Method of correcting rotational motion error in SAR and ISAR imagery
First Claim
1. A method of correcting rotational motion error in SAR and ISAR imagery, comprising the steps of:
- shifting the center of the image of a target to zero doppler and thus at the center of rotation of the target being imaged;
selecting a dominant scatterer in a range cell to provide a phase reference;
calculating the rotational motion error function from the phase reference provided by the selected scatterer;
interpolating raw radar return image data between the original unequal angular samples by using the rotational motion error function to obtain equal angular samples of a reflectivity function for the target; and
performing an image quality check to produce a value which constitutes a relative measure of focus of the corrected image.
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Abstract
A method of correcting rotational motion error in SAR and ISAR imagery includes shifting the center of the image to zero doppler and thus to the center of rotation of the target being imaged, selecting a dominant scatterer at an off-center range cell to provide a phase reference, calculating the rotational motion error function from the phase of the selected scatterer, using the rotational motion error function to interpolate raw radar return image data between the original unequal angular samples to obtain equal angular samples of the target reflectivity function, and performing an image quality check and producing a value which is a relative measure of focus of the image. Also, the method includes repeating the steps starting with selecting a new dominant scatterer as a phase reference. Further, the performing step of the method includes storing and comparing the relative measures of focus provided by repeating of the steps to arrive at the corrected image which is the most focused and then saving the corrected image determined to be the the most focused.
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Citations
8 Claims
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1. A method of correcting rotational motion error in SAR and ISAR imagery, comprising the steps of:
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shifting the center of the image of a target to zero doppler and thus at the center of rotation of the target being imaged; selecting a dominant scatterer in a range cell to provide a phase reference; calculating the rotational motion error function from the phase reference provided by the selected scatterer; interpolating raw radar return image data between the original unequal angular samples by using the rotational motion error function to obtain equal angular samples of a reflectivity function for the target; and performing an image quality check to produce a value which constitutes a relative measure of focus of the corrected image. - View Dependent Claims (2, 3, 4, 5)
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6. A method of correcting rotational motion error in SAR and ISAR imagery, comprising the steps of:
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shifting the center of the image of a target to zero doppler and thus at the center of rotation of the target being imaged; selecting a dominant scatterer in a range cell to provide a phase reference; calculating the rotational motion error function from the phase reference provided by the selected scatterer; interpolating raw radar return image data between the original unequal angular samples by using the rotational motion error function to obtain equal angular samples of a reflectivity function for the target; repeating the steps starting with selecting a new dominant scatterer as a phase reference; and performing an image quality check at the end of each repeating of the steps to producing a plurality of values constituting relative measures of focus of the corrected image achieved with each selected dominant scatterer. - View Dependent Claims (7, 8)
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Specification