Linear quadtree coding scheme with hierarchical structure and rotational operator

A new coding scheme for linear quadtree and a basic geometric operation are proposed in this paper. There are two objectives in this paper. The first objective is to find a coding scheme with which the requirement of large storage for storing raster data can be improved from the past research. The second objective is to verify the feasibility of the proposed coding scheme for spatial data operations. The proposed linear quadtree coding scheme is developed on the basis of the hierarchical structure of the quadtree. Techniques of breadth-first search, Morton sequence with two data structures of branch list and data list are used to derive the proposed coding scheme. The branch list maintains the outputs of the quadtree decomposition, and uses only one bit to record each node; all terminal nodes, representing different spatial data, in the quadtree are recorded in the data list. The application of the data list has an advantage that the number of bits required to represent various objects are extendible, so that the requirement of the construction of new quadtrees is no longer necessary. The feasibility of the proposed linear quadtree coding scheme is verified by two raster images of spatial data. Results of experimental tests reveal that the proposed scheme has the least storage requirement among various coding schemes. A basic operation, rotation, is also implemented to demonstrate the applicability of the proposed coding scheme for geometric operations. Due to the characteristic of the proposed coding scheme, the problem of multicolor quadtrees is also solvable by the method proposed in this paper.