ON-GROUND OR NEAR-GROUND DISCRETE OBJECT DETECTION METHOD AND SYSTEM

• US 20150248577A1
• Filed: 09/20/2013
• Published: 09/03/2015
• Est. Priority Date: 09/21/2012
• Status: Active Grant

• Current Assignee: Anditi Pty Ltd
• Original Assignee: Umwelt (Australia) Pty Ltd
• Inventors: Goodwin, Andrew, Jamieson, Peter, Pengilly, Jennifer, Poissant, Patrick, Swabey, Stephen
• Granted Patent: US 9,530,055 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4802 using analysis of echo signal for target characterisation; Target signature; Target cross-section
• CPC Class Codes: G06T 17/05 Geographic models
• CPC Class Codes: G06V 20/13 Satellite images

Abstract

A method for detection of on-ground or near-ground discrete objects having characteristic features from terrain height data characterising a search area comprising the steps of: processing the terrain height data to form a regular grid containing elevation and slope data at each grid point; and analysing said gridded terrain height data to identify said on-ground or near-ground discrete objects within said search area.

Claims

1. A method for detection of on-ground or near-ground discrete objects having characteristic features from terrain height data characterising a search area, the method comprising the steps of:

processing the terrain height data to form a regular grid containing elevation and slope data at each grid point; and

analysing said gridded terrain height data to identify said on-ground or near-ground discrete objects within said search area.

2. A method as claimed in claim 1 wherein said forming of said regular grid comprises the steps of:

determining the characteristic features of said on-ground or near-ground object (g) and the characteristic size of discriminatory elements (e) of said on-ground or near-ground object (g);

determining a slope analysis scale for the on-ground or near ground object (g) and for the discriminatory elements (e);

determining a suitable grid resolution with reference to the characteristic size of said discriminatory elements (e) such that the grid provides sufficient sampling points within the scale of the discriminatory elements (e) to permit identification of said discriminatory elements and thus identification of said on-ground or near ground object; and

processing the terrain height data to form gridded height data comprising a regular grid having the determined grid resolution wherein said gridded height data comprises elevation and slope data at each grid point.

3. A method as claimed in claim 1 wherein the characteristic features of the on-ground or near-ground discrete object comprises one or more of shape, changes in shape, size, height, reflectance, absorbance, shadow, slope, aspect, or land-form context.

5. A method as claimed in claim 1 wherein the gridded height data comprises a gridded height-field [A] having the determined grid resolution and elevation data at each grid point, said elevation data being determined by triangulation of ground points in the terrain height data.

6. A method as claimed in claim 2 wherein the slope data at each grid point is based on a 9-point grid centred at said grid point.

8. A method as claimed in claim 1 further comprising calculation of an elemental slope (S_g) a general slope (S_e) and a feature slope (FS) at each said grid point [B].

9. A method as claimed in claim 8 wherein the elemental slope is determined at a scale that is related to the size of the discriminatory element within the object.

10. A method as claimed in claim 8 wherein;

the general slope is determined at a scale that relates to the size of the object as a whole.

11. A method as claimed in claim 1 wherein analysing said gridded terrain height data comprises the steps of:

using a Ground Feature Transform function (GFT) [C] [D], detecting features within said gridded height-field by analysing the slope of the terrain around each grid point of said gridded height-field.

12. A method as claimed in claim 11 wherein said GFT is adapted for detection of circular objects in said gridded height-field by analysing the slope of the terrain around each grid point.

13. A method as claimed in claim 12 wherein said circular objects comprise an on-ground or near-ground discrete object comprising a mallee-fowl mound, termite mound, drumlin, tumulus, crater or built object.

14. A method as claimed in claim 12 wherein said detection of circular objects comprises, for each grid point of the height-field data, analysing the slope of the height-field data radially from said grid point using at least one search radii characterising an on-ground or near-ground discrete object of interest at selected radial search increments.

16. A method as claimed in claim 14 wherein said radial analysis of said height-field data comprises use of four selected search radii representative of a characteristic size of a near-ground discrete object of interest for each radial search increment.

17. A method as claimed in claim 14 or wherein said analysing of said slope of said height-field data comprises executing a plurality of searches for on-ground or near-ground discrete objects around each grid point.

18. A method as claimed in claim 17 wherein each said search for on-ground or near-ground discrete objects around each grid point comprises use of different search radii for detection of near-ground discrete objects of different sizes.

19. A method as claimed in claim 17 or wherein for each search execution, said search for on-ground or near-ground discrete objects around each grid point comprises the steps of:

a) determining two values for calculation of the search radii to determine the size of the on-ground or near-ground discrete object to be detected comprising;

i) an elemental radius r_e extending from the centroid of the object to the centroid of a discriminatory element of said object; and

ii) an expected variation d_e in the size of discriminatory element of said object

b) determining an incremental search angle with reference to the density of available sampling points within the discriminatory element; and

c) searching radially from each grid point in the gridded height-field using said incremental search angle

23. A method as claimed in claim 19 further comprising the steps of:

d) calculating a Ground Feature Transform value for each grid point in the grid and where the resultant value exceeds a nominated threshold T, store the result in a grid; and

e) Repeating a) to d) for a new search radius.

24. A method as claimed in claim 23 further comprising the steps of:

aggregating the result grids obtained for each search radius;

aggregating result grids comprising clusters of grid cells corresponding to possible central grid points corresponding to said on-ground or near-ground discrete object of a given radius; and

storing the aggregated result grids in an aggregated spare matrix and displaying the aggregated sparse matrix for further analysis of probable on-ground or near-ground discrete object locations.

32. A method according to claim 11 wherein the GFT is based on a modified Hough transform.

4. (canceled)

7. (canceled)

15. (canceled)

20. (canceled)

21. (canceled)

22. (canceled)

25. (canceled)

26. (canceled)

27. A system for detection of on-ground or near-ground discrete objects having characteristic features from terrain height data characterising a search area, said system comprising:

Input means for receiving an input comprising said terrain height data;

Processing means for processing the terrain height data to form a regular grid containing elevation and slope data at each grid point;

Analysis means for analysing said gridded terrain height data to identify said near-ground discrete objects within said search area; and

Output means for outputting a representation of said analysed gridded terrain height data for detection of near-ground discrete objects.

28. (canceled)

29. A non-transitory computer readable medium comprising a program for detection of on-ground or near-ground discrete objects having characteristic features from terrain height data characterising a search area, said program controlling the operation of a data processing apparatus on which the program executes to perform the steps of:

processing the terrain height data to form a regular grid containing elevation and slope data at each grid point;

analysing said gridded terrain height data to identify said on-ground or near-ground discrete objects within said search area.

30. (canceled)

31. (canceled)