Leading and lagging aperture for linear ground penetrating radar array

• US 8,040,272 B1
• Filed: 04/21/2008
• Issued: 10/18/2011
• Est. Priority Date: 04/20/2007
• Status: Expired due to Fees

• Current Assignee: Miitek, Inc.
• Original Assignee: NIITEK, Inc.
• Inventors: Clodfelter, James F., Hibbard, Mark W.
• Primary Examiner(s): Tarcza; Thomas
• Assistant Examiner(s): BRAINARD, TIMOTHY A
• Application Number:
  US12/148,677
• Time in Patent Office: 1,275 Days
• Field of Search: 342/22
• US Class Current: 342/22
• CPC Class Codes: G01S 13/86 Combinations of radar systems with non-radar systems, e.g. sonar, direction finder
• CPC Class Codes: G01S 13/865 Combination of radar systems with lidar systems
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01S 13/89 for mapping or imaging
• CPC Class Codes: G01S 7/4004 of parts of a radar system
• CPC Class Codes: H01Q 21/06 Arrays of individually energised antenna units similarly polarised and spaced apart

Abstract

A radar array linearly traverses an area of ground. Additional radar elements fore and aft of the array detect changes in elevation and orientation of the array. These elements act as a preview for the height changes due to ground variation. Any variation in height that is not detected by these fore and aft-mounted elements is thus due to variation in radar elevation and/or orientation and can be subtracted from the resulting data without introducing distortion. Correction factors are applied to the range data returned from each element in the array, which normalizes the data and makes it appear as if the array did not change orientation or elevation.

Claims

1. A ground contour mapping array, comprising:

a ground-based movable structure traversable over a ground area to be mapped,

an array of sensor elements attached to the movable structure,

additional sensor elements fore and aft of the array for detecting changes in elevation and orientation of the array to prevent distortion of data gathered by the array, and

electronic means for adjusting the data from the sensor array to remove the effect of changes in the elevation or orientation of the sensor array.

2. The ground contour mapping array of claim 1, wherein the array is traversed along a downtrack direction and the array is attached along a cross-track perpendicular to the down-track direction.

3. A method of mapping ground contours, comprising:

providing a ground-based movable structure, providing first sensor elements in an array attached to the movable structure,

providing second sensor elements fore and aft of the array,

linearly traversing the movable structure over an area of ground, gathering data periodically from the first sensor elements while the movable structure traverses the area of ground,

detecting distances between the second sensor elements and the ground at the same time as data is gathered from the first sensor elements,

determining a change in elevation and orientation of the first sensor elements based on data gathered by the first sensor elements and distances detected by the second sensor elements,

normalizing the data gathered from the first sensor elements to remove the effect of changes in the elevation or orientation of the first sensor elements,

storing the normalized data, and

creating a 3-dimensional image of a ground surface using the normalized data.

4. The ground contour mapping array of claim 3, wherein the array of sensor elements is a linear array.

5. The ground contour mapping array of claim 3, wherein the array of sensor elements is an array of ground penetrating radar elements.

6. The ground contour mapping array of claim 5, wherein the additional second sensor elements are LADAR or ultrasound.

7. The ground contour mapping array of claim 5, wherein the second sensor elements are ground penetrating radar elements, each consisting of a transmitter and receiver pair.

8. The ground contour mapping array of claim 3, wherein the array of sensor elements is a planar array.

9. The ground contour mapping array of claim 3, wherein the second sensor elements are placed fore and aft of sensor elements near opposite ends of the array.

10. The ground contour mapping array of claim 3, further comprising a processor and a memory operatively coupled to the processor, wherein the processor adjusts the data gathered by the array according to the changes in elevation and orientation detected with the second sensor elements and the memory records the adjusted data.

11. The ground contour mapping array of claim 3, wherein the sensor elements of the array of sensor elements are mounted rigidly with respect to one another, such that the distance between them is always the same.

12. The method of mapping ground contours of claim 3, wherein the providing second sensor elements fore and aft of the array comprises providing second sensor elements fore and aft of first sensor elements at opposite ends of the array that are first and last sensor elements in the array in a direction perpendicular to a direction of motion.

13. The method of mapping ground contours of claim 12, wherein the determining a change in elevation and orientation of the first sensor elements based on data gathered by the first sensor elements and distances detected by the second sensor elements comprises determining the change in elevation of the end first sensor elements due to changes in the array and not due to ground variation, based on the distance between the first sensor elements at opposite ends of the array and the ground and the distance between each of the second sensor elements and the ground at the present position and at least one previous position, and determining the change in elevation of the first sensor elements other than the first sensor elements at opposite ends of the array due to changes in the array and not due to ground variation by taking a linear combination of the changes in elevation of each of the end first sensor elements due to changes in the array and not due to ground variation.

14. The method of mapping ground contours of claim 13, wherein the distance between the first sensor elements at opposite ends of the array and the ground and the distance between each of the second sensor elements and the ground at least one previous position are normalized to remove the effect of changes in the elevation or orientation of the first and second sensor elements at the previous position.

15. The method of mapping ground contours of claim 13, wherein the determining the change in elevation of the first sensor elements near opposite ends of the array due to changes in the first sensor elements and not due to ground variation comprises comparing a distance measured between a first or second sensor element and the ground and a distance measured between another first or second sensor element and the ground, wherein the first or second sensor element and the another first or second sensor element were each above the same location on the ground when the measurements were taken.

16. The method of mapping ground contours of claim 12, wherein the gathering data periodically comprises gathering data from the first sensor elements each time the movable structure traverses a distance equal to a given percentage of the distance between the end first sensor elements and the second sensor elements fore and aft of the first sensor elements at opposite ends of the array.

17. The method of mapping ground contours of claim 16, wherein the given percentage is 100%.

18. The method of mapping ground contours of claim 3, wherein the first or second sensor elements are ground penetrating radar elements, each consisting of a transmitter and receiver pair.

19. The method of mapping ground contours of claim 3, wherein the first and second sensor elements are mounted rigidly with respect to one another, such that the distance between them is always the same.

20. The method of claim 3, wherein the traversing further comprises traversing the array along a down-track direction and providing the array along a cross-track perpendicular to the down-track direction.