A schema provides for the storage of geographic information on a personal digital assistant (PDA). Embodiments provide differential encoding and indexing of raster and vector based data. A schema provides for compact and performable storage of both data and metadata for raster, vector, and redlining information. A single database is utilized for mapset metadata and data. Timestamp/history information allows smart, incremental updates of the database. Indexing information allows compact and efficient storage and retrieval of objects and vector geometry. The schema allows a variable number of mapsets, maps, raster tiles, and geometry layers. Metadata for geometry types and redlining markup information are permitted. Geo-referencing information for raster and vector data allows the display of objects at the correct map location. Raster data is augmented with compact vector data. The vector data may be used for efficiently storing and retrieving the map data, allowing interactive selection, and the highlighting and querying of objects. Vectors are generalized by removing detail without losing shape information in a manner appropriate to PDA display resolution. Object location data is differentially encoded to provide precision using a fewer number of bytes (2 bytes per coordinate). The vector object includes spatial indexing information, to allow for spatial filtering of objects that fall within a specified view. Thus, the invention uses cartographic generalization, encoding, and indexing to provide for compact, and efficient spatial storage structures that deal with the PDA constraints of limited storage, processing power, memory and bandwidth.
Generalized, differentially encoded, indexed raster vector data and schema for maps on a personal digital assistant