JPH08201504A - Gps receiver - Google Patents

Abstract

PURPOSE: To provide a GPS receiver for reducing the processing time of the estimation value calculation of position measurement error and for improving accuracy. CONSTITUTION: A pseudo distance error dispersion estimation means 4 assumes the dispersion of pseudo distance error as the normal distribution of an average 0 for estimation and a position measurement calculating means 3 detects the information of the layout of a GPS satellite. A first position measurement error estimating means 5 outputs the estimation value of position measurement error based on the dispersion estimation value of the pseudo distance error and the layout information of the GPS satellite, thus reducing calculation count required for extracting the position measurement error.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a GPS that orbits the earth.
GP that calculates its own position and moving speed using satellites
The present invention relates to an S receiver.

[0002]

2. Description of the Related Art GPS (Global Positioning System)
Is a system for calculating the position and moving speed of a GPS receiving device by simultaneously receiving satellite signals (radio waves) from a plurality of GPS satellites and acquiring navigation messages (orbit information, time information, etc.) from the GPS satellites. Is.

Assuming that the clocks of the GPS satellite and the GPS receiving device are correctly set, the GPS is obtained by multiplying the difference between the time when the GPS satellite transmits the radio wave and the time when the GPS receiving device receives the radio wave. The relative distance between the satellite and the GPS receiver can be obtained. The distance thus obtained is called a pseudo distance.

Also, the absolute position of the GPS satellite can be known from the orbit information in the navigation message. Therefore,
In principle, in order to calculate the position of the GPS receiver in three dimensions, it is sufficient to know the position of the GPS satellite and the pseudo range for three or more GPS satellites.

In reality, there is an error between the clock of the GPS satellite and the clock of the GPS receiving apparatus, so the error of the clock is set as an unknown number. Therefore, simultaneous equations for four or more GPS satellites must be established. At this time, GP
The altitude information of the S receiver is obtained. Further, when calculating a two-dimensional position, it is sufficient to receive radio waves from three or more GPS satellites.

However, the calculated pseudorange includes an error due to atmospheric layer delay and ionospheric delay and an error artificially added. Errors due to atmospheric layer delay and ionospheric delay can be removed to some extent by a correction calculation using a correction value. The error that can be predicted on the GPS satellite side at the time of transmission is given in the navigation message in the form of accuracy.

Due to the error of the pseudo distance, an error occurs in the positioning result (hereinafter, referred to as positioning error). Therefore, the error of the pseudo distance between the GPS receiver and each GPS satellite is estimated from the accuracy and each correction value, and this estimated value and GP
The positioning error is estimated from the information on the S satellite arrangement. Then, the maximum value of the positioning error that can be considered as the positioning error is output.

An example of the above-mentioned conventional GPS receiver will be described below with reference to the drawings. FIG. 4 is a block diagram showing the configuration of a conventional GPS receiver. FIG.
1, 1 is a GPS antenna, 2 is satellite signal receiving means, 3 is positioning calculation means, 6 is pseudorange error estimation means, and 7 is
Is a second positioning error estimation means.

FIG. 5 shows a conventional method for extracting an estimated value of positioning error.
It is a flowchart shown. In step # 51, pseudo
The pseudo distance error is calculated by the distance error estimating means 6.
Rush, error due to atmospheric delay, error due to ionospheric delay
Extrapolate from Errors due to atmospheric and ionospheric delays
Only the value equal to each correction value is expected. Acurasi,
Atmospheric layer correction value and ionosphere correction value_acu > 0, u
_tro > 0, u _ion > 0, the pseudo-range error r becomes
It is assumed that it is expressed as in 1).

[0010]

[Equation 1]

This is considered to be positive (r> 0) when the estimated value of the pseudorange is overestimated by the pseudorange error r, as shown in FIG. 6, and is overestimated (r> 0).
This is because there are two ways of underestimating (r <0).

In step # 52, the positioning calculation means 3 transmits the satellite signals from the GPS satellites received by the satellite signal reception means 2 through the GPS antenna 1,
A matrix H representing the arrangement of GPS satellites is obtained. Here, the origin is the position of the GPS receiver, and the positive directions of the x-axis, y-axis, and z-axis are the north, east, and zenith directions, respectively.

An azimuth angle in which the rotation in the east (y-axis) direction with respect to the north (x-axis) is the positive direction is θ _azm . GPS satellite i
Azimuth angle is θ _azmi , elevation angle of GPS satellite i is θ _elvi , GP
When the number of GPS satellites used for the positioning calculation of the S receiver is n, the matrix H is expressed by (Expression 2) and (Expression 3). H = (h ₁ , h ₂ , ..., H _n ) ^T (Equation 2)

[0014]

[Equation 2]

In step # 53, the second positioning error estimating means 7 calculates and estimates the positioning error. A pseudo-distance error of the GPS satellite i and _{r i, r = (r 1} , r 2, ...,
r _n ) ^T.

Letting the positioning error be e, its x-axis, y-axis, z
The axial component e _x, as e _y, and e _z, a clock error of the GPS receiver when a reference clock of the GPS satellites _{e t, e = (e x} , e y, e z, e t) putting a ^{T, e = (H T H} ) -1 H T r ··· ( equation 4) G = (H ^T H) putting the ^-1 H ^T, (equation 4) from equation (5)
Is required. e = Gr (Equation 5) The element of the 1st row and the i-th column of G is set to α ₁ , and the element of the 2nd row and the i-th column is β.
_{1, P = (e x,} e r) and put the ^T,

[0017]

(Equation 3)

Pseudo range of GPS satellite i obtained from (Equation 1)
Estimated value of separation error r_SiBy using (Equation 4), (Equation 5) and
And the estimation of the positioning error shown in (Equation 7) based on (Equation 6)
Value u _S Is output.

[0019]

[Equation 4]

In step # 54, the second positioning error estimating means 7 determines whether or not the value of the positioning error e is the maximum value. For one GPS satellite, the estimated value r _Si of the pseudorange error is positive (r _Si > 0) and negative (r _Si <0
Since the calculation must be performed in two ways (0), 2 ⁿ / 2 ways of calculation are required to calculate the maximum value of the positioning error when n GPS satellites are used in the positioning calculation.

[0021]

However, in the conventional GPS receiver as described above, when the maximum value of the positioning error is calculated, a large number of GPS satellites are required for the positioning calculation. There is a problem that the processing time increases because of the increase in number.

Further, since the estimated value of the positioning error is calculated by obtaining the maximum value of the positioning error, it is often overestimated, and the accuracy of the calculation of the estimated value of the positioning error becomes poor. Was.

In view of the above problems, it is an object of the present invention to provide a GPS receiver which can shorten the processing time and improve the accuracy when calculating the estimated value of the positioning error. And

[0024]

In order to achieve the above object, the GPS receiving apparatus of the present invention uses a GPS signal received from a GPS satellite from a GPS antenna to position itself by a positioning calculation means. In the apparatus, the positioning calculation means is configured to detect the GPS satellite location information based on the propagation time of the satellite signal to itself and the data, and the accuracy information and the atmospheric layer in the navigation message of the satellite signal are detected. Based on the correction value and the ionosphere correction value,
The pseudo-range error variance estimation means for estimating the variance of the error with respect to the pseudo distance between itself and the GPS satellite, and the positioning calculation means based on the estimated value of the variance of the error with respect to the pseudo distance and the GPS satellite arrangement information. And a positioning error estimating means for estimating a positioning error with respect to the result of the positioning.

[0025]

According to the above construction, the pseudorange error variance estimation means estimates the variance of the pseudorange error assuming a normal distribution with an average of 0, and the positioning calculation means detects information on the arrangement of GPS satellites.

The variance estimation values of these pseudo range errors and GPS
The positioning error estimation means outputs an estimated value of the positioning error based on the satellite arrangement information. In this way, the number of calculations required to extract the positioning error is reduced.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A GPS receiver according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the GPS receiver in this embodiment. In FIG. 1, 1 is GP
S antenna, 2 is satellite signal receiving means, 3 is positioning calculation means, 4 is pseudorange error variance estimation means, and 5 is first positioning error estimation means as positioning error estimation means.

FIG. 2 is a flow chart showing a method of extracting the estimated value of the positioning error. In step # 21, as shown in FIG. 3, assuming that the pseudo range error r _i of the GPS satellite i has a normal distribution with mean 0 and variance σ _i ² as shown in (Equation 8), the pseudo range error variance is calculated. The estimation means 4 estimates the variance σ _i ² . r _{i to} N (0, σ _i ² ) (Equation 8) Further, it is assumed that there is no correlation between the pseudo range errors of the GPS satellite i and the GPS satellite j (i ≠ j).

First, the error represented by accuracy,
Atmospheric layer correction error and ionosphere correction error are e _acu and e, respectively.
_{It is assumed} that _tro and e _ion are set, and that the acuracies, atmospheric layer correction values, and ionospheric correction values are u _acu , u _tro , and u _ion , respectively, and (Equation 9) holds.

[0031]

(Equation 5)

However, k ₁ , k ₂ , and k ₃ are constants.
Here, it is assumed that e _acu , e _tro , and e _ion are uncorrelated with each other, and the variance σ _i ² of the pseudorange error is represented by (Equation 10).

[0033]

(Equation 6)

However, k ₄ is a constant and r _i is e
It corresponds to the variance of the error of the part that cannot be represented by _acu , e _tro , and e _ion . The constants k ₁ , k _{2 of} (Equation 10)
k ₃ and k ₄ are conditions such that the pseudo distance error can be measured in advance, and the data of the pseudo distance error and the value of each variable on the right-hand side of (Equation 10) is sufficiently sampled to use multiple regression analysis or the like. To estimate.

In step # 22, the positioning calculation means 3 obtains a matrix H representing the arrangement of GPS satellites. Since the method of obtaining is the same as the method shown in the conventional example, the description is omitted here.

In step # 23, the first positioning error estimation
The means 5 estimates the positioning error as e. GPS guard
The pseudorange error of star i is r_i And r = (r₁ , R₂ ,
…, R _n )^T Then (n is the number of GPS satellites), r and positioning
Error e = (e_x , E_r , E_z , E_t )^T The relation of (Equation 1
It is represented by 1). e = (H^T H)^-1H^T r (Equation 11) G = (H^T H)^-1H^T From (Equation 11), (Equation 1
2) is required. e = Gr (Equation 12) The element of the first row and the i-th column of G is α_i And the element in the second row and the i-th column is β_i 
And P = (e_x , E _y )^T , A_n = (Α_n , Β_n )^T 
r_n Then, (Equation 13) is obtained. P = a₁ + A₂ + ... + a_n (Equation 13) If E [x] is an expected value of the random variable x (Equation 1)
4) is established.

[0037]

(Equation 7)

However, it is assumed that a _i and a _j are uncorrelated with each other, and (Equation 15) holds. E [a _i · a _j ] = 0 (Equation 15) However, in (Equation 15), (i ≠ j).

The estimated value u _S of the positioning error shown in (Expression 16) is output using the estimated value σ _Si ² of the variance of the pseudo range error of the GPS satellite i obtained from (Expression 10).

[0040]

(Equation 8)

Thus, assuming that the pseudorange error has a normal distribution with an average of 0, its variance is estimated using accuracy, atmospheric layer correction value, and ionosphere correction value, and based on this estimated variance, By taking the expected value of the positioning error, the accuracy of the estimated value of the positioning error can be improved when the assumption is correct. In addition, by using this means,
There is no need for the conventional iterative calculation, and the number of calculations is reduced, so that the calculation time can be shortened.

[0042]

As described above, according to the present invention, the pseudo-range error variance estimation means estimates the variance of pseudo-range errors assuming a normal distribution with an average of 0, and the positioning calculation means uses information on the arrangement of GPS satellites. Then, the positioning error estimation means can output the estimated value of the positioning error based on the variance estimated value of the pseudo distance error and the arrangement information of the GPS satellites.

Therefore, the number of calculations required to extract the positioning error can be reduced. As a result, when calculating the estimated value of the positioning error, the processing time can be shortened and the accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a GPS receiver according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the embodiment.

FIG. 3 is an operation explanatory view of the pseudo distance error variance estimation means of the embodiment.

FIG. 4 is a block diagram of a conventional GPS receiver.

FIG. 5 is a flowchart for explaining the operation of the conventional example.

FIG. 6 is an operation explanatory diagram of a pseudo distance error estimating means of the conventional example.

[Explanation of symbols]

 3 Positioning Calculation Means 4 Pseudo Distance Error Variance Estimating Means 5 First Positioning Error Estimating Means

Claims (1)

[Claims] 1. GPS received through a GPS antenna
In a GPS receiving device that positions itself by a positioning calculation means based on a satellite signal from a satellite, the positioning calculation means calculates GPS satellite placement information based on the propagation time of the satellite signal to itself and data. Configured to detect,
Pseudo-range error variance estimation means for estimating the variance of the error with respect to the pseudo-range between itself and the GPS satellite based on the accuracy information in the navigation message of the satellite signal, the atmospheric layer correction value and the ionosphere correction value, and the pseudo-range. A GPS receiving apparatus comprising: a positioning error estimating means for estimating a positioning error with respect to the positioning result of the positioning calculating means, based on an estimated value of the variance of the error and the positioning information of the GPS satellites.