Glossary             [A-D] - [E-J] - [K-P] - [Q-S] - [T-Z]

100-percent data
Information based on a limited number of basic population and housing questions collected from every inhabitant and housing unit in the United States.
Related term: Sample data

Accuracy*
The validity of data measured with respect to an independent source of higher reliability and precision.

Advanced Query
Advanced Queries are built by combining up to three individual queries. Each of these individual queries are basically simple queries where a field, a comparison operator and a value are specified. Each of the individual queries is then combined into a complex query using either AND or OR.

Age
Age is generally derived from date of birth information, and is based on the age of the person in complete years.

American Indian Areas
A Census Bureau term referring to these types of geographic areas: federal and state American Indian reservations, tribal designated statistical area, and state designated American Indian statistical area.

American Indian reservation
Land that has been set aside for the use of the tribe. There are two types of American Indian reservations, federal and state. These entities are designated as colonies, communities, pueblos, ranches, rancherias, reservations, reserves, tribal towns, and villages.

American Indian Reservation - federal
Areas with boundaries established by treaty, statute, and/or executive or court order recognized by the federal government as territory in which American Indian tribes have primary governmental authority. The U.S. Census Bureau contacts representatives of American Indian tribal governments to identify the boundaries. The Bureau of Indian Affairs (BIA) maintains a list of federally recognized tribal governments.

American Indian Reservation - state
Lands held in trust by state governments for the use and benefit of a given tribe. A governor-appointed state liaison provides the names and boundaries for state reservations. The names of the American Indian reservations recognized by state governments, but not by the federal government, are followed by "(state)" in the data presentations.

American Indian Tribal Subdivision
Administrative subdivisions of federally recognized American Indian reservations, known as an area, chapter, community, or district. Internal units of self-government or administration that serve social, cultural, and/or economic purposes for American Indians. Provided in 1980 as "American Indian subreservation areas." These areas were not available in 1990.

Amphibian Species Richness - see "Species Richness"

Ancestry
Refers to a person's self-identification of heritage, ethnic origin, descent, or close identification to an ethnic group.
Related terms: Nationality

Annual payroll (in thousands of dollars)
Payroll includes all forms of compensation, such as salaries, wages, commissions, dismissal pay, bonuses, vacation allowances, sick-leave pay, and employee contributions, to qualified pension plans paid during the year to all employees. For corporations, payroll includes amounts paid to officers and executives; for unincorporated businesses, it does not include profit or other compensation of proprietors or partners. Payroll is reported before deductions for social security, income tax, insurance, union dues, etc. This definition of payroll is the same as that used by the Internal Revenue Service (IRS) on Form 941.

Apportionment
The process of dividing up the 435 memberships, or seats, in the U. S. House of Representatives among the 50 states. The Census Bureau's role in apportionment is to conduct the census every 10 years as mandated by the Constitution. Apportionment does not affect Puerto Rico.
Related terms: Decennial census, Reapportionment, Redistricting

Apportionment population
The total resident population (citizens and non-citizens) of the 50 states. In Census 2000, the apportionment population also includes U.S. Armed Forces personnel and federal civilian employees stationed outside the United States (and their dependents living with them) that can be allocated, based on administrative records, back to a home state. This is the same procedure used in 1990. Private U.S. citizens living abroad, who are not employed by the Federal government are not included in the overseas counts for apportionment.
Related terms: Population, Resident population

Aquifer 1
A a water-bearing layer of rock or sediment capable of yielding supplies of water; typically is unconsolidated deposits or sandstone, limestone or granite. Can be classified as confined or unconfined.

Arc*
A line represented as a set of sequential points.

Area
The size, in square miles or square meters, recorded for each geographic entity.

Asian
Self-identification among people of Asian descent.

In 1997, the Federal Office of Management and Budget (OMB) revised the standards for how the Federal government would collect and present data on race and ethnicity. These new guidelines revised some of the racial categories used in 1990 and preceding censuses and allowed respondents to report as many race categories as were necessary to identify themselves on the Census 2000 questionnaire.
Related terms: Census (decennial), Race

Attribute*
A characteristic of a feature that contains a measurement or value for the feature. Attributes can be labels, categories, or numbers; they can be dates, standardized values, or field or other measurements. An item for which data are collected and organized. A column in a table or data file.

Average
The number found by dividing the sum of all quantities by the total number of quantities.
Related terms: Mean, Median

Average family size
A measure obtained by dividing the number of members of families by the total number of families (or family householders).
Related term: Family

Average household size
A measure obtained by dividing the number of people in households by the total number of households (or householders).
Related term: Household

Average household size of owner-occupied units
A measure obtained by dividing the number of people living in owner-occupied housing units by the number of owner-occupied housing units.
Related term: Owner-occupied housing unit

Average household size of renter-occupied units
A measure obtained by dividing the number of people living in renter-occupied housing units by the number of renter-occupied housing units.
Related term: Renter-occupied housing unit

Basic Query
Basic Queries are simple queries where you are allowed to search for particular features by name. For each basic query, enter all or part of a particular feature name you are looking Measure -- interactively measures the distance (in both miles and kilometers) between two points on the map.

Bird Species Richness - see "Species Richness"

Border*
The area between the neat line and the edge of the medium or display area on which a map is being displayed. Occasionally, information can be placed within the border, but this area is usually left blank.

Boundary
The extent or limit of a geographic area such as a block, census tract, county, or place. A boundary may or may not follow a visible geographic physical feature.

Bounding rectangle*
The rectangular region defined by the maximum extent of a map feature in the x and y directions. All parts of the feature must lie within or on the edge of the bounding rectangle.

Browse*
A method of search involving repeated examination of records until a suitable one is found.

Business and the Economy (Map theme)
This map theme focuses on Arizona's economy and includes employment statistics, agricultural output and mining. It focuses on communities such as counties, census tracts, and American Indian areas. Using this theme will allow you to view the types of products Arizona growers produce as well as the locations of farming and livestock grazing. Additionally, you can map employment rates and business statistics. The information comes primarily from federal sources such as the U.S. Bureau of the Census and the U.S. Department of Agriculture.

Cartographic elements*
The primitive component part out of which a map is assembled, such as the neat line, legend, scale, titles, figure, and so on.

Cartography*
The science, art, and technology of making, using, and studying maps.

CD-ROM*
Compact disk read-only memory, a hardware storage device capable of making extensive data and software available for distribution on removable CDs or as off-line storage for a microcomputer.

Census
A complete enumeration, usually of a population, but also of businesses and commercial establishments, farms, governments, and so forth.

Census (decennial)
The census of population and housing, taken by the Census Bureau in years ending in 0 (zero). Article I of the Constitution requires that a census be taken every ten years for the purpose of reapportioning the U.S. House of Representatives.
Related terms: Apportionment, Reapportionment, Redistricting

Census (economic)
Collective name for the censuses of construction, manufactures, minerals, minority- and women-owned businesses, retail trade, service industries, transportation, and wholesale trade, conducted by the Census Bureau every five years, in years ending in 2 and 7.

Census designated place (CDP)
A statistical entity, defined for each decennial census according to Census Bureau guidelines, comprising a densely settled concentration of population that is not within an incorporated place, but is locally identified by a name. CDPs are delineated cooperatively by state and local officials and the Census Bureau, following Census Bureau guidelines. Beginning with Census 2000 there are no size limits.
Related term: Incorporated place

Census geography
A collective term referring to the types of geographic areas used by the Census Bureau in its data collection and tabulation operations, including their structure, designations, and relationships to one another.

Census tract
A small, relatively permanent statistical subdivision of a county delineated by a local committee of census data users for the purpose of presenting data. Census tract boundaries normally follow visible features, but may follow governmental unit boundaries and other non-visible features in some instances; they always nest within counties. Designed to be relatively homogeneous units with respect to population characteristics, economic status, and living conditions at the time of establishment, census tracts average about 4,000 inhabitants. They may be split by any sub-county geographic entity.

Child
A son or a daughter by birth, a stepchild, or an adopted child of the householder, regardless of the child's age or marital status.
Related terms: Own children, Related children

City
A type of incorporated place in 49 states and the District of Columbia. In 23 states and the District of Columbia, some or all cities are not part of any Minor Civil Division (MCD), and the Census Bureau also treats these as county subdivisions, statistically equivalent to MCDs.
Related terms: Incorporated place

Clarity*
The property of visual representation using the absolute minimum amount of symbolism necessary for the map user to understand map content without error.

Climate 2
The average of weather over at least a 30-year period. Note that the climate taken over different periods of time (30 years, 1000 years) may be different. The old saying is climate is what we expect and weather is what we get.

Color balance*
The achievement of visual harmony between colors on a map, primarily by avoiding colors that show simultaneous contrast when adjacent to each other.

Compression*
Any technique that reduces the physical file size of data in a spatial or other data format.

Computer mapping*
Producing maps using the computer as the primary or only tool.

Congressional district (CD)
An area established by law for the election of representatives to the United States Congress. Each CD is to be as equal in population to all other CDs in the state as practicable, based on the decennial census counts. The number of CDs in each state may change after each decennial census, and the boundaries may be changed more than once during a decade.
Related terms: Apportionment, Reapportionment, Redistricting

Contour interval*
The vertical difference in measurement units such as meters or feet between successive contour lines on a contour map.

Contour map*
An isoline map of topographic elevations.

Contract rent
The monthly rent agreed to or contracted for, regardless of any furnishings, utilities, fees, meals, or services that may be included. For vacant units, it is the monthly rent asked for the rental unit at the time of interview.
Related term: Gross rent

Coordinate pair*
An easting and northing in any coordinate system, absolute or relative. Together these two values, usually termed (x, y) describe a location in two-dimensional geographic space.

Coordinate system*
A system with all the necessary components to locate a position in two- or three-dimensional space: that is, an origin, a type of unit distance, and axes.

Coverage
see Layer

Data*
A set of measurements or other values, such as text for at least one attribute and at least one record.

Data dictionary*
The part of a database containing information about the files, records, and attributes rather than just the data.

Data format*
A specification of a physical data structure for a feature or record.

Data retrieval*
The ability of a database management system to get back from computer memory records that were previously stored there.

Data structure*
The logical and physical means by which a map feature or an attribute is digitally encoded.

Database*
The body of data that can be used in a database management system. A GIS has both a map and an attribute database.

Database manager*
A computer program or set of programs that allows a user to define the structure and organization of a database, to enter and maintain records in the database, to perform sorting, data reorganization, and searching, and to generate useful products such as reports and graphs.

Datum*
A base reference level for the third dimension of elevation for the earth's surface. A datum can depend on the ellipsoid, the earth model, and the definition of sea level.

DBMS*
Database management system. Part of a GIS, the set of tools that allow the manipulation and use of files containing attribute data.

Decennial census
The census of population and housing, taken by the Census Bureau in years ending in 0 (zero). Article I of the Constitution requires that a census be taken every ten years for the purpose of reapportioning the U.S. House of Representatives.
Related terms: Apportionment, Reapportionment, Redistricting

Default*
The value of a parameter or a selection provided for the user by the GIS without user modification.

DEM*
Digital elevation model. A raster format gridded array of elevations.

Desktop mapping*
The ability to generate easily a variety of map types, symbolization methods, and displays by manipulating the cartographic elements directly.

Digital elevation model*
A data format for digital topography, containing an array of terrain elevation measurements.

Digital orthophoto quad (DOQ)*
One element of a national mapping effort to cover the lower 48 United States at a 1-meter ground resolution with monochrome air photos in digital format with a 1:12,000 equivalent ground extent. Collections of DOQs are distributed compressed on CD-ROM.

Digital Raster Graphics (DRG's)*
A digital raster graphic is a scanned image of a United States Geological Survey (U.S.G.S.) topographic map. The map is georeferenced to actual locations on the earth. The accuracy and datum of the DRG matches the accuracy and datum of the source map. It is scanned at a minimum resolution of 250 dots/inch.

Disability
A long-lasting physical, mental, or emotional condition. This condition can make it difficult for a person to do activities such as walking, climbing stairs, dressing, bathing, learning, or remembering. This condition can also impede a person from being able to go outside the home alone or to work at a job or business.

Distortion*
The space distortion of a map projection, consisting of warping of direction, area, and scale across the extent of the map.

Download*
To move a file across a network for eventual residence locally.

Dueker's definition (of GIS)*
"A special case of information systems where the database consists of observations on spatially distributed features, activities or events, which are definable in space as points, lines, or areas. A geographic information system manipulates data about these points, lines, and areas to retrieve data for ad hoc queries and analyses."

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* Clarke, Keith C. Getting Started with Geographic Information Systems. 4th edition. Upper Saddle River, N.J., 2003.
1 EPA Groundwater Primer - http://www.purdue.edu/dp/envirosoft/groundwater/src/terms1.htm
2 National Weather Service Climate Prediction Center Glossary - http://www.cpc.ncep.noaa.gov/products/outreach/glossary.shtml
All other definitions from American Factfinder - http://factfinder.census.gov/servlet/BasicFactsServlet - click on Glossary

For other Glossaries, see http://www.gis.com/whatisgis/glossaries.html