Coherent correlation addition for increasing match information in scene matching navigation systems
First Claim
1. A method for increasing match area in an image matching system comprising the step of combining at least two correlation surfaces to form a composite correlation surface, wherein each correlation surface is formed by;
- comparing a sensed image to a reference image at every location in said reference image at which said sensed image is entirely within said reference image; and
computing a correlation amplitude for each location of said sensed image in said reference image, said correlation amplitudes forming said correlation surface.
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Abstract
A method and apparatus are described for image matching, particularly for increasing match information in scene matching navigation systems. The invention correlates a sequence of sensed images with a reference map and stores the resultant correlation surfaces. The correlation surfaces are then added so that match point correlations combine coherently by superposing the individual correlation surfaces using short term accurate navigation data. As a result, a composite correlation surface is formed in which the values at the peak (or antipeak) position add up and the effective match area is greatly increased. Both peaks and antipeaks are then detected to determine a match point and provide a navigation position update.
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Citations
26 Claims
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1. A method for increasing match area in an image matching system comprising the step of combining at least two correlation surfaces to form a composite correlation surface, wherein each correlation surface is formed by;
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comparing a sensed image to a reference image at every location in said reference image at which said sensed image is entirely within said reference image; and computing a correlation amplitude for each location of said sensed image in said reference image, said correlation amplitudes forming said correlation surface. - View Dependent Claims (2, 3, 4, 5)
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6. A method for matching a sequence of sensed images with a reference map comprising the steps of:
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correlating at least two of said sensed images with said reference map to generate a correlation surface for each of said sensed images comprising the steps of; comparing each of said sensed images to said reference map at every location in said reference map at which said sensed image is entirely within said reference map, and computing a correlation amplitude for each location of said sensed image in said reference map, said correlation amplitudes forming said correlation surface; combining said correlation surfaces to form a composite correlation surface; and determining a match point for said sequence of sensed images in said reference map using said composite correlation surface. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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7. An image matching method comprising the steps of:
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acquiring a sequence of sensed images with at least two of said sensed images being located within a reference map; correlating each of said sensed images with said reference map to generate a correlation surface for each of said sensed images comprising the steps of; comparing each of said sensed images to said reference map at every location in said reference map at which said sensed image is entirely within said reference map, and computing a correlation amplitude for each location of said sensed image in said reference map, said correlation amplitudes forming said correlation surface; combining said correlation surfaces to form a composite correlation surface; and determining a match point for said sequence of sensed images in said reference map using said composite correlation surface.
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19. An image matching method comprising the steps of:
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acquiring a sequence of sensed images with at least three of said sensed images being located within a larger reference map; correlating each of said sensed images with said reference map to generate a correlation surface for each of said sensed images comprising the steps of; comparing each of said sensed images to said reference map at every location in said reference map at which said sensed image is entirely within said reference map, and computing a correlation amplitude for each location of said sensed image in said reference map, said correlation amplitudes forming said correlation surface; adding coherently said correlation surfaces to form a composite correlation surface; searching said composite correlation surface for a maximum correlation amplitude that exceeds an upper threshold value and for a minimum correlation amplitude which is below a lower threshold value wherein said upper and lower threshold values are adjusted based on the standard deviation of actual correlation amplitudes excluding the extremes; computing peak-to-sidelobe ratio (PSR) and antipeak-to-sidelobe ratio (ASPR) for said composite correlation surface using said maximum and minimum correlation amplitudes; using said PSR or APSR to determine a match point of said sequence of sensed images in said reference map; forming a new composite correlation surface when said match point cannot be determined using said composite correlation surface comprising the steps of; subtracting from said composite correlation surface said correlation surface generated form the oldest acquired of said sensed images; and adding to said composite correlation surface said correlation surface generated from the latest acquired of said sensed images to form said new composite correlation surface; redetermining said match point of said sequence of sensed images in said reference map using said new composite correlation surface; and repeating said above forming and redetermining steps until said match point with greatest PSR or APSR is determined or until the last acquired of said sensed images located in said reference map is correlated, whichever occurs first.
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20. A correlation processor comprising:
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means for correlating a sequence of sensed images with a reference map to generate a correlation surface for each of said sense images, said correlating means comprising; means for comparing each of said sensed images to said reference map at every location in said reference map said correlation amplitudes forming said correlation surface; means for combining said correlation surfaces to form a composite correlation surface; and means for determining a match point for said sequence of sensed images in said reference map using said composite correlation surface. - View Dependent Claims (21, 22, 23, 24, 25, 26)
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Specification