filtering with raster signatures
Efficient evaluation of spatial queries is an important issue in spatial database. Among spatial operations, spatial join is very useful, intersection being the most common predicate. However, the exact intersection test of two spatial objects is the most time-consuming and I/O-consuming step in processing spatial joins. On the other hand, the use of approximations can reduce the need for examining the exact geometry of spatial objects in order to find the intersecting ones. This work proposes a new raster approximation (Three-Color Raster Signature - 3CRS) for representing different data types (polygons, polylines and points), and to be used as filter in the second step of the Multi-Step Query Processor. We have also executed experimental tests over real datasets, the results having demonstrated the effectiveness of our approach.
spatial databases spatial join raster approximation three-colors raster signature multi-step query processor four-colors raster signature gis