A Raster-encoded Polygon Data Structure for Land Resource Analysis Applications

A prototype structure for areal data sets is discussed in the context of providing efficient data storage, retrieval, and analysis as required by land resource analysis applications. The prototype is a "raster-encoded polygon format" and is derived from a run-length ras ter format in which each run has multiple attributes associated with it. A transformation program, involving the first phase of the rasterto-vector conversion process, associates each run with a parent polygon entity. The total size of each entity, and information concerning its adjacency to other entities, are recorded in an entity table along with all attribute values for the entity. This results in a reduction of total volume of the run-length raster file, and simplified subsequent manipulation and retrieval operations based upon attribute values of the data. The underlying raster structure retains its advantages for overlaying new data sets and complex retrieval operations. Since the parent polygon area and adjacency relationships are identified, queries based upon threshold size or adjacency can now be addressed with what is essentially a raster data structure.