METHODS AND INSTRUMENTS FOR ESTIMATING TARGET MOTION

• US 20100149518A1
• Filed: 03/08/2007
• Published: 06/17/2010
• Est. Priority Date: 03/08/2007
• Status: Active Grant

• Current Assignee: Trimble AB (Trimble Inc.)
• Original Assignee: Trimble AB (Trimble Inc.)
• Inventors: Klang, Thomas, Nordenfelt, Mikael
• Granted Patent: US 8,330,942 B2
• Time in Patent Office: Days
• US Class Current: 356/4.10
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105
• CPC Class Codes: G01S 13/72 for two-dimensional tracking, e.g. combination of angle and range tracking, track-while-scan radar
• CPC Class Codes: G01S 17/66 Tracking systems using electromagnetic waves other than radio waves

Abstract

The present invention relates to a measuring instrument and methods for such a measuring instrument for tracking a moving object, measuring a distance to an object. According to the invention, sets of target position data including at least horizontal (Ha) and vertical angle (Va) between the measuring instrument (1) and said at least one target (9) in consecutive measurements during a measurement session are obtained (40; 50; 60; 70); a model describing a path of and/or a distance to the target (9) is calculated; at least a present position of the target is estimated (44; 53; 65; 74) using the model; and, the estimated position of the target (9) is used (45; 56; 67; 79) when searching for the target (9).

Claims

1. A method for a measuring instrument comprising a position calculating circuit including a tracker and a servo system, an angle measuring system and a distance measuring system for sending out measuring beams for distance and angle measurements and for receiving reflected beams during measurement sessions, said angle measuring system being adapted to calculate position data including at least horizontal and vertical angle between said measuring instrument and a target using said measuring beams and reflecting beams, comprising the steps of:

obtaining sets of target position data including at least horizontal and vertical angle between said measuring instrument and said at least one target in consecutive measurements during a measurement session;

calculating a model describing a path of and/or a distance to said target based on at least one data set obtained at a preceding measurement, said model predicting positions of said target;

estimating at least a present position of said target and/or at least a present distance to said target using said calculated model; and

at initiation of a new measurement session, using said estimated position of said target when searching for said target.

2. The method according to claim 1, wherein said distance measuring system is adapted to calculate position data including at least distance between said measuring instrument and said target using said measuring beams and reflecting beams, wherein said step of obtaining sets of target position data includes obtaining sets of target position data including at least horizontal and vertical angle, and distance between said measuring instrument and said at least one target in said consecutive measurements.

3. The method according to claim 1, wherein the step of calculating a model describing a path of and/or a distance to said target comprises the step of:

determining a state vector comprising at least a preceding position of said target and a velocity of said target based on sets of target position data including at least horizontal and vertical angle and/or distance between said measuring instrument and said target, said data sets being obtained during at least one preceding measurement.

4. The method according to claim 3, wherein the step of estimating at least a present position of said target and/or at least a present distance to said target using said calculated model further comprising the steps of:

obtaining a present time; and

calculating a present position of said target using said state vector and said present time.

5. The method according to claim 1, further comprising the steps of:

converting said obtained position data including at least horizontal and vertical angle and/or distance to Cartesian coordinates;

determining a state vector comprising at least a preceding position of said target and a velocity of said target at said preceding position based on said converted Cartesian coordinates.

6. The method according to claim 5, further comprising the steps of:

converting said estimated present position of said target defined in Cartesian coordinates into spherical coordinates comprising predicted horizontal and vertical angle and distance to said target; and

using said predicted position comprising horizontal and vertical angle and distance to said target when searching for said target when performing said new measurement session.

7. The method according to claim 1, further comprising the steps of:

at predetermined intervals, comparing a set of target position data obtained at a last measurement

with a predicted present position of said target; and

if a deviation between said last obtained set of position data and said predicted position exceeds a predetermined limit, calculating a new model using at least said last obtained set of target data.

8. The method according to claim 1, further comprising the step of:

updating said model each time a new set of target position data is obtained.

9. The method according to claim 1, wherein said predicted position is obtained when said position calculation circuit has failed to find reflecting beams from said target during a predetermined period of time during a measurement session.

10. The method according to claim 1, wherein said step of calculating a model describing a path of and/or a distance to said target based on at least one data set obtained at a preceding measurement occasion, comprises the step of:

using recursive estimation, wherein at least the estimated position from the previous time step and the current measured target position data is used.

11. The method according to claim 1, further comprising the steps of:

wherein the step of obtaining sets of target position data includes obtaining signal strength of said at least one target during said consecutive measurements;

calculating a model describing a path of and/or a distance to said target based on at least one data set including the signal strength obtained at a preceding measurement, said model predicting positions of said target;

estimating a present distance to said target using said calculated model including the signal strength; and

at initiation of a new measurement session, using said estimated distance to said target when searching for said target.

23. A computer program product, directly loadable into an internal memory of measuring instrument, comprising software code portions for causing said measuring instrument to perform steps in accordance with claim 1.

12. A measuring instrument comprising a position calculating circuit including a tracker and a servo system, an angle measuring system and a distance measuring system for sending out measuring beams for distance and angle measurements and for receiving reflected beams during measurement sessions, said angle measuring system being adapted to calculate position data including at least horizontal and vertical angle between said measuring instrument and a target using said measuring beams and reflecting beams, comprising:

a target predicting system adapted to obtain sets of target position data including at least horizontal and vertical angle between said measuring instrument and said at least one target in consecutive measurements during a measurement session;

said target predicting system comprising a state estimator adapted to calculate a model describing a path of and/or a distance to said target based on at least one data set obtained at a preceding measurement, said model predicting positions of said target;

said target predicting system comprising a target predictor adapted to estimate at least a present position of said target and/or at least a present distance to said target using said calculated model; and

wherein said position calculating system is adapted to, at initiation of a new measurement session, use said estimated position of said target when searching for said target.

13. The measuring instrument according to claim 12, wherein said distance measuring system is adapted to calculate position data including at least distance between said measuring instrument and said target using said measuring beams and reflecting beams, and wherein said target predicting system is adapted to obtain sets of target position data including at least horizontal (Ha) and vertical angle, and distance between said measuring instrument and said at least one target in said consecutive measurements.

14. The measuring instrument according to claim 12, wherein said state estimator is adapted to determine a state vector comprising at least a preceding position of said target and a velocity of said target based on sets of target position data including at least horizontal and vertical angle and/or distance between said measuring instrument and said target, said data sets being obtained during at least one preceding measurement.

15. The measuring instrument according to claim 14, wherein said state estimator is adapted to obtain a present time;

and calculate a present position of said target using said state vector and said present time.

16. The measuring instrument according to claim 12, wherein said target predicting system further comprises a spherical to Cartesian transformer adapted to convert said obtained position data including at least horizontal and vertical angle and/or distance to Cartesian coordinates;

and wherein said state estimator is adapted to determine a state vector comprising at least a preceding position of said target and a velocity of said target at said preceding position based on said converted Cartesian coordinates.

17. The measuring instrument according to claim 16, wherein said target predicting system further comprises a Cartesian to spherical transformer adapted to convert said estimated present position of said target defined in Cartesian coordinates into spherical coordinates comprising predicted horizontal and vertical angle and distance to said target;

and wherein said position calculation system is adapted to use said predicted position comprising horizontal and vertical angle and distance to said target when searching for said target when initiating said new measurement session.

18. The measuring instrument according to claim 12, wherein said target predictor is adapted to, at predetermined intervals, compare a set of target position data obtained at a last measurement with a predicted present position of said target;

and wherein said state estimator is adapted to, if a deviation between said last obtained set of position data and said predicted position exceeds a predetermined limit, calculate a new model using at least said last obtained set of target data.

19. The measuring instrument according to claim 12, wherein said state estimator is adapted to update said model each time a new set of target position data is obtained.

20. The measuring instrument according to claim 12, wherein said position calculating system is adapted to, when said position calculation circuit has failed to find reflecting beams from a target during a predetermined period of time during a measurement session, obtain said predicted position of said target from said target predictor.

21. The measuring instrument according to claim 12, wherein said state estimator comprises a Kalman filter adapted to use recursive estimation, wherein at least the estimated position from the previous time step and the current measured target position data is used.

22. The measuring instrument according to claim 12, wherein said target predicting system is adapted to obtain sets of target position data including signal strength of a target in consecutive measurements during a measurement session;

said state estimator is adapted to calculate a model describing a path of and/or a distance to said target based on at least one data set including said signal strength obtained at a preceding measurement;

said target predictor is adapted to estimate at least present distance to said target using said calculated model; and

wherein said position calculating system is adapted to, at initiation of a new measurement session, use said estimated distance to said target.