Feathered Tiles with Uniform Payload Size for Progressive Transmission of Vector Data

We introduce Feathered Tiles, a novel vector data tiling method for web mapping. This method eliminates redundant data transfer, greatly reduces the amount of excess data transmitted for progressive refinements, and supports smooth zooming operations with on-the-fly generalization. For a given set of geometries, the effective area of each vertex is computed and stored as a third coordinate, along with the bounds of the effective area. The results are partitioned in three dimensions into tiles of a desired byte length. Each tile is stored along with the 3-dimensional bounds encapsulating the effective area of all vertices contained within. Individual tiles can then be retrieved on demand with 3-dimensional queries to reproduce a simplified set of geometries for a given scale and viewport. The key to reducing excess data transfer lies in associating tiles with the effective bounds of individual vertices rather than the bounds of the geometries that contain the vertices. This tiling method is implemented in the open source visualization framework, Weave.