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Scientists from the U.S. Naval Research Laboratory have invented a technique for efficiently converting an image from a first map projection to a second map projection image by combining cartographic materials into a single projection composite map. The patented technology is available via patent license agreement to companies that would make, use, or sell it commercially.
A common method of re-projecting a georeferenced image is via rubber sheeting whereby several control points are chosen from both the source and destination space and a linear transformation matrix defined. The technique works well when the transformation can be accomplished with a set of linear equations. However, the transformation from UTM (Universal Transverse Mercator, a grid reference system) to geodetic (a coordinate system and set of reference points used to locate places on earth) is nonlinear. The result of rubber sheeting on UTM images can be visible discontinuities between adjacent re-projected images. Where high levels of accuracy are required, rubber sheeting is not appropriate for UTM to geodetic reprojection.
A need exists for a way to efficiently and accurately convert any image type from one projection into another. In response, Navy scientists have developed a technique to do just that. The technique involves precomputing UTM coordinates for a subset of the total number of pixels in a geodetic image, and subsequently, for remaining pixels in the geodetic projection image, finding the UTM coordinates of a pixel by linear interpolation using the precomputed UTM coordinates of the nearest surrounding precomputed pixels. Color can be assigned to a pixel in the geodetic image using bilinear interpolation with the color values of the four closest UTM pixels.
Not only for UTM to geodetic transformations, but the process also allows for the transforming of images between any two projections for which accurate point transformations can be made. The resulting image can be printed, saved as a file to a storage device, or exported to another program or device for further processing.
- Decreased image processing time
- Eliminates unnecessary pixel conversion
- Preserves continuity between images
- Not limited to earth projections
- Data associated with the image pixels is not limited to color - can be intensity, temperature, or other physical measurements or representations
- Images can include data from sensors located on aircraft, satellites, ships, or other platforms or vehicles
- Businesses can commercialize the technology by licensing U.S. Patent 7,791,616 from the Navy
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