Method for estimating the accuracy of azimuthal orientations and portable sighting device

• US 7,325,320 B2
• Filed: 04/15/2005
• Issued: 02/05/2008
• Est. Priority Date: 04/17/2004
• Status: Active Grant

• Current Assignee: Vectronix AG (Safran SA)
• Original Assignee: Vectronix AG (Safran SA)
• Inventors: Gnepf, Silvio, Gees, Jürg
• Primary Examiner(s): Bennett; G. Bradley
• Assistant Examiner(s): JOHNSON, AMY COHEN
• Application Number:
  US11/108,133
• Publication Number:
  US 20050229411A1
• Time in Patent Office: 1,026 Days
• Field of Search: 333/56, 333/57, 333/55.R, 332/76, 702/5, 702/85, 702/92, 702/93, 702/94
• US Class Current: 33/356
• CPC Class Codes: F41G 3/02 using an independent line of sight
• CPC Class Codes: F41G 3/06 with rangefinder rangefinders per se G01C
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

In a method according to the invention for estimating the accuracy of azimuthal orientations (a) of a measuring device (1) having an electronic magnetic compass (2), a plurality of determinations of an azimuthal orientation (a, a′, a″, a′″, a″″) are carried out, in which the measuring device is aligned with one and the same measuring points at different measuring locations (P, P′, P″, P′″, P″″) adjacent to one another. On the basis of these determined azimuthal orientations (a, a′, a″, a′″, a″″), the value of the accuracy is automatically estimated by the measuring device (1) by means of a computational method. The adjacent measuring locations (P, P′, P″, P′″) are advantageously located one above the other or along a straight line to the measuring point. By means of this method, stationary stray fields of local scale can be detected and the effects thereof on the accuracy can be estimated. Further methods according to the invention are designed in each case specifically for further types of stray fields.

Claims

1. Method for estimating the accuracy of azimuthal orientations of a measuring device, in which

the azimuthal orientations are determined by measuring components of a magnetic field by means of an electronic magnetic compass and

a value of the accuracy is automatically estimated by means of a computational method which is based on a plurality of determinations of an azimuthal orientation, in which the measuring device is aligned with the same measuring point at different measuring locations adjacent to one another.

2. Method for estimating the accuracy according to claim 1, wherein

the magnetic compass has sensors for measuring the horizontal field strength of the magnetic field and

the computational method is additionally based in each case on the product of the measured horizontal field strength and of the sine of the determined azimuthal orientation and/or the product of the measured horizontal field strength and the cosine of the determined azimuthal orientation.

3. Method for estimating the accuracy according to claim 2, wherein

the magnetic compass has sensors for the, measurement of the components of the magnetic field and means for measuring components of a gravitational vector and

the computational method is additionally based in each case on the measured vertical field strength of the magnetic field.

4. Method for estimating the accuracy according to any of claims 1 to 3, wherein the different measuring locations are arranged substantially perpendicularly.

5. Method for estimating the accuracy according to any of claims 1 to 3, wherein the different measuring locations are arranged substantially on a straight line through the measuring point.

6. Method for estimating the accuracy according to any of claims 1 to 3, wherein the different measuring locations are substantially normal to a sighting axis and the measuring point is remote.

18. Method for providing an azimuthal orientation of a portable sighting device and n estimated value of the accuracy thereof, in which

the value is estimated by means of a method according to any one of claims 1, 7, or 10 and

a signal with information about an azimuthal orientation and the estimated value is provided at an interface of the measuring device.

7. Method for estimating the accuracy of azimuthal orientations of a measuring device, the location of which is known on a regional scale, in which

the azimuthal orientations are determined by means of an electronic magnetic compass which has sensors for a three-dimensional, measurement of components of a magnetic field, and

a value of the accuracy is automatically estimated by means of a computational method, in which, as a function of the measuring location, at least one field parameter of a model of the Earth'"'"'s magnetic field is related to at least one determined value of the magnetic field coordinated with the field parameter.

8. Method for estimating the accuracy according to claim 7, wherein said one field parameter is the magnetic field strength and/or the magnetic inclination.

9. Method for estimating the accuracy according to claim 7, wherein the electronic magnetic compass additionally has sensors for a measurement of components of a gravitational vector.

10. Method for estimating the accuracy of azimuthal orientations of a measuring device, in which

the azimuthal orientations are determined by means of an electronic magnetic compass which has sensors arranged in a fixed manner in relation to the device for three-dimensional measurement of components of a magnetic field,

in a determination of azimuthal orientations stray magnetic fields relating to the device itself are arithmetically compensated by means of a vector equation whose parameters were determined by means of an optimization method which is based on values of a specified sequence of measurements of components of the magnetic field in which sequence the measuring device is in each case oriented differently in space, and

a value of the accuracy of azimuthal orientations is automatically estimated by means of a statistical compensation calculation, which calculation is based on the values of the sequence of measurements, taking into account the parameters of the vector equation.

11. Method for estimating the accuracy according to claim 10, in which

a plurality of control measurements of the components of the magnetic field are carried out at the same measuring location, in which control measurements the measuring device is oriented in each case differently in space,

the differences between determined values of the magnetic field being coordinated with at least one field parameter related to a specified threshold value and

when the threshold value is exceeded, the value of the accuracy is correspondingly adapted or the parameters of the vector equation for the arithmetic compensation of the stray magnetic fields relating to the device itself are determined again by means of the specified sequence of measurements.

12. Method for estimating the accuracy according to claim 11, in which the differences between the respective product of the horizontal field strength and of the sine of the azimuthal orientation and/or the product of the horizontal field strength and of the cosine of the azimuthal orientation are additionally related to a further threshold value.

13. Method for estimating the accuracy according to claim 11, wherein the measuring device is in each case differently azimuthally oriented in the control measurements.

14. Method for estimating the accuracy according to claim 11 or 12, wherein the measuring device is in each case oriented identically with respect to azimuth and differently with respect to zenith in the control measurements.

15. Method for estimating the accuracy according to claim 11 or 12, wherein the measuring device is in each case tilted identically with respect to azimuth and differently about the sighting axis of the measuring device in the control measurements.

16. Method for estimating the accuracy according to claim 11, wherein

the electronic magnetic compass additionally has sensors arranged in a fixed manner in relation to the device for a measurement of components of a gravitational vector and

the optimization method is also based on values of a specified sequence of measurements of components of the gravitational vector.

17. Method for estimating the accuracy according to claim 12, in which

a plurality of control measurements of the components of the magnetic field and of the gravitational vector are carried out at one measuring location, in which control measurements the measuring device is oriented in each case differently in space,

the differences between determined values of the magnetic field being coordinated with at least one field parameter related to a specified threshold value and

when the threshold value is exceeded, the value of the accuracy is correspondingly adapted or the parameters of the vector equation for the arithmetic compensation of the stray magnetic fields relating to the device itself are determined again by means of the specified sequence of measurements.

19. Portable sighting device comprising

an electronic magnetic compass for determining azimuthal orientations of such sighting device and

an interface for providing a signal including information about the azimuthal orientation and a value of the accuracy thereof,

characterized in that

means for estimating the value of the accuracy of the azimuthal orientation determined by the magnetic compass, said means including sensors for measuring the magnetic field coordinated remote from the magnetic compass.