Technique for ship/wake detection
First Claim
1. A computer-readable storage medium that provides instructions that, if executed by a machine, will cause the machine to perform operations comprising:
- accessing data associated with an image of a portion of Earth, the data including reflectance values;
masking a first portion of pixels within the image with a cloud and land mask based on spectral flatness of the reflectance values associated with the pixels, wherein the reflectance values comprise a near infrared (NIR) reflectance value and a visible reflectance value for each of the pixels of the image and wherein the spectral flatness of the reflectance values is determined based on a ratio of the NIR reflectance value to the visible reflectance value for each of the pixels;
unmasking a given pixel selected from the first portion of pixels when a threshold number of localized pixels surrounding the given pixel are not masked by the cloud and land mask;
generating a spatial variability image based on spatial derivatives of the reflectance values of the pixels which remain unmasked by the cloud and land mask; and
thresholding the spatial variability image to identify one or more regions within the image as possible ship detection regions.
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Abstract
An automated ship detection technique includes accessing data associated with an image of a portion of Earth. The data includes reflectance values. A first portion of pixels within the image are masked with a cloud and land mask based on spectral flatness of the reflectance values associated with the pixels. A given pixel selected from the first portion of pixels is unmasked when a threshold number of localized pixels surrounding the given pixel are not masked by the cloud and land mask. A spatial variability image is generated based on spatial derivatives of the reflectance values of the pixels which remain unmasked by the cloud and land mask. The spatial variability image is thresholded to identify one or more regions within the image as possible ship detection regions.
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Citations
28 Claims
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1. A computer-readable storage medium that provides instructions that, if executed by a machine, will cause the machine to perform operations comprising:
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accessing data associated with an image of a portion of Earth, the data including reflectance values; masking a first portion of pixels within the image with a cloud and land mask based on spectral flatness of the reflectance values associated with the pixels, wherein the reflectance values comprise a near infrared (NIR) reflectance value and a visible reflectance value for each of the pixels of the image and wherein the spectral flatness of the reflectance values is determined based on a ratio of the NIR reflectance value to the visible reflectance value for each of the pixels; unmasking a given pixel selected from the first portion of pixels when a threshold number of localized pixels surrounding the given pixel are not masked by the cloud and land mask; generating a spatial variability image based on spatial derivatives of the reflectance values of the pixels which remain unmasked by the cloud and land mask; and thresholding the spatial variability image to identify one or more regions within the image as possible ship detection regions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A computer automated method for detecting ships in water, the method comprising:
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accessing data associated with an image of a portion of Earth, the data including reflectance values, wherein the reflectance values comprise a near infrared (NIR) reflectance value and a visible reflectance value for each of the pixels of the image; categorizing pixels within the image into first or second categories based on spectral flatness of the reflectance values associated with the pixels, wherein categorizing the pixels within the image into the first or second categories comprises categorizing each of the pixels based on a ratio of the NIR reflectance value to the visible reflectance value for each of the pixels; re-categorizing a given pixel into the second category when a threshold number of localized pixels surrounding the given pixel, which was previously categorized into the first category, are categorized into the second category; calculating spatial derivatives on the reflectance values of the pixels categorized into the second category; and marking a region of the image as a possible ship detection when the spatial derivatives associated with the pixels in the region have an absolute value greater than a threshold value. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A computer-readable storage medium that provides instructions that, if executed by a machine, will cause the machine to perform operations comprising:
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accessing data associated with an image of a portion of Earth, the data including reflectance values, wherein the reflectance values comprise a near infrared (NIR) reflectance value and a visible reflectance value for each of the pixels of the image; categorizing pixels within the image into first or second categories based on spectral flatness of the reflectance values associated with the pixels, wherein categorizing the pixels within the image into the first or second categories comprises categorizing each of the pixels based on a ratio of the NIR reflectance value to the visible reflectance value for each of the pixels; re-categorizing a given pixel into the second category when a threshold number of localized pixels surrounding the given pixel, which was previously categorized into the first category, are categorized into the second category; calculating spatial derivatives on the reflectance values of the pixels categorized into the second category; and marking a region of the image as a possible ship detection when the spatial derivatives associated with the pixels in the region have an absolute value greater than a threshold value. - View Dependent Claims (24, 25, 26, 27, 28)
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Specification