Spatial Data Models

Spatial Data Models Three common spatial data models Vector Raster Triangulated Irregular Network (TIN)

Vector Data Model Defines discrete objects Ex: Fire hydrants, roads, ponds, cadastre 3 basic types of vector data Point Line Polygon Composed of coordinates and attributes

Point Uses a single coordinate pair to define location Considered to have no dimension (They may have actual real-world dimensions, but for the purposes of a GIS, no dimension is assumed) Attribute information is attached to the point Ex: Light poles, manhole covers, crime location

Line Use an ordered set of coordinates to define location Each line (and curve) is made up of multiple line segments Occasionally, curved lines are represented mathematically Starting point of a line is a node. Intermediate point of a line is a vertex. Attributes may be attached to whole line, or node, or vertex Ex: Road, pipeline, object outlines, powerline

Polygon Formed by a set of connected lines Polygons must close. The start and end point must have the same coordinate, or the polygon must close to an adjacent feature Polygons have an interior region Attribute information is attached to the polygon Ex: Lake, city, tree stand, political boundary