Methods and instruments for estimating target motion

• US 8,330,942 B2
• Filed: 03/08/2007
• Issued: 12/11/2012
• Est. Priority Date: 03/08/2007
• Status: Active Grant

• Current Assignee: Trimble AB (Trimble Inc.)
• Original Assignee: Trimble AB (Trimble Inc.)
• Inventors: Nordenfelt, Mikael, Klang, Thomas
• Primary Examiner(s): RATCLIFFE, LUKE D
• Application Number:
  US12/450,013
• Publication Number:
  US 20100149518A1
• Time in Patent Office: 2,105 Days
• Field of Search: 356/4.01, 356/27, 356/318, 250/203.1
• US Class Current: 356/4.01
• 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 an optical distance measuring system for sending out measuring beams including optical radiation for distance and angle measurements and for receiving reflected beams during measurement sessions, said angle measuring system being adapted to calculate target position data including at least horizontal and vertical angle between said measuring instrument and a target using said measuring beams and reflecting beams, the method comprising:

using the measuring instrument 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;

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;

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

check whether said target has been lost, and if said target has been lost during a period of time, determine that said estimated position of said target and/or said estimated distance to said target is to be used in a search for said target; and

use, at initiation of a new measurement session, 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 target position data including at least distance between said measuring instrument and said target using said measuring beams and reflecting beams, wherein said using the measuring instrument to obtain 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 using the measuring instrument to calculate a model describing a path of and/or a distance to said target comprises:

using the measuring instrument 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.

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

using the measuring instrument to,

obtain a present time; and

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

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

using the measuring instrument to,

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

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.

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

using the measuring instrument 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

use 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:

using the measuring instrument to,

compare, at predetermined intervals, a set of target position data obtained at a last measurement with a predicted present position of said target; and

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

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

using the measuring instrument to update 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 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:

using the measuring instrument to perform recursive estimation, wherein the estimated position of said target and the current measured target position data is used.

11. The method according to claim 1, wherein the using the measuring instrument to obtain sets of target position data includes obtaining signal strength of said at least one target during said consecutive measurements;

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

the using the measuring instrument to estimate a present distance to said target using said calculated model includes the signal strength, and the method further comprising;

using the measuring instrument to use, at initiation of a new measurement session, 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 the method 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 an optical distance measuring system for sending out measuring beams comprising optical radiation for distance and angle measurements and for receiving reflected beams during measurement sessions, said angle measuring system being adapted to calculate target 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;

wherein said position calculating system is adapted to check whether said target has been lost during a period of time, and wherein said position calculating system is adapted to determine, that said estimated position of said target and/or said estimated distance to said target is to be used in a search for said target if said target has been lost; 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 target 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 target 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 target 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 the estimated position of said target 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.