A

acceptance test

Test performed by the user or owner of a system to determine if the system is functioning correctly according to specifications (as indicated in a prior contract or written agreement). 

accessibility

Ease or difficulty of reaching a specified location from other locations. Some GIS allow for accessibility to be determined. 

accuracy

Degree to which an estimated, observed, or calculated value approaches the actual or true value (or what is believed to be the actual or true value). 

address -- municipal

Administrative spatial identifier used to provide a unique geographical label to features. A municipal address has a number of components: street identifier, street type, quadrant, house number, unit number, etc. An address acts as both a label and as nominal geocoding. 

address range -- municipal

Range is usually the lowest and highest numbers possible along a street. The address range is often separated into even and odd number ranges -- even numbers for one side of the street and odd numbers for the other side. 

aerial photograph

Refers to a photograph taken from an aircraft. 

aeronautical chart

Map showing features seen from the air and considered necessary for air navigation and/or airport planning. 

affine transformation

Transformation between any two Euclidean spaces -- consists of a combination of translation, rotation, and scaling. 

aggregation

Combining different data or layers of data into one composite display. 

algorithm

Set of steps to be followed in a specific order to solve a problem. 

alias

Alternate name used for identification, e.g., a building may be known by more than one name; a street may be known by more than one name. 

aliasing -- in computer graphics

Refers to the "jagged" or "stair-stepped" appearance of diagonal lines. 

alphanumeric

Data that contains letters of the alphabet and the numeric digits (a to z, A to Z, 0 to 9). Often will also contain the special punctuation characters. 

AM/FM

See Automated Mapping/Facilities Management 

anaglyph

Generation of stereo images in two different colours (e.g., blue and green) with images displayed overlapping -- one on top of the other. Resultant image is viewed with anaglyphic glasses -- one lens red and the other blue or one lens red and the other green. 

annotation

Any marking on a map used for the purpose of clarification. This can include numbers, letters, symbols, and signs. The name of a town or river could be considered map annotation. 

anti-aliasing -- in computer graphics

Refers to techniques used to smooth the appearance (remove the "jagged" look) of diagonal lines. 

application -- GIS

The employment of GIS technology for a specific and practical use, e.g., site analysis, transport analysis, etc. 

arc

Directed line connecting a set of points. May also be referred to as chain, string, or edge. In a GIS, an arc is usually stored internally as part of a directed graph or network data structure. 

archival capability -- storage format

Ability of a "storage format" to archive cartographic data -- goes beyond simple storage of data. 

archival format

Format designed for archival purposes of GIS related data. Digital cartographic information is likely to be of historical significance in the future. The fact that this data can be easily modified and deleted is of concern to archivists and historians. 

area

Usually planar in nature. One of the basic units of geographical information. The word "area" may also be used to describe the extent or measurement of a surface, e.g., "the area of the polygon is ...". 

area measurement

See measurement -- area 

ASCII

American Standard Code for Information Interchange. It is a system of 7-bit codes for representing numbers, letters, and other characters in a standard form within a computer for information exchange purposes. Developed by the American National Standards Institute (ANSI). 

aspect

Direction of the maximum slope. Aspect is usually given in 8 cardinal directions N, NE, E, SE, S, SW, W, NW. An additional value is often assigned for the characteristic of "flat". 

aspect ratio

The ratio of picture width to height when discussing the video display frame used to hold an image. 

attribute

In GIS, the non-graphic defined characteristic associated with an entity, e.g., an attribute for an area entity might be soil type. 

attribute input

The way in which attribute values may be entered into the database and associated with map elements. Attribute values may be entered during digitizing or may be transferred to the database and related to the map elements using a matching key. 

attribute validity checking

Process or procedures used to check that admissible attribute values are being entered into the database. Checking may include the range of the attribute or its format. 

attribute value

Actual specific "value" (quantitative or qualitative) given to an attribute. 

Auto Carto #

Name given to an international symposium on automated cartography. "#" indicates the number of the symposium. Sponsored by (and proceedings published by) American Society of Photogrammetry and the American Congress on Surveying and Mapping. 

automated contouring

Computer system to generate contour lines from point data. 

automated digitizing

Computer system to scan an image and determine the points, lines, annotation, etc., contained within that image. Meant to automate the human process of digitizing. 

Automated Mapping/Facilities Management

Use of GIS technology to map, site, inventory, track, and maintain buildings and/or other man-made structures (often distributed over large areas). AM/FM links computer mapping with facilities information into a common information system. 

automated names placement

A computer system that automatically positions and places text associated with points, lines, and area features occurring on a map. The system automatically determines and resolves text placement conflicts (e.g., text overlap with other text or other map features). 

AUTONAP

One of the first automated text placement systems. 

axis

One of a set of reference lines for a coordinate system. 

azimuth

Direction of a line given as an angle measured clockwise from a reference direction, usually north. For example, due east is 90 degrees, due south is 180 degrees, and due west is 270 degrees. 

B

base map

A map used for the construction of other maps or which is used as a base by which other data is related to or referenced to. 

batch processing

Execution of system commands (one or more) without direct supervision of an operator. Most commands executed in batch mode are also executable in interactive mode. 

bathymetric map

Map showing the shape of the bottom of a body of water. This may be accomplished with the use of depth contours (isobaths). 

BC-SAIF

British Columbia - Spatial Archive and Interchange Format. A new format proposed in British Columbia to replace the MOEP (or TRIM) format. It is based on the new proposed United States format (US-SDTS) and meant to incorporate modern concepts and principles. Feature classification within this format is provided via a hierarchical feature coding scheme similar to the one defined for CCOGIF. 

bearing

Direction from one point to another, which is expressed as an angle in degrees from a reference meridian. 

benchmark

Critical point in the analysis of a system or operation. Used as a verb to describe the action of evaluating a system or operation. Used as a noun when referring to a test that is used to determine system capabilities. 

blanking -- raster

A DTM raster operation. Blanking indicates that parts of grid or raster data should be excluded from analysis. For example, blanking may be used to prevent a contouring algorithm from generating contours over an area that has not been sampled. 

blind interchange

Refers to an automated data exchange process where the exchange format contains information on what is to be exchanged and how it should be handled (is self describing). 

boolean operations

Logical operations performed on sets. The result of these operations is either "TRUE" or "FALSE". The BOOLEAN operators include: 'and', 'or', 'not' (negation), 'xor' (exclusive or) and their combinations. 

boundary

Specifically, the dividing line between political states. In general, the division or dividing line between discrete entities, e.g., division between geological features, social areas, climatic zones, etc. 

buffering -- raster

Buffering as a raster operation -- the classification of pixels by their distance from a specific feature (represented by a point, line, or area). 

buffering -- vector

Buffering as a vector operation -- the determination of distance zones from a selected coverage feature (which may be a point, line, or polygon). This operation often includes the rebuilding of topology for the new coverage with the distance zones (buffers) defined as polygons. 

byte

Common unit of computer storage. A single byte can be used to store a single character or a number from 0 to 255. A byte holds 8 bits of binary data. 

C

CAD and CADD

Acronyms for Computer Aided Drafting and Computer Aided Design and Drafting. Often these acronyms are used interchangeably. 

cadastral map

Map showing boundaries of land subdivision for legal and ownership purposes. Often the dimensions of the boundaries are included. Map may sometimes show features relating to land use. 

cadastre

Survey that creates information (boundaries, subdivisions, etc.) from which a cadastral map may be produced. 

calibration -- when modeling

Process of fitting and adjusting a theoretical model to a particular data set. 

CAM

Acronym that usually stands for Computer Aided Manufacturing, which uses computer graphic systems (in one way or another) to assist in producing maps. In GIS, it refers to Computer Aided Mapping or Computer Automated Mapping.

Canadian Council on Geomatics (CCOG)

Previous called the Canadian Council of Surveying and Mapping (CCSM). Consists of federal and provincial government representatives. Has undertaken standards activities relating to topographic features and data exchange for a number of years. 

cardinal points

Principal directions. In GIS applications this usually consists of N, NE, E, SE, S, SW, W, NW. 

cartesian coordinates

Coordinate system in which the location of points in space are given by reference to three orthogonal planes, called coordinate planes. 

cartogram

See topological map

cartographic enhancement

Addition of names, boundaries, and other information to a map base. 

cartography

Science of map and chart construction. 

catchment area

Area drained by a river. Sometimes the catchment area is referred to as the watershed of the river. Properly, the catchment area is defined by a surrounding watershed or divide. 

CCOG

See Canadian Council on Geomatics

CCOGIF

Canadian Council on Geomatics (CCOG) Interchange Format. This format was previously referred to as the CCSM format (from Canadian Council on Surveying and Mapping - the previous name of CCOG). CCOGIF is designed for the exchange of topographic data and is built upon a sequential tape storage format. 

CCSM

Canadian Council on Surveying and Mapping. Now known as Canadian Council on Geomatics (CCOG). In the past the acronym CCSM was also used to refer to the topological digital exchange format being promoted by the Council. This format is now known by the acronym CCOGIF. 

ceiling/floor display

Display technique that shows both a 2-D and a 3-D representation of a surface. A 3-D representation of the surface is shown with the corresponding 2-D (flat) projection of the surface usually displayed beneath. 

cell

Basic element of information in a raster or grid description of spatial data. Its shape is usually rectangular and it has an implicitly defined size and geographic position (due to its position within the grid). 

census tract

U.S. Census Bureau's term for enumeration district. Smallest area for which census data is collected and reported on. 

census

Collection of demographic and socio-economic information on the population (or samples of the population) in well defined areas at a particular time. 

centroid

Selected coordinate point usually within an area (a polygon) on a map. In a GIS, a centroid is usually associated with a polygon. See seed point 

CGM

Computer Graphics Metafile. Used for the exchange of graphic images between different types of display devices. 

chart

Map used for nautical or aeronautical purposes. 

check plot

Graphic produced from digital data in a GIS and used to verify positional accuracy by overlaying on the original source graphic from which the data was captured. Check plots are usually produced on transparent or translucent material. 

choropleth map

Map that represents area based data using different grey shades, colours, or patterns. 

class

In general, any set of things that can be distinguished from others on the basis of some quality or quantity. 

classification

In general, the systematic grouping of things or events into classes. 

classification -- raster

As a raster operation -- assigning of codes or values to cells according to some classification criteria, e.g., all cells that have a value between 10 and 15 are assigned the value of 2. Sometimes the process of classification is referred as reclassification. 

classification -- vector

As a vector operation -- assigning of a new attribute value based on an arbitrary algorithm. 

clipping -- general

Permanent elimination of parts of a coverage located outside (and often an option is given for inside) given limits or boundaries. 

clipping -- raster

As a raster operation -- elimination of raster elements outside spatial limits. This does not necessarily (and usually does not) mean that the raster cells are gone, but rather they no longer have any value. 

closed-loop/loopback test -- data exchange

Test where data in one system is transmitted to another system, processed, and then transmitted back to the originating system. The original data and the subsequent processed data should be the same. 

COGO

COordinate GeOmetry analysis system. See coordinate geometry system. 

command line

Instruction that has been entered at the command line location is often referred to as the command line. 

command line location

Location on a display or screen where the system prompts the user to enter a command. A command is an instruction of some form (usually from the keyboard). 

command-driven

Refers to a system that accepts typed in letters and words (commands) specifying actions to be performed. This is contrast to menu or icon driven systems that provide options to be selected. 

Committee on Geomatics -- CGSB

A committee under the Canadian General Standards Board assigned the task of developing a number of national standards in the area of geomatics/GIS. Aim is "to develop/adopt standards for the sharing of geomatics data". A number of sub-committees have been established to deal with data transfer/interchange, data modelling, feature classification, and data dictionary/cataloguing. 

compression

Techniques/procedures used to reduce the amount of storage space required to store information. 

computer aided drafting/mapping

See CAM 

computer assisted mapping (CAM)

See CAM 

connectivity analysis

Identification of areas/points connected (or not connected) to other areas/points by means of linear features. 

contiguity analysis

Identification of areas that have a common boundary or node, e.g., identification of all land parcels bordering a landfill location. 

contour line

Line on a map connecting points with equal elevation. The difference in value between two adjacent contour lines is known as the contour interval. Often the word contour is used when describing isolines. 

control points

Points whose location is considered accurate and that are used as a reference by other points in a data set. 

coordinate geometry system

System used for entering and calculating geometric coordinates that may be applied to survey control, highway design, right-of-way surveys, bridge geometry, subdivision work, land surveying, and construction layout. Often the word "COGO" is used to generically describe all packages that possess similar geometric functions. 

coordinates

Pairs or triplets of values (may be linear or angular) used to designate the position of a point. 

cost surface

3D surface where relief is used to indicate cost values or estimates. Low areas usually indicate low cost and high areas indicate high cost. Cost may be economic, environmental, etc. 

coverage

Refers to all of the graphic and attribute information (in one or more files) related to a specific area of interest. 

coverage management facilities

System that facilitates the manipulation of a set of data files or data sets defining a coverage. 

cross-section

Usually refers to profile revealed when a vertical plane is intersected with data contained in a digital terrain model. 

CUI

Acronym for character-based user interface. Traditional type of user interface. 

curvature

Mathematically, is the second derivative of terrain elevation. Is an important feature in shape analysis and is used to indicate convexity/concavity of a surface. 

cut and fill

Procedure to determine change in volume given a DTM and a modified version of that DTM. This is often used to determine the amount of material (e.g. soil) that must be removed or added to achieve a new landscape.