Topological Vector Data

Vector data are categorized as topological and non-topological. Topology, as used in GIS, expresses explicitly the spatial relationships between features, such as two line meeting perfectly at a point and a directed line having an explicit left and right side. Topology is useful for detecting digitizing errors in digital maps and is necessary for some map overlay operations and network analysis. Non-topological data display faster and more importantly they can be used directly in different GIS software packages. In ESRI softwares , topological based digital maps termed as coverage and non-topological based digital maps are termed as shapefiles. GIS users should know whether their data are topological or not.

Topological vector data can be further categorized into simple and higher data.

Simple vector data can be consisting of points, lines and polygons. Higher level data are built upon simple points, line and polygons. The triangulated irregular network (TIN) approximates the terrain with a set of non-overlapping triangles. Each triangle in a TIN consists of points and edges (lines) that connect these points to form triangles. A region is a collection of polygons, which may or may not be connected, and region may overlap with one another or form a nested set. Dynamic segmentation is a data model that is built upon lines of a network and allows the use of real-world coordinates with linear measures such as mileposts.+