This technology is used to link extensive two-dimensional graphical representations with diverse textual and visual descriptions. The six theme feature classes are point, line, polygon, annotation, tic and record. A point feature is a single x,y coordinate pair that is too small to be displayed as a line or an area. Examples are wells, epicenters, station locations. A line feature contains arcs, which are sets of connected and ordered points representing features that have no width or are too narrow to be represented as an area.
Examples are roads, streams, contour lines and faults.
A polygon is closed figure whose boundary encloses a homogeneous area. Examples are lakes, counties and geological outcrops. An annotation is a text string used to label features on a map not spatially related to any other feature class and used only for display purposes. A tic provides registration or geographic control points by representing known locations on a surface. Each of the geoscience data sets we wish to include in GIS must fall in one of these feature classes in order to be usable by current GIS software.