GIS Glossary/C

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GIS Glossary

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C

C

A common, flexible, programming language.

C/A code

The standard PRN code used by most civilian GPS receivers.

C++

An object-oriented programming language, extended from C.

C4I

In defense, an abbreviation used to signify that a computer program or system supports command, control, communication, computers, and information.

CAD

Acronym for computer-aided design. A computer-based system for the design, drafting, and display of graphical information. Also known as computer-aided drafting, such systems are most commonly used to support engineering, planning, and illustrating activities.

CAD dataset

The feature representation of a CAD file in a geodatabase-enforced schema. A CAD feature dataset is comprised of five read-only feature classes: points, polylines, polygons, multipatch and annotation. ArcGIS supported formats include DWG (AutoCAD), DXF (AutoDesk Drawing Exchange Format), and DGN (the default Microstation file format).

CAD drawing

The digital equivalent of a drawing, figure, or schematic created using a CAD system.

CAD drawing dataset

The pictorial representation of an entire CAD file that can be viewed in any ArcGIS application with a display. The CAD drawing dataset is a vector data source of a mixed feature type in which the symbology is set to mimic that of the originating CAD application. The graphic properties of a CAD drawing dataset's objects can be identified, but the dataset is not usable for feature class-based queries or analysis.

CAD feature class

A read-only member of a CAD feature dataset, comprised of one of the following: polylines, points, polygons, multipatch, or annotation. The feature attribute table of a CAD feature class is a virtual table comprised of select CAD graphic properties and any existing field attribute values.

CAD feature dataset

The feature representation of a CAD file in a geodatabase-enforced schema. A CAD feature dataset is comprised of five read-only feature classes: points, polylines, polygons, multipatch and annotation. ArcGIS supported formats include DWG (AutoCAD), DXF (AutoDesk Drawing Exchange Format), and DGN (the default Microstation file format).

CAD file

The digital equivalent of a drawing, figure, or schematic created using a CAD system. CAD files are the data source for CAD drawing datasets, feature datasets and feature classes. ArcGIS software-supported formats include DWG (AutoCAD), DXF (AutoDesk Drawing Exchange Format), and DGN (the default Microstation file format). A CAD file is represented in ArcCatalog with a CAD feature dataset and a CAD drawing dataset.

CAD layer

A layer that references a set of CAD data. CAD data is vector data of a mixed feature type. CAD layers may be of two types: CAD drawing dataset layers, in which one map layer represents the entire CAD file, and CAD feature layers, in which data is organized by geometry type.

CAD staging geodatabase

A normalized, fixed set of feature classes and data tables of a predefined schema from a collection of input CAD drawings.

cadastral fabric

In Survey Analyst - Cadastral Editor, a network of connected parcels. Parcels are represented by parcel line features, parcel point features, and parcel polygon features, referred to in aggregate as parcel features. Parcel topology in the cadastral fabric is stored explicitly through shared or common parcel point features.

cadastral fabric accuracy levels

In Survey Analyst - Cadastral Editor, a number assigned to a parcel line that determines how much the line influences the coordinates that result from a least-squares adjustment. A line with a high accuracy level will have more influence than a line with a lower accuracy level. The highest accuracy level in the cadastral fabric is 1.

cadastral fabric history

In Survey Analyst - Cadastral Editor, the record of changes to the legal and system state of the cadastral fabric.

cadastral fabric job

In Survey Analyst - Cadastral Editor, a collection of parcels that have been extracted from the cadastral fabric for editing and least-squares adjustment. Parcels in the cadastral fabric are always edited in cadastral fabric jobs.

cadastral fabric layer

In Survey Analyst - Cadastral Editor, the map representation of a cadastral fabric for which display properties may be set; a layer in ArcMap that represents the cadastral fabric.

cadastral fabric line point

In Survey Analyst - Cadastral Editor, a point that allows a parcel corner to lie on an adjacent parcel boundary line without splitting the boundary line. Line points are constrained to lie on their parcel lines.

cadastral fabric parcel line

In Survey Analyst - Cadastral Editor, a parcel line feature in the cadastral fabric that contains dimension information. Represents parcel boundaries. Parcel lines connect up to form parcel polygons and always connect two point features in the cadastral fabric.

cadastral fabric parcel line category

In Survey Analyst - Cadastral Editor, a line type that defines how a parcel line in the cadastral fabric will be managed by the cadastral fabric editor. For example, connection lines are managed differently than boundary lines.

cadastral fabric parcel point

In Survey Analyst - Cadastral Editor, a point represents a parcel corner or the end of a connection line. A parcel point always has computed x- and y-coordinates.

cadastral fabric sublayer

In Survey Analyst - Cadastral Editor, an internal feature class that forms part of the cadastral fabric. Cadastral Fabric sublayers include lines, points, polygons, line points, and control points.

cadastral fabric topology

In Survey Analyst - Cadastral Editor, the topological relationships explicit in the cadastral fabric data model.

cadastral survey

A boundary survey taken for the purposes of ownership and taxation.

cadastre

An official record of the dimensions and value of land parcels, used to record ownership and assist in calculating taxes.

calibration

The comparison of the accuracy of an instrument's measurements to a known standard.

callout line

A line on a map extending between a feature's geographic position and its corresponding symbol or label, used in areas where there is not enough room to display a symbol or label in its correct location.

camera

In ArcScene and ArcGlobe, an object that defines the perspective of a scene or globe's display.

camera station

In aerial photography, each point in the flight path at which the camera exposes the film.

candidate

A record returned as a potential match for an address in the geocoding process.

candidate key

In a relational database, any key that can be used as the primary key in a table.

capacity

In location-allocation, the maximum number of people or units that a center can service, contain, or have assigned to it.

caption

In ArcGIS, the text for a command that appears with the "Text Only" and "Image and Text" display types. As part of the user interface, captions are customizable by the user.

cardinal direction

One of the four compass directions on the earth's surface: north, south, east, or west.

cardinal point

One of the four compass directions on the earth's surface: north, south, east, or west.

cardinality

The correspondence or equivalency between sets; how sets relate to each other. For example, if one row in a table is related to three rows in another table, the cardinality is one to many.

carrier

An electromagnetic wave, such as radio, with modulations that are used as signals to transmit information.

carrier-aided tracking

Signal processing that uses the GPS carrier signal to lock onto the PRN code generated by the satellite.

carrier-phase GPS

GPS measurements that are calculated using the carrier signal of a satellite.

carrying contour

A single line representing multiple coincident contour lines, used to show vertical topographic features such as cliffs, cuts, and fills.

Cartesian coordinate system

A two-dimensional, planar coordinate system in which horizontal distance is measured along an x-axis and vertical distance is measured along a y-axis. Each point on the plane is defined by an x,y coordinate. Relative measures of distance, area, and direction are constant throughout the Cartesian coordinate plane. The Cartesian coordinate system is named for the French mathematician and philosopher René Descartes (1596-1650).

cartogram

A diagram or abstract map in which geographical areas are distorted proportionally to the value of an attribute.

cartographer

One who practices the art and science of expressing graphically, usually through maps, the natural and social features of the earth.

cartographic generalization

The abstraction, reduction, and simplification of features so that a map is clear and uncluttered at a given scale.

cartography

The art and science of expressing graphically, usually through maps, the natural and social features of the earth.

cartouche

An ornamental frame on a map, usually around the map's title. Cartouches are rarely used on modern maps.

Cascading Style Sheets

A standard for defining the layout or presentation of an HTML or XML document. Style information includes font size, background color, text alignment, and margins. Multiple style sheets may be applied to "cascade" over previous style settings, adding to or overriding them. The World Wide Web Consortium maintains the CSS standard.

CASE

Acronym for computer-aided software engineering. Any software that assists with the development and maintenance of software, especially the analysis and design. Complex tasks that often require many lines of code are simplified with CASE user interfaces and code generators.

Catalog tree

In ArcCatalog, a hierarchical view of folder connections which provide access to GIS data stored on local disks or shared on a network that allows users to manage connections to databases and GIS servers.

catchment

A basin-like terrestrial region consisting of all the land that drains water into a common terminus.

categorical raster

A raster that typically represents phenomena that have clear boundaries with attributes that are descriptions, classes, or categories. Generally, integers are used for the cell values. In a raster of land cover, for example, the value 1 might represent forestland, the value 2 urban land, and so on. It is assumed that the phenomena that each value represents fill the entire area of the cell. Rasters representing land use, political boundaries or ownership are examples of discrete rasters.

category

In ArcWeb Services, a collection of related data files, layers, data sources, or classes that show the primary use for data and help with display and navigation. Administrative, cultural, and elevation are examples of categories within ArcWeb Services.

CATID

Acronym for Component Category ID. A unique string assigned to locally related COM classes to group them together. A CATID is a type of Globally Unique IDentifier (GUID).

CBSA

A geographic region containing at least one urban area with a population of at least 10,000, defined by the U.S. Office of Management and Budget for use by federal statistical agencies, including the U.S. Census Bureau. A core-based statistical area can be a metropolitan statistical area or a micropolitan statistical area.

CD

An optical disk, slightly less than 5 inches in diameter, used to store up to approximately 650 megabytes of data.

celestial sphere

The sky, considered as the inside of a sphere of infinitely large radius that surrounds the earth, on which all celestial bodies except the earth are imagined to be projected.

cell

The smallest unit of information in raster data, usually square in shape. In a map or GIS dataset, each cell represents a portion of the earth, such as a square meter or square mile, and usually has an attribute value associated with it, such as soil type or vegetation class.

cell selection

The process of selecting raster cells either interactively or by using a SQL query.

cell size

The dimensions on the ground of a single cell in a raster, measured in map units. Cell size is often used synonymously with pixel size.

cell statistics

An ArcGIS Spatial Analyst function that calculates a statistic for each cell of an output raster that is based on the values of each cell in the same location of multiple input rasters.

cellular automaton

A mathematical construction consisting of a row or grid of cells in which each cell has an initial value—from a known and limited number of possible values—and all cells are simultaneously evaluated and updated according to their internal states and the values of their neighbors. The simplest cellular automaton is a row in which each cell has one of two values, such as red or green. In this case, there are eight possible value combinations for a cell and its neighbors. (If a green cell with two red neighbors is notated RGR, then the eight combinations are RRR, RRG, RGR, GRR, RGG, GRG, GGR, GGG.) A set of rules determines whether or not a cell changes value when it is evaluated. A sample rule might be, "A green cell becomes red if it has a red neighbor on both sides." Successive updates, or generations, of a cellular automaton may produce complex patterns. Cellular automata are of interest in spatial modeling and are often used to model land-cover change.

census block

The smallest geographic entity for which the U.S. Census Bureau tabulates decennial census data. Many blocks correspond to city blocks bounded by streets, but blocks in rural areas may include several square miles and have some boundaries that are not streets. The Census Bureau established blocks covering the entire nation for the first time in 1990. Previous censuses dating back to 1940 had blocks established only for part of the nation.

census geography

Any one of various types of precisely defined geographic areas used by the U.S. Census Bureau to collect and aggregate data. The largest unit of area is the entire United States, while the smallest is a census block.

census tract

A small, statistical subdivision of a county that usually includes approximately 4,000 inhabitants but may include from 2,500 to 8,000 inhabitants. A census tract is designed to encompass a population with relatively uniform economic status, living conditions, and some demographic characteristics. Tract boundaries normally follow physical features but may also follow administrative boundaries or other nonphysical features. A census tract is a combination of census block groups.

center

The point in a circle or in a sphere equidistant from all other points on the object.

centerline

A line digitized along the center of a linear geographic feature, such as a street or a river, that at a large enough scale would be represented by a polygon.

centerline vectorization

The generation of vector features along the center of connected cells. It is typically used for vectorizing scanned parcel and survey maps.

centerpoint

In aerial photography, the point at the exact center of an aerial photograph.

central meridian

The line of longitude that defines the center and often the x-origin of a projected coordinate system. In planar rectangular coordinate systems of limited extent, such as state plane, grid north coincides with true north at the central meridian.

centroid

The geometric center of a feature. Of a line, it is the midpoint; of a polygon, the center of area; of a three-dimensional figure, the center of volume.

CGI

Acronym for Common Gateway Interface. A standard for scripts that run external programs from a World Wide Web server. CGI typically specifies how to pass arguments to the program via HTTP requests; defines a set of environmental variables made available to the program; and generates output, usually in HTML format, that is passed back to the browser. CGI scripts are frequently designed to access information in a database and format the results as HTML, convert information retrieved from an interactive Web page into a database, send datasets, and so on.

chain

A unit of length equal to 66 feet, used especially in U.S. public land surveys. Ten square chains equal 1 acre.

chain code

A method of drawing a polygon as a series of straight line segments defined as a set of directional codes, with each code following the last like links in a chain.

change detection

A process that measures how the attributes of a particular area have changed between two or more time periods. Change detection often involves comparing aerial photographs or satellite imagery of the area taken at different times. The process is most frequently associated with environmental monitoring, natural resource management, or measuring urban development.

character

A letter, digit, or special graphic symbol treated as a single unit of data and usually stored as one byte.

chart

A map used to plot a course for air or water navigation.

check-in

In disconnected editing, the procedure that transfers a copy of data into a master geodatabase, overwriting the original copy of that data and reenabling it so it can be accessed and saved from that location. In checkout/check-in replication, check-in is the procedure that synchronizes the data in the parent replica with that in the child replica.

checkout

A procedure in disconnected editing that records the duplication of data from one geodatabase to another and disables the original data so that both versions cannot be accessed or saved at the same time.

checkout geodatabase

In ArcGIS versions 8.3–9.1, a personal or ArcSDE geodatabase that contains data checked out from a master geodatabase during disconnected editing.

checkout version

The data version created in a checkout geodatabase when data is checked out to that database during disconnected editing. The checkout version is created as a copy of the synchronization version. Only the edits made to this checkout version can be checked back in to the master geodatabase.

checkout/check-in replication

A type of geodatabase replication that involves copying data to a destination geodatabase, editing that data in the destination, and then merging the changes with the source geodatabase. In ArcGIS and ArcSDE, the destination can be a file, personal, or ArcSDE geodatabase, while the source must be an ArcSDE geodatabase. Once the data is merged (synchronized), checkout/check-in replication is completed.

child replica

In geodatabase editing, data that has been copied to a destination geodatabase during the replication process.

chi-square statistic

A statistic used to assess how well a model fits the data. It compares categorized data with a multinomial model that predicts the relative frequency of outcomes in each category to see to what extent they agree.

chord

A straight line that joins two points on a curve.

choropleth map

A thematic map in which areas are distinctly colored or shaded to represent classed values of a particular phenomenon.

chroma

The saturation, purity, or intensity of a color.

chronometer

An extremely accurate clock that remains accurate through all conditions of temperature and pressure. The chronometer was developed in the eighteenth century for determining longitude at sea, but its scientific and navigational use has been made obsolete by the invention of quartz and atomic clocks.

CHUM

Acronym for Chart Updating Manual. A document containing updates to aeronautical information, used by the U.S. military to update their current published products with the latest information.

circle

A two-dimensional geometric shape for which the distance from the center to any point on the edge is equal; the closed curve defining such a shape.

circular arc

A curved line that is a section of a circle, with two vertices, one situated at each endpoint.

circular variance

A measure of directional variation, on a scale from zero to one, among a set of line vectors. Circular variance approaches zero when all vectors point in roughly the same direction and approaches one when the vectors point in markedly different directions.

civilian code

The standard PRN code used by most civilian GPS receivers.

Clarke Belt

An orbit 22,245 miles (35,800 kilometers) above the equator in which a satellite travels at the same speed that the earth rotates. The Clarke Belt was named after the writer and scientist Arthur C. Clarke. It is also referred to as a geostationary orbit.

Clarke ellipsoid of 1866

A reference ellipsoid having a semimajor axis of approximately 6,378,206.4 meters and a flattening of 1/294.9786982. It is the basis for the North American Datum of 1927 (NAD27) and other datums. The Clarke ellipsoid of 1866 is also known as the Clarke spheroid of 1866.

Clarke spheroid of 1866

A reference ellipsoid having a semimajor axis of approximately 6,378,206.4 meters and a flattening of 1/294.9786982. It is the basis for the North American Datum of 1927 (NAD27) and other datums. The Clarke ellipsoid of 1866 is also known as the Clarke spheroid of 1866.

class

A set of entities grouped together on the basis of shared attribute values.

class identifier

A COM term referring to the globally unique number that is used by the system registry and the COM framework to identify a particular coclass.

class intervals

A set of categories for classification that divide the range of all values so that each piece of data is contained within a nonoverlapping category.

classification

The process of sorting or arranging entities into groups or categories; on a map, the process of representing members of a group by the same symbol, usually defined in a legend.

classification table

An ASCII file in the geocoding rule base that identifies and classifies keywords that may appear in an address, such as street types and directions. Classification tables have a .cls file extension.

CLDC

Acronym for Connected Limited Device Configuration. A framework for developing J2ME applications for devices with very limited resources, such as wireless devices.

clean data

Data that is free from error.

cleaning

Improving the appearance of scanned or digitized data by correcting overshoots and undershoots, closing polygons, performing coordinate editing, and so on.

clearinghouse

A repository structure, physical or virtual, that collects, stores, and disseminates information, metadata, and data. A clearinghouse provides widespread access to information and is generally thought of as reaching or existing outside organizational boundaries.

client

An application, computer, or device in a client/server model that makes requests to a server.

client sample

A set of live and downloadable code samples designed to show users how to access an ArcWeb service. The live samples allow users to interact with an ArcWeb service using a browser. The downloadable code samples are available in several programming languages.

client/server architecture

A software system with a central processor (server) that accepts requests from one or more user applications, computers, or devices (clients). Although client/server architecture can exist on one computer, it is more relevant to (and is typically thought of as relating to) network systems that distribute applications over computers in different locations.

client-side address locator

An address locator that is created and used on the same computer.

clinometric map

A map that represents slope with colors or shading.

clip

A command that extracts features from one feature class that reside entirely within a boundary defined by features in another feature class.

cloning

In object-oriented programming, the process of creating a new instance of a class with the same state as an existing instance.

close coupling

A high or complex degree of interconnections between the components within a program or between programs, that requires substantial overlap between methods, ontologies, class definitions, and so on.

closed loop traverse

In surveying, a traverse that starts and ends with the same survey point.

closest facility analysis

In ArcGIS Network Analyst, a type of network analysis for finding the closest locations (facilities) from sites (incidents), based on the impedance chosen—for example, finding hospitals near a car accident. When finding closest facilities, users can specify how many to find and whether the direction of travel is toward or away from the site (incident). Users can also specify a cutoff threshold beyond which ArcGIS Network Analyst will not search for a facility—for example, finding hospitals within 6 miles of a car accident.

closure error

A discrepancy between existing coordinates and computed coordinates that occurs when the final point of a closed traverse has known coordinates and the final course of a traverse computes different coordinates for the same survey point.

closure report

The summary of the difference between the endpoint coordinate of a traverse and the calculated endpoint.

CLR

Acronym for common language runtime. The execution engine for .NET Framework applications, providing services such as code loading and execution and memory management.

CLSID

Acronym for class identifier. A COM term referring to the globally unique number that is used by the system registry and the COM framework to identify a particular coclass.

cluster analysis

A statistical classification technique for dividing a population into relatively homogeneous groups. The similarities between members belonging to a class, or cluster, are high; while similarities between members belonging to different clusters are low. Cluster analysis is frequently used in market analysis for consumer segmentation and locating customers, but it is also applied to other fields.

cluster tolerance

The minimum tolerated distance between vertices in a topology. Vertices that fall within the set cluster tolerance are snapped together during the topology validation process.

clustering

A part of the topology validation process in which vertices that fall within a specified distance (cluster tolerance) of each other are snapped together.

CMYK

A color model that combines the printing inks cyan, magenta, yellow, and black to create a range of colors. Most commercial printing uses this color model.

CNT

A component of the PLTS knowledge base that contains SQL statements and custom code for feature validation extended beyond standard geodatabase domains. PLTS utilizes condition tables for enhanced validation during both database production and quality control.

Coarse/Acquisition code

The standard PRN code used by most civilian GPS receivers.

coclass

A template for an object that can be instantiated in memory.

coded value domain

A type of attribute domain that defines a set of permissible values for an attribute in a geodatabase. A coded value domain consists of a code and its equivalent value. For example, for a road feature class, the numbers 1, 2, and 3 might correspond to three types of road surface: gravel, asphalt, and concrete. Codes are stored in a geodatabase, and corresponding values appear in an attribute table.

code-phase GPS

GPS measurements calculated using the PRN code transmitted by a GPS satellite.

cognitive map

A person's perception of a place. A mental map may include the physical characteristics of a place, such as boundaries of a neighborhood, or the attributes of a place, such as a neighborhood's perceived unsafe areas. A mental map is primarily a psychological construct, although it may also be rendered as an actual map.

COGO

Acronym for coordinate geometry. A method for calculating coordinate points from surveyed bearings, distances, and angles.

COGO composite measurement

In Survey Analyst for field measurements, measurements that comprise a set of interdependent COGO simple measurements.

COGO simple measurement

In Survey Analyst for field measurements, measurements that model values that define vectors, directions, lengths, and orthogonal offsets.

coincident

Occupying the same space. Coincident features or parts of features occupy the same space in the same plane.

coincident geometry

In a geodatabase, how the coordinates of coincident features are stored. For example, if two lines are coincident, they will both be drawn in ArcMap, with one line lying precisely on top of the other. For two adjacent polygons, the coordinates for the shared boundary will be stored with each polygon and the boundary will be drawn twice.

cokriging

A form of kriging in which the distribution of a second, highly correlated variable (covariate) is used along with the primary variable to provide interpolation estimates. Cokriging can improve estimates if the primary variable is difficult, impossible, or expensive to measure, and the second variable is sampled more intensely than the primary variable.

ColdFusion

A Macromedia software product that integrates databases and Web pages using a server and development tools. ColdFusion Web pages include elements written in ColdFusion Markup Language that simplify integration with databases.

ColdFusion Connector

An ArcIMS Application Server Connector. In this environment, a request that includes ColdFusion tags is first executed on the ColdFusion Server. The ArcIMS custom ColdFusion tags are then passed to the ArcIMS Application Server for processing.

color composite

A color image made by assigning red, green, and blue colors to each of the separate monochrome bands of a multispectral image and then superimposing them.

color map

A set of values that are associated with specific colors. Color maps are most commonly used to display a raster dataset consistently on many different platforms.

color model

Any system that organizes colors according to their properties for printing or display. Examples include RGB (red, green, blue), CMYK (cyan, magenta, yellow, black), HSB (hue, saturation, brightness), HSV (hue, saturation, value), HLS (hue, lightness, saturation), and CIE-L*a*b (Commission Internationale de l'Eclairage-luminance, a, b).

Color Palette

In ArcWeb Services, a tool for selecting colors and transparency. The Color Palette lets a user select an object's fill and outline color by choosing from a color spectrum or by defining colors numerically. A user can also define the transparency of the color for an object.

color ramp

A range of colors used to show ranking or order among classes on a map.

color separation

In printing, the use of a separate printing plate for each ink color used.

column

An item in an attribute table.

COM

Acronym for Component Object Model. A binary standard that enables software components to interoperate in a networked environment regardless of the language in which they were developed. Developed by Microsoft, COM technology provides the underlying services of interface negotiation, life-cycle management (determining when an object can be removed from a system), licensing, and event handling. The ArcGIS system is created using COM objects.

COM contract

The COM requirement that interfaces, once published, cannot be altered.

COM interface

A grouping of logically related virtual functions, implemented by a server object, allowing a client to interact with the server object. Interfaces form the basis of COM’s communication between objects and the basis of the COM contract.

combinatorial operator

A kind of mathematical operator that interprets input with Boolean values. Combinatorial operators assign a different number to each unique combination of input values.

combo box

A user interface tool that combines the features of a text box and a drop-down list. For example, the Location combo box in ArcCatalog allows the selection of an item in the Catalog tree by typing its path or choosing its path from a drop-down list.

command

An instruction to a computer program, usually one word or concatenated words or letters, given by the user from a control device, such as a keyboard, or read from a file by a command interpreter.

command bar

A toolbar, menu bar, menu, or shortcut menu in an ArcGIS application.

command line

A string of text that acts as a command, typed at an interface prompt.

command line interface

A format of the input and output of a program in which the user enters commands by means of strings of text typed on a keyboard, as opposed to selecting commands from graphical prompts such as icons or dialog boxes.

Command Line Window

In geoprocessing, a window that provides a command line for running tools and a message window for viewing the status messages created when running those tools.

command prompt window

A window accessible from the Windows Start menu in which MS-DOS commands are typed.

comment

In Survey Analyst for field measurements, a field that provides additional information about the computation.

commercial off-the-shelf

Commercially available software or systems that are ready to use and which do not require significant customization.

committed read

The isolation level in a database management system (DBMS) in which transactions read committed data only — they don't read data that has not been committed.

Common Gateway Interface

A standard for scripts that run external programs from a World Wide Web server. CGI typically specifies how to pass arguments to the program via HTTP requests; defines a set of environmental variables made available to the program; and generates output, usually in HTML format, that is passed back to the browser. CGI scripts are frequently designed to access information in a database and format the results as HTML, convert information retrieved from an interactive Web page into a database, send datasets, and so on.

common language runtime

The execution engine for .NET Framework applications, providing services such as code loading and execution and memory management.

compact disc

An optical disk, slightly less than 5 inches in diameter, used to store up to approximately 650 megabytes of data.

compaction

A process that rearranges and consolidates the data in a file so that it occupies a single, contiguous space, allowing the data in each file to be accessed more efficiently.

comparison threshold

The degree of uncertainty that can be tolerated in the spelling of a keyword used in a search, including phonetic errors and the random insertion, deletion, replacement, or transposition of characters.

compass

An instrument used to find the direction of north from one's current location, consisting of a case with compass points marked around its edge and a floating magnetic needle that pivots to point to magnetic north.

compass north

The direction from a point on the earth's surface following a great circle toward the magnetic north pole, indicated by the north-seeking end of a compass.

compass point

An indication of direction. One of the 32 divisions into which the circle around the needle of a compass is divided, each equal to 11.25 degrees.

compass rose

A diagram of compass points drawn on a map or chart, subdivided clockwise from 0 to 360 degrees with 0 indicating true north. On older maps and charts a compass rose was a decorated diagram of cardinal points, divided into 16 or 32 points.

compass rule

A widely used rule for adjusting a traverse that assumes the precision in angles or directions is equivalent to the precision in distances. This rule distributes the closure error over the whole traverse by changing the northings and eastings of each traverse point in proportion to the distance from the beginning of the traverse. More specifically, a correction factor is computed for each point as the sum of the distances along the traverse from the first point to the point in question, divided by the total length of the traverse. The correction factor at each point is multiplied by the overall closure error to get the amount of error correction distributed to the point's coordinates. The compass rule is also known as the Bowditch rule, named for the American mathematician and navigator Nathaniel Bowditch (1773-1838).

compiler

A program used in software development that translates the lines of a programmer's code from one programming language to another, usually from a high-level language to the ones and zeros of machine language.

complex dynamic event

In ArcGIS Tracking Analyst, a type of complex temporal event that includes two components and involves a moving object, such as an airplane. The moving object's geographical location changes through time, so its additional attributes are stored in an input table.

complex edge feature

In a geodatabase, a linear network feature that corresponds to one or more network elements in the logical network.

complex junction feature

In ArcGIS 8.3 and previous versions, a junction feature in a geodatabase that corresponds to more than one network element in the logical network. For example, the state of the junction determines whether features can be connected or disconnected. This is not a concept that can be modeled in ArcGIS 9.0 and later versions.

complex market area

An area calculated by finding the outermost customers of a store along several vectors and connecting them. Complex market areas are more accurate than simple market areas because they respond to physical and cultural barriers. They are sometimes called amoebas because of their irregular shapes.

complex stationary event

A type of complex temporal event in ArcGIS Tracking Analyst that includes two components and involves a stationary object, such as a traffic sensor. The sensor's geographical location will not change, so its location information is stored in the input feature class.

complex temporal event

An event in ArcGIS Tracking Analyst that contains two components: one with persistent object information, and one with observations of the object through time. The merger of the temporal observations with the temporal object creates a complex event record or message. There are two types of complex temporal events: dynamic and stationary.

component

In COM, a binary unit of code that can be used to create COM objects.

component category

A section of the registry that can be used to categorize classes by their functionality. Component categories are used extensively in ArcGIS to allow extensibility of the system.

Component Category Manager

An ArcGIS utility program (Categories.exe) that can be used to view and manipulate component category information.

Component Object Model

A binary standard that enables software components to interoperate in a networked environment regardless of the language in which they were developed. Developed by Microsoft, COM technology provides the underlying services of interface negotiation, life-cycle management (determining when an object can be removed from a system), licensing, and event handling. The ArcGIS system is created using COM objects.

composite measurement

In Survey Analyst for field measurement, a set of simple measurements that are related and applied as a group.

composite relationship

A link or association between objects where the lifetime of one object controls the lifetime of its related objects. For example, the association between a highway and its shield markers is a composite relationship, since the shield markers should not exist without the highway.

composition

A UML term used to describe a form of association in which the lifetime of the whole controls the lifetime of the parts. In a composition, the instances of two classes depend on each other. The whole controls the location and lifetime of its parts. For example, in ArcMap, a map is composed of layers. If you move a map on a layout, the layers move, and if you delete the map, its layers get deleted; therefore, the lifetime of these objects depend on one another.

compound element

Within metadata, a group of data elements (including other compound elements) that together describe a characteristic of a spatial dataset in more detail than can be described by an individual data element.

compound key

A primary key that requires two or more fields to be unique.

compression

The process of reducing the size of a file or database. Compression improves data handling, storage, and database performance. Examples of compression methods include quadtrees, run-length encoding, and wavelets.

compromise projection

A projection that does not have equal area, conformal, or equidistant characteristics. The compromise projection is an attempt at balance between these characteristics, and is often used in thematic mapping.

computation

In Survey Analyst for field measurements, a process that requires a set of input parameters to apply a set of rules, and an algorithm to calculate output parameters. The input parameters are typically coordinates and measurements. The output parameters are usually coordinates.

computation name

In Survey Analyst for field measurements, a unique identifier that calls or retrieves a specific type of computation, defined on the General tab of the Survey Explorer.

computation network

In Survey Analyst for field measurements, a sequence of computation dependencies—the output points of some computations are used as the input for one or more others.

Computation Network Analysis window

In Survey Analyst for field measurements, a window that displays information about the computation network, such as breaks in the sequence, computation states, and computation network cycles.

computation network cycles

In Survey Analyst for field measurements, a problem that occurs when a point's coordinates are used as both input and output within the same computation network. Cycles must be fixed before the whole network can be validated and brought to a state in which all computations are valid.

computation state

In Survey Analyst for field measurements, the condition of a computation. A computation may be in four different states: valid, out-of-date, incorrect, or incomplete.

Computation tool

In Survey Analyst for field measurements, a tool that interacts with the map to add measurement values to computation pages.

computational geometry

A branch of mathematics that uses algorithms to solve geometry problems. Computational geometry is used in many GIS operations, including proximity analysis, feature generalization, and automated text placement.

computer-aided design

A computer-based system for the design, drafting, and display of graphical information. Also known as computer-aided drafting, such systems are most commonly used to support engineering, planning, and illustrating activities.

computer-aided software engineering

Any software that assists with the development and maintenance of software, especially the analysis and design. Complex tasks that often require many lines of code are simplified with CASE user interfaces and code generators.

computer-assisted learning

Instruction or training that uses computer-based media instead of hard-copy materials. Computer-assisted learning is generally designed to use the strengths of computer-based media such as the ability to navigate in a nonlinear fashion through the use of hyperlinks.

concatenate

To join two or more character strings together, end to end; for example, to combine the two strings "spatial" and "analysis" into the single string "spatial analysis."

concatenate events

In linear referencing, a command that combines event records in tables containing events on the same route with the same value for specified fields. Only events in situations where the to-measure of one event matches the from-measure of the next event are combined. The concatenate events command is available for line event tables only.

concatenated key

In a relational database table, a primary key made by combining two or more keys that together form a unique identifier.

concentric rings

A method of defining the rings in an analysis so that the values inside the rings are cumulative. For example, if you had an analysis with three concentric rings and 10 households in each, the total number of households for ring 1 would be 10, the total for ring 2 would be 20 (ring 1 + ring 2), and the total for ring 3 would be 30 (ring 1 + ring 2 + ring 3).

concurrency

The ability of a DBMS to support simultaneous access by more than one user.

concurrency management

A database management process for maintaining the consistency of data while supporting simultaneous editing by more than one user. A typical technique involves locking portions of the database to prevent data corruption caused by multiple users simultaneously editing data.

concurrent use

Floating software products that are administered by a license manager. A central license manager (installed anywhere on a network) allows users to install the floating products on any number of machines. The number of seats or licenses purchased determines the number of users who can run the applications simultaneously.

condition table

A component of the PLTS knowledge base that contains SQL statements and custom code for feature validation extended beyond standard geodatabase domains. PLTS utilizes condition tables for enhanced validation during both database production and quality control.

conditional operator

A symbol or keyword that specifies the relationship between two values and is used to construct queries to a database. Examples include = (equal to), < (less than), and > (greater than).

conditional statement

A programming language statement that executes one option if the statement is true, and another if it is false. The if-then-else statement is an example of a conditional statement.

confidence level

In a statistical test, the risk, expressed as a percentage, that the null hypothesis will be incorrectly rejected because of sampling error when the null hypothesis is true. For example, a confidence level of 95 percent means that if the same test were performed 100 times on 100 different samples, the null hypothesis would be incorrectly rejected five times.

configuration file

In ArcIMS, the file that contains the core site information. ArcIMS configuration files contain all the basic information about the content to be delivered, such as location of the data and layer symbology. Typically, a configuration file contains data that defines map content and has a file extension of .axl, but it can also be used to deliver metadata or route data (as .axl files) and to serve maps created in ArcMap (.mxd or .pmf files). Regardless of their type, configuration files contain content that the service registers to the ArcIMS spatial server and Web server for processing.

configuration keyword

In ArcSDE, a name for a group of parameters that defines how geodatabase objects are stored.

conflation

A set of procedures that aligns the features of two geographic data layers and then transfers the attributes of one to the other.

conflict

In database editing, a state of incompatibility that occurs when multiple users simultaneously edit a version or reconcile two versions. Conflicts occur when the same feature or topologically related features are edited in two versions, and it is unclear which representation of the database is valid.

conflict resolution

The process of solving uncertainty within a database that occurs when two versions of the same data are edited at the same time. Conflicts can occur when multiple users simultaneously edit the same feature or topologically related features, or reconcile two versions of a dataset. Resolving a conflict requires that the user make a decision about the feature's correct representation and identify it in the Conflict Resolution dialog box.

conformal projection

A projection that preserves the correct shapes of small areas. In a conformal projection, graticule lines intersect at 90-degree angles, and at any point on the map the scale is the same in all directions. A conformal projection maintains all angles at each point, including those between the intersections of arcs; therefore, the size of areas enclosed by many arcs may be greatly distorted. No map projection can preserve the shapes of larger regions.

conformality

The characteristic of a map projection that preserves the shape of any small geographic area.

congressional district

A geographical and political division in which voters elect representatives to the U.S. House of Representatives. Each state establishes its congressional districts based on population counts, with the goal of having districts as equal in population as possible.

conic projection

A projection that transforms points from a spheroid or sphere onto a tangent or secant cone that is wrapped around the globe in the manner of a party hat. The cone is then sliced from the apex (top) to the bottom, and flattened into a plane.

conjoint boundary

A boundary common to two features. For example, in a parcel database, adjacent parcels share a boundary. Another example is a parcel that shares a boundary on one side with a river. The segment of the river that coincides with the parcel boundary shares the same coordinates as the parcel boundary.

connection

In ArcCatalog, a mechanism used to access remote file systems and shared databases.

connection line

A cadastral fabric line with bearing and distance data attached to it, commonly used to tie parcels across roads, tie in control points, or tie the point of survey commencement to the point of beginning for a particular parcel. Connection lines do not necessarily indicate parcel boundaries.

connectivity

The way in which features in GIS data are attached to one another functionally or spatially.

connectivity analysis

Any method of solving network problems such as traversability, rate of flow, or capacity, using network connectivity.

connectivity group

In network datasets, a logical grouping of point features, line features, or both, that controls how network elements are connected. Connectivity groups are defined when a network dataset is built. A network dataset may have multiple connectivity groups.

connectivity policy

In a network dataset, a property of network sources that defines how network elements connect to each other within a connectivity group. There are two types of edge-edge connectivity policies (end-point connectivity and any-vertex connectivity) and two types of edge-junction connectivity policies (honor and override).

connectivity rule

In geometric networks, a rule that constrains the type and number of network features that can be connected to one another. There are two types of connectivity rules: edge-edge and edge-junction.

connector

A visual representation of the relationship between elements in a model. Connectors join elements together to create processes. Typical processes connect an input data element, a tool element, and a derived data element.

constant azimuth

A complex curve on the earth's surface that crosses every meridian at the same oblique angle. A rhumb line path follows a single compass bearing; it is a straight line on a Mercator projection, or a logarithmic spiral on a polar projection. A rhumb line is not the shortest distance between two points on a sphere.

constrained adjustment

In Survey Analyst for field measurements, one of two phases involved when performing a least squares adjustment for a measurement network. In this phase, the emphasis is on testing the reference points as well as computing final coordinates.

constraints

Limits imposed on a model to maintain data integrity. For example, in a water network model, an 8-inch pipe cannot connect to a 4-inch pipe.

construct features

In ArcMap, an edit command that takes selected features from one or more feature classes and creates new features in a target feature class. The Construct Features tool uses the input geometries of the selected features to construct polygons or lines following polygon boundaries, depending on the geometry of the target feature class.

construction line

In Survey Analyst - Cadastral Editor, a line with a bearing and distance that is used to create geometry for a new cadastral fabric parcel.

container account

The operating system account that server object container processes run as, which is specified by the GIS server postinstallation utility. Objects running in a server container process have the same access rights to system resources as the container account.

container process

A process in which one or more server objects are running. Container processes run on SOC machines, and are started and shut down by the SOM. They are visible in the Windows Task Manager as ArcSOC.exe.

containment

A spatial relationship in which a point, line, or polygon feature or set of features is enclosed completely within a polygon.

content

In ArcWeb Services, data that may include data files, layers, or services.

Content Finder Web Service

A SOAP ArcWeb service that allows users to search the metadata information for available content in the ArcWeb system.

Content Library

A Web-based tool for viewing and maintaining information about data files, layers, and services used in ArcWeb Services. Users can access Content Library through the ArcWeb Services Web site.

Content Standard for Digital Geospatial Metadata

A publication authored by the FGDC that specifies the information content of metadata for digital geospatial datasets. The purpose of the standard is to provide a common set of terminology and definitions for concepts related to the metadata. All U.S. government agencies (federal, state, and local) that receive federal funds to create metadata must follow this standard.

conterminous

Having the same or coincident boundaries.

context menu

A list menu that pops up when the right mouse button is clicked in Windows applications. Some keyboards also have an application key that opens shortcut menus.

contiguity

In a coverage, the topological identification of adjacent polygons by recording the left and right polygon for each arc.

contiguous

Of polygons: adjacent; having a common boundary; sharing an edge.

continuous data

Data such as elevation or temperature that varies without discrete steps. Since computers store data discretely, continuous data is usually represented by TINs, rasters, or contour lines, so that any location has either a specified value or one that can be derived.

continuous feature

A feature that is not spatially discrete. The transition between possible values on a continuous surface is without abrupt or well-defined breaks.

continuous raster

A raster in which cell values vary continuously to form a surface. In a continuous raster, the phenomena represented have no clear boundaries. Values exist on a scale relative to each other. It is assumed that the value assigned to each cell is what is found at the center of the cell. Rasters representing elevation, precipitation, chemical concentrations, suitability models, or distance from a road are examples of continuous rasters.

continuous tone image

A photograph that has not been screened and so displays all the varying tones from dark to light.

contour interval

The difference in elevation between adjacent contour lines.

contour line

A line on a map that connects points of equal elevation based on a vertical datum, usually sea level.

contour tagging

Assigning elevation values to contour lines.

contrast

In remote sensing and photogrammetry, the ratio between the energy emitted or reflected by an object and that emitted or reflected by its immediate surroundings.

contrast ratio

The ratio between the maximum and minimum brightness values in an image.

contrast stretch

Increasing the contrast in an image by expanding its grayscale range to the range of the display device.

control

A basic element of a software application's GUI. Examples of controls include menus, buttons, tools, check boxes, slider bars, text input boxes, and combo boxes.

control point

An accurately surveyed coordinate location for a physical feature that can be identified on the ground. Control points are used in least-squares adjustments as the basis for improving the spatial accuracy of all other points to which they are connected.

conventional alternative hypothesis

In statistical testing, a set of assumptions that will be accepted by test data if the null hypothesis is rejected. In surveying, the alternative hypothesis assumes that there is an outlier present in a single measurement in a measurement network. The test associated with this hypothesis is the W-test.

convergence angle

The angle between a vertical line (grid north) and true north on a map.

conversion

The process of changing input data from one representation or format to another, such as from raster to vector, or from one file format to another, such as from x,y coordinate table to point shapefile.

convex hull

The smallest convex polygon that encloses a group of objects, such as points. In ArcGIS, TIN boundaries are convex hulls by default.

convex polygon

A polygon in which a straight line drawn between any two points inside the polygon is completely contained within the polygon. Visually, the boundary of a convex polygon is the shape a rubber band would take around a group of objects.

cookie cutter

A command that extracts features from one feature class that reside entirely within a boundary defined by features in another feature class.

coordinate geometry

A method for calculating coordinate points from surveyed bearings, distances, and angles.

coordinate geometry traverse

In Survey Analyst, a process of computing a sequence of survey point locations starting from an initial known point. Each new survey point is defined by a traverse course and is used as the takeoff point for the next point in the sequence. A traverse course can be defined using various combinations of directions, distances, angles, and circular arc parameters. The coordinate geometry traverse is primarily used to define coordinates based on values taken from subdivision plans.

coordinate system

A reference framework consisting of a set of points, lines, and/or surfaces, and a set of rules, used to define the positions of points in space in either two or three dimensions. The Cartesian coordinate system and the geographic coordinate system used on the earth's surface are common examples of coordinate systems.

coordinate transformation

The process of converting the coordinates in a map or image from one coordinate system to another, typically through rotation and scaling.

coordinated universal time

The official timekeeping system of the world's nations since 1972. It refers local time throughout the world to time at the prime meridian, and is based on atomic clocks, but is periodically artificially adjusted so as to always remain within 0.9 seconds of universal time. The adjustment is made by the addition of leap seconds to the course of atomic time. Coordinated universal time is abbreviated "UTC." (The abbreviation UTC does not represent the word order of "coordinated universal time" in either English or French. It is an extension of the "UT*" pattern established for versions of universal time.)

coordinates

A set of values represented by the letters x, y, and optionally z or m (measure), that define a position within a spatial reference. Coordinates are used to represent locations in space relative to other locations.

core-based statistical area

A geographic region containing at least one urban area with a population of at least 10,000, defined by the U.S. Office of Management and Budget for use by federal statistical agencies, including the U.S. Census Bureau. A core-based statistical area can be a metropolitan statistical area or a micropolitan statistical area.

correlation

An association between data or variables that change or occur together. For example, a positive correlation exists between housing costs and distance from the beach; generally, the closer a home is to the beach, the more it costs. Correlation does not imply causation. For example, there is a statistical correlation between ice cream sales and crime rates, but neither causes the other. The correlation coefficient is an index number between -1 and 1 indicating the strength of the association between two variables.

corridor

A buffer drawn around a line.

corridor analysis

A form of spatial analysis usually applied to environmental and land-use data in order to find the best locations for building roads, pipelines, and other linear transportation features.

cost

A function of time, distance, or any other factor that incurs difficulty or an outlay of resources.

cost grid

A raster dataset that identifies the cost of traveling through each cell in the raster. A cost raster can be used to calculate the cumulative cost of traveling from every cell in the raster to a source or a set of sources.

cost raster

A raster dataset that identifies the cost of traveling through each cell in the raster. A cost raster can be used to calculate the cumulative cost of traveling from every cell in the raster to a source or a set of sources.

cost-benefit analysis

An appraisal that attempts to compare the benefits (including social benefits) expected from a project with the costs (sometimes including social costs) incurred by the project over its lifetime. Generally cost-benefit analyses are used to compare alternative proposals, or to make a case for the implementation of a particular plan or system.

cost-distance analysis

The calculation of the least cumulative cost from each cell to specified source locations over a cost raster.

cost-weighted allocation

An ArcGIS Spatial Analyst function that identifies the nearest source from each cell in a cost-weighted distance grid. Each cell is assigned to its nearest source cell, in terms of accumulated travel cost.

cost-weighted direction

An ArcGIS Spatial Analyst function that provides a road map from the cost weighted distance grid, identifying the route to take from any cell, along the least-cost path, back to the nearest source.

cost-weighted distance

An ArcGIS Spatial Analyst function that uses a cost grid to assign a value—the least accumulative cost of getting back to the source—to each cell of an output grid.

COTS

Acronym for commercial off-the-shelf. Commercially available software or systems that are ready to use and which do not require significant customization.

county

The primary legal subdivision of all U.S. states except Alaska and Louisiana. The U.S. Census Bureau uses counties or equivalent entities (boroughs in Alaska, parishes in Louisiana, the District of Columbia in its entirety, and municipios in Puerto Rico) as statistical subdivisions.

county subdivision

A statistical division of a county recognized by the U.S. Census Bureau for data presentation. County subdivisions can include census county divisions, census subareas, minor civil divisions, and unorganized territories.

covariance

A statistical measure of the linear relationship between two variables. Covariance measures the degree to which two variables move together relative to their individual mean returns.

coverage

A data model for storing geographic features. A coverage stores a set of thematically associated data considered to be a unit. It usually represents a single layer, such as soils, streams, roads, or land use. In a coverage, features are stored as both primary features (points, arcs, polygons) and secondary features (tics, links, annotation). Feature attributes are described and stored independently in feature attribute tables. Coverages cannot be edited in ArcGIS 8.3 and subsequent versions.

coverage feature class

In ArcInfo, a classification describing the format of geographic features and supporting data in a coverage. Feature classes include point, arc, node, route, route system, section, polygon, and region. One or more coverage features are used to model geographic features; for example, arcs and nodes can be used to model linear features, such as street centerlines. The tic, annotation, link, and boundary feature classes provide supporting data for coverage data management and viewing.

coverage units

The units of the coordinate system in which a coverage is stored (for example, feet, meters, inches).

cracking

In ArcGIS, a part of the topology validation process in which vertices are created at the intersection of feature edges.

Crandall rule

A special-case, least-squares-based method for adjusting the closure error in a traverse. The Crandall rule is most frequently used in a closed traverse that represents a parcel from a subdivision plan to ensure that tangency between courses remains intact as, for example, when applied to a tangent curve. It assumes that course directions and angles have no error and, therefore, all error corrections are applied only to the distances. This method uses a least-squares adjustment to distribute the closure error, and applies infinite weight to the angles or direction measurements to ensure that they are not adjusted. In some circumstances the results of this adjustment method may be unexpected, or the adjustment may not be possible, and an alternative method is required. The Crandall rule was developed by C.L. Crandall around 1901.

creation date

In Survey Analyst for field measurements, an attribute of the computation that records the date of origin.

creation time

The time it takes to initialize an instance of a server object when server objects are created in the GIS server either as a result of the server starting or in response to a request for a server object by a client.

credit

A charge to access an ArcWeb service. Users use credits each time they request an ArcWeb service to perform a task, such as find a route.

critical value

The specific cutoff point that determines acceptance or rejection of a hypothesis. Critical values are determined by the choice of a level of significance (α).

crop guide

Marks that indicate the edge of the page of a finished, printed map. Cropmarks are used as a reference for trimming excess paper after printing.

crop marks

Marks that indicate the edge of the page of a finished, printed map. Cropmarks are used as a reference for trimming excess paper after printing.

cross correlation

Statistical correlation between spatial random variables of different types, attributes, names, and so on, where the correlation depends on the distance or direction that separates the locations.

cross covariance

The statistical tendency of variables of different types, attributes, names, and so on, to vary in ways that are related to each other. Positive cross covariance occurs when both variables tend to be above their respective means together, and negative cross covariance occurs if one variable tends to be above its mean when the other variable is below its mean.

cross tabulation

In a GIS, comparing attributes in different coverages or map layers according to location.

cross validation

A procedure for testing the quality of a predicted data distribution. In cross validation, a piece of data whose value is known independently is removed from the dataset and the rest of the data is used to predict its value. Full cross validation is done by removing, in turn, each piece of data from the dataset and using the rest of the data to predict its value.

cross variogram

A function of the distance and direction separating two locations, used to quantify cross correlation. The cross variogram is defined as the variance of the difference between two variables of different types or attributes at two locations. The cross variogram generally increases with distance, and is described by nugget, sill, and range parameters.

cross-reference database

A database containing tables with information defining the mapping between a data source schema and an output geodatabase schema. Cross-reference databases are used by the PLTS data loader to batch populate a geodatabase from a variety of sources.

cross-tile indexing

A technique for indexing features that cross tile boundaries in a map library by storing them as one or more features in each tile, instead of storing them each as a single feature.

CSDGM

A publication authored by the FGDC that specifies the information content of metadata for digital geospatial datasets. The purpose of the standard is to provide a common set of terminology and definitions for concepts related to the metadata. All U.S. government agencies (federal, state, and local) that receive federal funds to create metadata must follow this standard.

CSS

Acronym for Cascading Style Sheets. A standard for defining the layout or presentation of an HTML or XML document. Style information includes font size, background color, text alignment, and margins. Multiple style sheets may be applied to "cascade" over previous style settings, adding to or overriding them. The World Wide Web Consortium maintains the CSS standard.

cubic convolution

A technique for resampling raster data in which the average of the nearest 16 cells is used to calculate the new cell value.

cull

In ArcScene and ArcGlobe, to selectively choose not to draw one side of an areal feature.

cultural feature

A human-made feature represented on a map, such as a building, road, tower, or bridge.

cultural geography

The field of geography concerning the spatial distribution and patterns created by human cultures and their effects on the earth.

curb approach

In network analysis, a network location property that models a path for approaching a stop from a specific side based on edge direction. For example, a school bus must approach a school from its door side so that students exiting the bus will not have to cross the street. There are three types of curb approaches: left, right, or both.

current cadastral fabric

In Survey Analyst - Cadastral Editor, the most up-to-date legal state of the cadastral fabric.

current coordinate

In Survey Analyst for field measurements, the single coordinate for a survey point that is the best representation for its location within each project. A current coordinate is required when the same project computes or imports more than one coordinate for a particular survey point.

current task

During editing in ArcMap, a setting in the Task drop-down list that determines which operation the sketch construction tools will perform. Examples of edit tasks include creating new features and modifying existing features. The edit task is set by clicking a task in the Task drop-down list.

current workspace

A user-specified path to a container for file-based geographic data, set in the Environment Settings dialog box. Data from the current workspace can be accessed from any tool dialog box (including script and model dialog boxes), or at the command line simply by typing its name.

curve fitting

Converting short connected straight lines into smooth curves to represent features such as rivers, shorelines, and contour lines. The curves that result pass through or close to the existing points.

custom behavior

A set of methods, functions or operations associated with a database object that has been specifically created or overridden by a programmer.

custom feature

In geodatabases, a feature with specialized behavior instantiated in a class by a programmer.

custom functionality

A modification to or enhancement of standard software functionality to meet a specific user's needs.

custom group layer

A layer created in ArcMap using the ArcGIS Image Server extension. Custom group layers display the contents of an image service definition, including the footprint, boundary, seamline and preview raster layer.

custom object

An object with custom behavior provided by a developer.

custom tool

In geoprocessing, a tool created by a user and added to a toolset and/or toolbox. Custom tools may only be added to custom toolsets and/or toolboxes.

custom toolset

In geoprocessing, a subset of a toolbox created by a user to hold custom tools or a group of frequently used tools.

customer market analysis

A type of market analysis that focuses on data about customers, rather than about a store or stores. An example is desire line analysis.

customer profiling

A process that establishes common demographic characteristics for a set of customers within a geographic area.

customer prospecting

A type of market analysis that locates regions with appropriate demographic characteristics for targeting new customers.

cut/fill

An ArcGIS Spatial Analyst and 3D Analyst function that summarizes areas and volumes of change between two surfaces.

cycle

A set of lines forming a closed polygon.

cylindrical projection

A projection that transforms points from a spheroid or sphere onto a tangent or secant cylinder. The cylinder is then sliced from top to bottom and flattened into a plane.

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