JPS636478A - Satellite navigation system - Google Patents

Abstract

PURPOSE:To eliminate measurement errors by excluding radio waves which are greatly different in reception level from a prescribed value and vary in dummy distance abruptly when radio waves from plural satellites are received to calculate the dummy distance and then find the position of a moving body. CONSTITUTION:Signals from the plural satellites which are received by an antenna 11 are inputted to a reception part 12 and navigation data is demodulated to measure the dummy distance, which is inputted to a position measurement arithmetic part 13. The arithmetic part 13 solve a navigation equation wherein those data are combined to calculate the position of the moving body, which is displayed on a display part 14. A decision circuit 15 excludes signals which are smaller or larger in the reception level of the reception part 12 than the prescribed value. Further, when the dummy distance found by the reception part 1 varies abruptly from the last value, the signals are excluded. Consequently, errors in position measurement due to a ghost and a reflected wave are eliminated. This device is suitable to an automobile which runs in an area where there is much radio wave trouble.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a satellite that is mounted on a moving object such as a car and receives signals from a satellite to calculate and display the current position and speed of the moving object. It relates to navigation equipment.

[Conventional technology]

Conventionally, r-GPS (Global Position
There is a navigation system (oning system).

To determine the user's position three-dimensionally using a GPS navigation device, three components (x, y, z) in an earth-centered, earth-fixed coordinate system are required.
Find the three unknowns. The relationship between this unknown quantity, latitude, longitude, and height is well known.

Since it is calculated using nine signals obtained by unidirectional propagation of radio waves from the satellite to the user, originally the transmitter side (
It is necessary to place highly accurate and well-matched clocks on both the satellite (satellite) and the receiving side (user), and to directly measure the propagation time of radio waves using these two clocks. However, it is not practical to equip each user with such a highly accurate clock, so the user receives radio waves from multiple satellites at the same time and checks the time between each satellite and the user. The user's position is calculated using pseudorange data including offset and position data of each satellite. That is, it is necessary to add the time T that matches the satellite's clock as another unknown, and to solve the four unknowns (X, Y, Z, T) in addition to the three unknowns related to the position. To do this, it is necessary to receive radio signals from four satellites scattered in the sky.Since the height of moving vehicles such as cars does not change much, even if there is a slight error in height, it is possible to receive radio signals from four satellites scattered in the sky. It is rare that the 2D position of the 2D position is measured by a large margin, so we enter a known value for the height, solve for the 3 unknowns J degrees, longitude, and time from the 3 satellites, and calculate the 2D side position. are doing.

Such GPS navigation devices have been attracting particular attention recently because they have the advantage of having higher positioning accuracy than other navigation devices, such as dead reckoning navigation devices that calculate estimated positions from measurement data from azimuth sensors and distance meters. There is.

[Problem that the invention seeks to solve]

However, when driving in an area such as a city where there are many radio wave obstructions such as buildings, it is often impossible to receive direct waves from the satellite. From time to time, we receive various ghosts, such as composite waves of waves and direct waves, and direct waves attenuated by forests, overpasses, etc. There was a problem in that when the CPS navigation equipment received these waves and calculated the position, it would give incorrect results.

The present invention has been made to solve these problems, and provides a satellite navigation device that can calculate accurate positions even when cars are driving in areas with a lot of radio interference, such as in urban areas. It provides:

[Means for solving problems]

The inventors conducted numerous positioning tests using conventional GPS navigation devices, and found that radio waves affected by reflected waves from buildings, land bridges, etc. either attenuate and become weaker in strength, or become composite waves. It becomes stronger. Therefore, it was found that the signal level was deviated from the signal level in the case of direct reception (normal reception).

It was also found that the pseudorange data measured by receiving reflected waves was extremely different from the pseudorange data measured by direct reception, and lacked continuity.

In order to solve the above problems, a satellite navigation device to which the present invention, which was made based on the above knowledge, is applied will be explained with reference to the block diagram shown in FIG. As shown in the figure, the satellite navigation device of the present invention has an antenna section 11 for receiving a plurality of satellite radio waves.
, a receiving section 12 that demodulates the navigation data of the received satellite radio waves and measures the pseudorange, a positioning calculation section 13 that calculates the position of the moving object from the navigation data and the pseudorange, and a display section that displays the position of the moving object. 14 and a determination circuit 15.

The determination circuit 15 compares the received satellite signal level with a reference signal level, compares the pseudoranges of each satellite in time series, determines the received satellite signal level, and instructs the operation of the positioning calculation unit 13.

[Effect]

The antenna section 11, the receiving section 12, the positioning calculation section 13, and the display section 14 calculate and display the position of the moving object according to a conventional method.The judgment circuit 15 compares the received satellite signal level with the reference signal level and Discrimination is made by comparing the pseudoranges of each satellite over time. If the satellite signal level deviates from the reference signal level, or if the measured pseudorange differs discontinuously and significantly compared to the pseudorange for each satellite, it is likely that a ghost is being received. The determination circuit 15 issues a command to stop the calculation to the positioning calculation unit 13. As a result, an incorrect position will not be displayed on the display unit 14.

〔Example〕

Hereinafter, embodiments of a satellite navigation device to which the present invention is applied will be described in detail.

FIG. 1 is a block diagram of an embodiment of the satellite navigation device of the present invention. In the figure, 11 is an antenna unit that receives satellite radio waves, 12 is a reception unit that demodulates navigation data and measures pseudoranges, 13 is a positioning calculation unit that solves known navigation equations, and 14
1 is a display section including a cathode ray tube display, and 15 is a determination circuit.

The judgment circuit 15 includes a circuit that compares whether the level of the satellite signal being received is within the lower limit signal level and the upper limit signal level, and the judgment circuit 15 stores the pseudo distance of each satellite at the time of previous measurement. Next, we will explain the 6th order operation, which also includes a circuit that compares the pseudorange with the corresponding pseudorange for each satellite in the current measurement and determines whether it falls within the limit value and does not change rapidly.

Satellite signals received from the antenna section 11 enter the receiving section 12, where navigation data is demodulated and pseudoranges are measured. The receiving section 12 sends satellite navigation message data and satellite pseudorange data to the positioning calculation section 13 . The positioning calculation unit 13 calculates the position of the vehicle by solving a navigation equation combining these data. The position is output to the display section 14.

While operating according to the conventional method as described above, the judgment circuit 15
obtains the signal level of each satellite from the receiving section 12. The determination circuit 15 checks whether this signal level is within the lower limit signal level and upper limit signal level of the receiving satellite. Furthermore, the pseudorange of each satellite is obtained from the receiving unit 12, and whether or not it is significantly different from the previous pseudorange is checked.
Check to see if it changes smoothly. If these determinations are satisfied, normal reception is occurring, and the position of the vehicle is determined by the operation of the satellite navigation device described above, and the position is displayed. If these determinations are not satisfied, it means that a ghost has been received, and the determination circuit 15 instructs the positioning calculation unit 13 to stop calculation.

〔Effect of the invention〕

As explained above, the satellite navigation device to which the present invention is applied can detect ghosts such as reflected waves, composite waves, and attenuated direct waves when a vehicle equipped with the device drives in an area with a lot of radio wave interference, such as an urban area. Since positioning is aborted even when a signal is being received, an incorrect position will not be displayed.

Therefore, it is most suitable for application to automobiles and the like that drive in areas where there is a lot of radio wave interference.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing an embodiment of a satellite navigation device to which the present invention is applied. 11, antenna section 12, receiving section 13, ,
Positioning calculation unit 14 Display unit 15...Judgment circuit

Claims (1)

[Claims] 1. an antenna unit that receives a plurality of satellite radio waves; a reception unit that demodulates the navigation data of the received satellite radio waves and measures a pseudorange; a positioning calculation unit that calculates the position of the moving object from the navigation data and the pseudorange; A display section that displays the position of the moving object, and a received satellite signal level that is compared with a reference signal level, as well as a time-series comparison of pseudoranges for each satellite to determine the operation and instruct the operation of the positioning calculation section. A satellite navigation device characterized by having a determination circuit.