GIS Glossary/F

GIS Glossary

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F
A ratio of variances, calculated from a sample of data and used to provide information about a whole dataset. For example, statistic F may be used to provide estimates of variance, or differences, in a population, based on observations from two or more random samples.

F statistic
A ratio of variances, calculated from a sample of data and used to provide information about a whole dataset. For example, statistic F may be used to provide estimates of variance, or differences, in a population, based on observations from two or more random samples.

F test
A statistical test for determining the probability that the variances of two different samples are the same. The F test uses a statistic known as statistic F to test statistical hypotheses about the variances of distributions from which samples have been drawn.

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

face
A planar surface of a geometric shape, bounded by edges.

facility
In ArcGIS Network Analyst, a network location used in closest facility and service area analyses.

false easting
The linear value added to all x-coordinates of a map projection so that none of the values in the geographic region being mapped are negative.

false northing
The linear value added to all y-coordinates of a map projection so that none of the values in the geographic region being mapped are negative.

feature
A representation of a real-world object on a map.

feature attribute table
A database or tabular file containing information about a set of geographic features, usually arranged so that each row represents a feature and each column represents one feature attribute. In raster datasets, each row of an attribute table corresponds to a certain zone of cells having the same value. In a GIS, attribute tables are often joined or related to spatial data layers, and the attribute values they contain can be used to find, query, and symbolize features or raster cells.

feature class
In ArcGIS, a collection of geographic features with the same geometry type (such as point, line, or polygon), the same attributes, and the same spatial reference. Feature classes can be stored in geodatabases, shapefiles, coverages, or other data formats. Feature classes allow homogeneous features to be grouped into a single unit for data storage purposes. For example, highways, primary roads, and secondary roads can be grouped into a line feature class named "roads." In a geodatabase, feature classes can also store annotation and dimensions.

feature code
In Survey Analyst for field measurements, a block of text included in data collector file format, used to describe features surveyed in the field.

feature data
Data that represents geographic features as geometric shapes.

feature dataset
In ArcGIS, a collection of feature classes stored together that share the same spatial reference; that is, they share a coordinate system, and their features fall within a common geographic area. Feature classes with different geometry types may be stored in a feature dataset.

feature displacement
The movement of features that would otherwise overprint or conflict with other features. For example, if a river, a road, and a railway run through a narrow valley, it is necessary, at some scales, to displace at least one of the features that represent them on the map to keep their symbols distinct.

feature extraction
In image processing, a method of pattern recognition in which patterns within an image are measured and then classified as features based on those measurements.

feature layer
A layer that references a set of feature data. Feature data represents geographic entities as points, lines, and polygons.

feature server
A public ArcIMS virtual server for feature services.

feature service
A service that uses the ArcIMS spatial server feature streaming capabilities. The server bundles data and streams it to the requesting client. Since more of the processing is done in the Java applet, requests are sent to an ArcIMS spatial server only when additional data is needed.

feature streaming
The process of delivering vector feature data defined for a service that uses the feature server component. On the client side, feature streaming allows you to access a published map and then add feature data for overlays, sharing, making EditNotes, and performing analysis. Feature streaming functionality minimizes the need for multiple server requests.

feature table
A table in an ArcSDE geodatabase that stores geometric shapes for each feature. Feature tables are used in geodatabases that store data as a binary data type, such as SQL Server geodatabases. They are related to the business table of a feature class through the feature ID. In the database, feature table names are prefaced with an f and are stored in the schema of the user who owns the feature class.

feature weight
In ArcMap, a ranking system that indicates whether features from a given feature class may be covered by a label in cases where the label cannot be placed in free space. Feature classes with lower weights will tend to have labels placed over their features before feature classes with higher weights. Polygon feature classes have two types of weights: boundary weights and interior weights.

feature-linked annotation
Annotation that is stored in the geodatabase with links to features through a geodatabase relationship class. Feature-linked annotation reflects the current state of features in the geodatabase: it is automatically updated when features are moved, edited, or deleted.

Federal Geographic Data Committee
An organization established by the United States Federal Office of Management and Budget responsible for coordinating the development, use, sharing, and dissemination of surveying, mapping, and related spatial data. The committee is comprised of representatives from federal and state government agencies, academia, and the private sector. The FGDC defines spatial data metadata standards for the United States in its Content Standard for Digital Geospatial Metadata and manages the development of the National Spatial Data Infrastructure (NSDI).

FGDC
Acronym for Federal Geographic Data Committee. An organization established by the United States Federal Office of Management and Budget responsible for coordinating the development, use, sharing, and dissemination of surveying, mapping, and related spatial data. The committee is comprised of representatives from federal and state government agencies, academia, and the private sector. The FGDC defines spatial data metadata standards for the United States in its Content Standard for Digital Geospatial Metadata and manages the development of the National Spatial Data Infrastructure (NSDI).

FGDC Clearinghouse
An Internet server that hosts a collection of metadata and data maintained and stored on a computer server by a data provider. An NSDI Clearinghouse Node provides information about geographic data within the data provider's areas of responsibility. Nodes must host FGDC-compliant metadata and data and use a common access protocol.

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

FID
In ArcGIS, a system-managed value that uniquely identifies a record or feature.

field
A column in a table that stores the values for a single attribute.

field mapping
In geoprocessing, defining the field structure and content for an output dataset.

field precision
The number of digits that can be stored in a field in a table.

field scale
The number of decimal places for float or double-type geodatabase table fields.

field view
A philosophical view of geographic space in which space is completely filled by occurrences of phenomena, and in which phenomena are described by a range of values on a numeric scale. In this view, every spatial location is something, even if it is the zero value of a phenomenon.

file
A collection of uniquely named information stored on a drive, disk, or tape. A file generally resides within a directory.

file geodatabase
A geodatabase stored as a folder of files. A file geodatabase can be used simultaneously by several users, but only one user at a time can edit the same data.

file name
The name that distinguishes a file from all other files in a particular directory. It can refer to the name of the file by itself (harold), the name plus the file extension (harold.shp), or the whole path of a file up to and including the file name extension (C:\mygisdata\shapefiles\harold.shp).

file name extension
The abbreviation following the final period in a file name that indicates the file's format, such as .shp, .zip, or .tif. File name extensions are usually one to four letters long.

File Transfer Protocol
A protocol that allows the transmission of files between computers over a network.

fill
The interior of a polygon; the area inside the perimeter.

fill symbol
A color or pattern used to fill polygons on a map.

fillet
A segment of a circle used to connect two intersecting lines. Fillets are used to create smoothly curving connections between lines, such as pavement edges at street intersections or rounded corners on parcel features.

filter
On a raster, an analysis boundary or processing window within which cell values affect calculations and outside which they do not. Filters are used mainly in cell-based analysis where the value of a center cell is changed to the mean, the sum, or some other function of all cell values inside the filter. A filter moves systematically across a raster until each cell has been processed. Filters can be of various shapes and sizes, but are most commonly three-cell by three-cell squares.

Find Addresses
An ArcWeb tool for ArcGIS that enables users to input a street address and receive a candidate list of matched locations for display on a map.

Find Places
An ArcWeb tool for ArcGIS that allows users to search for place-names and receive a candidate list of place-names and associated coordinates for display on a map.

Find Points of Interest
An ArcWeb tool for ArcGIS that enables users to define spatial or attribute queries and display the results on a map.

Find Route
An ArcWeb tool for ArcGIS that lets users generate multipoint driving directions between user-defined locations. The Find Route tool determines the shortest or the quickest path between locations and creates a map of the travel route and a list of travel directions.

Find Similar analysis
A process that seeks out new market areas based on the characteristics of an existing market area.

first normal form
The first level of guidelines for designing table and data structures in a relational database. The first normal form guideline recommends creating a unique key for every row in a database table, eliminating duplicate columns from a table, and creating separate tables to contain related data. A database that follows these guidelines is said to be in first normal form.

fitness for use
The degree to which a dataset is suitable for a particular application or purpose, encompassing factors such as data quality, scale, interoperability, cost, data format, and so on.

fix
A single position obtained by surveying, GPS, or astronomical measurements, usually given with altitude, time, date, and latitude-longitude or grid position.

fixed reference point
In Survey Analyst for field measurements, a survey point used as an input to a computation. The coordinates are not updated by the computation.

fixed use
In software licensing, a software product that can be used on only one machine.

fixed-time data
In ArcGIS Tracking Analyst, stored temporal data that can be viewed in past, future, and past-and-future time windows. This data is stored in a shapefile or as a feature class in a geodatabase.

flag
A marker that identifies or calls attention to something, indicating importance or the need for further attention.

Flash
A browser-independent, vector graphic technology for creating interactive Web sites with video, graphics, and animation. Browsers need plug-ins for Flash animations.

flatbed scanner
A type of scanner with a flat, clear surface on which a map or image remains stationary while a sensor beam moves across it and captures a digital image.

flattening
A measure of how much an oblate spheroid differs from a sphere. The flattening equals the ratio of the semimajor axis minus the semiminor axis to the semimajor axis.

Flex
A set of tools that allows developers to create cross-platform, browser-independent Web applications using a standards-based programming language. Created by Macromedia in 2004 and now developed by Adobe, the Flex family of products includes Flex SDK, Flex Builder, Flex Data Services, and Flex Charting.

floating layer
A layer in ArcGlobe that has been categorized to float independently above or below the globe surface.

floating point
A type of numeric field for storing real numbers with a decimal point. The decimal point can be in any position in the field and, thus, may "float" from one location to another for different values stored in the field. For example, a floating-point field can store the numbers 23.632, 0.000087, and -96432.15.

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

flow direction
The route or course followed by commodities proceeding through edge elements in a network.

flow map
A map that uses line symbols of variable thickness to show the proportion of traffic or flow within a network.

focal analysis
The computation of an output raster where the output value at each cell location is a function of the value at that cell location and the values of the cells within a specified neighborhood around the cell.

focal functions
The computation of an output raster where the output value at each cell location is a function of the value at that cell location and the values of the cells within a specified neighborhood around the cell.

focus field
In Survey Analyst for field measurements, the field that is the current target for data entry.

folder
A location on a disk containing a set of files, other folders, or both.

folder connection
In ArcCatalog, a top-level item in the Catalog tree that provides quick access to geographic data stored on local disks (including CD-ROMs) or shared on a network. Folder connections may provide access to individual folders.

follow feature mode
In ArcGIS, a method for placing geodatabase annotation relative to a line or polygon feature. For example, text next to a river may be dragged along it so that the text curves like the river.

font
A single typeface or a set of related patterns representing characters or symbols at one size.

footprint
In ArcGIS Image Server, the extent (often rectangular) of each raster dataset in the image service definition. The footprint is stored as a polygon shapefile within the image service definition.

force concentration
In MOLE, a component of a map display that shows where force units are located so that the map reader can see where forces are the strongest and weakest.

force element
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.

foreground
In a scene or display, the area that appears to be closest to an observer.

foreign key
An attribute or set of attributes in one table that match the primary key attributes in another table. Foreign keys and primary keys are used to join tables in a database.

form lines
Lines on a map that approximate the shape of terrain in lieu of actual contours. Form lines do not refer to a true datum and do not necessarily use regular intervals.

format
In computing, the structure and organization of digital information.

formatted text 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.

fractal
A geometric pattern that repeats itself, at least roughly, at ever smaller scales to produce self-similar, irregular shapes and surfaces that cannot be represented using classical geometry. If a fractal curve of infinite length serves as the boundary of a plane region, the region itself will be finite. Fractals can be used to model complex natural shapes such as clouds and coastlines.

frame
In MOLE, the geometric border of a graphic that indicates the affiliation, battle dimension, and status of the war fighting element that the MOLE graphic represents.

framework
The existing ArcObjects components that comprise the ArcGIS system.

free network adjustment
In Survey Analyst for field measurements, one of two phases involved when performing a least squares adjustment for a measurement network. The free network adjustment phase examines the overall geometry of the network by processing only the measurements and using the reference points only for position scale and orientation of the network. The emphasis is on testing the quality of the measurements rather than computing the coordinates.

free representation
In ArcGIS, the representation of a single feature that has been disconnected from its representation rule to create an independent rule whose structure can be changed, allowing full freedom of display. Geometric effects within the rule can be converted so that their results become static parts of the feature representation.

freeze
To fix a column in place in a table for better viewing of the table's contents. A frozen column will stay in place while the other columns scroll normally.

frequency
The number of oscillations per unit of time in a wave of energy, or the number of wavelengths that pass a point in a given amount of time.

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

FTP
Acronym for File Transfer Protocol. A protocol that allows the transmission of files between computers over a network.

full cache
In ArcGlobe, a layer cache saved on disk that contains complete levels of details for the entire layer.

function
An operation. In GIS, functions include data input, editing, and management; data query, analysis, and visualization; and output operations.

functional surface
In 3D Analyst, a surface that stores a single z-value for any given x,y location.

fuzzy boundary
A boundary that has a vague or indeterminate location, or that is a gradual transition between two zones.

fuzzy classification
Any method for classifying data that allows attributes to apply to objects by membership values, so that an object may be considered a partial member of a class. Class membership is usually defined on a continuous scale from zero to one, where zero is nonmembership and one is full membership. Fuzzy classification may also be applied to geographic objects themselves, so that an object's boundary is treated as a gradated area rather than an exact line. In GIS, fuzzy classification has been used in the analysis of soil, vegetation, and other phenomena that tend to change gradually in their physical composition and for which attributes are often partly qualitative in nature.

fuzzy set
In mathematics, a collection of elements that belong together based on specified criteria, so that elements with partial or uncertain degrees of membership may be included in the collection.

fuzzy tolerance
The distance within which coordinates of nearby features are adjusted to coincide with each other when topology is being constructed or polygon overlay is performed. Nodes and vertices within the fuzzy tolerance are merged into a single coordinate location. Fuzzy tolerance is a very small distance, usually from 1/1,000,000 to 1/10,000 times the width of the coverage extent, and is generally used to correct inexact intersections.