System and method for automatically determining the position of landmarks in digitized images derived from a satellite-based imaging system
First Claim
1. A method of determining offset errors between line and pixel coordinates of landmarks in a digitized image generated by a passive imaging system disposed on a spacecraft and line and pixel coordinates predicted by a mathematical model of the imaging system, said method comprising the steps of:
- defining and storing a plurality of landmarks in a landmark database that are each defined as having a perimeter comprising a plurality of boundary vertices;
generating a digitized image of a softcopy map derived from a database that is viewed on a display;
selecting a landmark in the softcopy map for processing;
reading out the plurality of boundary vertices of the landmark stored in the landmark database that corresponds to the selected landmark in the softcopy map;
processing the plurality of boundary vertices of the stored landmark using a mathematical model of the passive imaging system to generate absolute coordinates of boundary pixels of the stored landmark;
upsampling and rasterizing the absolute coordinates of boundary pixels of the stored landmark to generate a landmark mask;
processing the digitized image derived from the passive imaging system to extract an image patch containing the selected landmark;
upsampling the image patch so that it has the same magnification as the upsampled landmark mask; and
processing the upsampled image patch and the upsampled landmark mask by an image matching algorithm to determine offset errors between the respective images.
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Accused Products
Abstract
A system and method for determining offset errors between line and pixel coordinates of landmarks in a digitized image generated by an imaging system disposed on a spacecraft and line and pixel coordinates predicted by a mathematical model of the imaging system using landmark geodetic coordinates on the Earth. The system and method use landmarks in symbolic form, such as perimeters of lakes and islands that are stored in a database. A digitized image generated by the satellite-based imaging system is processed to extract a patch of the image containing a landmark. The image patch is then upsampled (magnified). The landmark boundary is processed using a mathematical model of the imaging system to generate absolute coordinates of the boundary pixels, which are upsampled and rasterized to produce a landmark mask. The landmark mask and the upsampled image patch are then processed by one or more matching algorithms to generate line and pixel offset error values indicative of the offset between the predicted position of the landmark and the actual position of the landmark in the image. A match figure of merit is also generated that is indicative of the reliability and accuracy of the computed offset. Optionally, the upsampled image patch is processed using an image enhancement algorithm that increases the contrast and robustness of the images by converting pixel gray scale values into likelihood ratios.
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Citations
20 Claims
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1. A method of determining offset errors between line and pixel coordinates of landmarks in a digitized image generated by a passive imaging system disposed on a spacecraft and line and pixel coordinates predicted by a mathematical model of the imaging system, said method comprising the steps of:
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defining and storing a plurality of landmarks in a landmark database that are each defined as having a perimeter comprising a plurality of boundary vertices; generating a digitized image of a softcopy map derived from a database that is viewed on a display; selecting a landmark in the softcopy map for processing; reading out the plurality of boundary vertices of the landmark stored in the landmark database that corresponds to the selected landmark in the softcopy map; processing the plurality of boundary vertices of the stored landmark using a mathematical model of the passive imaging system to generate absolute coordinates of boundary pixels of the stored landmark; upsampling and rasterizing the absolute coordinates of boundary pixels of the stored landmark to generate a landmark mask; processing the digitized image derived from the passive imaging system to extract an image patch containing the selected landmark; upsampling the image patch so that it has the same magnification as the upsampled landmark mask; and processing the upsampled image patch and the upsampled landmark mask by an image matching algorithm to determine offset errors between the respective images. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A system for determining offset errors between line and pixel coordinates of landmarks in a digitized image generated by a passive imaging system disposed on a spacecraft and line and pixel coordinates predicted by a mathematical model of the imaging system, said system comprising:
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a landmark database that stores a plurality of landmarks that are each defined as having a perimeter comprising a plurality of boundary vertices; a display for viewing the digitized image generated from softcopy map databases; imaging extraction means for processing the digitized image derived from the passive imaging system to extract an image patch therefrom that contains a selected landmark; and a landmark position system comprising a computer for reading the plurality of boundary vertices of the landmark in the landmark database that corresponds to the selected landmark in the digitized image derived from the passive imaging system, for processing the plurality of boundary vertices of the stored landmark using the mathematical model of the imaging system to generate absolute coordinates of boundary pixels of the stored landmark, for upsampling and rasterizing the absolute coordinates of boundary pixels of the stored landmark to generate a landmark mask, for processing the digitized image derived from the passive imaging system to extract an image patch containing the selected landmark, for upsampling the image patch so that it has the same magnification as the upsampled landmark mask, and for processing the upsampled image patch and the upsampled landmark mask by an image matching algorithm to determine offset errors between the respective images. - View Dependent Claims (8, 9, 10, 11, 12, 19, 20)
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13. A method of determining offset errors between line and pixel coordinates of landmarks in a digitized image generated by an imaging system disposed on a spacecraft and line and pixel coordinates predicted by a mathematical model of the imaging system, said method comprising the steps of:
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defining and storing a plurality of landmarks in a landmark database that are each defined as having a perimeter comprising a plurality of boundary vertices; generating a digitized image of a softcopy map derived from a database that is viewed on a display; selecting a landmark in the softcopy map for processing; reading out the plurality of boundary vertices of the landmark stored in the landmark database that corresponds to the selected landmark in the softcopy map; processing the plurality of boundary vertices of the stored landmark using a mathematical model of the imaging system to generate absolute coordinates of boundary pixels of the stored landmark; upsampling and rasterizing the absolute coordinates of boundary pixels of the stored landmark to generate a landmark mask; processing the digitized image to extract an image patch containing the selected landmark; upsampling the image patch so that it has the same magnification as the upsampled landmark mask; and processing the upsampled image patch and the upsampled landmark mask by an image matching algorithm to determine offset errors between the respective images, which processing includes generating a figure of merit that is indicative of the reliability and accuracy of the computed offset errors. - View Dependent Claims (14, 15, 16, 17)
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18. A system for determining offset errors between line and pixel coordinates of landmarks in a digitized image generated by an imaging system disposed on a spacecraft and line and pixel coordinates predicted by a mathematical model of the imaging system, said system comprising:
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a landmark database that stores a plurality of landmarks that are each defined as having a perimeter comprising a plurality of boundary vertices; a display for viewing the digitized image generated from softcopy map databases; imaging extraction means for processing the digitized image to extract an image patch therefrom that contains a selected landmark; and a landmark position system comprising a computer for reading the plurality of boundary vertices of the landmark in the landmark database that corresponds to the selected landmark in the digitized image, for processing the plurality of boundary vertices of the stored landmark using the mathematical model of the imaging system to generate absolute coordinates of boundary pixels of the stored landmark, for upsampling and rasterizing the absolute coordinates of boundary pixels of the stored landmark to generate a landmark mask, for processing the digitized image to extract an image patch containing the selected landmark, for upsampling the image patch so that is has the same magnification as the upsampled landmark mask, and for processing the upsampled image patch and the upsampled landmark mask by an image matching algorithm to determine offset errors between the respective images including generating a figure of merit that is indicative of the reliability and accuracy of the computed offset errors.
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Specification