Method of detecting moving objects and estimating their velocity and position in SAR images

• US 6,952,178 B2
• Filed: 06/13/2003
• Issued: 10/04/2005
• Est. Priority Date: 06/14/2002
• Status: Expired due to Term

• Current Assignee: Airbus Defence and Space GmbH
• Original Assignee: EADS Deutschland GmbH (Airbus SE)
• Inventors: Kirscht, Martin
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): ALSOMIRI, ISAM A
• Application Number:
  US10/460,647
• Publication Number:
  US 20040032361A1
• Time in Patent Office: 844 Days
• Field of Search: 342/25, 342/90, 342/95, 342/96, 342/104, 342/107, 342/112, 342/114, 342159-160, 342/162, 342/188, 342/189, 342/25.R, 342 25 A- 25 B
• US Class Current: 342/25.00B
• CPC Class Codes: G01S 13/9029 specially adapted for moving target detection within a single SAR image or within multiple SAR images taken at the same time

Abstract

A method of detecting moving objects and of estimating their velocity and position in SAR images includes the steps of generating a sequence of single-look SAR images which have the same polarization, are successive in time, and have a look center frequency which varies from one image to the next; detecting candidates for moving objects in the single-look SAR images of the sequence by searching for regions with a course of intensity that deviates from the environment; estimating the velocity of the detected candidates; and verifying the detected candidates as moving objects. The estimation of one or more velocity components of a detected candidate takes place jointly with the estimation of one or more position components of the candidate. A cost function is established as a function of the components to be estimated, taking into account the positions of the candidate in the individual single-look SAR images of the sequence, which cost function is minimized by means of an optimization method for the parameter or parameters to be estimated.

Claims

1. A method for detecting moving objects and estimating their velocity and position in SAR images, comprising:

generating a sequence of single-look SAR images which are of the same polarization, are successive with respect to time, and have a look center frequency which varies from one image to the next;

detecting candidates for moving objects in said single-look SAR images by searching for regions with a course of intensity which deviates from a surrounding environment;

estimating velocity of detected candidates by estimation of at least one displacement vector of one candidate respectively, utilizing a correlation between successive single-look SAR images; and

verifying detected candidates as moving objects;

wherein

estimation of at least one velocity component of a detected candidate takes place jointly with an estimation of at least one position component of the candidate;

a cost function is established as a function of the components to be estimated, taking into account positions of the candidate in the individual single-look SAR images of the sequence;

the cost function is minimized by means of an optimization method for the parameter or parameters to be estimated; and

the cost function also takes into account time-dependent amplitudes of the candidates in the individual single-look SAR images of the sequence.

2. The method according to claim 1, wherein the cost function is minimized taking into account another parameter to be estimated for compensation of aliasing in the Doppler spectrum.

3. The method according to claim 1, wherein:

an estimated value for an azimuth component of a velocity vector of a respective candidate is determined from azimuth components of the displacement vectors of the candidate; and

the estimated value for the azimuth component is kept constant in the optimization method for the joint position and velocity estimation of the other parameters to be estimated.

4. The method according to claim 1, wherein:

an estimated value for a range component of a position vector of a respective candidate is determined from individual range positions of a candidate in individual single-look SAR images; and

the estimated value for the range component is kept constant in the optimization method for the joint position and velocity estimation of other parameters to be estimated.

5. The method according to claim 1, wherein during the detecting of the candidates, corresponding regions in respective single-look SAR images are assigned to each detected candidate as individual initial shapes.

6. The method according to claim 1, wherein corresponding to estimated velocity of a candidate, the shape of a candidate is estimated by equalizing respective initial shapes.

7. The method according to claim 5, wherein image defects of the moving objects within a sequence of the single-look SAR images are compensated by extracting the moving objects with the corresponding initial shapes from the single-look SAR images, and are inserted again in the estimated or computed positions by means of the initial shapes or the estimated shapes into the single-look SAR images.