JP2995852B2 - GPS navigation system for vehicles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a navigation system, and more particularly to a GPS navigation system suitable for use in a vehicle.

(Prior art) Conventionally, in this kind of GPS navigation system,
As shown in Japanese Unexamined Patent Publication No. 3-198887, the distance between the position of each artificial satellite and its own position is measured based on the reception of each information relating to the satellite orbit and time from each artificial satellite to determine the position of its own. Further, there is a method in which a direction in which an error occurs from the position of each artificial satellite is obtained, and the positioning value is corrected using road map information in association with the error direction.

(Problems to be Solved by the Invention) In such a configuration, when performing positioning using three artificial satellites, it is necessary to perform two-dimensional positioning in the same altitude plane after giving an altitude value. Therefore, the positioning result includes an altitude value setting error in addition to the distance measurement error described above. However, the above configuration does not consider the influence of the altitude setting error on the positioning result, and as a result, there is a problem that the accuracy of the positioning error prediction in the two-dimensional positioning is low.

In view of the above, the present invention is intended to improve the accuracy of positioning error prediction in a two-dimensional positioning in a GPS navigation system for a vehicle in consideration of an altitude setting error. is there.

(Means for Solving the Problems) In solving the above problems, according to the present invention, as shown in FIG. 1, transmission radio waves from a plurality of artificial satellites S1, S2,. In a GPS navigation system comprising: a receiving means 1 for receiving; and a positioning calculation means 2 for positioning the position of the vehicle based on a radio wave received by the receiving means 1 and calculating a prediction accuracy of an error of the positioning value. Means 2 is a prediction means for predicting an altitude setting error.
2a, and a distance measuring accuracy calculating means 2b for calculating a distance measuring accuracy caused by an altitude setting error predicted by the predicting means 2a, and combining the distance measuring accuracy with at least the predicting accuracy at the time of two-dimensional positioning. And calculating a prediction accuracy of a new positioning error.

(Effects) As described above, the present invention employs a configuration in which the effect of the altitude setting error in the two-dimensional positioning on the positioning result is taken, so that the accuracy of the positioning error prediction can be improved. As a result, by utilizing the prediction accuracy, it is possible to more accurately grasp the position of the vehicle.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows an example in which the present invention is applied to a vehicle navigator. This navigator has a direction sensor 10, which detects the direction of the vehicle and generates a direction detection signal. The vehicle speed sensor 20 detects the vehicle speed of the vehicle and sequentially generates a vehicle speed pulse proportional to the detection result. The GPS receiving apparatus 30 receives each transmission radio wave from four or three artificial satellites at the receiving unit 30a, and based on the received radio waves, according to each flowchart shown in FIGS. To perform arithmetic processing for three-dimensional positioning or two-dimensional positioning and its prediction accuracy. However, the positioning program is stored in the ROM of the microcomputer 30b in advance.

The map memory 40 is composed of a large-capacity storage element such as a compact disk, and a predetermined range of map data (including road shape data) is stored in the map memory 40 in advance. The control switch 50 is operated when selecting a display map from the map data stored in the map memory 40 or when inputting an initial value to the microcomputer 60. The microcomputer 60 executes a display program,
In accordance with the flowchart shown in FIG. 8, the process is executed in cooperation with the direction sensor 10, the vehicle speed sensor 20, the GPS receiver 30, the map memory 40, and the control switch 50. During the execution, the control of the CRT controller 70 connected to the CRT 80 is performed. Perform the necessary arithmetic processing. However, the display program is stored in the ROM of the microcomputer 60 in advance.

In the present embodiment configured as described above, if the device of the present invention is operated in the running state of the vehicle, the microcomputer 30b starts executing the positioning program in step 100 according to the flowchart of FIG. The microcomputer 60 starts executing the display program in step 200 according to the flowchart of FIG. After starting the execution in step 100, the microcomputer 30b
However, as shown in FIG. 3 and FIG. 4, the positioning program proceeds to the first positioning error calculation routine 110.

In the first positioning error calculation routine 110, the receiving unit of the GPS
The three-dimensional position of each satellite is calculated based on each transmission wave representing each orbital data from the four satellites received by 30a, and each satellite and the GPS are calculated from the arrival time of the satellite wave.
The distance to the receiving device 30 is calculated, and the three-dimensional position of the GPS receiving device 30 (that is, longitude,
Latitude and altitude) are calculated as the measured positions. However, if there are only three satellites that can receive the transmitted radio wave,
By arbitrarily setting the altitude value, the two-dimensional position (that is, longitude and latitude) of the GPS receiver 30 is calculated as a positioning value in step 111 using three artificial satellites. Therefore, the operations in the following steps 112 to 115 are different between the case where three-dimensional positioning is performed and the case where two-dimensional positioning is performed.

However, in the case of three-dimensional positioning, step 11
2, in the east, around the positioning value of the GPS receiver 30
An x, y, z orthogonal coordinate system having three axes of north and directly above is determined, unit vectors heading toward the position of each artificial satellite are obtained from the positioning values of the GPS receiver 30, and these unit vectors are referred to as the above-described orthogonal coordinates. The system is divided into each coordinate axis component, and a coefficient “1” for the clock shift amount t between the time of the clock of each artificial satellite and the time of the GPS receiver 30 is added to complete the matrix A as follows.

However, if i = 0, 1, 2, 3 in the A matrix, αi
_{= ∂r i / ∂Lg, β i} = ∂r i / ∂Lt, is γi = ∂r _i / ∂h established. Here, γi represents the distance between the GPS receiver 30 and the satellite. Lg, Lt, h represent longitude, latitude, and altitude for specifying the three-dimensional position of the GPS receiver 30. Also, L
g, Lt, and h correspond to the x, y, and z coordinates, respectively.

Thereafter, in step 113, based on the matrix A in step 112, the variance-covariance matrix (A ^T
A) ^-1 is calculated.

Next, in step 114, the eigenvalue λ of the variance / covariance matrix (A ^T · A) ⁻¹ is calculated. In such cases,
The eigenvalue λ is, as follows, the variance λ in the direction in which the error component is maximum and the variance λ in the direction in which the error component is minimum.
s and two values.

However, the eigenvalue λ of (A ^T · A) ⁻¹ indicates that the distance measurement error is “1”.
In consideration of the fact that the variance of the positioning error when given is given, the equations (3) and (4) regarding λ and λs are used for positioning in User Equivalent Range Error (hereinafter referred to as UERE). UERE the largest of the available satellites
By multiplying by max, λ and λs are obtained as the variance (1σ) of the actual positioning error. “1σ” is 68.3
% Probability.

In such a case, UERE is based on one of the following equations (5) and (6) and responds to a distance measurement error occurring inside the URA and GPS receiver 30 (hereinafter referred to as a distance measurement error in the receiver). Is calculated.

However, URA ≠ 15. Note that URA = 15 indicates that no error is predicted. URA is a parameter representing a predicted value of a ranging error for each satellite specified by a radio wave received from each satellite, and a ranging error component caused by a clock and detailed orbit data of each satellite. including.

When the calculation processing in step 114 is completed in this way, in the next step 115, the direction in which the variance of the positioning error is the maximum, that is, the positioning value at the time of three-dimensional positioning has the probability 1
The direction θ _L of the major axis length σ _L of the ellipse existing at σ and the direction in which the variance of the positioning error is minimized, that is, the direction θ _S of the minor axis length σ _S of the ellipse are represented by the following equations ( It is calculated by 7) and (8).

The above-described equations (1) to (8) are stored in the ROM of the microcomputer 30b in advance.

Next, each of steps 112 to 115 when the two-dimensional
The calculation of is shown below. In step 112, the altitude measurement is not performed in the case of the two-dimensional lateral position, so that there is no γ term from the elements of the A matrix. Further, since three satellites are used for positioning, the term of the fourth satellite is eliminated and the matrix A is completed as follows.

The variance / covariance matrix (A ^T · A) ^{−1 in} step 113 is as follows.

Hereinafter, steps 114 and 115 can be obtained in exactly the same way as in the three-dimensional case. In the case of three-dimensional positioning, the positioning calculation ends here. In the case of two-dimensional positioning, an error in the altitude setting value can be considered as a factor of the positioning error. Therefore, in order to obtain an error given to the positioning value, the positioning program is executed by the second positioning error calculation routine 120 (FIG. 3 and FIG. 3). (See Fig. 5). This means that routine 120
Means that it is executed only at the time of two-dimensional positioning.

Then, the microcomputer 30b executes step 121
Then, the altitude obtained in step 111 at the time of three-dimensional positioning is adopted as an altitude setting value, and the accuracy (VDOP × UERE) is set as an altitude setting error Δh. Here, VDOP is an index indicating deterioration of positioning accuracy in the height direction. When two-dimensional positioning is continuous, in addition to the above-described altitude setting error Δh, the amount of movement of the GPS receiver 30 obtained from the three-dimensional positioning value used for setting the altitude value and the current two-dimensional positioning value Also consider the increase in altitude setting error proportional to. This increase is a value based on the gradient of the land, and is set to a relatively large value on the assumption of a mountainous area in order not to output a positioning value having an error larger than the predicted value of the positioning accuracy. There is a need.

Then, the microcomputer 30b is, at step 122, directed from the GPS receiver 30 based on the following equation (9) the ranging error [Delta] r _i for each satellite resulting from the advanced setting error Δh to each satellite the The calculation is performed according to the direction cosine of the unit vector in the height direction (corresponding to γ ₀ , γ ₁ , γ ₂ in step 112) and the altitude setting error Δh.

Thereafter, the microcomputer 30b determines in step 123 that the positioning error caused by the distance measurement error Δr _i , that is, the deviation ΔLg in the longitude direction, the deviation ΔLt in the latitude direction, and the GPS
The deviation ΔB between the clock of the receiving device 30 and the clock of each artificial satellite is calculated based on the following equation (10) according to the matrix of the two-dimensional positioning equivalent component of the A matrix in step 112 (equation (1a)).

In such a case, when the altitude setting error Δh is different from the predicted value, the magnitude of the positioning error changes in proportion to the altitude setting error Δh even if the direction of the deviation is the same, according to Equation (1).
0) is understood. If the magnitude of 1 σ is predicted as the predicted value of the altitude setting error, the measured value is (ΔLt, ΔLg) and (−ΔLt, −Δ) centered on the true position.
Lg) is predicted to be obtained with a probability of 1σ. The above equations (9) and (10) are stored in the ROM of the microcomputer 30b in advance.

When the execution of the second positioning error calculation routine 120 is completed in this manner, the microcomputer 30b, in step 130 (see FIG. 3), calculates the respective positioning errors obtained by the first and second positioning error calculation routines 110 and 120. Are synthesized as shown in FIG. According to this synthesis, the center of the ellipse indicating the distribution of the positioning error due to the ranging error is set to (ΔLt, ΔLt) in the rectangular coordinate system centered on the true position of the GPS receiver 30.
It is predicted that the positioning point is included at 1σ within the range of the elliptical figure formed when moving from (g) by (−ΔLt, −ΔLg). In the case of three-dimensional positioning, as determined in step 110, the positioning point is 1σ within the range of the elliptical figure shown in FIG.
It is predicted to be included in This means that the GPS receiver 30
Means that the positioning accuracy in the two-dimensional positioning and the three-dimensional positioning can be predicted with high accuracy. However, since the true position is unknown in reality, if a range of the prediction accuracy is drawn around the measured value, the true position is included in this range with a probability of 1σ. In step 130, the microcomputer 30b compares the above-described positioning value and its prediction accuracy with the microcomputer 30b.
To be given.

On the other hand, after the start of the execution in step 200 as described above, the microcomputer 60 advances the display program to the dead reckoning arithmetic processing routine 210. In the dead reckoning calculation processing routine 210, the final position of the vehicle stored in the microcomputer 60 or the position of the vehicle input by the control switch 50 is used as an initial value, and the azimuth detection from the azimuth sensor 10 is performed. Based on the value of the signal and the vehicle speed based on each vehicle speed pulse from the vehicle speed sensor 20, the relative movement amount of the vehicle is calculated to estimate the current position of the vehicle.

After execution of the dead reckoning arithmetic processing routine 210 as described above, the microcomputer 60 shifts to execution of the map matching processing routine 220. In the map matching processing routine 220, when an error is mixed in the azimuth detection signal from the azimuth sensor 10 and each vehicle speed pulse from the vehicle speed sensor 20, the dead reckoning navigation processing routine
The accumulated position error is corrected based on the road shape data in the map memory 40 in consideration of the fact that an error also occurs in the estimated calculation position of the vehicle in 210 and this error is cumulatively increased. In such a case, the accuracy of the current position by this correction is kept very high because the accuracy of the current position refers to the road shape.

Thereafter, the microcomputer 60 determines in step 230 whether the deviation between the guess calculation processing corrected by the map matching processing routine 220 and the input positioning value from the microcomputer 30b is within the prediction accuracy of the microcomputer 30b. It is determined whether or not it is not. Then
If not within the prediction accuracy, the microcomputer 60 determines "NO" in step 230, sets the positioning value by the microcomputer 30b to the current position of the vehicle in step 240, and sets the current position in step 250. The position is combined with the map data from the map memory 40 as data to create display data, and the display data is generated as a display output signal. On the other hand, if the determination in step 230 is “YES”, the microcomputer 60
At 0, display data is generated by combining the current position obtained by the above-described map matching with the map data in the same manner as described above, and a display output signal is generated. If the positioning by the GPS receiving device 30 is not possible due to the interruption of the transmission radio wave from the artificial satellite or the like, the above-described display data is created by using the current position obtained by the map matching.

When the microcomputer 60 generates the display output signal as described above, the CRT controller 70 causes the CRT 80 to display the contents of the display data. In such a case, if the determination in step 230 is “NO” as described above, the current position of the vehicle specified by the positioning value of the GPS receiving device 30 is displayed on a map. On the other hand, as described above, step 23
If the determination at 0 is “YES”, the current position corrected by map matching is displayed on the map.

As described above, the second positioning error calculation routine 12
0, the current position of the vehicle is determined in consideration of the influence of the positioning error due to the altitude setting error during two-dimensional positioning.
When the OP is small, the accuracy of the current position can be improved without erroneously determining that the accuracy of the positioning value is good. Therefore, the position of the vehicle can be accurately recognized based on the display content of the CRT 80. In such cases, intentional degradation (Selective availability) may occur,
Alternatively, even when the accuracy is deteriorated due to a failure of the artificial satellite or aging, accurate prediction can be performed by incorporating the value of URA as a parameter of the prediction accuracy as described above.

Note that, in the above-described embodiment, an example in which the altitude value during three-dimensional positioning is adopted for setting the altitude during two-dimensional positioning has been described. Or the like, or an altimeter output using an altimeter or an altitude value specified by a sign having position information such as a sign post may be used.

Further, in the above-described embodiment, the method of accurately calculating the prediction error has been described. However, the present invention is not limited to this, and it is assumed that accurate longitude and latitude are obtained by utilizing the second positioning error calculation routine 120. Alternatively, an altitude value may be obtained. In such a case, for example, when accurate position determination is possible due to information from a sign post or a map turn, such as when making a right or left turn at an intersection, etc., the two-dimensional positioning of the GPS receiver 30 is performed when accurate longitude and latitude are known. Is completed and the measured values are shifted in a certain direction, it is considered that there is an error in the altitude setting value. On the other hand, when calculating the actual altitude value,
Positioning error when Δh in 121 is “1” Is calculated. Then, a distance between the positioning value of the GPS receiving device 30 and the true position obtained from other information is obtained, and this distance is divided by the calculated positioning error to obtain an altitude setting error. Note that the direction of deviation from the true value of the positioning value is Δ
In the direction indicated by Lg and ΔLt, the set value of the altitude is large.
On the other hand, in the case of a deviation in the reverse direction, the set value of the altitude is small.

In the above embodiment, when the current position determined by the map matching exists outside the prediction accuracy 1σ of the GPS receiver 30, the measured position of the GPS receiver 30 is set as the current position of the vehicle. However, when accurate map matching is possible because the map is created in detail, the range of use of the positioning values of the GPS receiver 30 is expanded from the prediction accuracy of 1σ to 2σ or 3σ. May be implemented.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to the description of the claims, FIG. 2 is a block diagram of a vehicular navigator to which the present invention is applied, and FIGS. 3 to 5 are functions of the microcomputer of the GPS receiver shown in FIG. FIG. 6 is an explanatory diagram of the synthesis of the positioning error at the time of two-dimensional positioning, FIG. 7 is an explanatory diagram of the positioning error at the time of three-dimensional positioning, and FIG. 8 shows the operation of the microcomputer 60 of FIG. It is a flowchart shown. EXPLANATION OF SYMBOLS 30: GPS receiver, 30a: Receiver, 30b: microcomputer.

Continuation of the front page (56) References JP-A-63-198887 (JP, A) JP-A-63-127172 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01S 5 / 00-5/14 G01C 21/00-21/24

Claims (1)

(57) [Claims] 1. A receiving means mounted on a vehicle for receiving radio waves transmitted from a plurality of artificial satellites, a position of the vehicle is measured based on the radio waves received by the receiving means, and a prediction accuracy of an error of the measured value is determined. In a GPS navigation system comprising: a positioning calculation means for calculating, the positioning calculation means includes: a prediction means for predicting an altitude setting error; and a distance measurement for calculating a ranging accuracy caused by the altitude setting error predicted by the prediction means. A GPS navigation system for a vehicle, comprising: an accuracy calculation means, wherein at the time of two-dimensional positioning, the prediction accuracy of a new positioning error is calculated by combining at least the prediction accuracy with the distance measurement accuracy.