18 February 2011

A glossary of terms commonly used in GIS

following are terms used to describe data in the format used with ESRI products :

Arcs - Lines that begin and end with a node. Intersections of arcs are always connected with a node. Arcs also make up part of a polygon. An example of data that would use this form would be roads.

Node - Beginning, connecting and ending points of an arc. An example of data that would be represented by this form would be manholes or inlets in a stormwater system.

Point - A single "dot" location. A point is also called a "label point". A label point is the element that holds information in the polygon. An example of data that would be stored in the system using this form would be fire hydrants, or a set of individual address locations.

Polygon - An arc that closes on itself to make a circle or a closed shape. An example of a set of data that would be stored in the GIS in this format would be parks or lakes.

ArcView - Desktop GIS software developed by ESRI used to do some basic GIS operations and print maps.

Shapefile - A set of files that contain a set of points, arcs, or polygons (or features) that hold tabular data and a spatial location. This file format is used in ArcView software. - A set of files that contain a set of points, arcs, or polygons (or features) that hold tabular data and a spatial location. This file format is used in ArcView software.

Arc/INFO - The GIS software developed by ESRI that is used to do more robust GIS operations

Coverage - A file format used in Arc/INFO software developed by ESRI that contain a set of points, arcs, or polygons (or features) that hold tabular data and a spatial location.

Common GIS Terms
Area - A description of the dimension or content of a polygon.

Coordinate System - A fixed reference framework superimposed onto the surface of an area to designate the position of a point within it by using x and y coordinates. The State Plane Coordinate System and the system of latitude and longitude used on the Earth's surface are common examples.

Data - A collection of facts, concepts or instructions in a formalized manner suitable for communication or processing by human or automatic means. Generally used in the GIS field as a reference to all spatial information.

Feature - A spatial element which represent a real-world entity by having specific characteristics. Often used synonymously with the term object. A generalized description of a point, line or polygon.

Field - A location in a data record in which a unit of information is stored. For example, in a database of addresses, one field would be 'city'.

Geocoding - The process by which the geographic coordinates of a location are determined by its address, postal code, or other explicitly non-geographic descriptor.

Legend - The description of the symbology representing features on a map.

Map - A graphic representation of geographically distributed phenomena. The information displayed may be in the form of symbols or signs.

North Arrow - The graphical representation of which direction north is on the map.

Scale - The ratio or fraction between the distance on a map, chart or photograph and the corresponding distance in the real world.

Scale Bar - A map element which shows the scale of a map graphically.

Set - A group of features and their data.

Spatial - (pro. Spay-shawl) An adjective. Of, relating to, or occurring in space.

Table - A means of organizing data in rows and columns in which each row represents an individual entity, record, or feature and each column represents a single field or attribute value.

Query - A way of selecting features based on a set of common characteristics. For example, the act of selecting all the buildings that have an area greater than 2000 sq. ft. out of a database.

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