performed on the expression (3) in the second time variation component extraction unit 13 of FIG.

を分離する。
そして、共分散行列算出部１４において、これらの共分散行列を計算する。共分散行列は、以下の式（９）、式（１０）で表される。

Isolate.
Then, the covariance matrix calculation unit 14 calculates these covariance matrices. The covariance matrix is expressed by the following equations (9) and (10).

式（９）、（１０）で表される共分散行列の相関係数は、以下の式（１１）により表される。

The correlation coefficient of the covariance matrix expressed by the equations (9) and (10) is expressed by the following equation (11).

相関係数・比例係数推定部１５は、２変量相関に関する一般論に基づき、得られた共分散行列の成分を用いて比例係数σ_αβ／σ_ααを計算し、推定雑音算出部１８は、第２の時間変動成分（電離層遅延項Ｉを含む線形結合から抽出した時間変動成分）と比例係数σ_αβ／σ_ααとから、式（１２）の計算を行い、第１の線形結合のうちの測定雑音由来項の推定値を得る。

The correlation coefficient / proportional coefficient estimation unit 15 calculates the proportional coefficient σ _αβ / σ _αα using the components of the obtained covariance matrix based on the general theory regarding bivariate correlation, and the estimated noise calculation unit 18 From the two time-varying components (time-varying components extracted from the linear combination including the ionospheric delay term I) and the proportionality coefficient σ _αβ / σ _αα , the calculation of Expression (12) is performed, and the measurement of the first linear combination Obtain an estimate of the noise-derived term.

そして、式（１２）により表される第１の線形結合のうちの測定雑音の推定値を、式（１３）に示すように幾何距離項ρを含む線形結合（すなわち式（６））から減算する。

Then, the estimated value of the measurement noise in the first linear combination represented by the equation (12) is subtracted from the linear combination including the geometric distance term ρ as shown in the equation (13) (that is, the equation (6)). To do.

これにより、幾何距離項ρを含む線形結合から測定雑音が除去される。
図３は、本実施形態に係る雑音低減方法を用いて搬送波位相測定値から雑音成分を除去した場合の幾何距離項ρを含む線形結合の時系列値を示す例のグラフである。ただしグラフ内に収まるように幾何距離の既知オフセット成分は除去してグラフ化している。

Thereby, measurement noise is removed from the linear combination including the geometric distance term ρ.
FIG. 3 is a graph of an example showing a linear combination time series value including the geometric distance term ρ when the noise component is removed from the carrier phase measurement value using the noise reduction method according to the present embodiment. However, the known offset component of the geometric distance is removed so as to fit in the graph.

  As shown in FIG. 3, a geometric distance measurement including smaller noise is obtained by estimating a noise component from a linear combination including an ionospheric delay term I and removing the estimated noise component from a linear combination including a geometric distance term ρ. Therefore, the accuracy of coordinate calculation can be improved.

In addition, about the correlation coefficient shown to Formula (11), even during the position measurement of the GPS receiver 1, the value is always monitored and it can respond to the possibility that a correlation changes.
Specifically, the update determination unit 16 determines whether or not the correlation coefficient obtained by the correlation coefficient / coefficient estimation unit 15 satisfies a predetermined condition. As a predetermined condition, in the embodiment, when the correlation coefficient takes a value of 0.5 or more, it is determined that the noise component has a significant correlation, and the noise component is estimated using the proportional coefficient σ _αβ / σ _αα. To use. When the correlation coefficient is less than 0.5, since the proportional coefficient σ _αβ / σ _αα when the condition of “0.5 or more” has been satisfied in the past is stored in the estimated coefficient storage unit 17, it is read out therefrom. The noise component is estimated using the read value.

Furthermore, in the GPS receiver 1 mounted on a moving body or the like, it may be difficult to estimate the correlation effect of measured value noise due to the influence of fluctuations in the receiver coordinates, for example. Even in such a case, the proportionality coefficient σ _αβ / σ _αα under conditions that have been estimated in the past can be stored and used to estimate the magnitude of the measured value noise.

  As for the presence or absence of the influence of the receiver coordinate fluctuation, the presence or absence of movement of the GPS receiver 1 is determined by a stationary sensor. When it is determined that the GPS receiver 1 is moving, for example, the speed fluctuation is calculated from the coordinates calculated in the GPS receiver 1. When the GPS receiver 1 is mounted on an automobile or the like, acceleration is calculated from the number of rotations of the tire, and the speed of a moving body such as an automobile is obtained from the acceleration.

Then, by calculating the speed fluctuation amount by the above method, extracting the time fluctuation component by the high-pass filter and comparing it with the geometric distance, it is possible to determine the presence or absence of the influence of the receiver coordinate fluctuation. For example, the time constant is 180 seconds. When it is determined that the influence of the receiver coordinate fluctuation is large, the measurement noise is estimated using the proportionality coefficient σ _αβ / σ _αα stored in the estimated proportionality coefficient storage unit 17.

  As described above, according to the noise reduction method according to the present embodiment, the carrier phase measurement value is expressed by the linear combination amount, and the term derived from the measurement noise is estimated from the expression expressed by the linear combination, and the geometric By removing from the linear combination including the distance term ρ, the influence of the estimated noise in the coordinate calculation is reduced. There is no need to provide a special receiving antenna or signal processing circuit in order to eliminate measurement noise. That is, it is possible to reduce the influence of measurement noise in the coordinate calculation of the GPS receiver 1 by mounting the program for causing the computer to execute the above method in the GPS receiver 1 with a simple configuration. .

It is a block diagram of the global positioning system containing the GPS receiver which concerns on embodiment. It is a block diagram of the noise reduction part which concerns on embodiment. It is a graph which shows the example of the time series value of the linear combination containing the geometric distance term at the time of removing a noise component from a carrier wave phase measured value using the noise reduction method concerning an embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 GPS receiver 2 Carrier phase measurement part 3 Noise reduction part 4 Coordinate calculation part 10 GPS satellite 11 Linear combination amount calculation part 12 1st time fluctuation component extraction part 13 2nd time fluctuation component extraction part 14 Covariance matrix calculation part 15 Proportional Coefficient / Correlation Coefficient Estimating Unit 16 Update Determination Unit 17 Estimated Proportional Coefficient Storage Unit 18 Estimated Noise Calculation Unit 19 Noise Removal Unit

Claims (5)

A noise component removal program for removing noise components from carrier phase measurement values measured by a global positioning system receiver or a global navigation satellite system (GNSS) receiver,
A second linear combination including a first linear combination and an ionospheric delay term including a geometric distance term for a received signal of two frequencies based on a carrier phase measurement measured by the global positioning system receiver or the global navigation satellite system receiver; Calculate the linear combination of
First and second time variation components are extracted from the calculated first and second linear combinations, respectively.
Calculating a covariance matrix based on the extracted values of the first and second time-varying components;
Using the proportional coefficient value based on the calculated covariance matrix component and the second time-varying component, calculate a value that estimates the measurement noise-derived term included in the first linear combination;
A noise component removal program that causes a computer to execute processing. The noise component removal program according to claim 1, further causing the computer to execute a process of subtracting a value obtained by estimating the term derived from the measurement noise from the first linear combination. Further causing the computer to execute a process of determining whether or not a value of a correlation coefficient for the covariance matrix satisfies a predetermined condition,
In the process of calculating a value that estimates the term derived from the measurement noise, if it is determined that the value of the correlation coefficient does not satisfy the condition, the proportional coefficient value at that time is not used, and the storage means before that The noise component removal program according to claim 2, wherein a value obtained by estimating the term derived from the measurement noise is calculated using the stored proportional coefficient value. In the process of determining whether the value of the correlation coefficient satisfies a predetermined condition,
Determining whether the value of the correlation coefficient takes a correlation value equal to or greater than a predetermined threshold;
When the value of the correlation coefficient takes a correlation value equal to or greater than the predetermined threshold value, the proportional coefficient at time t is stored in the storage means,
In the process of calculating a value obtained by estimating the term derived from the measurement noise, if it is determined that the correlation coefficient value at time t + n takes a correlation value less than the predetermined threshold value, it is stored in the storage means. The noise component elimination program according to claim 3, wherein a value obtained by estimating the term derived from the measurement noise is calculated using a proportional coefficient of time t. Includes a first linear combination and ionospheric delay term that includes a geometric distance term for a received signal at two frequencies based on a carrier phase measurement measured with a Global Positioning System receiver or a Global Navigation Satellite System (GNSS) receiver A linear combination amount calculating means for calculating a second linear combination;
Time variation component extraction means for extracting the first and second time variation components from the first and second linear combinations calculated by the linear combination amount calculation means;
A covariance matrix calculating means for calculating a covariance matrix based on values obtained by extracting the first and second time varying components by the time varying component extracting means;
A value obtained by estimating a measurement noise-derived term included in the first linear combination by using a proportional coefficient value based on the component of the covariance matrix calculated by the covariance matrix calculating means and the second time variation component. An estimation means for calculating
A noise component removing apparatus comprising:

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