Spatial predicate implementation for modern internet map server

It is a critical technique in GIS about how to implement spatial relation/spatial predicate with high performance. To avoid the disadvantages of computational geometry algorithm approach, we propose one improved method, combined with the rendering engine, which can enhance the filter accuracy and avoid drawbacks of four color raster signature (4CRS). This proposal can record coverage area of border grid cells accurately based on subpixel accuracy, so it can determine whether two polygons overlap through judging coverage area of the corresponding grid cells. As side effects, the rendering engine can preserve feature attribute information(polygon IDs etc.) in the cell structure which offers more useful hints for spatial relation judgment.