Detecting an underground object

• US 9,581,687 B2
• Filed: 09/29/2015
• Issued: 02/28/2017
• Est. Priority Date: 05/30/2012
• Status: Active Grant

• Current Assignee: Trimble Inc.
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Peetz, Bruce
• Primary Examiner(s): WINDRICH, MARCUS E
• Application Number:
  US14/869,389
• Publication Number:
  US 20160018517A1
• Time in Patent Office: 518 Days
• Field of Search: 342/22
• US Class Current: 1/1
• CPC Class Codes: G01S 13/06 Systems determining position data of a target
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

In a method of detecting an underground object which is at least partially under a surface of ground, a first view of the object determined by transmitting a first radar signal from a first known geolocation. A second view of the object is determined by transmitting a second radar signal from a second known geolocation. The respective first and second trajectories of the first and second radar signals are oblique with respect to the surface of the ground and the respective first and second trajectories are at a first angle with respect to each other. A position of the object is estimated by maximizing a correlation between the first view and the second view by adjusting an estimated dielectric constant associated with medium between the object and the surface of the ground.

Claims

1. A method of detecting an underground object, the method comprising:

determining a first view of the object, which is at least partially under a surface of ground, by transmitting a first radar signal from a first known geolocation;

determining a second view of the object by transmitting a second radar signal from a second known geolocation, wherein respective first and second trajectories of the first and second radar signals are oblique with respect to the surface of the ground and the respective first and second trajectories are at a first angle with respect to each other;

determining a velocity that at least one of the first radar signal and the second radar signal traveled through a medium between the object and the surface of the ground;

estimating a dielectric constant associated with the medium based on the velocity that at least one of the first radar signal and the second radar signal traveled through the medium; and

estimating a position of the object by maximizing a correlation between the first view and the second view by adjusting the estimated dielectric constant associated with the medium between the object and the surface of the ground, wherein the determining of the first view, the determining of the second view, and the estimating are performed by one or more computer processors.

2. The method as recited by claim 1, wherein the determining of the second view further comprises:

determining the second view of the object by transmitting the second radar signal from the second known geolocation, wherein the first angle between the first trajectory and the second trajectory is approximately 90 degrees.

3. The method as recited by claim 1, wherein the method further comprises:

determining a third view of the object by transmitting a third radar signal from a third known geolocation, wherein a third trajectory of the third radar signal is oblique with respect to the surface of the ground and the first trajectory and the third trajectory are at a second angle with respect to each other; and

refining the estimated dielectric constant associated with the medium between the object and the surface of the ground by correlating information pertaining to the first view, the second view, and the third view.

4. The method as recited by claim 3, wherein the determining of the third view further comprises:

determining the third view of the object by transmitting the third radar signal from the third known geolocation, wherein the second angle between the first trajectory and the third trajectory is approximately 180 degrees.

5. The method as recited by claim 3, wherein the method further comprises:

determining a fourth view of the object by transmitting a fourth radar signal from a fourth known geolocation, wherein a fourth trajectory of the fourth radar signal is oblique with respect to the surface of the ground and the first trajectory and the fourth trajectory are at a third angle with respect to each other; and

refining the estimated dielectric constant associated with the medium between the object and the surface of the ground by correlating information pertaining to the first view, the second view, the third view, and the fourth view.

6. The method as recited by claim 5, wherein the determining of the fourth view further comprises:

determining the fourth view of the object by transmitting the fourth radar signal from the fourth known geolocation, wherein the third angle between the first trajectory and the fourth trajectory is approximately 270 degrees.

7. The method as recited by claim 1, wherein the method further comprises:

transmitting the first radar signal and the second radar signal at an angle with respect to the surface of the ground that approximates a Brewster angle.

8. The method as recited by claim 1, wherein the method further comprises:

determining a first interception of the first radar signal with the ground based on information describing a contour of the surface of the ground; and

determining a second interception of the second radar signal with the ground based on information describing the contour of the surface of the ground.

9. The method as recited by claim 8, wherein the method further comprises:

determining a first length of a first air path based on the first angle and the first interception; and

determining a second length of a second air path based on the first angle and the second interception.

10. The method as recited by claim 9, wherein the method further comprises:

determining a first velocity of the first radar signal through a first earth path based on the first length and the first angle;

determining a second velocity of the second radar signal through a second earth path based on the second length and the first angle; and

determining the estimated dielectric constant based on the first velocity and the second velocity.

11. A system for detecting an object that is underground, the system comprising:

a transmitting radar antennae;

a receiving radar antennae;

a view-determining-component configured for;

determining a first view of the object, which is at least partially under a surface of ground, by transmitting a first radar signal from a first known geolocation; and

determining a second view of the object by transmitting a second radar signal from a second known geolocation, wherein respective trajectories of the first and second radar signals are oblique with respect to the surface of the ground and the respective trajectories are at a first angle with respect to each other; and

a position-estimating-component configured for;

determining a velocity that at least one of the first radar signal and the second radar signal traveled through a medium between the object and the surface of the ground;

estimating a dielectric constant associated with the medium based on the velocity that at least one of the first radar signal and the second radar signal traveled through the medium; and

estimating a position of the object by maximizing a correlation between the first view and the second view by adjusting the estimated dielectric constant associated with the medium between the object and the surface of the ground.

12. The system of claim 11, wherein the system further comprises:

one or more synthetic aperture radar (SAR) devices configured for transmitting the first radar signal and transmitting the second radar signal.

13. The system of claim 11, wherein the position-estimating-component:

employs a model of a shape of the object.

14. The system of claim 11, wherein the first radar signal and the second radar signal are transmitted at an angle with respect to the surface of the ground that approximates a Brewster angle.

15. The system of claim 11, wherein the trajectories are a first trajectory of the first radar signal and a second trajectory of the second radar signal and wherein:

the view-determining-component is further configured for determining a third view of the object by transmitting a third radar signal from a third known geolocation, wherein a third trajectory of the third radar signal is oblique with respect to the surface of the ground and the first trajectory and the third trajectory are at a second angle with respect to each other; and

the position-estimating-component is further configured for refining the estimated dielectric constant associated with the medium between the object and the surface of the ground by correlating information pertaining to the first view, the second view, and the third view.

16. The system of claim 15, wherein:

the view-determining-component is further configured for determining a fourth view of the object by transmitting a fourth radar signal from a fourth known geolocation, wherein a fourth trajectory of the fourth radar signal is oblique with respect to the surface of the ground and the first trajectory and the fourth trajectory are at a third angle with respect to each other; and

the position-estimating-component is further configured for refining the estimated dielectric constant associated with the medium between the object and the surface of the ground by correlating information pertaining to the first view, the second view, the third view, and the fourth view.

17. The system of claim 11, wherein:

the view-determining-component is further configured for determining a first interception of the first radar signal with the ground based on information describing a contour of the surface of the ground; and

the view-determining-component is further configured for determining a second interception of the second radar signal with the ground based on information describing the contour of the surface of the ground.

18. The system of claim 17, wherein:

the view-determining-component is further configured for determining a first length of a first air path based on the first angle and the first interception; and

the view-determining-component is further configured for determining a second length of a second air path based on the first angle and the second interception.

19. The system of claim 18, wherein the position-estimating-component is further configured for:

determining a first velocity of the first radar signal through a first earth path based on the first length and the first angle;

determining a second velocity of the second radar signal through a second earth path based on the second length and the first angle; and

determining the estimated dielectric constant based on the first velocity and the second velocity.

20. A non-transitory computer readable storage medium having computer-executable instructions stored thereon for causing a computer system to perform a method of detecting an underground object, the method comprising:

determining a first view of the object, which is at least partially under a surface of ground, based on transmission of a first radar signal from a first known geolocation;

determining a second view of the object based on transmission of a second radar signal from a second known geolocation, wherein respective first and second trajectories of the first and second radar signals are oblique with respect to the surface of the ground and the respective first and second trajectories are at a first angle with respect to each other;

determining a velocity that at least one of the first radar signal and the second radar signal traveled through a medium between the object and the surface of the ground;

estimating a dielectric constant associated with the medium based on the velocity that at least one of the first radar signal and the second radar signal traveled through the medium; and

estimating a position of the object by maximizing a correlation between the first view and the second view by adjusting the estimated dielectric constant associated with the medium between the object and the surface of the ground.

21. The non-transitory computer readable storage medium of claim 20, wherein the determining of the second view further comprises:

determining the second view of the object based on transmission of the second radar signal from the second known geolocation, wherein the first angle between the first trajectory and the second trajectory is approximately 90 degrees.

22. The non-transitory computer readable storage medium of claim 20, wherein the method further comprises:

determining a third view of the object based on transmission of a third radar signal from a third known geolocation, wherein a third trajectory of the third radar signal is oblique with respect to the surface of the ground and the first trajectory and the third trajectory are at a second angle with respect to each other; and

refining the estimated dielectric constant associated with the medium between the object and the surface of the ground by correlating information pertaining to the first view, the second view, and the third view.

23. The non-transitory computer readable storage medium of claim 22, wherein the determining of the third view further comprises:

determining the third view of the object based on transmission of the third radar signal from the third known geolocation, wherein the second angle between the first trajectory and the third trajectory is approximately 180 degrees.

24. The non-transitory computer readable storage medium of claim 23, wherein the method further comprises:

determining a fourth view of the object based on transmission of a fourth radar signal from a fourth known geolocation, wherein a fourth trajectory of the fourth radar signal is oblique with respect to the surface of the ground and the first trajectory and the fourth trajectory are at a third angle with respect to each other; and

refining the estimated dielectric constant associated with the medium between the object and the surface of the ground by correlating information pertaining to the first view, the second view, the third view, and the fourth view.

25. The non-transitory computer readable storage medium of claim 24, wherein the determining of the fourth view further comprises:

determining the fourth view of the object based on transmission of the fourth radar signal from the fourth known geolocation, wherein the third angle between the first trajectory and the fourth trajectory is approximately 270 degrees.

26. The non-transitory computer readable storage medium of claim 20, wherein the method further comprises:

determining a first interception of the first radar signal with the ground based on information describing a contour of the surface of the ground; and

determining a second interception of the second radar signal with the ground based on information describing the contour of the surface of the ground.

27. The non-transitory computer readable storage medium of claim 26, wherein the method further comprises:

determining a first length of a first air path based on the first angle and the first interception; and

determining a second length of a second air path based on the first angle and the second interception.

28. The non-transitory computer readable storage medium of claim 27, wherein the method further comprises:

determining a first velocity of the first radar signal through a first earth path based on the first length and the first angle;

determining a second velocity of the second radar signal through a second earth path based on the second length and the first angle; and

determining the estimated dielectric constant based on the first velocity and the second velocity.