Affine-invariant querying of spatial data using a triangle-based logic

If the same land area is photographed from two different angles, then a computer can recognize the two images to show the same land area by proving that the images are affine-invariant . In practice, images are abstracted as a type of spatial data that is a finite set of triangles. Hence we propose a simple affine-generic query language with variables over finite sets of triangles. The proposed query language is intuitive and has the same expressive power as the affine-generic fragment of first-order logic over the reals on triangle databases.