Glossary for Geospatial Science

CAD object:  A CAD object, in RVC format, like a vector object, is composed of coordinate data, but uses a different data structure.  A CAD object has a free-form topology, so it may be useful for applications that do not require an exact description of the relationships between the elements in the object.  CAD object topology does not reconcile things like line intersections, polygon overlap, and polygon islands.

A CAD object also allows for descriptions of geometric shapes.  For example, in a vector object, a circle is always stored as a polygon, and at a high enough magnification, the discrete point and line elements become visible.  By contrast, a CAD object stores a circle by its center point and radius.  Thus, at any magnification, it looks circular.

Since they have reduced topological constraints, CAD objects generally require less storage than their vector object counterparts.  [See also: element (CAD).]