JPH0255750B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for measuring the heading direction of a ship using radio waves from an artificial satellite of the NAV STAR/GPS system.

(Prior Art and its Problems) Conventionally, magnetic compasses, gyro compasses, and the like have been widely used as devices for measuring the heading of a ship. Since the pointer of a magnetic compass does not point to true north and south, but points to the magnetic north pole, there are errors unique to each location on the earth, making it difficult to obtain sufficient azimuth measurement accuracy. Nakatsuta. Furthermore, since the gyroscope compass uses the earth's rotation to act on a spinning top to provide direction, it has the disadvantage of requiring frequent periodic inspections of its moving parts. Furthermore, both magnetic compasses and gyroscope compasses cannot be used when ships are navigating in polar regions.

(Means for Solving the Problems) The present invention provides a method for transmitting a signal transmitted from any one of the artificial satellites in the NAV STAR/GPS system that is within an angle of suppression suitable for measuring the direction of a ship. , is received by two antennas placed 1/2 wavelength apart from each other, and the received 2
In addition to measuring the phase difference between two signals, it is also used for positioning.
The present invention is characterized in that the precise direction of the ship relative to due north is determined by calculating the direction of the artificial satellite relative to the ship's heading using a GPS receiver.

(Embodiment) In the embodiment shown in FIG.
3 and 6 are two-way multipliers, 7 is a phase difference measuring device, 8 is a GPS receiver for positioning, 9 is an azimuth calculator, and 10 is a display device.

(Operation) As shown in FIG. 2, the receiving antennas 1 and 4 are spaced apart from each other by λ/2 and are placed on or parallel to a straight line connecting the bow and stern. Here λ is
This is one wavelength of the GPS carrier signal.

The output of the receiving antenna 1 is input to one input terminal of the receiving demodulator 2. One input terminal of the reception demodulator 2 is connected to the positioning GPS receiver 8 that is currently receiving data.
Select one of the GPS satellites within the angle of suppression suitable for direction measurement and input the PN code assigned to that satellite. The receiving demodulator 2 detects all the signals within the field of view induced by the receiving antenna 1 based on the signals input to the two input terminals.
Among the signals emitted by the GPS satellites, a signal from the GPS satellite to which a PN code is attached is sent from a positioning GPS receiver 8 to a reception demodulator 2, and is transmitted to a 2-way multiplier 3. 2Tay multiplier 3 is the reception demodulator 2
By multiplying the output by 2, two-phase modulation components such as orbit information of the GPS satellite being received contained in the output of the reception demodulator 2 are removed and transmitted to the phase difference measuring device 7.

The signal from the receiving antenna 4 is also processed by the receiving demodulator 5 and the 2-tay multiplier 6 in exactly the same manner as described above.
As a result, a signal from which two-phase modulation components have been removed from the output signal of the receiving demodulator 5 is sent to the phase difference measuring device 7.

The phase difference measuring device 7 measures the phase difference between the outputs of the two-way multipliers 3 and 6 and transmits it to the azimuth calculator. If this phase difference is θ ₀ , then the phase difference between the carrier waves output from the receiving demodulators 2 and 5 is θ ₀ /2.

On the other hand, as mentioned before, the receiving antennas 1 and 4 are installed on the bow and stern line at a distance of λ/2 as shown in FIG.
Radio waves from GPS satellites in the direction of propagation path 1
As is clear from Fig. 2, the difference in propagation distance through 4 and 4 before reaching receiving antennas 1 and 4 is 4.
=λ/2 cosθ. However, point P is the point where the perpendicular line drawn from the receiving antenna 1 to the propagation path 4 intersects with the propagation path 4. Therefore, the reception phase difference of the signal from the GPS satellite occurring between the receiving antennas 1 and 4 is P4/-/λ・2π=π・cosθ, and this phase difference corresponds to the above-mentioned θ ₀ /2. It will be easily understood.

That is, πcosθ=θ ₀ /2 From this, by obtaining the measured value θ ₀ from the phase difference measuring device 7, the orientation of the GPS satellite with respect to the bow-tail line' can be calculated as θ=cos ^-1 θ ₀ /2π. I can do it. This calculation of the azimuth θ is performed by the azimuth calculator 9.
The positioning GPS receiver 8 selects one of the GPS satellites being received that is within an angle of suppression suitable for direction measurement, and transmits the PN code assigned to that satellite to the receiving demodulator 2 and the receiving demodulator 2. At the same time, the current direction of the satellite relative to due north (FIG. 3) is calculated from the orbit data of the satellite and sent to the direction calculator 9. The azimuth calculator 9 calculates the azimuth θ with respect to the bow and tail line of the GPS satellite from the phase difference θ ₀ transmitted from the phase difference measuring device 7 as θ=cos ^-1 θ ₀ /2π as described above, and The current azimuth with respect to due north of the GPS satellite used for azimuth measurement transmitted from the receiver is received from the positioning GPS receiver 8, and the heading is calculated as -θ and sent to the display 10.

Figure 3 shows true north N, the orientation of the GPS satellite relative to the true north, the orientation θ of the GPS satellite relative to the bow and stern line',
It shows the relative relationship between the GPS satellite S and the current ship position O.

The display 10 displays the heading (
-θ) is received and displayed using a display means such as a CRT.

In the embodiment described above, two receiving antennas 1,
4 is arranged on the bow and stern line', but they may also be arranged on a straight line perpendicular to the line', in which case -θ
−90° will be calculated.

Moreover, the receiving demodulators 5 and 2 in the above-mentioned embodiment
The TAY multiplier 6 is omitted, and instead, the receiving antennas 1 and 4 are switched alternately in time series and inputted to a single receiving demodulator 2, and in synchronization with this switching operation, a single TAY multiplier 3 is input. It is also possible to switch the output from and input it to the phase difference measuring device 7. In this way, the reception demodulator 5 and the 2-Tay multiplier 6 can be omitted and the circuit configuration can be simplified.

(Effects of the Invention) As explained above, the present invention makes it possible to measure the heading of a ship with high accuracy even when the ship is navigating in polar regions without being affected by geomagnetism or the earth's rotation. Since it does not include mechanical moving parts like a gyro compass,
This method has the advantage that the measured values are quickly stabilized, and furthermore, it is possible to measure the ship's heading with high precision without being affected by the movement of the ship.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing an embodiment of the present invention, and FIGS. 2 and 3 are drawings showing the measurement principle of the present invention. 1, 4... Receiving antenna, 2, 5... Receiving demodulator, 3, 6... 2-Tay multiplier, 7... Phase difference measuring device, 8... GPS receiver for positioning.

Claims (1)

[Claims] 1. Two devices installed at a distance of 1/2 wavelength from each other.
A GPS signal receiving antenna, a receiving demodulator that receives and demodulates a signal from a GPS satellite to which a PN code is assigned based on the output of the antenna and a PN code transmitted from a positioning GPS receiver, and an output of this receiving demodulator. A 2-Tay multiplier for multiplying the 2-Tay multiplier, a phase difference measuring device for measuring the phase difference between the received outputs of the two antennas from the output of the 2-Tey multiplier, and a phase difference measuring device for measuring the phase difference between the received outputs of the two antennas, Select one of the satellites existing within an elevation angle suitable for measurement, send the PN code assigned to that satellite to the receiving demodulator, and calculate the satellite orientation with respect to true north of that satellite. It is comprised of the positioning GPS receiver, a direction calculator that calculates the ship's heading with respect to true north from the phase difference and the satellite direction, and a display that visually displays the output of the direction calculator, that is, the ship's heading. A ship's heading measuring device characterized by: 2. The ship's heading measuring device according to claim 1, wherein the receiving demodulator and the 2-tay multiplier are provided for each of the two antennas. 3. In the device according to claim 1, each of the receiving demodulator and the 2-way multiplier is composed of a single unit, and the outputs of the two antennas are alternately switched in time series to control the receiving demodulation. A heading measuring device characterized in that the output of the two-way multiplier is switched in synchronization with the switching operation and applied to the phase difference measuring device.