JP2007171071A - Azimuth measuring device and signal processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To acquire accurate azimuth information even when a gyro compass is under a statically determinate operation. <P>SOLUTION: This device includes the gyro compass for outputting the first azimuth signal including a long-period error component from the starting time to finish of the statically determinate operation, and showing the stabilized azimuth in a short time; an azimuth detection means for outputting the second azimuth signal including a short-period error component from the starting time, and showing the stabilized azimuth on the average in a long time; and a signal processing means for generating a true azimuth signal showing the true azimuth based on the first azimuth signal and the second azimuth signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an azimuth measuring apparatus and a signal processing method.

  For example, a gyrocompass is known as one of the orientation measuring devices. As is well known, a mechanical gyro compass indicates true north by utilizing the direction-retaining property of a high-speed rotating body (gyro) having three degrees of freedom and the rotation and gravity of the earth. . Such a gyrocompass is mainly used as a ship heading measurement device, and plays an important role of transmitting heading information to a navigation function of a ship such as an autopilot (for example, the following non-patent document). 1).

  By the way, in the case of a mechanical gyrocompass using a gyro as described above, it takes several hours to stabilize and point to true north after starting (settling time), during which accurate heading information can be obtained. There is no problem. Therefore, in the case of the Sperry type gyrocompass, a method is adopted in which the gyrocompass is forcibly pointed to a direction close to true north by directly applying torque to the gyro to shorten the settling time.

 In the case of the gyro compass of the Anschutz / Tse-Platz type, since the rolling ball including the gyro is floating in the liquid called the supporting liquid, the torque is directly applied to the gyro as described above. Therefore, the stabilization time is shortened by providing a device called a short-time static determinator. This short-term static device uses the fact that if the rotational speed of the gyro is slowed, the cycle of the non-extinguishing shake becomes short and the elevation angle of the non-extinguishing shake becomes small. In other words, when the gyrocompass is started, the frequency of the AC power supplied to the gyro is first set to 60 Hz by a short-term stat, so that the gyro rotation speed is slowed down, and in the direction near true north in a short time. Indestructible shaking is generated. After that, the frequency of the AC power source is switched to 333 Hz, and a normal operation state is shifted to realize a short time stabilization.

Further, in recent years, a gyrocompass having a pre-settling function using a timer has been put into practical use so that the gyrocompass is activated in advance and the settling operation is completed and a desired performance can be obtained when used.
Maebata; Gyrocompass and Autopilot; Naruyamado Shoten; 1985; P1-6

However, in the case of a gyrocompass equipped with a function for directly applying torque to the gyro and a short-term static adjuster as described above, there is a problem that the number of parts increases, resulting in an increase in cost and an increase in the size of the apparatus. In addition, in the case of a gyrocompass having a pre-settling function using a timer, there is a problem that if the user forgets to put in the timer, the settling operation is not completed before use.
Furthermore, even when these short-term stabilization functions are used, the heading information output from the gyrocompass during the stabilization operation contains large errors, so the heading during the stabilization operation The information could not be used.

 The present invention has been made in view of such circumstances, and an object of the present invention is to obtain accurate azimuth information even when the gyrocompass is in a static operation.

 In order to solve the above-mentioned problem, in the present invention, as a first solution means for an azimuth measuring apparatus, a long-cycle error component is included from the time of start-up until the completion of the static stabilization operation, but stable in a short time. A gyro compass that outputs a first azimuth signal indicating azimuth, and an azimuth detecting means that outputs a second azimuth signal indicating an average stable azimuth over a long period of time while including an error component of a short period from the time of startup And a signal processing means for generating a true azimuth signal indicating a true azimuth based on the first azimuth signal and the second azimuth signal.

 In the present invention, as the second solving means relating to the bearing measuring device, in the first solving means, the signal processing means calculates a difference between the first bearing signal and the second bearing signal. A first difference means for outputting a difference signal, a filter for reducing a high frequency error component included in the difference signal and outputting a gyrocompass error signal, the first azimuth signal and the gyrocompass error signal, And a second difference means for generating a true azimuth signal.

 In the present invention, as a third solving means relating to the azimuth measuring apparatus, in the first or the second solving means, the signal processing means calculates a speed error for calculating a speed error included in the first azimuth signal. A calculating means; and a subtracting means for subtracting the speed error from the first azimuth signal, and when measuring the azimuth while moving toward a place other than east or west at a predetermined speed, Signal processing is performed using one azimuth signal.

 In the present invention, as a fourth solving means relating to the bearing measuring device, in any one of the first to third solving means, the bearing detection means is a THD (Transmitting Heading Devices). It is characterized by that.

  Furthermore, in the present invention, as a first solving means related to the signal processing method, a first signal that includes a long-cycle error component and stably shows a value related to a predetermined parameter in a short time, and a short cycle The true value related to the parameter is determined based on the second signal indicating the value related to the parameter that is stable on average over a long period of time.

 In the present invention, as a second solving means related to the signal processing method, a step of calculating a difference between the first signal and the second signal in the first solving means to generate a difference signal; Reducing a high-frequency error component included in the difference signal, generating an error signal, calculating a difference between the first signal and the error signal, and calculating a true value related to the parameter based on the difference And a step of determining.

 According to the present invention, a gyrocompass output signal indicating a stable orientation in a short time while including a long-cycle error component from the start to the completion of the static stabilization operation and a short-cycle error component from the start On the other hand, by complementing each other's weak points using two signals with the output signal of the direction detection means (for example, GPS compass) that shows an average stable direction over a long period of time, the gyro compass It is possible to obtain accurate azimuth information even during a static operation.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration block diagram of a ship provided with a bow direction measuring device (direction measuring device) according to an embodiment of the present invention. In FIG. 1, only the steering function configuration of the ship is shown, and other functional configurations such as a screw drive function are omitted.

  As shown in this figure, the heading measurement apparatus D includes a gyrocompass 1, a GPS (Global Positioning System) compass 2, a navigation speed measurement unit 3, a speed error calculation unit 4, a first subtractor 5, a second The subtractor 6 includes an LPF (Low Pass Filter) 7 and a third subtractor 8.

The gyrocompass 1 is, for example, a mechanical gyrocompass such as a Sperry type or an Anschutz / Tse-Platz type, and is capable of maintaining the direction of a high-speed rotating body (gyro) having three axes of freedom, the rotation of the earth, and gravity. Are used to measure the heading of the ship, and a gyrocompass heading signal φ _GYRO indicating the heading is output to the first subtractor 5. The GPS compass 2 is one of THD (Transmitting Heading Devices), measures the heading using the Global Positioning System, and indicates a GPS compass heading signal indicating the heading. and it outputs the phi _GPS to the speed error calculator 4 and the second subtractor 6. The GPS compass 2 measures the latitude of the ship and outputs a latitude signal s1 indicating the latitude to the speed error calculation unit 4.

The navigation speed measurement unit 3 is, for example, an electromagnetic log, measures the navigation speed of the ship, and outputs a navigation speed signal s2 indicating the navigation speed to the speed error calculation unit 4. Based on the GPS compass direction signal φ _GPS and latitude signal s1 input from the GPS compass 2 and the navigation speed signal s2 input from the navigation speed measurement unit 3, the speed error calculation unit 4 A speed error ε _VEL generated in the gyrocompass heading signal φ _GYRO of the gyrocompass 1 when traveling on a course other than the above is calculated, and a speed error signal s3 indicating the speed error ε _VEL is output to the first subtractor 5. To do. Details of the method of calculating the speed error ε _VEL will be described later.

The first subtractor 5 calculates a difference between the gyro compass direction signal _φGYRO input from the gyrocompass 1 and the speed error signal s3 input from the speed error calculation unit 4, and indicates the first difference. and it outputs the differential azimuth signal phi _G1 to the second subtractor 6 and the third subtractor 8. The second subtractor 6 calculates the difference between the first differential bearing signal φ _G1 input from the first subtractor 5 and the GPS compass bearing signal φ _GPS input from the GPS compass 2, a second differential bearing signals phi _G2 representing a difference output to LPF 7.

LPF7, said with (specifically, components having a period of a few seconds) a second second differential azimuth signal phi _G2 of the high-frequency component inputted from the subtractor 6 for attenuating the low-frequency component (specifically Is passed to a third subtracter 8 as a gyrocompass error signal s4. Third subtracter 8 calculates the first and difference azimuth signal phi _G1 inputted from the first subtracter 5, a difference between the gyro compass error signal s4 supplied from LPF 7. The difference between these first difference direction signal phi _G1 and a gyro compass error signal s4 is indicative of the true value of heading. That is, the third subtracter 8 outputs a heading signal φ _G3 indicating the true value of the heading to the steering unit 9.

The steering unit 9 has an autopilot function, and a rudder angle for controlling the rudder angle of the rudder 11 based on the bow direction signal φ _G3 input from the third subtracter 8 in the bow direction measuring device D. A control signal is output to the rudder drive unit 10. The rudder drive unit 10 drives the rudder 11 based on the rudder angle control signal. The rudder 11 is driven by the rudder driving unit 10 and defines the course of the ship by the rudder angle indicated by the steering unit 9.

Note that the heading signal phi _G3 obtained from the heading measuring device D, as well as steering unit 9, may be used to repeater compasses and other navigational equipment. The steering unit 9 may have not only an autopilot function but also a function of controlling the rudder angle of the rudder 11 based on a manual operation by the operator.

  Next, the operation of the heading measurement apparatus D configured as described above will be described.

[If the ship is stationary]
First, the operation of the heading measurement apparatus D when the ship is stationary will be described.
FIG. 2 shows the temporal variation of the gyrocompass heading signal _φGYRO output from the gyrocompass 1. In this figure, the horizontal axis indicates the elapsed time since the gyrocompass 1 is activated, and the vertical axis indicates the azimuth of the ship, that is, the azimuth angle. In the vertical axis, true north is shown when the azimuth angle is 0 °. As can be seen from FIG. 2, during the static operation, the gyro compass bearing signal φ _GYRO fluctuates in a sinusoidal shape with a period of about 84 (min) around the true north azimuth, and this fluctuation attenuates over time. I will do it. When such fluctuation does not occur and the azimuth of the true north is completely displayed, the stabilization is completed.
As described above, the gyrocompass heading signal φ _GYRO output from the gyrocompass 1 during the static operation is fluctuating over a long period of time, that is, includes an error, and therefore is used as accurate bow heading information. It is not possible.

Further, FIG. 3 shows temporal changes in the GPS compass direction signal φ _GPS output from the GPS compass 2. In this figure, the horizontal axis represents the elapsed time since the GPS compass 2 was activated, and the vertical axis represents the azimuth of the ship. In the vertical axis, true north is shown when the azimuth angle is 0 °. As can be seen from FIG. 3, GPS compass heading signal phi _GPS is pointing substantially true azimuth on average over a long period of time immediately after the start, the short time basis contains many high-frequency components . That is, when the GPS compass 2 is used, the settling time can be almost ignored, but since it includes a lot of high frequency errors in a short time, it cannot be used as accurate heading information. On the other hand, the gyrocompass azimuth signal φ _GYRO includes a large error for a long time as shown in FIG. 2, but shows a substantially constant azimuth for a short time of about several tens of seconds.
By performing the signal processing described below using the gyrocompass direction signal φ _GYRO and the GPS compass direction signal φ _GPS exhibiting the above characteristics, it is possible to obtain accurate bow direction information in a short time. .

Here, the true azimuth angle at rest .phi.s, the inherent error of the gyro compass 1 and epsilon _GYRO, gyro compass heading signal phi _GYRO is expressed by the following equation (1). The gyrocompass 1 outputs a gyrocompass direction signal φ _GYRO expressed by the following relational expression (1) to the first subtracter 5.

Further, assuming that the inherent error of the GPS compass 2 is ε _GPS , the GPS compass bearing signal φ _GPS is expressed by the following relational expression (2). The GPS compass 2 outputs a GPS compass bearing signal φ _GPS represented by the following relational expression (2) to the speed error calculation unit 4 and the second subtracter 6.

When the ship is stationary, it is not necessary to calculate the speed error component ε _VEL included in the gyro compass heading signal φ _GYRO , so the speed error calculation unit 4 does not operate and the speed error signal s3 is not output. In this case, the first subtracter 5 outputs the gyrocompass bearing signal φ _GYRO to the second subtractor 6 and the third subtracter 8 as the first differential bearing signal φ _G1 .

The second subtracter 6 calculates a difference between the gyrocompass bearing signal φ _GYRO and the GPS compass bearing signal φ _GPS, and outputs a second differential bearing signal φ _G2 indicating the difference to the LPF 7. That is, the second differential azimuth signal phi _G2 represented by the following equation (3).

It shows such a second differential bearing signals phi _G2 in FIG. As can be seen from this figure, the second differential azimuth signal phi _G2, although a sinusoidal decay curve for long, the simple interval moving average or primary short time basis in the order of tens of seconds Smoothing is possible by formula approximation.

LPF7 is configured to attenuate the second differential azimuth signal phi _G2 of the high frequency component (i.e. GPS compass 2-specific error epsilon _GPS), is passed through a low-frequency component (i.e. gyrocompass 1-specific error epsilon _GYRO), gyrocompass The error signal s4 is output to the third subtracter 8. FIG. 5 shows the gyro compass error signal s4 when the time constant of the LPF 7 is set to 10 (s). As can be seen from this figure, the high-frequency component (that is, the error ε _GPS specific to the GPS compass 2) is almost removed, and the gyrocompass error signal s4 is a signal indicating only the error _εGYRO specific to the gyrocompass 1.

Third subtracter 8 outputs the _GYRO gyro compass heading signal phi as a first differential azimuth signal phi _G1, a heading signal phi _G3 to the steering unit 9 calculates the difference between the gyro compass error signal s4 . That is, the heading signal φ _G3 is expressed by the following relational expression (4).

Thus, heading signal phi _G3 is a signal indicating a true azimuth angle φs at rest. FIG. 6 shows the heading signal φ _G3 . As can be seen from this figure, the heading signal φ _G3 is a signal from which a low frequency error component seen in a long time and a high frequency error component seen in a short time are substantially eliminated. Regardless of the elapsed time, a substantially constant azimuth angle φs can be obtained.

[If the ship is navigating and turning]
Next, the operation of the heading measurement apparatus D when the ship is navigating and turning at a predetermined navigation speed will be described.
FIG. 7 shows the temporal fluctuation of the gyrocompass bearing signal _φGYRO when the ship is turned from 0 ° to 5 ° after about 2 hours from the start of the gyrocompass 1. As shown in this figure, it can be seen that the gyro compass bearing signal φ _GYRO changes greatly during turning. FIG. 8 shows the temporal variation of the GPS compass bearing signal φ _GPS when the ship is turned from 0 ° to 5 ° after about 2 hours from the start of the GPS compass 2. As can be seen from this figure, similar to FIG. 7, GPS compass heading signal phi _GPS varies greatly during turning.

As can be seen from FIG. 7, the turning component φ _SHIP is included in the gyro compass direction signal φ _GYRO during turning. Furthermore, when the ship is navigating a course other than east or west, the gyrocompass heading signal _φGYRO includes an error called a speed error. This speed error is an error that always occurs in the gyrocompass 1 configured based on the earth rotation, and does not occur in a compass that does not use the earth rotation such as the GPS compass 2. Therefore, if the true azimuth angle during turning is φs, the inherent error of the gyrocompass 1 is ε _GYRO , and the speed error is ε _VEL , the gyrocompass direction signal φ _GYRO during turning is expressed by the following relational expression (5). The During turning, the gyrocompass 1 outputs a gyrocompass bearing signal φ _GYRO expressed by the following relational expression (5) to the first subtracter 5.

Similarly, during turning, the GPS compass bearing signal φ _GPS also includes a turning component φ _SHIP . Therefore, if the inherent error of the GPS compass 2 is ε _GPS , the GPS compass direction signal φ _GPS at the time of turning is expressed by the following relational expression (6). At the time of turning, the GPS compass 2 outputs a GPS compass bearing signal φ _GPS represented by the following relational expression (6) to the speed error calculation unit 4 and the second subtracter 6. The GPS compass 2 measures the latitude of the ship and outputs a latitude signal s1 indicating the latitude to the speed error calculation unit 4.

  The navigation speed measurement unit 3 measures the navigation speed V of the ship and outputs a navigation speed signal s2 indicating the navigation speed to the speed error calculation unit 4.

The speed error calculation unit 4 includes a navigation speed V (m / s), a compass course θ (deg), an earth equatorial radius R (m), an earth rotation angular speed ω (rad / s), and a latitude λ (deg). A speed error ε _VEL (rad) is calculated based on the following relational expression (7), and a speed error signal s3 indicating the speed error ε _VEL is output to the first subtracter 5. The following relational formula (7), the sailing speed V using the navigation speed signal s2, as the compass heading θ using GPS compass heading signal phi _GPS, and as the latitude λ using the latitude signal s1.

Then, the first subtracter 5 calculates a difference between the gyrocompass bearing signal φ _GYRO and the speed error signal s3, and uses the second subtractor 6 and the third subtractor 6 to calculate the first difference bearing signal φ _G1 indicating the difference. Is output to the subtracter 8. That is, the first differential azimuth signal phi _G1 is represented by the following equation (8).
Thus, the first subtracter 5 removes the speed error ε _VEL from the gyrocompass bearing signal φ _GYRO .

The second subtractor 6 calculates a difference between the first differential azimuth signal φ _G1 and the GPS compass azimuth signal φ _GPS, and outputs a second differential azimuth signal φ _G2 indicating the difference to the LPF 7. That is, the second differential azimuth signal phi _G2 represented by the following equation (9).

It shows such a second differential bearing signals phi _G2 in FIG. As shown in the figure, the turning component φ _SHIP can be removed by taking the difference between the first differential bearing signal φ _G1 and the GPS compass bearing signal φ _GPS . Therefore, the gyrocompass error signal s4 obtained by the filtering process of the LPF 7 is a signal indicating only the error _εGYRO specific to the gyrocompass 1 as in the above-described stationary state, and the accurate error _εGYRO specific to the gyrocompass 1 is obtained. Can be estimated. FIG. 10 shows such a gyrocompass error signal s4.

The third subtracter 8 calculates a difference between the first differential bearing signal φ _G1 and the gyrocompass error signal s4 and outputs a bow bearing signal φ _G3 to the steering unit 9. That is, the heading signal φ _G3 is expressed by the following relational expression (10). FIG. 11 shows the heading signal φ _G3 . As shown in this figure, heading signal phi _G3 is made similarly to the static state, the error component of the low frequency seen in a long time, the signal and the high frequency error components found is substantially removed in a short time Therefore, regardless of the elapsed time since the start of the gyrocompass 1, accurate heading information including the turning component can be obtained.

  As described above, according to the present embodiment, the gyrocompass 1 has a characteristic that a large error is included for a long time, but a substantially constant azimuth is exhibited for a short time of about several tens of seconds. 2 of the output signal and the output signal of the GPS compass 2 having the characteristic that it can ignore the settling time and shows a substantially constant azimuth angle for a long time, but includes a lot of high frequency errors in a short time. By complementing each other's weak points using two signals, it is possible to obtain accurate heading information even when the gyrocompass 1 is in a static operation.

 In addition, since it is not necessary to provide a function for directly applying torque to the gyro or a short-term static adjuster as in the past, it is possible to prevent an increase in cost and size of the apparatus, and it is not necessary to provide a timer function. There is no human error such as forgetting to put the timer.

In the above-described embodiment, it is desirable to use only the gyrocompass direction signal φ _GYRO output from the gyrocompass 1 as the heading information after the stabilization operation of the gyrocompass 1 is completed.

  Further, the present invention is not limited to the above embodiment, and for example, the following modifications can be considered.

(1) In the above embodiment, the bow heading measuring device D that measures the heading of the ship has been described as an example. However, the present invention is not limited thereto, and any device that has a function of measuring heading using a gyrocompass may be used. It can be applied to other devices.

(2) In the above-described embodiment, the GPS compass is used as the direction detection means. However, the present invention is not limited to this, and the direction signal includes a high-frequency error component from the start-up and shows an average stable direction when viewed over a long period of time. Any other THD (for example, an electronic magnetic compass) may be used.

(3) In the above embodiment, calculates the speed error epsilon _VEL by the speed error calculator 4, it had gained an accurate heading information by removing the velocity error epsilon _VEL from the gyro compass heading signal phi _GYRO. However, it is not always necessary to calculate such a speed error ε _VEL, and although the accuracy of the heading information is reduced to some extent, the speed error calculation unit 4 and the navigation speed measurement unit 3 are not essential components. However, if it is important to ensure the accuracy of the heading information, it is desirable to include the speed error calculation unit 4 and the navigation speed measurement unit 3.
Further, the navigation speed measuring unit 3 may be provided inside the heading measurement apparatus D, or may be configured to obtain navigation speed information from a navigation speed measuring instrument originally provided in the ship. Further, the navigation speed and latitude may be manually input.

(4) In the above embodiment, the output signal of the gyrocompass that shows a stable orientation when viewed in a short time including a long-cycle error component and the high-frequency error component from the time of startup while viewed in a long time True direction information was obtained by complementing each other's weak points using two signals, the output signal of the direction detection means showing an average stable direction. In this way, similar signal processing can be applied even when the true value of the value related to other parameters is obtained in addition to the orientation. That is, the first signal including a long-cycle error component and stable in a short time and showing a value related to a predetermined parameter, and the average signal stable in a long time including a high-frequency error component. Thus, when two signals with the second signal indicating the value relating to the parameter are obtained, the true value relating to the predetermined parameter can be determined by complementing each other's weak points using the two signals. Is possible.

 Specifically, a difference signal is generated by calculating a difference between the first signal and the second signal, and filtering is performed so as to reduce a high-frequency error component included in the difference signal. And the true value regarding a predetermined parameter can be calculated | required by calculating the difference of the signal after filtering, and a 1st signal.

It is a functional lineblock diagram of a ship provided with a bow direction measuring device concerning one embodiment of the present invention. FIG. 6 is a first explanatory diagram showing a signal processing procedure when a ship according to an embodiment of the present invention is stationary. It is 2nd explanatory drawing which shows the signal processing procedure in case the ship concerning one Embodiment of this invention is still. It is 3rd explanatory drawing which shows the signal processing procedure in case the ship concerning one Embodiment of this invention is stationary. It is a 4th explanatory view showing a signal processing procedure in case a ship concerning one embodiment of the present invention is still. It is 5th explanatory drawing which shows the signal processing procedure in case the ship concerning one Embodiment of this invention is stationary. FIG. 5 is a first explanatory diagram showing a signal processing procedure when a ship according to an embodiment of the present invention is navigating and turning. It is 2nd explanatory drawing which shows the signal processing procedure in case the ship concerning one Embodiment of this invention is navigating and turning. It is 3rd explanatory drawing which shows the signal processing procedure in case the ship concerning one Embodiment of this invention is navigating and turning. It is the 4th explanatory view showing a signal processing procedure in case a ship concerning one embodiment of the present invention is navigating and turning. It is 5th explanatory drawing which shows the signal processing procedure in case the ship concerning one Embodiment of this invention is navigating and turning.

Explanation of symbols

  DESCRIPTION OF SYMBOLS D ... Heading measuring apparatus, 1 ... Gyrocompass, 2 ... GPS (Global Positioning System) compass, 3 ... Navigation speed measurement part, 4 ... Speed error calculation part, 5 ... 1st subtractor, 6 ... 2nd subtraction 7 ... LPF (Low Pass Filter), 8 ... Third subtractor, 9 ... Steering unit, 10 ... Rudder drive unit, 11 ... Rudder

Claims (6)

A gyro compass that outputs a first azimuth signal indicating a stable azimuth in a short time while including an error component of a long period from the start to the completion of the static operation;
An azimuth detecting means for outputting a second azimuth signal indicating an azimuth which is stable on the average for a long time while including an error component of a short period from the time of startup;
And a signal processing unit that generates a true azimuth signal indicating a true azimuth based on the first azimuth signal and the second azimuth signal. The signal processing means includes
First difference means for calculating a difference between the first azimuth signal and the second azimuth signal and outputting the difference signal;
A filter that reduces a high-frequency error component included in the differential signal and outputs a gyrocompass error signal;
The azimuth measuring apparatus according to claim 1, further comprising: second difference means for calculating a difference between the first azimuth signal and the gyrocompass error signal and generating a true azimuth signal. The signal processing means includes
Speed error calculating means for calculating a speed error included in the first azimuth signal;
Subtracting means for subtracting the speed error from the first azimuth signal,
The signal processing is performed using the first azimuth signal after subtracting the speed error when measuring the azimuth while moving toward a place other than east or west at a predetermined speed. The azimuth measuring device described.   The azimuth measuring device according to claim 1, wherein the azimuth detecting means is a THD (Transmitting Heading Devices).   While including a long-cycle error component, the first signal indicating a value related to a predetermined parameter stably in a short time, and including a short-cycle error component, stable in an average over a long time A signal processing method comprising: determining a true value related to the parameter based on a second signal indicating a value related to the parameter. Calculating a difference between the first signal and the second signal, and generating a difference signal;
Reducing a high-frequency error component included in the differential signal and generating an error signal;
The signal processing method according to claim 5, further comprising: calculating a difference between the first signal and the error signal, and determining a true value related to the parameter based on the difference.

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