Change subtraction of synthetic aperture radar data

A method for coherent change subtraction of mission synthetic aperture radar (SAR) data and reference SAR data, said method comprising:

• forming a mission image from said mission SAR data;
• forming a reference image from said reference SAR data;
• registering said mission and reference images to form registered mission and reference images;
• forming at least one patch of said registered mission and reference images, wherein said at least one patch contains mission data, being data from said registered mission image, and reference data, being data from said registered reference image;
• processing said at least one patch, said processing activity e) comprising:
• a) removing linear phase terms from at least said mission data in said at least one patch in a frequency domain;
• b) removing linear phase terms from at least said mission data in said at least one patch in an image domain;
• c) trimming non-overlapping spectrum from said mission data and reference data in said at least one patch in said frequency domain;
• d) balancing phases and amplitudes of said mission data in said at least one patch in said frequency domain;
• and
• e) balancing phases and amplitudes of said mission data in said at least one patch in said image domain producing a processed mission image and a processed reference image from said mission data and said reference data, respectively;
• subtracting a first one of said processed mission and reference images from a second one of said processed mission and reference images to form a delta image;
• and
• postprocessing said delta image.

A method for coherent change subtraction of mission synthetic aperture radar (SAR) data and reference SAR data for detection of a change in one of an amplitude and a phase of backscatter, said method comprising:

• a) forming a mission image from said mission SAR data;
• b) forming a reference image from said reference SAR data;
• c) registering said mission and reference images on a common plane to produce registered mission and reference images;
• d) removing linear phase terms from at least said registered mission image in a frequency domain;
• e) removing linear phase terms from at least said registered mission image in an image domain;
• f) trimming non-overlapping spectra of said registered mission and reference images;
• g) balancing phases and amplitudes of said mission and reference images in said frequency domain;
• h) balancing phases and amplitudes of said mission and reference images in said image domain;
• i) subtracting a first one of said processed mission and reference images from a second one of said processed mission and reference images to form a delta image;
• and
• j) computing one of an amplitude and a phase of said delta image;
• and
• k) detecting, in response to said one of said amplitude and said phase of said delta image, a target in said delta image using constant false alarm rate detection.

A method for coherent change subtraction of mission synthetic aperture radar (SAR) data and reference SAR data for suppression of combined noise and backscatter energy, said method comprising:

• a) forming a mission image from said mission SAR data;
• b) forming a reference image from said reference SAR data;
• c) registering said mission and reference images on a common plane to form registered mission and reference images;
• d) forming a plurality of patches containing mission data, being data from said registered mission image, and reference data, being data from said registered reference image, wherein each of said patches in said plurality of patches is substantially equal to separate substantially coincident portions of said registered mission and reference images;
• e) removing linear phase terms from at least said mission data in each of said patches in each of a frequency domain and an image domain;
• f) trimming non-overlapping spectra of said mission data and said reference data in each of said patches;
• g) balancing phases and amplitudes of said mission and reference data in each of said patches in each of said frequency and image domains;
• h) concatenating each of said patches to produce a processed mission image and a processed reference image from said mission data and said reference data, respectively;
• i) subtracting a first one of said processed mission and reference images from a second one of said processed mission and reference images to form a delta image, wherein said processed mission image, said processed reference image, and said delta image each have substantially a like number of pixels;
• j) determining, for each pixel of said processed reference image, if said each pixel has a clutter-to-noise ratio of less than one;
• and
• k) substituting, when said determining activity j) determines said each pixel has a clutter-to-noise ratio of less than one, a replacement pixel for said each pixel, wherein said replacement pixel is a coincident pixel from one of said processed mission image, said processed reference image, and said delta image having a lowest amplitude ratio.

A computer program for coherent change subtraction of mission synthetic aperture radar (SAR) data and reference SAR data for one of detection of a change in one of an amplitude and a phase of backscatter and suppression of combined noise and backscatter energy, said program comprising:

• a first program segment configured to produce a mission image from said mission SAR data;
• a second program segment configured to produce a reference image from said reference SAR data;
• a third program segment configured to register each of said mission and reference images on a common plane to produce registered mission and reference images;
• a fourth program segment configured to form at least one patch containing mission data, being data from said mission image, and reference data, being data from said reference image, wherein:
• when said program performs said coherent change subtraction for said detection of a change in one of an amplitude and a phase of backscatter, said fourth program segment forms one patch substantially equal to the whole of said mission and reference complex images;
• and
• when said program performs said coherent change subtraction for said suppression of combined noise and backscatter energy, said fourth program segment forms a plurality of patches, wherein each of said patches in said plurality of patches is substantially equal to separate substantially coincident portions of said registered mission and reference images;
• a fifth program segment configured to process said at least one patch to produce at least one processed patch;
• a sixth program segment configured to concatenate said at least one processed patch to produce processed mission and reference images;
• a seventh program segment configured to subtract a first one of said processed mission and reference images from a second one of said processed mission and reference images to form a delta image, wherein said processed mission image, said processed complex image, and said delta image each have substantially a like number of pixels;
• and
• an eighth program segment wherein:
• when said program performs said coherent change subtraction detection of a change in one of an amplitude and a phase of backscatter, said eighth program segment is configured to compute an amplitude of said delta complex image, and detect said moving target in said delta complex image in response to said amplitude;
• and
• when said program performs said coherent change subtraction for said suppression of combined noise and backscatter energy, said eighth program segment is configured to substitute, for each pixel of said delta complex image, when a coincident pixel of said processed reference image has a clutter-to-noise ratio of less than one, a replacement pixel, wherein said replacement pixel is a coincident pixel from one of said mission, reference, and delta complex images having a lowest amplitude ratio.