V
validation rule
Validation rules can be applied to objects in the geodatabase to ensure that their state is consistent with the system that the database is modeling. The geodatabase supports attribute, connectivity, relationship, and custom validation rules.
variogram
A function of the distance and direction separating two locations that is used to quantify autocorrelation. The variogram is defined as the variance of the difference between two variables at two locations. The variogram generally increases with distance and is described by nugget, sill, and range parameters.
variography
The process of estimating the theoretical variogram. It begins with exploratory data analysis, then computing the empirical variogram, binning, fitting a variogram model, and using diagnostics to assess the fitted model.
VAT
Value attribute table. A table containing attributes for a grid. In addition to user-defined attributes, the VAT contains the values assigned to cells in the grid and a count of the cells with those values.
VBA
Visual Basic for Applications. The embedded programming environment for automating and customizing ESRI end-user applications such as ArcMap and ArcCatalog. It offers the same powerful tools as Visual Basic (VB) in the context of an existing application and is the best option for customizing software that already meets most needs. By contrast, VB is a standalone tool for rapidly creating a special solution from scratch, be it an executable program, COM component, or an ActiveX® control. An application that uses ArcMap or ArcCatalog may require the development of a COM component; consequently, in such instances, VB is the appropriate development environment.
vector
A coordinate-based data structure commonly used to represent linear geographic features. Each linear feature is represented as an ordered list of vertices. Traditional vector data structures include double-digitized polygons and arc–node models.
vector model
A representation of the world using points, lines, and polygons. Vector models are useful for representing and storing discrete features such as buildings, pipes, or parcel boundaries.
version
In geodatabases, an alternative representation of the database that has an owner, a description, a permission (private, protected, or public), and a parent version. Versions are not affected by changes occurring in other versions of the database.
version merging
The process of reconciling two versions of a feature dataset into a common version. If conflicting edits have been made in either of the merged versions, these conflicts are resolved, either automatically or by an interactive process.
version reconciliation
The process of updating a version of a dataset with changes made in another version. Using this technique, a version can remain up to date with changes even if it is within a long transaction lasting many months.
vertex
One of a set of ordered x,y coordinate pairs that define a line or polygon feature.
vertical exaggeration
The amount by which the z-values in the scene are multiplied in order to enhance details in the shape of the surface. Scenes may appear flat when the range of x- and y-values is much larger than the z-values. In most cases, setting vertical exaggeration can compensate for this flattening by increasing relief.
viewer
An additional window that allows you to view the 3D data in a scene from another angle. You can have multiple viewers in a scene.
views
Different ways to see the contents of the selected item in the Catalog tree in ArcCatalog.
viewshed
The viewshed identifies the cells in an input grid that can be seen from one or more observation points or lines. This is useful for applications where the visibility of an object is important, such as finding well-exposed places for communications towers, or hidden places for parking lots or other facilities.
virtual page
The map page as seen in layout view in ArcMap.
volume
The space (measured in cubic units) between a TIN surface and a plane at a specified elevation. Volume may be calculated above or below the plane.
VPF
Vector Product Format. A U.S. Department of Defense military standard that defines a standard format, structure, and organization for large geographic databases. VPF data is read-only in ArcCatalog.

U
UIControl
A UIControl lets you create a custom command with VBA. There are four different types of UIControls: buttons, tools, combo boxes, and edit boxes.
UML
Unified Modeling Language. A standard for representing object designs. See also CASE.
undershoot
An arc that does not extend far enough to intersect another arc. See also dangling arc.
uninitialized flow direction
For an edge feature in a network, a condition that occurs when the edge feature is not topologically connected through the network to sources and sinks or if the edge feature is only connected to sources and sinks through disabled features.
union
A topological overlay of two polygonal spatial datasets that preserve features that fall within the spatial extent of either input dataset; that is, all features from both coverages are retained. See also intersect and identity.
unit of measure
See angular units or linear units.
username
The identification used for authentication when you log in to a geodatabase.
UTM
Universal Transverse Mercator. A projected coordinate system that divides the world into 60 north and south zones, six degrees wide.

T
table
A set of data elements that has a horizontal dimension (rows) and a vertical dimension (columns). See also attribute table.
table of contents
In ArcMap, the table of contents lists all the data frames and layers on the map and shows what features the symbols in each layer represent. ArcScene also has a table of contents.
tabular data
Descriptive information that is stored in rows and columns and can be linked to map features.
tag
An XML tag that identifies a particular element in an item's metadata. Tags use the form <tag> where tag is a text string up to eight characters.
tagged value
Used to set additional properties of UML elements. For example, you can set the length (in characters) of a string field by using a tagged value.
tangent projection
A form of map projection where the conceptual surface of the projection (cone, cylinder, or plane) just touches the earth's surface. See also secant projection.
target layer
Used in ArcMap editing, a setting in the Target Layer dropdown list that determines the layer to which new features will be added. The target layer is set by clicking a layer in the Target Layer dropdown list. For instance, if you set the target layer to Buildings, any features you create will be part of the Buildings layer. You must set the target layer whenever you're creating new features—whether you're creating them with the Sketch tool, by copying and pasting, or by buffering another feature.
TCP/IP
Transmission Control Protocol (TCP) is a communication protocol layered above the Internet Protocol (IP). These are low-level communication protocols that allow computers to send and receive data.
template
See map template.
temporary dataset
A raster dataset temporarily stored on disk. All output raster results from Spatial Analyst are temporary, unless you specify a location on disk and a filename in a function dialog box, you make the temporary dataset permanent, or you save the map document. In these three cases, temporary results will become permanent datasets on disk. See make permanent.
text box
See edit box.
text label
Text added to a map to help identify features.
3D feature
A representation of a real-world object in a map or scene, with z-values stored within the feature's geometry. Features have geometry and may also have attributes stored in a feature table. PointZ, PolylineZ, PolygonZ, and Multipatch feature classes and shapefiles may contain 3D features.
3D graphic
A graphic object in a map or scene with z-values stored in the graphic's geometry. Graphics do not have attributes.
thumbnail
A snapshot describing the geographic data contained in a data source or layer, or a map layout. A thumbnail might provide an overview of all the features in a feature class or a detailed view of the features in, and the symbology of, a layer. Thumbnails are not updated automatically; they will go out of date if features are added to a data source or if the symbology of a layer changes.
tic
Registration or geographic control points for a coverage representing known locations on the earth's surface. Tics allow all coverage features to be recorded in a common coordinate system such as Universal Transverse Mercator (UTM). Tics are used to register map sheets when they are mounted on a digitizer. They are also used to transform the coordinates of a coverage, for example, from digitizer units (inches) to the appropriate values for a coordinate system (meters for UTM).
TIN
Triangulated irregular network. A surface representation derived from irregularly spaced sample points and breakline features. The TIN dataset includes topological relationships between points and their neighboring triangles. Each sample point has an x,y coordinate and a surface or z-value. These points are connected by edges to form a set of nonoverlapping triangles used to represent the surface. TIN is also called an irregular triangular mesh or an irregular triangular surface model.
TIN dataset
A dataset containing a triangulated irregular network (TIN). The TIN dataset includes topological relationships between points and neighboring triangles. See also TIN.
tolerance
A coverage has many processing tolerances (fuzzy, tic match, dangle length) and editing tolerances (weed, grain, edit distance, snap distance, and nodesnap distance). Stored in a TOL file, ArcInfo uses the tolerance values as defaults in many automation, editing, and processing operations. You can edit a coverage's tolerances using its Properties dialog box in ArcCatalog.
tool
An entity in ArcToolbox that performs a specific geoprocessing task such as generalizing lines. A tool can belong to two or more toolsets.
A command that requires interaction with the user interface before an action is performed. For example, with the Zoom In tool, you must click or draw a box over the geographic data or map before it is redrawn at a larger scale. Tools can be added to any toolbar.
toolbar
A set of commands that let you carry out related tasks. The Main Menu toolbar has a set of menu commands; other toolbars typically have a set of buttons. Toolbars can float on the desktop in their own window, or you can dock them at the top, bottom, or sides of the main window.
Toolbox tree
Displays ArcToolbox toolsets and tools grouped by functionality.
toolset
A group of tools that perform similar geoprocessing tasks. Custom toolsets can be created within the My Tools toolset to hold custom tools as well as to group frequently used ArcToolbox tools.
topological association
The spatial relationship between features that share geometry such as boundaries and vertices. When you edit a boundary or vertex shared by two or more features using the topology tools in ArcMap, the shape of each of those features is updated.
topological feature
A feature that supports network connectivity that is established and maintained based on geometric coincidence.
topology
In geodatabases, relationships between connected features in a geometric network or shared borders between features in a planar topology.
In coverages, the spatial relationships between connecting or adjacent features (for example, arcs, nodes, polygons, and points). The topology of an arc includes its from- and to-nodes and its left and right polygons. Topological relationships are built from simple elements into complex elements: points (simplest elements), arcs (sets of connected points), areas (sets of connected arcs), and routes (sets of sections, which are arcs or portions of arcs). Redundant data (coordinates) is eliminated because an arc may represent a linear feature, part of the boundary of an area feature, or both.
tracing
The process of building a set of network features based on some procedure.
transaction
A logical unit of work as defined by a user. Transactions can be data definition (create an object), data manipulation (update an object), or data read (select from an object).
triangle
Triangles form the faces on a TIN surface. Each triangle on a TIN surface is defined by three edges and three nodes, and is adjacent to one to three other triangles on the surface. TIN triangles can be used to derive aspect and slope information, and may be attributed with tag values.
trigonometric functions
Operators within the Raster Calculator of Spatial Analyst. They perform various trigonometric calculations on the values in an input grid.
Available trigonometric functions: Sin, Cos, Tan, Asin, Acos, Atan
true curve
See parametric curve.
true-direction projection
A form of projection that shows lines with correct azimuths from one or two points.
tuple
A row in a relational table; synonymous with record, observation.</dd>

A Spatial Analyst option. Setting the snap extent to a specific raster will snap all layers to the cell registration of the specified raster. All layers will share the lower-left corner and cell size of the specified raster. Use snap extent to resample layers to the same registration and cell size in order to perform analysis.
snapping
The process of moving a feature to coincide exactly with the coordinates of another feature within a specified snapping distance or tolerance.
snapping environment
Settings in ArcMap's Snapping Environment window and Editing Options dialog box that help you establish exact locations in relation to other features. You determine the snapping environment by setting the snapping tolerance, snapping properties, and snapping priority.
snapping priority
During ArcMap editing, the order in which snapping will occur by layer. You can set the snapping priority by dragging the layer names in the Snapping Environment window to new locations.
snapping properties
You can choose the part of a feature, vertex, edge, or endpoint to which you want a new feature to snap (precisely connect) by setting the layer snapping properties in ArcMap's editing environment. For example, you can set the snapping properties so that the endpoint of a new feature will snap to the vertex of an existing feature. When the pointer comes within the snapping tolerance of the vertex, the endpoint of the new feature snaps to the vertex of the existing feature.
snapping tolerance
During ArcMap editing, the distance within which the pointer or a feature will snap to another location. If the location being snapped to (vertex, boundary, midpoint, or connection) is within the distance you set, the pointer will automatically snap. For example, if you want to snap a power line to a utility pole and the snapping tolerance is set to 25 pixels, whenever the power line comes within a 25-pixel range of the pole it will automatically snap to it. Snapping tolerance can be measured using either map units or pixels.
source
In networks, a junction feature at which flow originates. See also sink.
A necessary input to the Cost Weighted Distance function of the Spatial Analyst. The source is the point or group of points that the Cost Weighted Distance function uses when calculating the accumulated cost of traveling through each cell to the nearest source.
spatial analysis
The study of the locations and shapes of geographic features and the relationships between them.
The process of modeling, examining, and interpreting model results. Spatial analysis is useful for evaluating suitability and capability, for estimating and predicting, and for interpreting and understanding. There are four traditional types of spatial analysis: topological overlay and contiguity analysis; surface analysis; linear analysis; and raster analysis.
spatial bookmark
In ArcMap, identifies a particular geographic location that you want to save and refer to later—for example, a study area.
spatial data
The locations and shapes of geographic features with descriptions of each feature.
spatial database
Any DBMS that contains spatial data.
spatial domain
Describes the range and precision of x,y coordinates, and z- and m-values that can be stored in a feature dataset or feature class in a geodatabase.
spatial function
An operation that performs spatial analysis. All spatial operations on Spatial Analyst user interface are classified spatial functions, for example, distance, slope, or density.
spatial join
A type of spatial analysis in which the attributes of features in two different layers are joined together based on the relative locations of the features.
spatial modeling
Analytical procedures applied with a GIS. Three categories of spatial modeling functions can be applied to geographic features within a GIS:
Geometric models (calculating the Euclidean distance between features, generating buffers, calculating areas and perimeters)
Coincidence models (topological overlay)
Adjacency models (pathfinding, redistricting, and allocation)
All three model categories support operations on spatial data, including points, lines, polygons, TINs, and grids. Functions are organized in a sequence of steps to derive the desired information for analysis. See also model and analysis.
spatial overlay
The process of superimposing layers of geographic data that occupy the same space in order to study the relationship between them.
spatial query
See location query.
spatial reference
Describes both the coordinate system and spatial domain extent for a feature dataset or feature class in a geodatabase.
sphere
A three-dimensional shape obtained by rotating a circle around an axis defined by its diameter.
spherical coordinate system
A reference system using positions of latitude and longitude to define the locations of points on the surface of a sphere or spheroid.
spheroid
When used to represent the earth, the three-dimensional shape obtained by rotating an ellipse about its minor axis. This is an oblate ellipsoid of revolution, also called an ellipsoid.
Spline
An interpolation method in which cell values are estimated using a mathematical function that minimizes overall surface curvature, resulting in a smooth surface that passes exactly through the input points.
split policy
In geodatabases, all attribute domains have a split policy associated with them. When a feature is split into two new features in ArcMap, the split policies dictate what happens to the value of the attribute with which the domain is associated. Standard split policies are duplicate, default value, and geometry ratio.
SQL
Structured Query Language. A syntax for defining and manipulating data from a relational database. Developed by IBM in the 1970s, it has become an industry standard for query languages in most relational database management systems.
standard line
A line on a sphere or spheroid that has no length compression or expansion after being projected. Commonly, a standard parallel or central meridian.
standard parallel
The line of latitude where the projection surface touches the surface. A tangent conic or cylindrical projection has one standard parallel, while a secant conic or cylindrical projection has two. A standard parallel has no distortion.
State Plane Coordinate System
A projected coordinate system used in the United States that divides each state into one or more zones to minimize distortion caused by the map projection. Also known as SPCS and SPC.
steepest path
A line that follows the steepest downhill direction on a surface. Paths terminate at the surface perimeter or in surface concavities or pits.
storage keywords
A set of parameters that specify how data and indexes are stored in an ArcSDE database. Keywords are stored in a table in the ArcSDE database.
straight line allocation
A Spatial Analyst function that identifies which cells belong to which source, based on closest proximity in a straight line.
straight line direction
A Spatial Analyst function that identifies the azimuth direction from each cell to the nearest source.
straight line distance
A Spatial Analyst function that calculates the distance in a straight line from every cell to the nearest source.
stream mode digitizing
One of two methods of digitizing features from a paper map. Also known as streaming, stream mode digitizing provides an easy way to capture features when you don't require high precision—for example, to digitize rivers, streams, and contour lines. Within stream mode, you create the first vertex of the feature and trace over the rest of the feature with the digitizer puck. You can also use digitize in stream mode when editing "freehand" by using the Sketch tool on the Editor toolbar. See also point mode digitizing.
stream tolerance
The interval at which vertices are added along the feature you're digitizing in stream mode. When streaming, vertices are automatically created at a defined interval as you move the mouse. For example, if the stream tolerance is set to 10 map units, you must move the pointer at least 10 map units before the next vertex will be created. If you move the pointer more than 10 map units, there may be more space between vertices, but there will always be a minimum interval of 10 map units. Stream tolerance is measured in map units. See also stream mode digitizing.
stretch
Applied to a raster to increase the visual contrast between its cells. It involves mapping original input values to a 0-255 scale.
suitability modeling
The process of creating a model to find optimum locations. A suitability model might identify suitable locations for a new facility or a road.
surface
A set of continuous data such as elevation or air temperature over an area, or the boundary between two distinct materials or processes.
style
An organized collection of elements that you use to make your maps or put on your maps. Styles include elements such as symbols, scale bars, North arrows, and colors. You might create different styles that contain the specific elements for the specific types of maps you make.
Style Manager
The tool that you use to create new styles and edit existing ones.
stylesheet
In metadata documents, an XSL stylesheet, which selects data from an XML file, applies functions and formatting to the data and then specifies how to present the data.
subtypes
In geodatabases, although all objects in a feature class or object class must have the same behavior and attributes, not all objects have to share the same default values and validation rules. You can group features and objects into subtypes. Subtypes differentiate objects based on their rules.
surface
A geographic phenomenon represented as a set of continuous data such as elevation or air temperature over an area. A clear or sharp break in values of the phenomenon (breaklines) indicates a significant change in the structure of the phenomenon, such as a cliff, not a change in geographic feature. Surfaces can be represented by models built from regularly or irregularly spaced sample points on the surface, or by contour lines, isolines, bathymetry, or the like.
Sybase
A commercial RDBMS.
symbol
A graphic pattern used to represent a feature. For example, line symbols represent arc features; marker symbols, points; shade symbols, polygons; and text symbols, annotation. Many characteristics define symbols including color, size, angle, and pattern.
symbology
The criteria used to determine symbols for the features in a layer. A characteristic of a feature may influence the size, color, and shape of the symbol used.

S
scale
The relationship between the dimensions of features on a map and the geographic objects they represent on the earth, commonly expressed as a fraction or a ratio. A map scale of 1/100,000 or 1:100,000 means that one unit of measure on the map equals 100,000 of the same unit on the earth.
scale bar
A map element that shows the map scale graphically.
scale factor
In a coordinate system, a value (usually less than one) that converts a tangent projection to a secant projection. Represented by "k0" or "k". If a projected coordinate system doesn't have a scale factor, the standard lines of the projection have a scale of 1.0. Other points on the map have scales greater or lesser than 1.0. If a projected coordinate system has a scale factor, the defining parameters no longer have a scale of 1.0.
scanning
The process of capturing data in raster format with a device called a scanner. Some scanners also use software to convert raster data to vector data.
scene
A document containing 3D data that can be viewed in perspective.
schema
The structure or design of a database or database object such as a table.
The definition of the database. The schema can either be modeled in UML using a CASE tool or defined directly within ArcCatalog using wizards.
SDE
See ArcSDE.
SDE 3 layer
A standalone feature class in a geodatabase built with SDE version 3. Can be served by an SDE 3 or ArcSDE 8 server.
secant projection
A form of map projection in which the conceptual surface of the projection (cone, cylinder, or plane) cuts through the earth's surface. See also tangent projection.
segment
A line that connects vertices. For example, in a sketch of a building, a segment would represent one wall.
select
To choose from a number or group of features or records; to create a separate set or subset.
Selectable layers list
A list available from the Selection menu in ArcMap that lets you choose which layers you want to select. For example, you might want to select a large number of buildings by drawing a box around them; but as you drew the selection box, you selected a parcel by mistake. To avoid this, you might uncheck the Parcels layer in the Selectable Layers list so that parcels cannot be selected.
selected values
A subset of the features in a layer or records in a table. ArcMap provides several ways to select features and records graphically or according to their attribute values.
selection anchor
When editing in ArcMap, a small "x" located in the center of selected features. The selection anchor is used when you move features using snapping. It is the point on the feature or group of features that will be snapped to the snapping location. This is also the point around which your selection will rotate when you use the Rotate tool and around which your feature will scale when you use the Scale tool in ArcMap.
semimajor axis
The equatorial radius of a spheroid. Often known as "a".
semiminor axis
The polar radius of a spheroid. Often known as "b".
semivariogram
The variogram divided by two.
server
A computer program that receives a request from a client, processes it to generate results, and returns the results to the client.
A computer on which a server process runs.
service
A computer program that receives and processes requests from clients.
shape
The characteristic appearance or visible form of a geographic object. Geographic objects can be represented on a map using one of three basic shapes: points, lines, or polygons.
shapefile
A vector data storage format for storing the location, shape, and attributes of geographic features. A shapefile is stored in a set of related files and contains one feature class.
shared boundary
A segment or boundary common to two features. For example, in a parcel database, adjacent parcels will share a boundary. Another example might be a parcel that shares a boundary on one side with a river. The segment of the river that coincides with the parcel boundary would share the same coordinates as the parcel boundary.
shared vertex
A vertex common to multiple features. For example, in a parcel database, adjacent parcels will share a vertex at the common corner.
shortcut key
A command's shortcut key executes the command directly without first having to open and navigate a menu. For example, Ctrl+C is a well-known shortcut for copying a file in Windows.
shortest path
A Spatial Analyst function that calculates the least-cost path from a destination point to the cheapest source, using the Cost Weighted Distance and Cost Weighted Direction datasets created via the Cost Weighted Distance function.
sill
A parameter of a variogram or semivariogram model that represents a value that the variogram tends to when distances become very large. At large distances, variables become uncorrelated, so the sill of the semivariogram is equal to the variance of the random variable.
simple edge feature
In geodatabases, a line feature that corresponds to a single network element in the logical network. See also complex edge feature.
simple feature
A feature that implements ESRI Simple Feature. A point, multipoint, line, polyline, or polygon.
simple junction feature
In a geodatabase, a junction feature that corresponds to a single network element in the logical network. See also complex junction feature.
simple relationship
Describes associations between data sources that exist independently of each other. A coverage and table are independent of each other if, when you delete the primary object, the related object continues to exist. For example, a table contains measurements taken at different stations. If you stop using a station and delete that point, you might keep the measurements for historical purposes.
single precision
Refers to a level of coordinate accuracy based on the number of significant digits that can be stored for each coordinate. Single precision numbers store up to seven significant digits for each coordinate, retaining a precision of ±5 meters in an extent of 1,000,000 meters. ArcInfo datasets can be stored as either single or double precision coordinates. See also double precision.
single-user geodatabase
A personal geodatabase. It can handle a single editor and multiple readers.
sink
In a network, a junction feature at which flow terminates. See also source.
sketch
When editing in ArcMap, a shape that represents a feature's geometry. Every existing feature on a map has this alternate form, a sketch. A sketch lets you see exactly how a feature is composed with all vertices and segments of the feature visible. To modify a feature, you must modify its sketch. To create a feature, you must first create a sketch. You can only create line and polygon sketches, as points have neither vertices nor segments.
Sketches help complete the current task. For example, the Create New Feature task uses a sketch you create to make a new feature. The Extend/Trim Feature task uses a sketch you create to determine where the selected feature will be extended or trimmed. The Cut Polygon Feature task uses a sketch you create to determine where the polygon will be cut into two features.
sketch constraints
In ArcMap editing, the angle or length limitations you can place on segments you're creating. These commands are available on the Sketch tool context menu. For example, you can set a length constraint that specifies that the length of the segment you're creating will be 50 map units. At whatever angle you create that segment, its length will be constrained to 50 map units. Angle constraints work in the same way. For example, you can set an angle constraint that specifies that the angle of the segment you're creating will be 45 degrees measured from another feature that already exists. At whatever length you create that segment, its angle will be constrained to 45 degrees.
sketch operations
In ArcMap, editing operations that are performed on an existing sketch. Examples are Insert Vertex, Delete Vertex, Flip, Trim, Delete Sketch, Finish Sketch, and Finish Part. All of these operations are available from the Sketch context menu, which is available when you right-click any part of a sketch using any editing tools.
slope
The incline, or steepness, of a surface. The slope of a TIN face is the steepest downhill slope of a plane defined by the face. The slope for a cell in a raster is the steepest downhill slope of a plane defined by the cell and its eight surrounding neighbors. Slope can be measured in degrees from horizontal (0-90) or percent slope, which is the rise divided by the run, times 100. A slope of 45 degrees equals 100 percent slope. As slope angle approaches vertical (90 degrees), the percent slope approaches infinity.
snap extent

R
radius
The distance from the center to the outer edge of a circle or circular curve.
range
A parameter of a variogram or semivariogram model that represents a distance beyond which there is little or no autocorrelation among variables.
range domain
A type of attribute domain. Specifies a valid range of values for a numeric attribute.
raster
Represents any data source that uses a grid structure to store geographic information. See grid and image.
raster band
A measure of some characteristic or quality of the features being observed in a raster. Some rasters have a single band; others have more than one. For example, satellite imagery commonly has multiple bands representing different wavelengths of energy from along the electromagnetic spectrum.
Raster Calculator
A Spatial Analyst function that provides a powerful tool for performing multiple tasks. You can perform mathematical calculations using operators and functions, set up selection queries, or type in Map Algebra syntax.
raster catalog
A collection of rasters defined in a table of any format, in which the records define the individual rasters that are included in the catalog. A raster catalog is used to display adjacent rasters without having to merge or mosaic them together into one large file.
raster cell
A discretely uniform unit (square or rectangle) that represents a portion of the earth such as a square meter or square mile. Each pixel has a value that corresponds to the feature or characteristic at that site such as a soil type, census tract, or vegetation class.
raster dataset
Contains raster data organized into bands. Each band consists of an array of cells with optional attributes for each cell (pixel).
raster model
A representation of the world as a surface divided into a regular grid of cells. Raster models are useful for storing data that varies continuously such as in an aerial photograph, a satellite image, a surface of chemical concentrations, or an elevation surface.
raster resolution
The size of the cells in a raster. Only features larger than or equal to the cell size can be discerned in a raster.
RDBMS
Relational database management system. A database management system with the ability to access data organized in tables that can be related to each other by a common field (column). An RDBMS has the capability to recombine the data items from different files, providing powerful tools for data usage. ArcSDE supports several commercial RDBMS. See also database management system (DBMS).
reclassify
A Spatial Analyst function that takes input cell values and replaces them with new output cell values.
reconcile
In version management, reconciling is the process of merging all modified datasets, feature classes, and tables in the current edit session and a second target version. All features and rows that do not conflict are merged into the edit session, replacing the current features or rows. Features that are modified in more than one version are conflicts and require further resolution via the Conflict Resolution dialog box.
record
In an attribute table, a single "row" of thematic descriptors. In SQL terms, a record is analogous to a tuple.
A logical unit of data in a file. For example, there is one record in the ARC file for each arc in a coverage.
reference ellipsoid
See ellipsoid.
reference system
A method for identifying positions on the globe. This is often constructed with a grid that either refers to earth's latitude and longitude (graticule), or a planar equivalent that divides grid lines by a fixed length from a predefined point of origin.
referential integrity
A mechanism to ensure that data remains accurate and consistent as the database changes. When changes are made to a table related to another table by a common key, the changes are automatically reflected in both tables.
relate
An operation that establishes a temporary connection of records in two tables using an item common to both. See also relationship class and relational join.
relate manager
An ArcToolbox utility used to build, modify, save, and delete connections (relates) between tables. Saved connections can be reactivated in future ArcToolbox sessions.
relational database
A method of structuring data as collections of tables that are logically associated to each other by shared attributes. Any data element can be found in a relation by knowing the name of the table, the attribute (column) name, and the value of the primary key. See also RDBMS, relate, key attributes, and relational join.
relational database management system
See RDBMS.
relational join
The operation of relating and physically merging two attribute tables using their common item.
relational operators
Operators within the Raster Calculator of Spatial Analyst. These operators evaluate specific relational conditions. If a condition is TRUE, the output is assigned a value of 1. If the condition is FALSE, the output is assigned a value of 0.
Relational operators: ==, <, >, <>, >=, <=
relationship
An association or link between two objects in a database. Relationships can exist between spatial objects (features in feature classes), nonspatial objects (rows in a table), or between spatial and nonspatial objects.
relationship class
Objects in a real-world system often have particular associations with other objects in the database. These kinds of associations between objects in the geodatabase are called relationships. Relationships can exist between spatial objects (features in feature classes), between nonspatial objects (rows in a table), or between spatial and nonspatial objects. While spatial objects are stored in the geodatabase in feature classes, and nonspatial objects are stored in object classes, relationships are stored in relationship classes.
rematching
The process of regeocoding a subset of features in a geocoded feature class.
rendering
In 3D Analyst, the Rendering tab on the Layer Properties dialog box lets you control whether or not a layer is rendered during scene navigation, how it is shaded, and its drawing priority. It also lets you adjust how your computer's memory is allocated when rendering large images.
repository
A database that contains the schema information needed to create a geodatabase from a UML model created using a CASE tool.
resample
The process of extrapolating new cell values when transforming rasters to a new coordinate space or cell size. The three most common resampling techniques are nearest neighbor assignment, bilinear interpolation, and cubic convolution.
resolution
The accuracy at which a given map scale can depict the location and shape of geographic features. The larger the map scale, the higher the possible resolution. As the map scale decreases, resolution diminishes and feature boundaries must be smoothed, simplified, or not shown at all. For example, small areas may have to be represented as points.
The size of the smallest feature that can be represented in a surface.
The number of cells in the x- and y-directions in a raster.
rhumb line
A complex curve on the earth's surface that crosses every meridian at the same oblique angle; a straight line on the Mercator projection. Also called a loxodrome (Snyder and Voxland, 1989).
row
A record in an attribute table.
The horizontal dimension of a table composed of a set of columns containing one data item each.
A horizontal group of cells in a raster.

Q
query
A question or request used for selecting features. A query often appears in the form of a statement or logical expression. In ArcMap, a query contains a field, an operator, and a value.

P
pan
To move the viewing window up, down, or sideways to display areas in a geographic dataset that, at the current viewing scale, lay outside the viewing window.
parallel
A reference line on the earth's surface that runs east–west around a sphere or spheroid and is parallel to the equator.
parametric curve
A curved segment that has only two vertices as endpoints, instead of being made of numerous vertices. When editing features in ArcMap, you can create a parametric curve using the Arc tool or the Tangent Curve command. Also known as a true curve.
password
The password used for authentication when you log in to an RDBMS.
path
The location of a file or directory on a disk. A path is always specific to the computer operating system.
path label
Describes the nature of the association between the objects in a relationship. The forward path label describes the relationship when navigating from the origin to the destination; for example, station points "have" measurements. The backward path label describes the same relationship navigating from the destination to the origin, which might be "are taken at" in this example; measurements "are taken at" stations.
PC ARC/INFO coverage
A coverage created with PC ARC/INFO.
percent slope
One way slope is measured. With this method, the rise is divided by the run.
permanent dataset
A raster dataset permanently stored on disk. All output raster results from Spatial Analyst are temporary, unless you specify a location on disk and a filename in a function dialog box, you make the temporary dataset permanent, or you save the map document. In these three cases, temporary results will become permanent datasets on disk. See make permanent.
personal geodatabase
A geodatabase, usually on the same network as the client application (for example, ArcMap), that supports one editor at a time. Personal geodatabases are managed in a Microsoft Jet Engine database.
perspective view
Allows you to view the data in a scene in 3D from a perspective that you can control by navigating the scene or from a specified position.
pixel
Picture element. A raster cell in images. See also raster cell.
planar coordinate system
A two-dimensional measurement system that locates features on a map based on their distance from an origin (0,0) along two axes, a horizontal x-axis representing east–west and a vertical y-axis representing north–south.
planar projection
A form of projection where the earth is projected onto a conceptual tangent or secant plane. Usually, a planar projection is the same as an azimuthal projection (Snyder and Voxland, 1989). See also tangent projection and secant projection.
planar topology
Represents collections of topological feature classes that share geometry among their boundaries. One or more line and polygon feature classes that share geometry participate in a common planar topology. Updating shared boundaries updates all features in the topology.
point
A single x,y coordinate pair that represents a single geographic feature such as a telephone pole.
point mode digitizing
One of two methods of digitizing features using the Sketch tool in ArcMap or from a paper map using a digitizer. With point mode digitizing, you can create or edit features by digitizing a series of precise points, or vertices. Point mode digitizing is effective when precise digitizing is required—for example, when digitizing a perfectly straight line. See also stream mode digitizing.
polar aspect
A planar projection with its central point located at either the North or South Pole.
polygon
A two-dimensional feature representing an area such as a state or county.
polygon–arc topology
A coverage polygon is made up of arcs that define the boundary and a label point that links the polygon feature to an attribute record in the coverage polygon attribute table (PAT). ArcInfo stores polygons topologically as a list of arcs and a label for each polygon.
polyline
A two-dimensional feature representing a line containing one or more line segments—that is, any line defined by three or more points. Line features such as boundaries, roads, streams, and streets are usually polylines.
port number
The TCP/IP port number on which an ArcSDE geodatabase instance is communicating.
post
During versioned geodatabase editing, posting is the process of applying the current edit session to the reconciled target version.
power functions
Functions within the Raster Calculator of Spatial Analyst. These functions apply a Power to the values in a single input raster. Three Power functions are available: Sqrt, Sqr, and Pow.
pre-7.0 coverage
Coverages created with a version of ArcInfo prior to version 7.0. Can't be accessed by ArcCatalog and ArcMap until after the ConvertWorkspace command has been used to modify the coverage workspace.
precision
Refers to the number of significant digits used to store coordinate values. Precision is important for accurate feature representation, analysis, and mapping. ArcInfo supports single and double precision.
preliminary topology
In coverages, refers to incomplete region topology. Region topology defines region-arc and region–polygon relationships. A topological region has both the region–arc relationship and the region–polygon relationship. A preliminary region has the region–arc relationship but not the region–polygon relationship. In other words, preliminary regions have no polygon topology. Coverages with preliminary topology have red in their icons in ArcCatalog.
preview
A live view of GIS data in ArcCatalog. You can pan and zoom the preview, query features, and create thumbnail images to store in metadata.
primary key
One or more attributes whose values uniquely identify a row in a database table.
Used to create a relationship class, the primary key resides in the origin object class. To join two object classes together, the primary key and foreign key must share the same values.
See also foreign key, relate, and relationship class.
prime meridian
A meridian of reference that defines the origin of the longitude values, 0° east or west.
profile graph
A graph of the height of a surface along a specified line.
projected coordinate system
A reference system used to measure horizontal and vertical distances on a planimetric map. A coordinate system is usually defined by a map projection, a spheroid of reference, a datum, one or more standard parallels, a central meridian, and possible shifts in the x- and y-directions to locate x,y positions of point, line, and area features.
In ArcInfo, a system with units and characteristics defined by a map projection. A common coordinate system is used to spatially register geographic data for a given area.
A reference system consisting of a set of points, lines, and/or surfaces, and set of rules used to define the positions of points in space either in two or three dimensions.
projected coordinates
A measurement of locations on the earth's surface expressed in a two-dimensional system that locates features based on their distance from an origin (0,0) along two axes, a horizontal x-axis representing east–west and a vertical y-axis representing north–south. A map projection transforms latitude and longitude to x,y coordinates in a projected coordinate system. See also geographic coordinates.
projection
A mathematical formula that transforms feature locations between the earth's curved surface and a map's flat surface. A projected coordinate system includes the information needed to transform locations expressed as latitude and longitude values to x,y coordinates. Projections cause distortions in one or more of these spatial properties: distance, area, shape, and direction.
property
An attribute of an object defining one of its characteristics or an aspect of its behavior. For example, the Visible property affects whether a control can be seen at run time. You can set a data source's properties using its Properties dialog box.
pyramids
In raster datasets, reduced resolution layers, or pyramids, record the original data in decreasing levels of resolution. The coarsest level of resolution is used to quickly draw the entire dataset. As you zoom in, layers with finer resolutions are drawn; performance is maintained because you're drawing successively smaller areas.

O
object
In geodatabases, the representation of a real-world entity. An object has properties and behavior.
The interface by which an application program accesses an operating system and other services.
object class
While spatial objects (features) are stored in feature classes in a geodatabase, nonspatial objects are stored in object classes. A table is an object class if it has a column with the data type OID (Object Identifier), where each row in the table is an object. In a geodatabase, nonspatial objects can have custom behavior.
oblique aspect
A planar or cylindrical projection with its central point located at some point not on the equator or at the poles.
offset
To change the z-value for a surface or features in a scene by a constant amount or using an expression. Offsets may be applied to make features draw just above a surface.
OGC
OpenGIS Consortium. OpenGIS is defined as transparent access to heterogeneous geodata and geoprocessing resources in a networked environment. The goal is to provide a comprehensive suite of open interface specifications that enable developers to write interoperational components that provide these capabilities.
OLE DB provider
Object Linking and Embedding Database provider. Each provider communicates with and retrieves data from a different database, but you can work with data retrieved by any provider in the same way. Typically, they can only retrieve nonspatial data. However, if an OLE DB provider can retrieve geographic data in OpenGIS format, you can work with that data in ArcInfo.
operator
A mathematical symbol that performs an operation. Operators are provided in the Raster Calculator of Spatial Analyst to enable analysis to be performed within and between multiple rasters.
Oracle
A commercial RDBMS supported by ArcSDE.
origin
The primary object in a relationship. For example, a feature class containing points at which measurements are taken; the measurements are stored in the associated table. See also relationship and destination.
orthographic view
Allows you to view the data in a scene as a 2D plane seen from above. There is no perspective foreshortening in orthographic view, so scale is constant across the entire display.
Overlay wizard
An ArcToolbox wizard that uses overlay operations to create a new coverage by computing the geometric intersection of two coverages—an input coverage and an overlay coverage. See also identity, intersect, and union.
overshoot
That portion of an arc digitized past its intersection with another arc. See also dangling arc.

N
NAD 1927
North American Datum of 1927. A local datum and geographic coordinate system used in North America. Replaced by NAD 1983. Also known as NAD27.
NAD 1983
North American Datum of 1983. A geocentric datum and geographic coordinate system used in North America. Also known as NAD83.
natural neighbors
An interpolation method where cell values are estimated using weighted values of the input data points that are their natural neighbors, determined by creating a triangulation of the input points.
navigate
To interactively change the perspective view of a scene by moving the mouse.
nearest-neighbor resampling
Uses the value of the closest cell to assign a value to the output cell when resampling.
neatline
A border commonly drawn around geographic features, often to separate them from other map elements.
neighborhood statistics
A focal Spatial Analyst function that computes an output grid where the value at each location is a function of the input cells within a specified neighborhood of the location.
network
A set of edges and junctions that are topologically connected to each other. See also logical network.
network ancillary role
In a geometric network, junction features can act as sources or sinks for calculating flow direction. If a junction is a source or a sink, it is said to have an ancillary role in the network.
network feature
A feature that participates in a geometric network.
network trace
Navigates a network following connectivity defined by the geometric network. Specific kinds of network traces are:
Find connected
Find loops
Find common ancestors
Trace upstream
Trace downstream
See also geometric network.
nodata
Some rasters have empty cells within the area for which data was collected. For grids, these cells are nodata, while for other formats they are often assigned a special value, such as -9999. Rasters with some nodata cells are also created by some raster analysis tools, or Spatial Analyst's Reclassify function. You can control the display of nodata by setting the nodata color on the Symbology tab of the Layer Properties dialog box. See null value and background.
node
A location on a TIN surface at the intersection of two or more edges. Nodes on a TIN surface store elevation (z) values and may have tag values. Point features used to generate a TIN become nodes in the TIN. Additional nodes are added to the TIN at the intersection of edges.
normalize
Creating a ratio by dividing two data values. Normalizing data minimizes differences in values based on the size of areas or numbers of features in each area. For example, dividing a value by the area of a feature yields a value per unit area, or density.
North arrow
A map component that shows how a map is oriented.
NSDI
National Spatial Data Infrastructure. Coordinated by the FGDC. The NSDI encompasses policies, standards, and procedures for organizations to cooperatively produce and share geographic data. The NSDI is being developed in cooperation with organizations from state, local, and tribal governments; the academic community; and the private sector.
nugget
A parameter of a covariance or semivariogram model that represents independent error, measurement error, and/or microscale variation at spatial scales that are too fine to detect. The nugget effect is seen as a discontinuity at the origin of either the covariance or semivariogram model.
null value
The absence of a value. A geographic feature for which there is no associated attribute information.