Method of synthesizing topographic data

• US 6,573,856 B1
• Filed: 01/03/2002
• Issued: 06/03/2003
• Est. Priority Date: 01/03/2002
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Obenshain, Kenneth Fell
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): ANDREA, BRIAN K
• Application Number:
  US10/037,575
• Time in Patent Office: 516 Days
• Field of Search: 342/25, 342/190, 342/191, 342/194, 342/195
• US Class Current: 342/25.00R
• CPC Class Codes: G01S 13/9023 combined with interferometric techniques

Abstract

Synthetic aperture radar (SAR) data (118) of a target (108) is collected (12) over a substantially circular arc (128), wherein a.chord (130) of the arc (128) establishes (20) a radar aperture (102) having a substantially perpendicular construct baseline (104) through the target (108). The radar aperture (102) is partitioned (26) into first and second partial apertures (120) having substantially the construct baseline (104). First and second points (150) substantially vertically coincident with the construct baseline (104) are then determined (38) at means (152) of the first and second partial apertures (120), and first and second vectors (106) from the target (108) are established (40) by the first and second points (150), respectively. First and second portions (148) of the SAR data (118) are accumulated (32) over the first and second partial apertures (120), respectively, and first and second vector complex image data (164) of the target (108) is derived (54) in response thereto. The first and second vector complex image data (164) is then interferogrammetrically integrated (80) and the topographic data (116) of the target (108) is produced (14) thereby.

Claims

1. A method for synthesizing topographic data of a target, said method comprising:

a) collecting synthetic aperture radar (SAR) data of said target in only one pass;

b) generating full-aperture complex image data of said target from said SAR data;

c) generating first partial-aperture complex image data of said target from a first portion of said SAR data;

d) generating second partial-aperture complex image data of said target from a second portion of said SAR data;

e) deriving first vector complex image data of said target in response to said first partial-aperture complex image data and said full-aperture complex image data;

f) deriving second vector complex image data of said target in response to said second partial-aperture complex image data and said full-aperture complex image data; and

g) interferogrammetrically integrating said first vector complex image data and said second vector complex image data to produce said topographic data of said target.

2. A method as claimed in claim 1 wherein said collecting activity a) comprises:

transiting a radar aperture in said one pass over one data collection path, said radar aperture having a construct baseline through said target; and

accumulating said SAR data over said radar aperture during said one pass.

3. A method as claimed in claim 1 wherein said collecting activity a) comprises:

transiting a radar aperture in said one pass over one data collection path, said radar aperture having a construct baseline through said target;

partitioning said radar aperture to form a first partial aperture having substantially said construct baseline, wherein a mean of said first partial aperture establishes a first vector from said target having a first angle;

partitioning said radar aperture to form a second partial aperture having substantially said construct baseline, wherein a mean of said second partial aperture establishes a second vector from said target having a second angle not equal to said first angle;

accumulating said first portion of said SAR data over said first partial aperture; and

accumulating said second portion of said SAR data over said second partial aperture.

4. A method as claimed in claim 3 wherein said transiting activity comprises establishing said construct baseline substantially perpendicular to said radar aperture and passing through said target.

5. A method as claimed in claim 3 wherein said collecting activity a) additionally comprises:

establishing a vector of said first partial aperture where said mean of said first partial aperture intersect said construct baseline at an altitude of said data collection path; and

establishing a vector of said second partial aperture where said mean of said second partial aperture intersect said construct baseline at an altitude of said data collection path.

6. A method as claimed in claim 1 wherein said generating activity b) comprises:

extracting irrelevant data from said full-aperture complex image data; and

extracting low amplitude backscatter data from said full-aperture complex image data.

7. A method as claimed in claim 1 wherein said generating activity c) comprises increasing a number of data in said first partial-aperture complex image data to substantially match a number of data in said full-aperture complex image data.

8. A method for synthesizing topographic data of a target, said method comprising:

a) collecting synthetic aperture radar (SAR) data of said target;

b) generating full-aperture complex image data of said target from said SAR data;

c) generating first partial-aperture complex image data of said target from a first portion of said SAR data;

d) generating second partial-aperture complex image data of said target from a second portion of said SAR data;

e) transforming said first partial-aperture complex image data into partial-aperture azimuth frequency data;

f) merging said first partial-aperture complex image data and said full-aperture complex image data to produce merged complex image data;

g) transforming said merged complex image data into merged azimuth frequency data;

h) developing vector azimuth frequency data in response to said merged azimuth frequency data and said partial-aperture azimuth frequency data;

i) transforming said vector azimuth frequency data to produce said first vector complex image data;

j) deriving second vector complex image data of said target in response to said second partial-aperture complex image data and said full-aperture complex image data; and

k) interferogrammetrically integrating said first vector complex image data and said second vector complex image data to produce said topographic data of said target.

9. A method as claimed in claim 8 wherein said merging activity f) comprises:

substituting an amplitude of each of said first partial-aperture complex image data with an amplitude of a corresponding one of said full-aperture complex image data; and

preserving a phase of each of said first partial-aperture complex image data during said substituting activity.

10. A method as claimed in claim 8 wherein:

said method additionally comprises transforming said full-aperture complex image data into full-aperture azimuth frequency data; and

said developing activity h) comprises;

substituting a Doppler spectrum from said partial-aperture azimuth frequency data for a Doppler spectrum in said merged frequency data;

flattening said substituted Doppler spectrum in a growth area of said merged frequency data; and

trimming portions of said substituted Doppler spectrum,extending beyond a Doppler spectrum from said full-aperture azimuth frequency data.

11. A method as claimed in claim 10 additionally comprising iterating said deriving activity e) if said substituted Doppler spectrum does not extend to said Doppler spectrum from said full-aperture azimuth frequency data.

12. A method for synthesizing topographic data of a target, said method comprising:

transiting a radar aperture in only one pass over one data collection path;

partitioning said radar aperture to form first and second partial apertures;

accumulating first and second portions of synthetic aperture radar (SAR) data over said first and second partial apertures, respectively;

generating first and second partial-aperture complex image data of said target from said first and second portions of said SAR data, respectively;

generating full-aperture complex image data of said target from said first and second portions of said SAR data;

deriving first and second vector complex image data of said target in response to said full-aperture complex image data and said first and second partial-aperture complex image data; and

interferogrammetrically integrating said first-and second vector complex image data to produce said topographic data of said target.

13. A method for synthesizing topographic data of a target, said method comprising:

traversing substantially an arc in a data collection path;

establishing a radar aperture as substantially a chord of said arc;

partitioning said radar aperture to form first and second partial apertures;

accumulating first and second portions of synthetic aperture-radar (SAR) data over said first and second partial apertures, respectively;

generating first and second partial-aperture complex image data of said target from said first and second portions of said SAR data, respectively;

generating full-aperture complex image data of said target from said first and second portions of said SAR data;

deriving first and second vector complex image data of said target in response to said full-aperture complex image data and said first and second partial-aperture complex image data; and

interferogrammetrically integrating said first and second vector complex image data to produce said topographic data of said target.

14. A method as claimed in claim 13 wherein said partitioning activity comprises:

dividing said chord into three sequential portions;

defining an inner one of said portions as being said first partial aperture; and

defining outer ones of said portions as together being said second partial aperture.

15. A method for synthesizing topographic data of said target, said method comprising:

traversing a data collection path as substantially a plurality of consecutive chords of an arc substantially symmetrical about a base point closer to said target than any other point upon said arc;

establishing a radar aperture as substantially one of said chords;

substantially perpendicularly bisecting said radar aperture with a construct baseline extending through said base point and said target;

partitioning said radar aperture to form first and second partial apertures;

accumulating first and second portions of synthetic aperture radar (SAR) data over said first and second partial apertures, respectively;

generating first and second partial-aperture complex image data of said target from said first and second portions of said SAR data, respectively;

generating full-aperture complex image data of said target from said first and second portions of said SAR data;

deriving first and second vector complex image data of said target in response to said full-aperture complex image data and said first and second partial-aperture complex image data; and

interferogrammetrically integrating said first and second vector complex image data to produce said topographic data of said target.

16. A method for synthesizing topographic data of a target, said method comprising:

traversing a data collection path as substantially an arc substantially symmetrical about a base point closer to said target than any other point upon said arc;

establishing a radar aperture as substantially a chord of said arc;

substantially perpendicularly bisecting said radar aperture with a construct baseline extending through said base point and said target;

partitioning said radar aperture to form first and second partial apertures;

accumulating first and second portions of synthetic aperture radar (SAR) data over said first and second partial apertures, respectively;

generating first and second partial-aperture complex image data of said target from said first and second portions of said SAR data, respectively;

generating full-aperture complex image data of said target from said first and second portions of said SAR data;

deriving first and second vector complex image data of said target in response to said full-aperture complex image data and said first and second partial-aperture complex image data; and

interferogrammetrically integrating said first and second vector complex image data to produce said topographic data of said target.

17. A method as claimed in claim 16 wherein said partitioning activity additionally comprises:

dividing said radar aperture into four sequential and substantially equal portions thereof;

defining inner ones of said portions to form said first partial aperture; and

defining outer ones of said portions to form said second partial aperture.

18. A method as claimed in claim 17 wherein said partitioning activity additionally comprises:

determining a first mean point substantially vertically coincident with said construct baseline at a mean of said first partial aperture, wherein said first mean point establishes a first vector having a first angle from said target; and

determining a second mean point substantially vertically coincident with said construct baseline at a mean of said second partial aperture, wherein said second mean point establishes a second vector having a second angle from said target.

19. A method as claimed in claim 18 wherein said accumulating activity additionally comprises:

establishing a vector of said first partial aperture where said mean of said first partial aperture intersects said construct baseline and establishes said first angle with said target; and

establishing a vector of said second partial aperture where said mean of said first partial aperture intersects said construct baseline and establishes said second angle with said target.

20. A method for synthesizing topographic data of a target, said method comprising:

transiting a radar aperture in a data collection path;

partitioning said radar aperture to form first and second partial apertures;

accumulating first and second portions of synthetic aperture radar (SAR) data over said first and second partial apertures, respectively;

generating first and second partial-aperture complex image data of said target from said first and second portions of said SAR data, respectively;

generating full-aperture complex image data of said target from said first and second portions of said SAR data;

transforming said first and second partial-aperture complex image data into first and second partial-aperture frequency data, respectively;

merging said first and second partial-aperture complex image data and said full-aperture complex image data to produce first and second merged complex image data, respectively;

transforming said first and second merged complex image data into first and second merged azimuth frequency data, respectively;

developing first and second vector azimuth frequency data in response to said first and second merged azimuth frequency data and said first and second partial-aperture frequency data, respectively;

transforming said first and second vector azimuth frequency data into first and second vector complex image data, respectively; and

interferogrammetrically integrating said first and second vector complex image data to produce said topographic data of said target.

21. A method for synthesizing topographic data of a target, said method comprising:

transiting, in only one pass, a radar aperture partitioned into first and second partial apertures;

accumulating first and second portions of synthetic aperture radar (SAR) data over said first and second partial apertures, respectively, during said one pass;

producing first and second vector complex image data of said target in response to said first and second portions of said SAR data; and

interferogrammetrically integrating said first and second vector complex image data to produce said topographic data.

23. A method as claimed in claim 21 wherein said producing activity comprises:

generating full-aperture complex image data of said target from said first and second portions of said SAR data;

generating first and second partial-aperture complex image data of said target from said first and second portions of said SAR data, respectively;

deriving first and second vector complex image data of said target in response to said full-aperture complex image data and said first and second partial-aperture complex image data; and

interferogrammetrically integrating said first and second vector complex image data to produce said topographic data of said target.

22. A method for synthesizing topographic data of a target, said method comprising:

traversing substantially a circular arc in substantially a horizontal plane;

establishing a radar aperture as substantially a chord of said arc;

dividing said chord into four sequential and substantially equal portions thereof;

defining inner ones of said portions to form a first partial aperture;

defining outer ones of said portions to form a second partial aperture;

accumulating first and second portions of synthetic aperture radar (SAR) data over said first and second partial apertures, respectively;

producing first and second vector complex image data of said target in response to said first and second portions of said SAR data; and

interferogrammetrically integrating said first and second vector complex image data to produce said topographic data.

24. A method for synthesizing topographic data of a target, said method comprising:

collecting synthetic aperture radar (SAR) data of said target over a portion of a substantially circular arc, wherein a chord of said arc establishes a radar aperture having a substantially perpendicular construct baseline through said target;

partitioning said radar aperture into four sequential and substantially equal portions thereof, wherein inner ones of said portions form a first partial aperture having substantially said construct baseline, and outer ones of said portions form a second partial aperture having substantially said construct baseline;

determining first and second mean points substantially vertically coincident with said construct baseline at means of said first and second partial apertures, respectively;

establishing first and second vectors with said target at said first and second mean points, respectively;

accumulating first and second portions of said SAR data over said first and second partial apertures, respectively; and

producing said topographic data in response to said first and second portions of said SAR data.