Carleton University
Technical Report TR-217
December 1992
Indexing on Spherical Surfaces Using Semi-Quadcodes
Abstract
The conventional method of referencing a point on a spherical surface of known radius is by specifying the angular position of</> and A with respect to an origin at the centre. This is akin to the ( x, y) coordinates system in R2 cartesian plane. To specify a region in the cartesian plane, two points corresponding to the diagonal points (xi, Y1) and (x2, Y2) are sufficient to characterize the region. Given any bounded region, of 2h x 2h an alternate form of referencing a square subregion is by the linear quadtree address [9] or quadcode [12]. Corresponding encoding scheme for spherical surfaces is lacking. Recently a method similar to the quadtree recursive decomposition method has been proposed independently by Dutton and Fekete. Namely, the quaternary triangular mesh (QTM) [4] and the spherical quadtree (SDT) [7]. The addressing method of the triangular regions suggested are very similar. We present a new labeling method for the triangular patches on the sphere that allows for a better and more efficient operation and indexing on spherical surfaces.