JP2002040155A - Apparatus and method of measuring gravitation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a gravity anomaly accurately, using a gravimeter instrument carried on a navigator. SOLUTION: A gravitation measuring instrument structured which is constituted so as mounted on a navigator comprises a gravimeter, a platform for supporting the gravimeter, a horizontal stabilizer for horizontally supporting the platform, and a gyro compass for feeding attitude angle signals to the horizontal stabilizer. The platform mounts an accelerometer for detecting the horizontal acceleration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gravity measuring device and method for detecting gravity on the earth's surface, and more particularly to a gravity measuring device mounted on a navigation body and a gravity measuring method using the same.

[0002]

2. Description of the Related Art The value of gravity on the earth's surface varies slightly depending on the measurement site due to the density structure of rocks underground, changes in geocentric distance, and the like. The difference between the measured gravity and the standard gravity is called gravity anomaly. The measurement of gravity does not depart from the measurement of this gravity anomaly. When measuring gravity, portable gravimeters are used on flat ground, but in polar regions, in desert areas,
In a mountainous area, the sea, or the like, a gravity measuring device mounted on a navigating body or a moving body such as a vehicle or an aircraft is used.

[0003] When gravity is measured by a gravity measuring device mounted on a navigating body or a moving body, DGPS (differential global posi- tion) is required to accurately measure the position of a measuring point.
tioning system) is used.

[0004] DGPS has been developed to improve the measurement accuracy of GPS. In GPS, the position is measured only by the mobile station (user), whereas in DGPS, the position is measured by the mobile station (user) and the reference station (fixed station). In DGPS, a correction value is calculated from a pseudo distance from a GPS satellite, time information, and orbit data at a reference station whose exact position is measured in advance, and the correction value is transmitted to the mobile station. The mobile station corrects the signal from the GPS satellite using the correction value from the reference station.

[0005] There are two methods of DGPS, a code phase positioning method and a carrier phase positioning method. Code phase positioning uses the code phase as a measurement and is used for real-time positioning. Accuracy is about 1 to 10 m. The carrier phase positioning method uses a carrier phase as a measured value and is used for highly accurate position measurement. The accuracy is on the order of mm to cm.

An example of a conventional gravity measuring device and method will be described with reference to FIG. The gravity measuring device 20 is mounted on the navigation body 10 such as a helicopter. The DGPS includes at least four GPS satellites (only two GPS satellites 12 and 13 are shown in FIG. 4), two mobile stations (users) 14 and 15 mounted on the navigation body 10, and two reference stations (fixed stations) on the ground. ) 16,
17 is used.

A first mobile station (user) 14 and a reference station (fixed station) 16 are receivers for carrier phase positioning,
Second mobile station (user) 15 and reference station (fixed station) 17
Is a receiving device for code phase positioning.

[0008] The configuration and operation of a conventional gravity measuring device will be described with reference to FIG. The gravity measuring device 20 has a gyro compass 21 and a gravimeter 22 mounted on the base 10A of the navigation body 10. The gyro compass 21 may be a vertical gyro. The gravimeter 22 is mounted on a horizontal stabilizer 23 mounted on the base 10A. The horizontal stabilizer 23 is configured to hold the input shaft of the gravimeter 22 in the vertical direction, and its structure will be described later. The gravity measuring device 20 further includes a recording and calculating device 3 for inputting signals from the mobile stations 14 and 15.
1, 32.

The structure of the conventional horizontal stabilizer 23 will be described with reference to FIG. The horizontal stabilizer is platform 101
And a gimbal device for holding the platform 101 horizontally. A gravimeter 22 is arranged on the platform 101. The gimbal device includes roll shafts 103A, 1A mounted on both ends of the platform 101.
03B and the roll shaft torquer 1 provided at the outer end of the roll shaft
05A, 105B, the roll shafts 103A, 103B, and the gimbal rings 107 supporting the roll shaft torquers 105A, 105B, the pitch shafts 109A, 109B mounted on both ends of the gimbal rings 107, and the pitch shaft torquers provided at the outer ends of the pitch shafts. 111A, 111B and pitch axes 109A, 1
09B and support members 113A and 113B that support the pitch axis torquers 111A and 111B.

Roll axes 103A and 103B and pitch axis 1
09A and 109B are mounted so as to be orthogonal to each other.
Roll axes 103A, 103B and pitch axes 109A, 10A
9B is supported by a bearing (not shown). The support members 113A and 113B are mounted on the base 10A of the navigation body 10. The horizontal stabilizer 23 has a roll shaft 103A,
So that 3B is located along the line of success of navigation vehicle 10,
It is attached to the base 10A of the navigation body 10.

Referring again to FIG. The velocity signal from the code phase geodetic mobile station 15 is supplied to the gyro compass 21. The gyro compass 21 uses this speed signal as a speed log to accurately calculate the attitude angle (roll angle and pitch angle).

The attitude angles (roll angle and pitch angle) from the gyrocompass 21 are roll axis torquers 105A, 105A.
B and pitch axis torquers 111A and 111B. Thereby, the platform 101 is held horizontally, and the input shaft of the gravimeter 22 is held vertically.

A high-precision position signal and a time signal are output from the mobile station 14 for carrier phase geodetic recording, and are recorded in the first recording operation device 31. Mobile station 15 for code phase geodetic
Outputs a time signal, which is recorded in the second recording operation device 32. A gravity signal Gt is output from the gravimeter 22 and is recorded in the second recording operation device 32 in real time. The output of the gravimeter 22 is represented by the following equation.

[0014]

Gt = ΔG + A + C + Z + E

Gt is the output of the gravimeter 22, ΔG is abnormal gravity, A is reference ellipsoidal gravity, C is free air correction, Z is vertical acceleration, and E is Etobes effect. The gravity anomaly ΔG is a deviation between the gravity value of the measurement site and the standard gravity, and is 1 to 200 mG.
al. The gravity measurement device 20 detects this gravity anomaly ΔG
Is measured.

The reference ellipsoid gravity A is determined by the latitude of the measurement point, and is 979.7 Gal at a latitude of 35 degrees, for example. The free air correction C changes with altitude, and is -0.3
mGal / m. The vertical acceleration Z is a vertical acceleration caused by the vertical movement of the navigation body. This is obtained by precisely measuring the position of the vehicle and calculating its second derivative. Its value is 1
It is about 10 Gal. The Etobes effect E changes depending on the speed and altitude of the navigation body, Coriolis force, centrifugal force, and the like due to the influence of the shape of the reference ellipsoid, and is about 0.1 to 0.5 Gal.

The recording operation devices 31 and 32 first perform a filtering process on the input signal to remove noise such as vibration of the navigation body 10. Next, the second to second expressions on the right side of the equation (1)
The five terms are calculated and subtracted from the output of the gravimeter to determine the gravity abnormality ΔG. The calculations in the recording calculation devices 31 and 32 are performed off-line.

[0018]

In the conventional gravity measurement,
As shown in the equation (1), only the vertical acceleration Z acting on the gravimeter was considered. This assumes that the platform supporting the gravimeter is horizontal. However, in practice, the platform is not always held exactly horizontally. When the accuracy of the gravity abnormality ΔG is 1 mGal or less, the allowable inclination angle Δθ of the platform is as follows.

[0019]

## EQU2 ## Δθ = cos-1 (1-1 / 980000) =
0.082 [degrees] = 4.9 [minutes]

When the platform is tilted, the output of the gravimeter includes not only the vertical component of the gravitational acceleration but also the vertical component of the horizontal acceleration. This vertical component is an error. Therefore, the gravity abnormality ΔG cannot be measured accurately.

Accordingly, an object of the present invention is to accurately measure gravity even when the platform that supports the gravimeter is inclined when gravity is measured by a gravity measuring device mounted on a navigation body.

An object of the present invention is to measure the gravity accurately by using a gravity measuring device mounted on a navigation body, even when the acceleration of the navigation body is large.

[0023]

According to the present invention, a gravimeter, a platform for supporting the gravimeter, a horizontal stabilizer having a gimbal mechanism for horizontally supporting the platform, and the same surface as the horizontal stabilizer. A gyro compass mounted inside the gyro compass for supplying an attitude angle signal to the horizontal stabilizer, and in a gravity measuring device mounted on the navigation body, the platform has an accelerometer for detecting horizontal acceleration. It is characterized by being mounted.

Therefore, when the gravity is measured by the gravity measuring device mounted on the navigation body, even if the platform supporting the gravity measuring device is inclined, the gravity abnormality can be accurately measured.

According to the present invention, in the gravity measuring device,
A mobile station for carrier phase positioning by DGPS and a first recording operation device for recording position information and time information from the mobile station are provided. A mobile station for code phase positioning by DGPS and a second recording / processing device for recording position information and time information from the mobile station are provided. The second recording operation device records an output signal of the gravimeter, an output signal of the accelerometer, and an output signal of the gyro compass.

Therefore, when gravity (abnormal gravity) is measured by a gravity measuring device mounted on a navigation body, the abnormal gravity can be calculated by off-line processing.

According to the present invention, the east-west direction acceleration and the north-south direction acceleration are calculated based on the position signal from the carrier station for carrier wave phase positioning, and the east-west direction acceleration, the north-south direction acceleration, and the azimuth signal from the gyro compass are calculated. It is configured to calculate a roll direction acceleration and a pitch direction acceleration, and filter and calculate a roll angle error and a pitch angle error of the platform by a horizontal acceleration signal from the accelerometer, thereby correcting an output of the gravimeter. I have.

According to the present invention, the gravity measurement method is a gravity measurement method using a gravimeter mounted on a platform of a navigating body, wherein the acceleration in the east-west direction and the north-south acceleration are determined by position information from a mobile station for carrier wave phase positioning by DGPS. Calculating the roll direction acceleration and the pitch direction acceleration based on the east-west direction acceleration, the north-south direction acceleration, and the azimuth signal from the gyro compass, and the roll angle error of the platform based on the horizontal acceleration signal from the accelerometer. And calculating the pitch angle error, and correcting the output of the gravimeter with the roll angle error and the pitch angle error.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a gravity measuring device according to the present invention will be described with reference to FIGS. The gravitational measurement device of this example is a gyro compass 2 mounted on a base 10A of a navigation body 10.
1, a gravimeter 22, and accelerometers 24 and 25.

As shown in FIG. 2, the gravimeter 22 and the accelerometers 24 and 25 include a horizontal stabilizer 23 mounted on the base 10A.
Is mounted on the platform 101. The gravity measuring device 20 further has recording operation devices 31 and 32 for inputting signals from the mobile stations 14 and 15. Record operation device 3
1 and 32 may be provided separately as shown in the figure, but may be a single recording operation device.

The gravity measuring device of this embodiment is different from the conventional gravity measuring device shown in FIG. 5 in that accelerometers 24 and 25 are additionally mounted, and the other configurations are the same. May be.

The first accelerometer 24 detects the acceleration in the roll direction, and the second accelerometer 25 detects the acceleration in the pitch direction.

The signal flow and processing in the gravity measuring apparatus and method according to the present embodiment will be described with reference to FIG. East-west acceleration α of the vehicle 10 by the mobile station 14 for carrier phase geodetic
E and the north-south acceleration αN are detected and recorded in the first recording operation device 31. The gyro compass 21 detects the azimuth angle φ of the navigation body 10 and the second recording arithmetic unit 32
Will be recorded. From these signals, the following formulas are used to calculate the roll direction acceleration α1 and the pitch direction acceleration α2 of the vehicle.
Is required.

[0034]

Α1 = αEcosφ−αNsinφ α2 = αEsinφ + αNcosφ

As shown in the lower right picture of FIG. 3, the roll direction acceleration is an acceleration along the pitch axis direction of the navigation body, and the pitch direction acceleration is an acceleration along the roll axis direction of the navigation body. .

The output Gt of the gravimeter 22 is recorded in the second recording operation device 32. Here, the output of the gravimeter 22 is expressed by the following equation instead of the equation (1).

[0037]

Gt = ΔG + A + C + Z + E + H = G ₀ + H

Here, H is an error caused by the inclination of the platform. Other terms ΔG, A, C, Z, E
Is the same as the term in the equation of the formula 1. G ₀ is referred to herein as gravitational acceleration.

The outputs β1 and β2 of the accelerometers 24 and 25 are recorded in the second recording operation device 32. Accelerometer 24, 2
5 are expressed by the following equations.

[0040]

Β1 = α1 ′ + Gt · sin θ1 β2 = α2 ′ + Gt · sin θ2

The first terms α1 ′ and α2 ′ on the right side of the equation (5) are the roll acceleration and the pitch acceleration of the platform caused by the movement of the navigation body. Its size is 50
It is about Gal, and the period is about 2 to 3 minutes. The second term on the right side of the equation (5) is an error caused by the inclination of the platform. Its size is about 1 Gal, and has a considerably long period.

Roll angle error and pitch error θ1, θ2
Are the tilt angles about the roll axis and the pitch axis of the platform, respectively. Thus, when the platform is horizontal, this second term will be zero. Below, the outputs β1, β2 of the accelerometers 24, 25
A procedure for obtaining the roll angle error and the pitch errors θ1 and θ2 will be described.

In the first and second terms on the right side of the equation (5), their periods and spectra are different, so that both can be easily separated by appropriate filtering. Therefore, only the second term on the right side of the equation (5) can be extracted.

On the other hand, on the right side of the equation (4), the platform tilt error H is ignored because it is sufficiently smaller than the gravitational acceleration G ₀ . Further, at the gravitational acceleration G ₀ , the gravitational abnormality ΔG, the free air correction C, the vertical acceleration Z
Since the Etobes effect E is sufficiently smaller than the reference ellipsoidal gravity A, they are ignored here. Therefore, the following equation holds.

[0045]

Gt ≒ G ₀ ≒ A

The second term on the right side of the equation (5) is represented by γ
Assuming that 1, γ2, it is expressed as follows.

[0047]

Γ1 = Gt · sin θ1 {G ₀ · sin θ1}
A · sin θ1 γ2 = Gt · sin θ2 ≒ G ₀ · sin θ2 ≒ A · si
nθ2

Since the reference ellipsoidal gravity A is obtained in advance, the roll angle error and the pitch errors θ1 and θ2 are obtained.
When the roll angle error and the pitch errors θ1 and θ2 are obtained, the platform tilt error H is calculated by the following equation.

[0049]

H = α1 sin θ1 + α2 sin θ2

The reference ellipsoidal gravity A, the free air correction C, the vertical acceleration Z, and the Etoves effect E are obtained in advance. Therefore, when the platform tilt error H is obtained, the gravity abnormality ΔG is obtained from the equation (4). The vertical acceleration Z on the right side of the equation (4) is the mobile station 1 for carrier phase geodetic measurement.
4 is obtained by integral calculation from the position information and time information of the navigation body detected by 4.

As shown in FIG. 3, the east-west acceleration αE and the north-south acceleration αN from the mobile station 14 for the carrier wave phase geodesication, the azimuth φ from the gyro compass 21, the accelerometers 24 and 2,
The outputs β1 and β2 of 5 and the output Gt from the gravimeter 22 are obtained on the navigation body 10 in real time together with the position information and the time information of the measurement points.

The roll direction acceleration α1 and pitch direction acceleration α2 of the vehicle, the roll angle error θ1 and the pitch angle error θ
2. Platform inclination error H and gravity anomaly ΔG are obtained off-line on the ground. Output G of gravimeter 22
Various variables and constants A, C, Z, E, etc. included in t are obtained off-line on the ground.

Although the embodiments of the present invention have been described above, it is to be understood by those skilled in the art that the present invention is not limited to the above-described embodiments and various changes can be made within the scope of the present invention described in the appended claims. Will be easy to understand.

[0054]

According to the present invention, when gravity is measured by a gravity measuring device mounted on a navigation body, there is an advantage that the gravity abnormality can be accurately measured even if the platform supporting the gravity measuring device is inclined. Have.

According to the present invention, when gravity is measured by a gravity measuring device mounted on a navigation body, there is an advantage that gravity abnormalities can be calculated by off-line processing.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main part of a gravity measuring device according to the present invention.

FIG. 2 is a diagram showing a structure of a horizontal stabilizer of the gravity measuring device according to the present invention.

FIG. 3 is a diagram showing a calculation procedure in the gravity measuring device according to the present invention.

FIG. 4 is a diagram schematically illustrating a conventional gravity measuring device and method.

FIG. 5 is a diagram showing a main part of a conventional gravity measuring device.

FIG. 6 is a diagram showing a structure of a horizontal stabilizer of a conventional gravity measuring device.

[Explanation of symbols]

10 ... Navigation body, 10A ... Base, 12, 13 ...
GPS satellites, 14, 15, ... mobile stations, 16, 17, ...
・ Reference station, 20: Gravimeter, 21: Gyro compass, 22: Gravimeter, 23: Horizontal stabilizer, 24, 25: Accelerometer, 31, 32: Record operation apparatus

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Satoshi Yoshida 2-16-46 Minami Kamata, Ota-ku, Tokyo F-term in Tokimec Co., Ltd. (reference) 2F105 AA03 AA10 BB07 BB17 5J062 CC07 EE04 FF04

Claims (6)

[Claims] 1. A gravimeter, a platform for supporting the gravimeter, a horizontal stabilizer having a gimbal mechanism for horizontally supporting the platform, and a horizontal stabilizer mounted on the same plane as the horizontal stabilizer. A gyro compass that supplies an attitude angle signal, wherein the platform is equipped with an accelerometer for detecting horizontal acceleration. Gravity measuring device. 2. The gravity measuring device according to claim 1, wherein
A gravity measurement device comprising: a mobile station for carrier phase positioning by DGPS; and a first recording operation device for recording position information and time information from the mobile station. 3. The gravity measuring device according to claim 2,
A gravity measurement device comprising: a mobile station for code phase positioning by DGPS; and a second recording and calculating device for recording position information and time information from the mobile station. 4. The gravity measuring device according to claim 3,
The second recording and calculating device records the output signal of the gravimeter, the output signal of the accelerometer, and the output signal of the gyro compass. 5. The gravity measuring apparatus according to claim 4, wherein an east-west direction acceleration and a north-south acceleration are calculated based on a position signal from the carrier phase positioning mobile station, and the east-west direction acceleration, the north-south direction acceleration and the gyro are calculated. The roll direction acceleration and the pitch direction acceleration are calculated by the azimuth signal from the compass, and the roll angle error and the pitch angle error of the platform are filtered by the horizontal acceleration signal from the accelerometer. A gravity measurement device configured to correct. 6. A gravitational measurement method using a gravimeter mounted on a platform of a navigation body, wherein east-west acceleration and north-south acceleration are calculated based on position information from a mobile station for carrier phase positioning by DGPS. Calculating the roll direction acceleration and the pitch direction acceleration based on the direction acceleration, the north-south direction acceleration, and the azimuth signal from the gyro compass, and calculating the roll angle error and the pitch angle error of the platform based on the horizontal acceleration signal from the accelerometer. And correcting the output of the gravimeter with the roll angle error and the pitch angle error.