Method and Device for Determining Aspect Angle Progression

• US 20120001796A1
• Filed: 03/17/2010
• Published: 01/05/2012
• Est. Priority Date: 03/18/2009
• Status: Active Grant

• Current Assignee: Airbus DS Electronics And Border Security GmbH
• Original Assignee: EADS Deutschland GmbH (Airbus SE)
• Inventors: Berens, Patrick, Holzner, Juergen, Gebhardt, Ulrich
• Granted Patent: US 8,723,718 B2
• Time in Patent Office: Days
• US Class Current: 342/25.F
• 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
• CPC Class Codes: G01S 13/9064 Inverse SAR [ISAR]

Abstract

A method and a device are provided for specifying, in the context of the image generation of ISAR processing, the determination of the aspect angle course subject to which the radar illuminates the vehicle during the exposure and subject to which the vehicle echoes are reflected back to the radar. Using the distance between the radar sensor and the vehicle as well as the change in distance, both of which are determined from the radar data, the position and the velocity of the vehicle are determined at any time during the exposure through linkage with available road information. The aspect angle is then determined from the positions of the sensor and of the vehicle as well as from the direction of movement of the vehicle. The required road information can be acquired from digital maps or images (e.g. aerial photographs, SAR-images).

Claims

1-3. -3. (canceled)

4. A method for determining the progression of an aspect angle, the method comprising:

illuminating, by an aircraft- or satellite-borne Inverse Synthetic Aperture RADAR (ISAR), a vehicle traveling on a road;

receiving, by a radar sensor, echoes reflected back from the vehicle to the radar, wherein the radar signals themselves are used for determining the aspect angle;

determining distances and changes in distance between the radar sensor and the vehicle and between the radar sensor and a thoroughfare;

determining positions of the vehicle, using the determined distances and change in distance, for every point in time during an exposure of the vehicle by the radar by determining points of intersection;

determining velocity vectors of the vehicle at the determined positions of the vehicle using geometric conversions;

combining, using a mathematical process, the determined positions of the vehicle, the determined velocity vectors of the vehicle and a movement model of the vehicle, wherein contributions from the movement model and the determined positions of the vehicle and determined velocity vectors of the vehicle are weighted according to their accuracy, whereby the position, velocity, and acceleration of the vehicle are determined with greater accuracy;

determining, using a geometric calculation, an aspect angle of the illumination of the vehicle for each moment of the exposure from a viewing direction between radar sensor and vehicle, wherein the viewing direction is a direction of a connecting line from the radar sensor to the vehicle that results from positions of the sensor and the vehicle and the direction of the velocity vector of the vehicle whose direction coincides with the vehicle longitudinal axis.

5. A device for determining the progression of the aspect angle, the device comprising:

a radar front-end of an aircraft- or satellite-borne Inverse Synthetic Aperture RADAR (ISAR) with an antenna and a data acquisition component configured to illuminate a vehicle that is moving along a thoroughfare with radar pulses, to receive reflected echoes, to acquire the reflected echoes, and to calculate an ISAR image of the vehicle using information regarding carrier movement of an inertial navigation system/differential global positioning satellite system (INS/DGPS) system and road information from a database of thoroughfares;

a system configured to acquire information regarding a course of an air- or space-borne carrier of the ISAR on the basis of inertial sensors and a DGPS-receiver;

a database configured to provide information regarding thoroughfares in an area illuminated by the radar; and

an ISAR processor configured to preprocess an image for calibration, compression and movement compensation of radar echoes, aspect angle determination, and image generation for calculation of the ISAR image.

6. A non-transitory storage medium that includes a computer program, which when executed by a processor causes the processor to:

illuminate, by an aircraft- or satellite-borne Inverse Synthetic Aperture RADAR (ISAR), a vehicle traveling on a road;

receive, by a radar sensor, echoes reflected back from the vehicle to the radar, wherein the radar signals themselves are used for determining the aspect angle;

determine distances and changes in distance between the radar sensor and the vehicle and between the radar sensor and a thoroughfare;

determine positions of the vehicle, using the determined distances and change in distance, for every point in time during an exposure of the vehicle by the radar by determining points of intersection;

determine velocity vectors of the vehicle at the determined positions of the vehicle using geometric conversions;

combine, using a mathematical process, the determined positions of the vehicle, the determined velocity vectors of the vehicle and a movement model of the vehicle, wherein contributions from the movement model and the determined positions of the vehicle and determined velocity vectors of the vehicle are weighted according to their accuracy, whereby the position, velocity, and acceleration of the vehicle are determined with greater accuracy;

determine, using a geometric calculation, an aspect angle of the illumination of the vehicle for each moment of the exposure from a viewing direction between radar sensor and vehicle, wherein the viewing direction is a direction of a connecting line from the radar sensor to the vehicle that results from positions of the sensor and the vehicle and the direction of the velocity vector of the vehicle whose direction coincides with the vehicle longitudinal axis.