Process and apparatus for cross-correlating digital imagery
First Claim
1. A system for analyzing changes in image features comprising:
- image data classification means for classifying high resolution image data into groups and summary groups;
rasterizing means for processing said high resolution image data into cells of a unitary size;
low resolution input means for retrieving and processing low resolution image data that correspond to said classified high resolution image data, comprising;
selector means for selecting spectral bands of said low resolution image data best-suited for cross-correlation with said high resolution image data,geo-referencing means for geo-referencing said selected bands,co-registration means for co-registering said selected bands with said high resolution image data, andlow resolution rasterizing means for processing said selected bands into cells of said unitary size;
cross-correlation means for defining a statistical value representing degree of change between said classified high resolution image data and said corresponding low resolution image data;
threshold means for comparing said cross-correlation statistical value in order to redefine thresholds representing significant, medium and low degrees of image change; and
mapping means for producing maps representing cells having maximum amounts of change.
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Abstract
The present invention involves a system and method for processing information from high resolution data from maps, aerial photographs and other spatial data with low resolution data from limitation in order to accurately identify changes in the studied areas. The system and method relies upon a vectorized database which has been classified according to topographical features. Change is defined by a Z-statistic. The Z-statistic is calculated in a two-pass cross-correlation technique when pixel brightnesses are compared to a mean brightness for the typical topographical class and to a standard deviation for that class. The normalized difference values are accumulated across different bands, are scaled and then compared to a threshold which defines high, medium and low change values. A map is automatically produced illustrating areas of significant change.
76 Citations
9 Claims
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1. A system for analyzing changes in image features comprising:
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image data classification means for classifying high resolution image data into groups and summary groups; rasterizing means for processing said high resolution image data into cells of a unitary size; low resolution input means for retrieving and processing low resolution image data that correspond to said classified high resolution image data, comprising; selector means for selecting spectral bands of said low resolution image data best-suited for cross-correlation with said high resolution image data, geo-referencing means for geo-referencing said selected bands, co-registration means for co-registering said selected bands with said high resolution image data, and low resolution rasterizing means for processing said selected bands into cells of said unitary size; cross-correlation means for defining a statistical value representing degree of change between said classified high resolution image data and said corresponding low resolution image data; threshold means for comparing said cross-correlation statistical value in order to redefine thresholds representing significant, medium and low degrees of image change; and mapping means for producing maps representing cells having maximum amounts of change. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An image processing system for analyzing changes in image features comprising:
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a high resolution database for storing high resolution data as digital line graph ("DLG") data; a classification scheme for topographical features represented within said high resolution data; an attribute memory connected to said database for storing coding classifications according to said classification scheme; a converter for converting said DLG data into polygonal vectors conforming to said topographical features; a high resolution rasterizer for processing said high resolution data into 25 by 25 meter-sized pixel cells; a high resolution vector memory for storing said rasterized high resolution data; an attribute assignment device for assigning attribute data to said polygonal vectors; a selector device for selecting optimal spectral bands of low resolution data for cross-correlation with said high resolution data; a geo-referencing device for geo-referencing said selected bands of low resolution data; a co-registration device for registering said low resolution data to said high resolution data; a low resolution rasterizer for processing said low resolution data into 25 by 25 meter-sized pixel cells; a low resolution data memory for storing said rasterized low resolution data; and a cross-correlation device for defining a statistical value representing degree of change between said high resolution data and said associated low resolution data.
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Specification