Summary of coverage feature classes

A coverage is a collection of feature classes used to represent geographic phenomena. Each coverage is a directory stored as a series of files.

The set of features contained in a coverage depends on the type of geographic phenomena being modeled. The following table gives a brief description of the types of phenomena each feature class is used to model:

Coverage feature classes

Feature class	Application and use	Examples
Point	Point locations	Well sites, mountain peaks
Arc	Linear features	Street sections, contours, streams, sewers, power lines, gas lines
Node	Connecting points and endpoints of linear features	Valves on pipelines, intersections of streets, power poles, manhole covers
Route	Linear features	Streets, contours, stream networks, sewers, power line networks, gas line networks, street addresses
Section	Defines route features	Street section, traffic lanes, pipe condition, above- and below-ground transmission lines
Polygon	Area features	Soil units, land use, parcels, building footprints, forest stands, ownership
Region	Area features, multiple polygons	Census geography, state of Hawaii, overlapping wildlife habitat
Annotation	Feature labels	Street names, place-names on road maps
Tic	Geographic registration and control	Registration for digitizing
Link	Rubber sheeting and adjustment	Edgematching map sheets, feature snapping, datum adjustments
Coverage extent	Defines map extent	Rectangle describing outer boundary of coverage

Coverage feature classes

Coverage feature class file description

Feature class	Description	Attribute table name: <cover>.*
Point	A point defined by an x,y coordinate pair used to represent point features or assign User-IDs to polygons.	pat.adf
Arc	A line defined as a set of ordered x,y coordinates used to represent linear features and polygon boundaries.	aat.adf
Node	The endpoints of an arc or the point at which two or more arcs connect.	nat.adf
Route	A linear feature composed of one or more arcs or parts of arcs.	<route>.rat
Section	An arc or portion of an arc used to define a route or the building blocks of routes.	<route>.sec
Polygon	An area defined by the arcs that make up its boundary, including arcs defining any islands inside. User-IDs are assigned to label points.	pat.adf
Region	A collection of one or more contiguous or noncontiguous polygons defining a geographic feature.	<region>.pat
Annotation	A text string describing a geographic feature. Shape points are used to position and draw annotation.	<anno>.tat
Tic	A geographic reference or control point used to register and transform the coordinates in a coverage.	tic.adf

Coverage feature class file description