GIS Glossary/T

GIS Glossary

0-9 | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

table
A set of data elements arranged in rows and columns. Each row represents a single record. Each column represents a field of the record. Rows and columns intersect to form cells, which contain a specific value for one field in a record.

table of contents
In ArcGIS, a tabbed list of data frames and layers (or tables) on a map that shows how the data is symbolized, the source of the data, and whether or not each layer is selectable.

table view
A representation of tabular data for viewing and editing purposes. The table view created when a table is added to ArcMap is a copy of the actual table data stored in memory.

tabular data
Descriptive information, usually alphanumeric, that is stored in rows and columns in a database and can be linked to spatial data.

tactical graphic
In MOLE, a type of graphic that aids in regulating the movement of force units, such as lane boundaries and obstacles.

tactical symbol
In MOLE, a type of graphic that represents a military unit (such as Company A, 1st Battalion of the 135th Infantry), equipment, or installation (such as a hospital or radar site). Force elements are also known as force units or military units.

tag
In markup languages such as XML and HTML, a set of bracketed characters that define the structural purpose of a block of content.

tagged value
A pair of keywords used to set additional properties for elements that are not part of the UML specification, such as the point, line, and polygon geometry of a feature class, or the length of a field in a table.

tangent projection
A projection whose surface touches the globe's without piercing it. A tangent planar projection touches the globe at one point, while tangent conic and cylindrical projections touch the globe along a line. At the point or line of tangency, the projection is free from distortion.

target
In ArcScene and ArcGlobe, the center point in a scene's view at which the camera is aimed.

target computer
A computer to which an application is deployed.

target layer
In an ArcMap editing session, the layer to which edits will be applied. The target layer must be specified when creating new features and modifying existing features.

target offset
In ArcScene and ArcGlobe, the height of a target point above a surface used when calculating lines of sight and viewsheds.

target theme
In ArcView 3.x, the theme from which features are selected during a theme-on-theme selection operation. Multiple target themes may be specified for a theme-on-theme selection.

task
In ArcGIS Explorer and ArcGIS Server, a user interface combined with a particular piece of GIS functionality in a format that can be easily added to applications. Tasks make it easy for the end user of an application to perform common functions, such as querying, editing, or geoprocessing. In many cases, tasks also facilitate a developer's job because they can be added to an application without requiring any code to be written.

TAT
A table containing text attributes, such as color, font, size, location, and placement angle, for an annotation subclass in a coverage. In addition to user-defined attributes, the text attribute table contains a sequence number and text feature identifier.

TCP/IP
Acronym for Transmission Control Protocol/Internet Protocol. The most common protocol for Internet traffic. The Transmission Control Protocol (TCP) is a communication protocol layered above the Internet Protocol (IP), which is a suite of nonproprietary communication protocols, or sets of rules, that allow computers to send and receive data over networks.

TDOP
Acronym for dilution of precision. An indicator of satellite geometry for a constellation of satellites used to determine a position. Positions with a lower DOP value generally constitute better measurement results than those with higher DOP. Factors determining the total GDOP (geometric DOP) for a set of satellites include PDOP (positional DOP), HDOP (horizontal DOP), VDOP (vertical DOP), and TDOP (time DOP).

template
In ArcMap, a kind of map document that provides a quick way to create a new map. Templates can contain data, a custom interface, and a predefined layout that arranges map elements, such as north arrows, scale bars, and logos, on the virtual page. Map templates have a .mxt file extension.

temporal data
Data that specifically refers to times or dates. Temporal data may refer to discrete events, such as lightning strikes; moving objects, such as trains; or repeated observations, such as counts from traffic sensors.

temporal event
In ArcGIS Tracking Analyst, a type of event used to describe observations through time of particular objects or groups of objects.

temporal extent
All the temporal information, including the earliest and last observations, of a data layer in ArcGIS Tracking Analyst.

temporal GIS
An emerging capability in GIS for integrating temporal data with location and attribute data.

temporal object
In ArcGIS Tracking Analyst, an object being observed through time.

temporal object table
The component of a complex temporal event in ArcGIS Tracking Analyst that contains feature shape and attribute information.

temporal observation
In ArcGIS Tracking Analyst, data gathered for a given object through time.

temporal observation table
The component of a complex temporal event in ArcGIS Tracking Analyst that contains feature attribute information, and possibly time and date information.

temporal offset
A function in ArcGIS Tracking Analyst that allows users to play back the temporal display of data as if it had occurred at a user-defined date and time. The temporal offset does not change the underlying data; it simply allows the data to be displayed as if it were happening at a different time.

temporal window
In ArcGIS Tracking Analyst, the time range within which data will be displayed. Temporal windows can be set at the layer level on the Symbology tab.

temporary dataset
A dataset temporarily stored on disk or in memory.

terrain
An area of land having a particular characteristic, such as sandy terrain or mountainous terrain.

terrain dataset
A multiresolution, TIN-based surface built from measurements stored as features in a geodatabase. Associated and supporting rules help organize the data and control how features are used to define the surface. Terrain datasets are typically derived from sources such as lidar, sonar, and photogrammetric data.

terrain dataset pyramid
A data structure associated with a terrain dataset used to define a multi-resolution surface, which organizes data into different levels of detail, or pyramid levels, and serves to improve performance by enabling the terrain to access only the data required for a particular display or analysis function. Data that is over-sampled or redundant can be avoided.Two pyramid types can be used to build a terrain: z-tolerance and window size. Z-tolerance pyramids filter data into different pyramid levels based on their vertical significance. Window size pyramids filter the data through localized selection biased to max, min, or mean height.

terrain pyramid group
In a terrain dataset, a collection of line or polygon feature classes used to represent those geographic features at different levels of detail.

terrain pyramid level
An individual level of detail in a terrain dataset pyramid. Each level has a pair of properties: resolution and scale. The resolution defines the amount of detail represented by the level, and the scale is a threshold that indicates at which display scale the level becomes active.

terrain pyramid resolution bounds
The range of pyramid levels for which polygon or polyline features will be enforced in the surface of a terrain dataset.

terrain tiles
A spatially coherent organization of terrain data facilitating efficient retrieval and editing. Tile definition is based on the average point spacing of the source data.

tessellation
The division of a two-dimensional area into polygonal tiles, or a three-dimensional area into polyhedral blocks, in such a way that no figures overlap and there are no gaps.

text attribute table
A table containing text attributes, such as color, font, size, location, and placement angle, for an annotation subclass in a coverage. In addition to user-defined attributes, the text attribute table contains a sequence number and text feature identifier.

text box
An entity that displays text entered by a user or derived from another source for editing purposes.

text envelope
A rectangle that bounds a text string.

text formatting tag
Tags used with text in ArcGIS that allow formatting to be modified for a portion of a text string. This allows the creation of mixed-format text where, for example, one word in a sentence is underlined. Text formatting tags adhere to XML syntax rules and can be used most places where both a text string and a text symbol can be specified. The tags are most commonly used with labels, annotation, and graphic text.

text label
Text placed next to a feature on a map to describe or identify it.

text modifier
Nonspatial information about a geographic feature in a GIS, usually stored in a table and linked to the feature by a unique identifier. For example, attributes of a river might include its name, length, and sediment load at a gauging station.

text symbol
A text style defined by font, size, character spacing, color, and so on, used to label maps and geographic features.

texture
A digital representation of the surface of a feature.

texture coordinate
In ArcScene and ArcGlobe, a location embedded in a geometry that helps define how a texture is mapped.

texture mapping
The application of a texture to a 3D object in ArcScene and ArcGlobe.

thematic data
Features of one type that are generally placed together in a single layer.

thematic map
A map designed to convey information about a single topic or theme, such as population density or geology.

theme
In ArcView 3.x, a set of related geographic features such as streets, parcels, or rivers, along with their attributes. All features in a theme share the same coordinate system, are located within a common geographic extent, and have the same attributes. Themes are similar to layers in ArcGIS 8.x and 9.0.

theme table
In ArcView 3.x, a document object linked to the set of features in a theme. It serves as an interface to the underlying database, allowing manipulation of the data.

theme-on-theme selection
In ArcView 3.x, an operation in which features in one theme are selected based on their spatial relationships with features in another theme. Theme-on-theme selection is used to find features that intersect other features, completely contain other features, or are within a specified distance of other features.

theodolite
A surveying instrument for measuring vertical and horizontal angles, consisting of an alidade, a telescope, and graduated circles mounted vertically and horizontally.

Thiessen polygons
Polygons generated from a set of sample points. Each Thiessen polygon defines an area of influence around its sample point, so that any location inside the polygon is closer to that point than any of the other sample points. Thiessen polygons are named for the American meteorologist Alfred H. Thiessen (1872-1931).

thinning
Reducing the number of points that define a line while preserving its essential shape.

third normal form
The third level of guidelines for designing table and data structures in a relational database. The third-normal-form guideline incorporates the guidelines of first and second normal form; in addition, it recommends removing from a table those columns that do not depend on the table's primary key. A database that follows these guidelines is said to be in third normal form.

thread
A process flow through an application. An application can have many threads.

thread neutral apartment
An apartment that has no threads permanently associated with it; threads enter and leave the apartment as required.

three-dimensional shape
A point, line, or polygon that stores x-, y-, and z-coordinates as part of its geometry. A point has one set of z-coordinates; lines and polygons have z-coordinates for each vertex in a shape.

three-tier configuration
A software configuration in which three software applications (commonly a client program, application server, and database server) work together to accomplish a task.

threshold ring analysis
In business analysis, an operation that creates rings that contain a given population around a store or stores on a map.

thumbnail
A miniaturized version of a graphics file. A thumbnail can be used as a visual index for larger data or images.

tic
A registration or geographic control point for a coverage representing a known location on the earth's surface. Tics allow all coverage features to be recorded in a common coordinate system. 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 particular coordinate system.

tick marks
Graphics that mark divisions of measurement on a scale bar.

tidal datum
A vertical datum in which zero height is defined by a particular tidal surface, often mean sea level. Examples of tidal surfaces include mean sea level, mean low water springs, and mean lower low water. Most traditional vertical geodetic datums are tidal datums.

tie point
A point whose location is determined by a tie survey.

tie survey
A survey that uses a point of known location on the ground to determine the location of a second point.

tied candidates
In geocoding, two or more records that yield the same score when matching an address.

TIGER
Acronym for Topologically Integrated Geographic Encoding and Referencing. The nationwide digital database developed for the 1990 census, succeeding the DIME format. TIGER files contain street address ranges, census tracts, and block boundaries.

TIGER/Line files
A digital database of geographic features, covering the entire United States and its territories, that provides a topological description of the geographic structure of these areas. The files are a public product created from the U.S. Census Bureau Topologically Integrated Geographic Encoding and Referencing (TIGER) database. TIGER/Line files define the locations and spatial relationships of streets, rivers, railroads, and other features to each other and to the numerous geographic entities for which the Census Bureau tabulates data from its censuses and sample surveys.

tight 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.

tiling
An internal subsetting of a spatial dataset (commonly raster) into a manageable rectangular set, or rows and columns of pixels, typically used to process or analyze a large raster dataset without consuming vast quantities of computer memory.

time mode
One of two methods for displaying temporal data in ArcGIS Tracking Analyst: real-time mode or playback mode. Time modes are determined by the use of the Tracking Analyst Playback Manager.

time window
In networks, the time during which a stop can be visited. For example, on a bus route, each stop may have a time window of 15 minutes. If the bus arrives before its 15-minute time slot, it will wait until the appropriate time before proceeding. If a bus arrives after its 15-minute time slot, the stop will display a symbol to denote a time violation.

time window violation
In ArcGIS Network Analyst, a time window violation occurs when a route arrives at a network location after its associated time window has closed.

TIN
Acronym for triangulated irregular network. A vector data structure that partitions geographic space into contiguous, nonoverlapping triangles. The vertices of each triangle are sample data points with x-, y-, and z-values. These sample points are connected by lines to form Delaunay triangles. TINs are used to store and display surface models.

TIN dataset
A dataset containing a triangulated irregular network (TIN). The TIN dataset includes topological relationships between points and neighboring triangles.

TIN layer
A layer that references a set of TIN data. TIN data contains a triangulated irregular network (TIN) and includes topological relationships between points and neighboring triangles.

TIN line type
One of four types of edges that may be found in a TIN: regular lines, hard breaklines, soft breaklines, and outside lines. Regular lines define the TIN's basic structure, connecting triangle nodes. Hard breaklines represent features that mark pronounced changes in slope, like roads or rivers. Soft breaklines mark milder changes in slope and sometimes artificial boundaries, such as the border of a study area. Outside lines designate parts of a TIN structure that lie beyond the TIN's zone of interpolation. Every TIN contains regular lines; other line types may or may not be present.

Tissot indicatrix
A graphical representation of the spatial distortion at a particular map location. The indicatrix is the figure that results when a circle on the earth's surface is plotted to the corresponding point on a map. The shape, size, and orientation of an indicatrix at any given point depend on the map projection used. In conformal (shape-preserving) projections, the indicatrix is a circle; in nonconformal projections, it is an ellipse at most locations. As a visual aid, indicatrices convey a general impression of distortion; as mathematical tools, they can be used to quantify distortion of scale and angle precisely. The indicatrix is named for Nicolas Auguste Tissot, the French mathematician who developed it.

Tissot's indicatrix
A graphical representation of the spatial distortion at a particular map location. The indicatrix is the figure that results when a circle on the earth's surface is plotted to the corresponding point on a map. The shape, size, and orientation of an indicatrix at any given point depend on the map projection used. In conformal (shape-preserving) projections, the indicatrix is a circle; in nonconformal projections, it is an ellipse at most locations. As a visual aid, indicatrices convey a general impression of distortion; as mathematical tools, they can be used to quantify distortion of scale and angle precisely. The indicatrix is named for Nicolas Auguste Tissot, the French mathematician who developed it.

TLM
Acronym for topographic line map. A map that uses line contours to show elevations and depressions of the earth's surface. Topographic line maps may be used to portray topography, elevations, infrastructure, hydrography and vegetation.

TNA
Acronym for thread neutral apartment. An apartment that has no threads permanently associated with it; threads enter and leave the apartment as required.

Tobler's First Law of Geography
A formulation of the concept of spatial autocorrelation by the geographer Waldo Tobler (1930-), which states "Everything is related to everything else, but near things are more related than distant things."

TOC
In ArcGIS, a tabbed list of data frames and layers (or tables) on a map that shows how the data is symbolized, the source of the data, and whether or not each layer is selectable.

token
A line of encrypted code generated by an authenticating service that allows a client to access a Web service. In ArcWeb Services, a token must be regenerated by passing in a valid user name and password each time it expires.

tolerance
The minimum or maximum variation allowed when processing or editing a geographic feature's coordinates. For example, during editing, if a second point is placed within the snapping tolerance distance of an existing point, the second point will be snapped to the existing point.

to-node
Of an arc's two endpoints, the last one digitized. From- and to-nodes give an arc left and right sides and, therefore, direction.

tool
A command that requires interaction with the GUI before an action is performed. For example, a zoom tool requires a user to use the mouse to click on or draw a box over a digital map before the tool will cause the map to be redrawn at a larger scale.

toolbar
A graphical user interface (GUI) with buttons that allow users to execute software commands.

toolbox
In ArcGIS, an object that contains toolsets and geoprocessing tools. It takes the form of a .tbx file on disk, or a table in a geodatabase.

Toolbox tree
In ArcToolbox (part of ArcGIS 8.3 and earlier versions), a hierarchical view of toolsets and tools grouped by functionality.

toolkit
An application that software developers can use with their integrated development environment (IDE) to make programming easier. For example, SOAP toolkits allow users to interact with SOAP Web services through various languages such as Java and .NET.

toolset
In ArcGIS, a group of geoprocessing tools that perform similar tasks.

ToolTip
The description of a tool or control that is displayed on screen when the mouse is paused over it.

topo sheet
A rectangular map bounded by lines of latitude and longitude, often a map sheet in either the 7.5-minute or 15-minute series published by the U.S. Geological Survey. Quadrangles are also called topo sheets.

topographic line map
A map that uses line contours to show elevations and depressions of the earth's surface. Topographic line maps may be used to portray topography, elevations, infrastructure, hydrography and vegetation.

topographic map
A map that represents the vertical and horizontal positions of features, showing relief in some measurable form, such as contour lines, hypsometric tints, and relief shading.

topography
The study and mapping of land surfaces, including relief (relative positions and elevations) and the position of natural and constructed features.

topological association
The spatial relationship between features that share geometry such as boundaries and vertices. When a boundary or vertex shared by two or more features is edited 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.

topological overlay
A spatial operation in which two or more maps or layers registered to a common coordinate system are superimposed, either digitally or on a transparent material, for the purpose of showing the relationships between features that occupy the same geographic space.

topology
In geodatabases, the arrangement that constrains how point, line, and polygon features share geometry. For example, street centerlines and census blocks share geometry, and adjacent soil polygons share geometry. Topology defines and enforces data integrity rules (for example, there should be no gaps between polygons). It supports topological relationship queries and navigation (for example, navigating feature adjacency or connectivity), supports sophisticated editing tools, and allows feature construction from unstructured geometry (for example, constructing polygons from lines).

topology cache
A temporary collection of edges and nodes used in ArcMap to query and edit the topological coincidence between features. The cache is built for the current display extent and is stored in the computer's memory.

topology error
A measured, observed, calculated, or interpreted value that differs from the true value or the value that would be obtained by a perfect observer using perfect equipment and perfect methods under perfect conditions.

topology fix
In ArcMap, a predefined method for correcting topology errors. For example, predefined topology fixes for a dangling line include snapping, trimming, or extending to another line.

topology rule
An instruction to the geodatabase defining the permissible relationships of features within a given feature class or between features in two different feature classes.

toponym
A place-name.

tour
In ArcInfo Workstation, a network solver that determines the minimum-cost path to reach a series of stops, and also determines the order in which the stops are visited.

township
In the United States, a quadrangle approximately 6 miles on a side, bounded by meridians and parallels and containing 36 sections.

TPS measurement
In Survey Analyst for field measurements, an entry in an electronic or paper field book that represents observations from a theodolite. A slope distance, vertical angle, horizontal angle, and a height of target define a single TPS measurement.

TPS setup
In Survey Analyst for field measurements, a group of field book entries that belong together define a single setup of the instrument. Each observation (slope distance, vertical angle, horizontal angle, and a height of target) is recorded as a TPS measurement and is added to the TPS setup. TPS is an acronym for Total Positioning System</I>.

tracing
A function that performs network analysis on a geometric network. Specific kinds of network tracing include finding features that are connected, finding common ancestors, finding loops, tracing upstream, and tracing downstream.

track
In ArcMap, ArcScene, and ArcGlobe, an ordered collection of similar keyframes that, when played as an animation, shows a dynamic transition between them.

track identifier field
In ArcGIS Tracking Analyst, a field containing a unique identifier for a given object or objects being observed. This field is used to join the components of a complex temporal event.

tracking connection
A message or Internet connection whereby real-time data can stream into ArcGIS Tracking Analyst.

tracking data
Data that specifically refers to times or dates. Temporal data may refer to discrete events, such as lightning strikes; moving objects, such as trains; or repeated observations, such as counts from traffic sensors.

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.

transaction
A group of data operations that comprise a complete operational task, such as inserting a row into a table.

transform events
In linear referencing, an operation that produces a new table by copying and transforming events from one route reference to another. This allows the events to be used with a route reference having different route identifiers and/or measures.

transformation
The process of converting the coordinates of a map or an image from one system to another, typically by shifting, rotating, scaling, skewing, or projecting them.

transit rule
A rule for adjusting the closure error in a traverse. The transit rule distributes the closure error by changing the northings and eastings of each traverse point in proportion to the northing and easting differences in each course. More specifically, a correction is computed for each northing coordinate as the difference in the course's northings divided by the sum of all the courses' northing differences. Similarly, a correction is computed for each easting coordinate using the easting coordinate differences. The corrections are applied additively to each successive coordinate pair, until the final coordinate pair is adjusted by the whole closure error amount. The transit rule assumes that course directions are measured with a higher degree of precision than the distances. Usually, observed angles are balanced for angular misclosure prior to applying a transit rule adjustment, and corrections are proportional to the x and y components of the measured line. The tran

translation
Adding a constant value to a coordinate.

transverse aspect
A map projection whose line of tangency is oriented along a meridian rather than along the equator.

traveling salesperson problem
A Hamiltonian circuit problem in which a salesperson must find the most efficient way to visit a series of stops, then return to the starting location. In the original version of the problem, each stop may be visited only once.

traverse
A predefined path or route across or over a set of geometric coordinates.

traverse course
In ArcMap and Survey Analyst for field measurements, a group of observed values that define a new coordinate. A traverse course starts from a preexisting coordinate, or a coordinate computed from the previous course.

tree
A database that stores related information in a tree-like structure, where records can be traced to parent records, which in turn can be traced to a root record.

tree data structure
A common data structure consisting of a set of nodes&#8212;basic units of data&#8212;linked hierarchically. Each node can contain one or more subordinate nodes within it, in which case it is called a parent node. The subordinate nodes are called child nodes. A node without a parent node is the root node; a node without one or more child nodes is called a leaf node. A tree data structure is used to manipulate hierarchical data and make it easily searchable.

trend
In a spatial model, nonrandom variation in the value of a variable that can be described by a mathematical function such as a polynomial.

trend surface analysis
A surface interpolation method that fits a polynomial surface by least-squares regression through the sample data points. This method results in a surface that minimizes the variance of the surface in relation to the input values. The resulting surface rarely goes through the sample data points. This is the simplest method for describing large variations, but the trend surface is susceptible to outliers in the data. Trend surface analysis is used to find general tendencies of the sample data, rather than to model a surface precisely.

triangle
Any closed, three-sided, two-dimensional polygon.

triangulated irregular network
A vector data structure that partitions geographic space into contiguous, nonoverlapping triangles. The vertices of each triangle are sample data points with x-, y-, and z-values. These sample points are connected by lines to form Delaunay triangles. TINs are used to store and display surface models.

triangulation
Locating positions on the earth's surface using the principle that if the measures of one side and the two adjacent angles of a triangle are known, the other dimensions of the triangle can be determined. Surveyors begin with a known length, or baseline, and from each end use a theodolite to measure the angle to a distant point, forming a triangle. Once the lengths of the two sides and the other angle are known, a network of triangles can be extended from the first.

trigger
A piece of code in a database management system (DBMS) that executes in response to data being modified with an INSERT, UPDATE, or DELETE statement.

trigonometric function
An operator within the Raster Calculator of ArcGIS Spatial Analyst that performs various trigonometric calculations on the values in an input raster. Available trigonometric functions include Sin, Cos, Tan, Asin, Acos, and Atan.

trilateration
Determining the position of a point on the earth's surface with respect to two other points by measuring the distances between all three points.

trim 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.

true bearing
A bearing measured relative to true north.

true curve
A curve that is defined mathematically rather than by a series of connected vertices. A parametric curve has only two vertices, one at each end.

true north
The direction from any point on the earth's surface to the geographic north pole.

true-direction projection
A map projection that transforms points from a spheroid or sphere onto a tangent or secant plane. The azimuthal projection is also known as a planar or zenithal projection.

TSP
A Hamiltonian circuit problem in which a salesperson must find the most efficient way to visit a series of stops, then return to the starting location. In the original version of the problem, each stop may be visited only once.

tuple
An individual row or record in a database table. Each tuple records the values for the columns defined in the table.

turn
In network analysis, a movement that explicitly models transitions between edge elements during navigation.

turn feature class
A specialized feature class that defines turn movements in an ArcGIS network dataset. Turn features explicitly model subsets of possible transitions between edge elements during navigation, and may also store the turn impedance.

turn impedance
In network analysis, the cost of making a turn at a network node. The impedance for making a left turn, for example, can be different from the impedance for making a right turn or a U-turn at the same place.

turn table
In ArcInfo Workstation and ArcView GIS 3, a table that stores information about the cost of making each turn movement in a network. A turn table identifies the edge that the turn movement comes from, the junction where the turn occurs, and the edge that it turns onto.

turn-by-turn maps
A series of small maps detailing where route segments meet.

tween
In animated applications, the process of creating intermediate frames between two images so it seems like the first image merges smoothly into the second image.

two-tier configuration
A software configuration in which two software applications (commonly a client and a server) work together to accomplish a task.

two-way replication
A type of geodatabase replication that allows data changes to be sent multiple times from the parent replica to the child replica or from the child replica to the parent replica. The data on both replicas must be editable, versioned and have GlobalID columns. ArcSDE geodatabases are used to create two-way replicas.

type inheritance
In programming, a kind of inheritance in which an interface may inherit from a parent interface. A client may call the child interface as if it were the parent, as all the same members are supported.

type library
A collection of reusable classes, interfaces, enumerations, and so on that can be included in programs. Type libraries usually have the extension .olb.