Implementation of vague spatial objects
Pawalai Kraipeerapun · 2004
This thesis deals with the storage and manipulation of vague spatial objects in a geographical information system (GIS) software called GRASS. Vague spatial objects are defined by using fuzzy set theory. They are distinguished into general types and simple types. The general type are separated into vague points, vague lines, and vague regions. The simple types are separated into simple vague points, simple vague lines, and simple vague regions, which are the structural elements of the general types respectively. Data structures for vague points, vague lines, and vague regions are defined and implemented based on the simple types, which are easier to handle in a computer. These data structures support the storing and handling of vague objects in GRASS vector format. The information for vague objects is stored in several files. Three new file types are created to extend the existing GRASS file types for supporting vague objects. Their topological relations are created on the fly and kept in memory when a module working with vague objects is called. The union operator for vague objects is defined and implemented. The data stored using these data structures is retrieved to select objects. Vague objects belonging to the same theme can also be stored together in the same layer. The GRASS site format is also used to store vague points.