JPH0875478A - Method for calculating position in satellite navigation device - Google Patents

Abstract

PURPOSE: To measure the position on three-axial coordinate by the interpolation of the data even when the number of GPS satellites is small by using the data in the past measurement as a height axial coordinate value, and the value estimated from the calculated values twice in the past as a horizontal axial coordinate value. CONSTITUTION: A receiving device normally receives a radio wave from four (or three) GPS satellites in a point A to calculate the position (X1, Y1, Z1), and similarly calculates the position (X2, Y2, Z2) in a point B by the same number of satellites. When the receiving device has become possible to receive the radio wave from only one GPS satellite about the time when it has reached a point C, the point C is assumed to be one point C' (X3, Y3, Z3) on the extension of the line connecting both the points A, B to determine the position. The distance between the satellite and the receiving device is first determined, and the inclination of the straight line BC' to X-axis is determined, thereby, the Y-coordinate of the point C' is determined to determine the three axial coordinate, and the point C' can be thus estimated. After the calculation of the coordinate, the point C is determined by the map matching from the point C'.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calculating the position of a satellite navigation device which is effective in a place where the environment for receiving radio waves from artificial satellites is poor, such as in the shadow of a building.

[0002]

2. Description of the Related Art GP is one of the satellite navigation methods for calculating the position (latitude, longitude and altitude) of a moving body by receiving radio waves emitted from artificial satellites when moving by ship, air or land.
There is S (Global Positioning System) navigation. GP
S is a general term for a total of 24 artificial satellites (GPS satellites), satellite control ground stations, and GPS receivers. This G
The PS satellite orbits six circular satellite orbits located at an altitude of about 20,183 km above the ground in about 11 hours and 58 minutes. Then, the GPS receiving device receives the radio waves from the GPS satellites to obtain the position on the earth.

Each of the above-mentioned 24 GPS satellites receives an internal clock and correction of satellite orbit information from the satellite control earth station at every predetermined time. Each GPS satellite orbits an orbit of a certain altitude while transmitting an ID code including its number, position information or accurate time on radio waves. In the receiving device, the distance between the receiving device and the GPS satellite is obtained from the delay time of the time sent from the GPS satellite with respect to the internal time. FIG. 4 is a diagram showing a method for obtaining the distance between the GPS satellite 3 _-1 and the receiving device 2 on the earth 1.

At a certain time t ₀ , the GPS satellite 3 _-1 transmits its own position coordinates (u, v, w) at point P and information at the time t ₀ . At this time, the receiving device 2 is located at the point A _0, and the internal time of the receiving device 2 is set to t ₀ ′. At time t, the receiving device 2 receives the above information t ₀ , u, v, w at the point A (x, y, z). At this time, the internal time of the receiving device 2 is t ′, and the error between t and t ′ is Δt. These GPS satellites 3
The time and positional relationship between _-1 and the receiving device 2 are as shown in the table below. From the above, the true distance R between the GPS satellite 3 _-1 and the receiver 2
Is calculated as follows. R = C (t−t ₀ ) = C {(t′−Δt) −t ₀ } = C {(t′−t ₀ ) −Δt} = AP−C · Δt (1) Here, C Is the speed of light, AP is the apparent distance between the GPS satellite 3 _-1 and the receiver 2 (internal time of the receiver 2 and GP
This is the distance when it is assumed that the internal time of the S satellite 3 _-1 matches. On the other hand, the true distance R is R = {(u−x) ² + (v−y) ² + (w−z) ² } ^1/2 ... (2). From these equations (1) and (2), AP-C · Δt = {(u−x) ² + (v−y) ² + (w−z) ² } ^1/2 ∴AP = {(u−x) ^{2 + (v-y) 2} + (w-z) 2} 1/2 + C · Δt ... (3) becomes equation is obtained.

Next, in order to calculate the position of the receiving device based on the apparent distance AP between each GPS satellite and the receiving device, first, four out of the 24 GPS satellites located in the zenith direction are calculated. A GPS satellite is selected and radio waves from four GPS satellites are simultaneously received. In FIG. 5, the position coordinates (x, y, z) of the receiving device 2 on the earth 1 (for convenience, let x be the longitude, y be the latitude, and z be the altitude above the standard sea level).
The following is an example of the positional relationship between each of the above, when calculating using the radio waves transmitted by the GPS satellites 3 _{-1 to} 3 _-4 . The receiving device 2 has a clock 5 inside, but this clock 5
And the time indicated by the internal clocks (not shown) of the GPS satellites 3 _{-1 to} 3 _-4 has an error of Δt.

The GPS satellites 3 _{-1 to} 3 _-4 transmit position information (u ₁ , v ₁ , w ₁ ) to (u ₄ , v ₄ , w ₄ ) and time information, respectively. From the time information transmitted by the GPS satellites 3 _{-1 to} 3 _-4 and the time of the clock 5 of the receiving device 2, the apparent distance AP ₁ between the receiving device 2 and each of the GPS satellites 3 _{-1 to} 3 _-4. ~ A
P ₄ is required. From these apparent distances AP _{1 to} AP ₄ and position information (u ₁ , v ₁ , w ₁ ) to (u ₄ , v ₄ , w ₄ ),
By solving the following simultaneous equations, the position (x, y,
z) and the error time Δt are obtained. AP ₁ = {(u ₁ -x) ² + (v ₁ -y) ² + (w ₁ -z) ² } ^1/2 + C · Δt ... (4) AP ₂ = {(u ₂ -x) ² + (v ₂ −y) ² + (w ₂ −z) ² } ^1/2 + C · Δt (5) AP ₃ = {(u ₃ −x) ² + (v ₃ −y) ² + (w ₁ − (z) ² } ^1/2 + C · Δt (6) AP ₄ = {(u ₄ −x) ² + (v ₄ −y) ² + (w ₂ −z) ² } ^1/2 + C · Δt… ( 7)

Next, since the error time Δt is obtained from the above simultaneous equations, the time of the clock 5 is calculated based on Δt for each GPS.
Correct it to match the internal time of the satellite. After the error time Δt is corrected to 0 in this way, the position of the receiving device 2 can be calculated using the radio waves transmitted by the three GPS satellites 3 _{-1 to} 3 _-3 as shown in FIG. it can. GPS
The satellites 3 _{-1 to} 3 _-3 have position information (u ₁ , v ₁ , w ₁ ) to
(U ₃ , v ₃ , w ₃ ) and time information are transmitted. And from the time of radio wave propagation, the true distance BP ₁ to BP ₃ from the receiving apparatus 2 to each GPS satellite 3 _-1 to 3 _-3 sought.
These true distances BP _{1 to} BP ₃ and positions u ₁ , v ₁ , w ₁
The following simultaneous equations are solved from u ₃ , v ₃ and w ₃ to obtain the position x, y, z of the receiving device 2. BP ₁ = {(u ₁ -x) ² + (v ₁ -y) ² + (w ₁ -z) ² } ^1/2 ... (8) BP ₂ = {(u ₂ -x) ² + (v ₂ −y) ² + (w ₂ −z) ² } ^1/2 (9) BP ₃ = {(u ₃ −x) ² + (v ₃ −y) ² + (w ₃ −z) ² } ^{1 / 2} (10) In addition, in the above GPS navigation (see FIG. 5 or 6), the rate of change of each Doppler effect of the radio waves transmitted from each GPS satellite 3 _{-1 to} 3 _-4 is measured. By doing so, the moving speed and the moving direction (course) of the receiving device 2 can be obtained.

[0008]

By the way, the above-mentioned GP
S navigation is when 24 GPS satellites are in operation,
It is a radio navigation system that can be used 24 hours a day, but there are GPS satellites that have not been launched into their original orbits, and there are some GPS satellites that are not operating due to breakdowns or maintenance inspections.
Alternatively, it may not be possible to receive radio waves from three GPS satellites. Furthermore, when used in an automobile that moves in a place with many buildings such as an urban area, or when used in the mountains of a mountainous area, radio waves from GPS satellites with a low elevation angle from the receiving point may cause obstacles. Cannot be used because it is blocked by. That is, the number of GPS satellites received decreases, and GPS navigation cannot be used. The present invention has been made in the background as described above, and makes it possible to obtain the position on the triaxial coordinate by complementing the data even when the number of usable GPS satellites is small. It is intended to provide a method for calculating the position of a satellite navigation device.

[0009]

In order to solve the above-mentioned problems, the invention according to claim 1 receives time information and position information from a plurality of artificial satellites and makes them orthogonal to each other. 3 horizontal axis, second horizontal axis, and height axis
In the position calculation method of the satellite navigation device for calculating the axis coordinates, the data at the past measurement is used as the height axis coordinate value. Further, in the invention according to claim 2, it receives time information and position information from a plurality of artificial satellites, and comprises a first horizontal axis, a second horizontal axis, and a height axis which are orthogonal to each other. In the position calculation method of a satellite navigation device for calculating axial coordinates, data obtained in the past measurement is used as the height axis coordinate value, and the first or second horizontal axis coordinate value is calculated from the values calculated twice in the past. It is characterized by using an estimated value.

[0010]

According to the present invention, when the receiving device can receive only the radio waves of the two artificial satellites, the receiving device uses the past measurement data to make the first horizontal axis and the second horizontal axis of the receiving device orthogonal to each other. , Three-axis coordinates including the height axis are calculated. Further, when only the radio wave of one artificial satellite can be received, the position on the triaxial coordinate of the receiving device is calculated based on the traveling direction of the receiving device predicted from the measurement data of the past two times and the position information measured in the past. To do.

[0011]

EXAMPLE An example of the present invention will be described below.

(A) When only two radio waves from GPS satellites can be received. Once four radio waves from GPS satellites are received, the position (x, y, z) of the receiving device 2 and the error time Δ
t is calculated and the time of the clock 5 is set to each GPS satellite 3 _{-1 to} 3
_Now , description will be given of a case where only the radio waves transmitted by the GPS satellites 3 _-1 and 3 _-2 can be received as shown in FIG. 1 after the time is set to the internal clock of _-4 . Receiver 2
However, when mounted on a moving body such as an automobile, for example, the change in the position of the height axis is small compared to the change in the horizontal position, and can be normally ignored. Therefore, it is possible to obtain an approximate position by using the past data as the position of the height axis. That is, the true distance CP calculated from the propagation time of the radio waves transmitted by the GPS satellites 3 _-1 and 3 _-2.
1 , CP ₂ , position information (u ₁ , v ₁ , w ₁ ), (u ₂ , v ₂ ,
The following simultaneous equations are solved using w ₂ ), and the position z ₀ of the height axis of the receiving device 2 which is the past measurement data. Then, the absolute position x, y, z of the receiving device 2 is calculated. _{CP 1 = {(u 1 -x} ) 2 + (v 1 -y) 2 + (w 1 -z 0) 2} 1/2 ... (11) CP 2 = {(u 2 -x) 2 + (v ₂₋ y) ² + (w ₂ −z ₀ ) ² } ^1/2 (12) By solving the simultaneous equations in this way, the position of the receiving device 2 on the three-axis coordinates can be calculated. .

(B) When only one radio wave from the GPS satellite can be received. When the receiving device enters the shadow of a building or the shadow of a mountain after normally receiving radio waves from four GPS satellites, and therefore can receive radio waves from only one GPS satellite. The position calculation method of is described below. Fig. 2 shows the GPS satellite 3 _{-1 in} this case.
2 is a diagram showing the receiving device 2a. In this figure, 5 is a clock provided in the receiving device 2a, 6 is an automobile in which the receiving device 2a is installed, and 7 is a map memory provided in the receiving device 2a. . Further, FIG. 3 is an explanatory diagram for explaining the position calculation method.

Now, the receiving device 2a receives radio waves from four (or three) GPS satellites at point A shown in FIG. 3 to calculate the position (x ₁ , y ₁ , z ₁ ) and then At the point B, radio waves are received from four (or three) GPS satellites and the position (x ₂ ,
It is assumed that y ₂ , z ₂ ) is calculated. Next, the receiving device 2a
When reaching the point, it enters the shadow of the building and can receive radio waves from only one GPS satellite. In this case, the position is calculated on the assumption that the point C is located at one point C ′ (x ₃ , y ₃ , z ₃ ) on the extension of the line connecting the points A and B.

First, assuming that the time when the GPS satellite emits a radio wave is t and the time when the receiving device 2a receives the radio wave is t ', the distance DP between the GPS satellite and the receiving device 2a is DP = C (t It is calculated as'-t) (13). (However, GPS satellite and receiving device 2a
It is assumed that there is no time difference between them. ) Next, the inclination θ of the straight line BC ′ with respect to the X axis is θ = (y ₂ −y ₁ ) / (x ₂ −x ₁ ) ... (14) Therefore, the Y coordinate y _{3 of the} point C ′ is , Y ₃ = θ (x ₃ −x ₂ ) + y ₂ (15) Further, the Z coordinate of the point C ′ is approximated by the Z coordinate value z ₂ measured last time.

As a result of the above, when the position coordinates of the satellite emitted by the GPS satellite are (u ₁ , v ₁ , w ₁ ), the following equation holds. DP = [(u ₁ −x ₃ ) ² + {v ₁ −θ (x ₃ −x ₂ ) −y ₂ } ² + (w ₁ −z ₂ ) ² ] ^1/2 (16) This (16) X ₃ is calculated from the equation, and then (14), (1
By calculating y ₃ from the equation 5), the coordinates (x
₃ , y ₃ , z ₃ ) is obtained (where z ₃ is approximated by z ₂ ).
The above position calculation method is effective when there are fewer branches such as intersections such as highways than general roads. Note that the coordinates of the point C'calculated by the above method are often not on the actual road. Therefore, it is necessary to perform map matching so that the point on the road is closest to point C'after the coordinate calculation.

Although the present embodiment has been described with reference to an example of calculating the position of a moving automobile or the like, the present invention can also be applied to position calculation for a ship or when carrying it, or for railways and the like.

[0018]

As described above, according to the present invention,
Even if the number of GPS satellites that can be used is small, it is possible to obtain the effect that the position on the triaxial coordinate can be obtained by supplementing the data.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration for receiving radio waves from two GPS satellites and calculating a position in the present embodiment.

FIG. 2 is a diagram showing a configuration for estimating a position by receiving radio waves from one GPS satellite in the present embodiment.

FIG. 3 is a diagram for explaining a method of calculating the position of a vehicle 6 on a road 8 by receiving radio waves from one GPS satellite in this embodiment.

FIG. 4 is a diagram showing a method of receiving a radio wave transmitted by an artificial satellite and calculating a distance between the artificial satellite and a receiving device.

FIG. 5 is a diagram showing a configuration for receiving radio waves from four GPS satellites and calculating a position in the conventional technique.

FIG. 6 is a diagram showing a configuration for receiving radio waves from three GPS satellites and calculating a position in a conventional technique.

[Explanation of symbols]

2, 2a receiver 3 _{-1 to} 3 _-4 GPS satellite 5 clock 6 automobile

Claims (2)

[Claims] 1. A satellite navigation device that receives time information and position information from a plurality of artificial satellites and calculates three-axis coordinates composed of a first horizontal axis, a second horizontal axis, and a height axis that are orthogonal to each other. In the position calculating method, data of past measurement is used as the height axis coordinate value, and the position calculating method of the satellite navigation device is characterized. 2. A satellite navigation device that receives time information and position information from a plurality of artificial satellites and calculates three-axis coordinates composed of a first horizontal axis, a second horizontal axis, and a height axis that are orthogonal to each other. In the position calculation method, the data of the past measurement is used as the height axis coordinate value,
A method for calculating a position of a satellite navigation device, wherein a value estimated from calculated values of the past two times is used as the first or second horizontal axis coordinate value.