GIS Dictionary

[map projections] 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 … Read more

A tree data structure used for indexing data within a database or file system implementation. In a B-tree structure, data is sorted into a set of hierarchical nodes, usually using … Read more

[output] In ArcScene or ArcGlobe, the backdrop of the view. The color of the background can be set to suggest sky, empty space, or any color that improves visualization.

[remote sensing] Electromagnetic energy that is reflected back toward its source by terrain or particles in the atmosphere.

[cartography] Acronym for best available map. The most suitable data source for a map.

[remote sensing] A set of adjacent wavelengths or frequencies with a common characteristic. For example, visible light is one band of the electromagnetic spectrum, which also includes radio, gamma, radar … Read more

[digital image processing] A digital image-processing technique that enhances contrast between features by dividing a measure of reflectance for the pixels in one image band by the measure of reflectance … Read more

[remote sensing] An image format that stores each band of data in a separate file.

[remote sensing] A wave filter that allows signals in a certain frequency to pass through, while blocking or attenuating signals at other frequencies.

[computing] The amount of digital data that can be transferred over a computer network within a specified time period, usually measured in bits per second (bps).

1 [network analysis] In network analysis, an entity that prevents flow from traversing a network edge or junction. 2 [ESRI software] A line feature used to keep certain points from … Read more

[data analysis] Map data over which other, thematic information is placed.

In aerial photography, the height or altitude from which a photograph is taken.

1 [aerial photography] In aerial photography, the distance on the ground between the centers of overlapping photos, divided by aircraft altitude. In a stereomodel, base height ratio is used to … Read more

[data analysis] A data layer in a GIS to which all other layers are geometrically referenced.

[GPS] A GPS receiver at a known location that broadcasts and collects correction information for roving GPS receivers.

[ESRI software] In ArcGIS Tracking Analyst, the default symbol used to represent an event or a feature on a map.

[ESRI software] A text formatting tag that allows control of how the ESRI Maplex Labeling Engine places labels based on multiple fields relative to a feature. The field identified with … Read more

1 [surveying] An accurately surveyed line from which other lines or the angles between them are measured. 2 [surveying] In a U.S. land survey system, a line passing east and … Read more

1 [data analysis] A map depicting background reference information such as landforms, roads, landmarks, and political boundaries, onto which other thematic information is placed. A basemap is used for locational … Read more

[computing] A text file containing commands that is sent to the CPU to be executed automatically. A batch file allows the central processing unit (CPU) to process the commands at … Read more

[geocoding] The process of geocoding many address records at the same time.

[ESRI software] A procedure which uses a given ArcToolbox tool to process a set of information, or batch, rather than applying the tool to one piece at a time. Batch … Read more

[ESRI software] A method for processing data automatically in which the data is grouped into batches and executed by the computer at one time, without user interaction.

[ESRI software] In ArcToolbox, a table which displays the input name, user-selected parameters, and output name, where applicable, for all entries pertaining to a group, or batch, of jobs. Batch … Read more

[data conversion] An automated process that converts raster data into vector features for an entire raster or a portion of it based on user-defined settings.

[cartography] A map representing the topography of a seafloor or lake bed, using contour lines to indicate depth.

[cartography] The science of measuring and charting the depths of water bodies to determine the topography of a lake bed or seafloor.

[ESRI software] In MOLE, the primary area in which a force unit operates, such as air, space, ground, sea, surface, and subsurface.

[data transfer] In communications, the number of electrical cycles, or signals, transmitted per second. At lower transfer speeds the baud rate equals the data transfer rate measured in bps, or … Read more

A theorem developed by English mathematician Thomas Bayes (1702-1761) about conditional probability. It states that the probability of a given event, given the original data and some new data, is … Read more

A statistical approach to measuring likelihood. Bayesian estimates are based on the synthesis of a prior distribution and current sample data. Classical approaches to statistics estimate the probability of an … Read more

The horizontal direction of a point in relation to another point, expressed as an angle from a known direction, usually north, and usually measured from 0 degrees at the reference … Read more

[ESRI software] In Survey Analyst for field measurements, one of two methods for computing the coordinate geometry traverse. The bearing method uses compass directions for the orientation of each course.

[ESRI software] The actions or characteristics exhibited by an object in a database, as defined by a set of rules.

1 [surveying] A brass or bronze disk, set in a concrete base or similarly permanent structure, inscribed with a mark showing its elevation above or below an adopted vertical datum. … Read more

[ESRI software] The route of least impedance between two or more locations, taking into account connectivity and travel restrictions such as one-way streets and rush-hour traffic.

[Euclidean geometry] A curved line whose shape is derived mathematically rather than by a series of connected vertices. In graphics programs, a Bzier curve usually has two endpoints and two … Read more

[digital image processing] In digital image processing, a measure of the theoretical distance between two normal distributions of spectral classes, which acts as an upper limit on the probability of … Read more

[hardware] A computer hardware architecture in which, within a multibyte numeric representation, the most significant byte has the lowest address and the remaining bytes are encoded in decreasing order of … Read more

[graphics map display] A method for displaying graphics associated with features in a three-dimensional map display by posting them vertically as two-dimensional symbols and orienting them to always face the … Read more

[computing] In computing, having only two states, such as yes or no, on or off, true or false, or 0 or 1.

[computing] A file that contains data encoded as a sequence of bits (ones and zeros) instead of plain text. A binary file, such as a DLL or an executable file, … Read more

[programming] In computer programming, the process by which a program discovers an object’s methods and properties.

[statistics] A distribution describing the probability of obtaining exactly K successes in N independent trials, where each trial results in either a success or a failure.

The study of the geographical distribution of living things.

The total amount of organic matter in a defined area; usually refers to vegetation.

[computing] The smallest unit of information within a computer. A bit can have one of two values, 1 and 0, that can represent on and off, yes and no, or … Read more

[data structures] The range of values that a particular raster format can store, based on the formula 2n. An 8-bit depth dataset can store 256 unique values.

An image format in which one or more bits represent each pixel on the screen. The number of bits per pixel determines the shades of gray or number of colors … Read more

[data capture] A method of manual digitizing in which the operator has no graphic display on hand with which to see the digitized coordinates as they are captured.

1 [database structures] Acronym for binary large object. A large block of data, such as an image, a sound file, or geometry, stored in a database. The database cannot read … Read more

[ESRI software] In ArcGIS, a group of records in a compressed file geodatabase feature class or table that are stored together. The arrangement of compressed data into blocks helps optimize … Read more

[non-ESRI software] In CAD, a collection of objects that can be associated to form a single object.

[federal government] A unit of U.S. census geography that is a combination of census blocks. A block group is the smallest unit for which the U.S. Census Bureau reports a … Read more

A kriging method in which the average expected value in an area around an unsampled point is generated rather than the estimated exact value of an unsampled point. Block kriging … Read more

[ESRI software] In ArcGIS, a geocoding indexing process that reduces the number of potential matches that need to be checked.

[surveying] In surveying, a defective measurement that can be detected by a statistical test.

[mathematics] An expression, named for the English mathematician George Boole (1815-1864), that results in a true or false (logical) condition. For example, in the Boolean expression “HEIGHT > 70 AND … Read more

A GIS operation that uses Boolean operators to combine input datasets into a single output dataset.

[mathematics] A logical operator used in the formulation of a Boolean expression. Common Boolean operators include AND, which specifies a combination of conditions (A and B must be true); OR, … Read more

[data models] The arcs that create the boundary line of a polygon coverage.

[surveying] A line separating adjacent political entities, such as countries or districts; adjacent tracts of privately-owned land, such as parcels; or adjacent geographic zones, such as ecosystems. A boundary is … Read more

A problem created during spatial analysis, caused by arbitrary or discrete boundaries being imposed on spatial data representing nondiscrete or unbounded spatial phenomena. Boundary problems include edge effects, in which … Read more

[ESRI software] One of two types of feature weights that allow control of how labels are placed relative to polygon features in ArcMap. Higher feature weights prevent labels from being … Read more

[cartography] A division between adjacent political entities, tracts of private land, or geographic zones. Boundary lines may be imaginary lines, physical features that follow those lines, or the graphical representation … Read more

[surveying] An object that marks an accurately surveyed position on or near a boundary.

[ESRI software] In Survey Analyst – Cadastral Editor, an irregular mesh of parcel boundaries, connection lines and control points representing a cadastral fabric. A boundary network represents parcels implicitly joined … Read more

1 [cadastral and land records] A map that shows property lines and corner monuments of a parcel of land. 2 [cadastral and land records] The survey taken to gather data … Read more

[map display] The rectangle, aligned with the coordinate axes and placed on a map display, that encompasses a geographic feature or group of features or an area of interest. It … Read more

[ESRI software] In ArcGIS Network Analyst, an object used in vehicle routing problem (VRP) analysis. A break can be used to model a specified period of rest along a route … Read more

[3D GIS] A line in a TIN that represents a distinct interruption in the slope of a surface, such as a ridge, road, or stream. No triangle in a TIN … Read more

[data models] In 3D Analyst and Spatial Analyst for ArcView 3.x, a grid theme whose cell values are used to vary the brightness of another grid theme. The cell values … Read more

[ESRI software] An image associated with data to provide a general idea of what the service looks like.

[spatial analysis] A zone around a map feature measured in units of distance or time. A buffer is useful for proximity analysis.

[computing] In computing, a flaw or error in a software program or hardware component that prevents it from performing the way it should.

1 [network analysis] In ArcGIS, the process of creating a network system. For geometric networks, this includes establishing connectivity, creating network features, and creating logical network tables. For network datasets, … Read more

[ESRI software] In Survey Analyst – Cadastral Editor, a cadastral fabric editing command that creates a parcel from construction lines and legal records.

[computing] A set of conductors that provide communications links between the various functional components of a computer, such as memory and peripheral devices.

[ESRI software] In a geodatabase, the spatially-enabled DBMS table that holds the main attribute values of a dataset. A business table with a spatial column is a feature class, and … Read more

[programming] A command that executes a function, macro, or custom code when clicked.

[computing] The smallest addressable unit of data storage within a computer, almost always equivalent to 8 bits and containing one character.

[programming] A common, flexible, programming language.

[programming] An object-oriented programming language, extended from C.

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

[graphics computing] 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 … Read more

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 … Read more

1 [graphics computing] The digital equivalent of a drawing, figure, or schematic created using a CAD system. 2 [ESRI software] In ArcCatalog, an item in the Catalog tree representing all … Read more

[ESRI software] 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 … Read more

[ESRI software] 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 … Read more

[ESRI software] 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. … Read more

[ESRI software] 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 … Read more

1 [ESRI software] 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 … Read more

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

[ESRI software] 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 … Read more

[ESRI software] 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. … Read more

[ESRI software] In Survey Analyst – Cadastral Editor, the record of changes to the legal and system state of the cadastral fabric.

[ESRI software] 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 … Read more

[ESRI software] 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 … Read more

[ESRI software] 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 … Read more