F
false easting
An adjustment constant added to easting coordinate values to eliminate negative numbers. (See also: easting.)
false northing
An adjustment constant added to northing coordinate values to eliminate negative numbers. (See also: northing.)
feature
A feature is a continuous area (it may have holes in it) that does not touch any other area of the same type. (When two features of the same type touch, they immediately become a single larger feature.) Features may represent anything the user chooses to isolate and identify, like ponds, lakes, agricultural fields, a biological entity in an NMR scan, or bones in a CAT scan.
Feature attribute table
A table use to store attribute information for a specific coverage feature class ARC/INFO maintains the first several items of these table. Feature attribute tables support for coverage include: Pat for polygone or points, AAT for area, NAT for nodes, RAT for routes, SEC for section, PAT for regions, TAT for annotation (text) where is the coverage name.
feature class
A class is a set of all features of the same material. A class is named to identify the kind of material it contains (for instance "corn").
feature code
A set of characters (alpha, alpha/numeric or numeric) within the GIS, which uniquely identifies a feature class or homogenous group of features. The following examples are from the TRIM 1,20000 Mapping specifications: 33750000-wooded area. 25100190-Paved Road, 25000120-loose surface Road (Grovel).
feature mapping
A process for isolating, identifying, and typing areas in multivariable images. It can do most of the classification automatically when working with high-quality materials like satellite multispectral images. With more input from the user, the process may also successfully map features in images created from 35mm slides or noisy airvideo.
feature space
The theoretical n-dimensional space occupied by n input raster objects. Each raster object represents one dimension, and its cell values represent positions along one of the orthogonal coordinate axes in feature space. The set of raster values belonging to a cell define a vector in feature space.
FGCC
Federal Geodetic Control Committee: A standards committee concerned with accuray levels in geodetic control. Within the United States co-ordinate control is based on Nation Geodetic survey's published control points and is a basis for collecting data. Data collected using the basis co-ordinate points can be ready by ARC/INFO
FGDC
The United State Federal Geographic Data committee. Composed of representatives of several federal agencies and GIS vendors. The FGDS has the lead role in defining spatial data standards, which is described in the content Standards for spatial metadata.
fiducial marks
(photogrammetry) Index marks, usually four, which are rigidly connected with the camera body and which form images on the film negative and usually define the principal point of the photograph.
field
(database) One component in a database record. Fields report values (either qualitative or quantitative) for the individual represented by that record. For example, a database record in a table concerned with agricultural potential may contain fields that provide qualitative evaluations of a ground areas' production potential for grain, legumes, or trees, while a database record in a table of polygon statistics may contain fields that report quantitative information such as the polygon's area, boundary length, and centroid coordinates. (See also: database object, record, table.)
field
(video) Background: The image you see on a TV screen is composed of a set of about 480 horizontal lines. The lines are projected in two passes of the signal beam. Each pass only projects every other line of the image: the odd lines in one pass, and the even lines in the next pass. One scan takes 1/60 of a second, so the whole picture (the frame) is refreshed every 1/30th of a second.
A field contains every other line of the complete video image. The primary field contains the odd lines; the secondary field contains the even lines.
field
(window) An area of a window that allows keyboard entry of text.
Field data collector
An electronic device that collects and stores observation information from survey instruments. Two types of devices are available one records X,Y,Z coordinates using a satellete based global positioning systems (GPS) and the other devices records distance and bearing. ARC/INFO GENERATE is often used to convert GPS cooederates while ARC/INFO COGO has a FIELDDATA conversion program.
figure-ground separation
Separation of the foreground (figure) from the background (ground) in an image.
file
A stored collection of related material (programs and data) analogous to a physical file folder that is used to store a collection of papers on a particular subject.
file format
A particular, pre-described layout pattern for data in a computer file so it may be used or acted upon by a program.
File Transfer
The process of copying data from one computer to another or one DBMS to another.
fill color
A solid color used to fill a closed shaped in a vector or CAD object or an area defined by specified boundary colors in a raster object.
fill pattern
The drawing pattern for the interior of a polygon for display or printing. A fill pattern can be as simple as a solid color, or as detailed as a repeated image of a duck or tree. Soil types can be represented by traditional color cross-hatching. Fill patterns can be designed from the 64 standard colors plus transparent (so the underlying image shows through).
film recorder
An output device that works like a printer but produces slides or prints, usually on 35mm film.
filtering
Clarifying detail, sharpening contrast, smoothing edges, and otherwise enhancing image quality.
FIPS
The federal Information Processing Standards. FIPS deals with a wide range of computer system components of most GIS's: hardware, storage media, data file, codes, interfaces, data transmission, networking, data management, documentation programming languages, software engineering, performance security, and so forth. FIPS 173 is the precursor to SDTS/Spatial Data Transfer Standard), which includes standardized definitions for a variety of digital mapping terms, addressing federal requirements for accuracy.
flat
A raster cell that has the same cell value as its eight surrounding neighbors. Calculated from an elevation raster object, a raster object of flats provides a representation of locations with poorly defined drainage.
floppy disks, floppies, diskettes, or flexible disks
A thin, flexible magnetic disk for computer program and data files. Floppies are inserted into a computer's floppy disk drive much like a cassette tape is loaded into a tape player. Floppy disks come in different sizes and capacities, and must be used in the right kind of drive and computer. Floppies are slower and hold less data than a hard disk. (See also: hard disk, RAM disk.)
flow accumulation
In a raster-based analysis, the total number of cells, including non-neighboring cells, that drain into a selected cell.
flow direction
In a raster-based watershed analysis, each cell is assumed to drain into one of its eight neighbors (left, right, up, down, plus the four diagonals). The flow direction of a cell is expressed in degrees: left=0, up=90, right=180, down=270; and the diagonals: 45, 135, 225, 315.
flow path
The drainage path through a watershed that begins at any selected point (called the flow path "seed") and runs to one of the outlets of the study site.
flow path raster
A raster that indicates the flow path from one or more seed points to one of the outlets of the study site.
flow path seed point
(watershed analysis) Any point selected to be the origin or highest point in a flow, or drainage, path.
focal length
A measure of the "zoom" level of a camera lens. Longer focal lengths create a higher zoom level, capture a smaller area of the target scene, and introduce smaller displacement errors. 6-inch, 8.25-inch, and 12-inch focal lengths are common for aerial photography done by government surveying authorities in the United States. Focal length affects the geometry of the photo and must be provided as an input to computational orthoimage and DEM processes.
folder
A folder contains a set of logically related objects in a project file that have been organized so they can be accessed together.
font
A single set of glyphs (characters, symbols, numerals, and letters of both upper and lower case) of the same style (such as Times, Helvetica, or Schoolbook). Fonts can be stored and manipulated in computers as bitmapped or vector (outline, or stroke). Font sizes are specified in points. A 72-point font is one-inch high, from the highest ascender to the lowest descender in the set. A 12-point font is 1/6 inch high. (See also: bitmapped font, outline font, point size.)
font set
A collection of one or more fonts that provide all the characters used by a particular language.
foreign key
A primary key name in one table that occurs as a field name in another table within the same database. The identification and designation of foreign keys are automatic. (See also: database, field, primary key.)
form
See database form.
format
The preparation of optical, floppy, or hard disk media; a tape cartridge; or other storage media with basic locational information so that the media can be used. Some manufacturers provide preformatted media for their specific devices, such as hard drives. Other generic media, such as floppy disks, are usually not formatted when purchased. Some media, usually those with a serial recording format, such as open reel tape, are automatically formatted as they are used.
From interface
A graphic user interface characterised by user controlled movement of a cursor from one data field to another.
From - node
Of an arc's two endpoints, the one first digitized.
Fourier transform
A type of two-way frequency transform for identifying and removing unwanted spatial frequency components in an image. The Fourier process is normally used to identify and remove systematic noise "spikes," such as regular lines that may have been introduced by a faulty image collection device. The process works as a two-way operation. First the forward transform creates a pair of intermediate raster objects that reveal abnormal data variability. After the values in those raster objects have been edited to remove the data spikes, the inverse transformation creates a raster object with the same image as the original, but with lines or other noise removed.
frame
(video) A complete video image which consists of two interlaced fields. Odd lines of the frame are contained in the primary field which is alternated with the secondary field that contains the even lines. The primary field lasts 1/60 of a second in standard broadcast video. The secondary field follows in the next 1/60 of a second. The entire frame takes 1/30 of a second to display. There is a difference of 1/60 of a second between alternate lines in the image.
frame
(window) The active window (where any typing or selecting of options will occur) is indicated by a highlighted or different colored frame.
framegrabber and framegrabbing
Background - Composite video and US standard broadcasts repeat each field every 1/60 of a second. Two interlaced fields, each containing alternate lines of the image make up one video frame that lasts 1/30 of a second.
A video framegrabber is a microcomputer interface board that accepts a video input signal and passes it to a color monitor. A program signals the video frame-grabber to both freeze and digitize one video frame.
Digitizing a video frame may transform each picture element in the frame to a single byte in the board's memory. More commonly, it simultaneously captures, digitizes, and stores the video's separate red, green, and blue color values. Some framegrabbers can be set to grab only a single field to avoid the relative movement between a frame's two fields. If the video comes from a camera that has high-speed electronic shuttering (like 1/1000 of a second), movement in the 1/30 of a second between the primary field and the secondary field causes saw-toothed edges on alternate lines in straight features like road edges, and vertical poles.
As soon as the video is saved in the board memory (1/30 or 1/60 of a second), picture motion on the monitor freezes (even if the live video input continues) while the data in the board memory is converted into a display image.
Framegrabber boards should not be confused with video digitizing boards, which gradually sample and construct a digital representation of a still scene video image. Sampling video boards represent an older technology, but are still used for non-standard, higher resolution video sources. (See also: video digitizing board.)
frequency transform
An operation that breaks down an image into its fundamental spatial frequency components for subsequent analysis or filtering.
Functional Surface
A surface representation which stores a single Z value (as opposed to multiple Z values) for any given x, y location TIN represents data as functional surfaces. Functional surfaces are also referred to as 2.5 dimensional surfaces.
fuzzy C-means
An unsupervised classification or clustering process developed by Robert Cannon et al. and documented in: Robert L. Cannon, Jitendra V. Dave, James C. Bezdek, and Mohan M. Trivedi (1986) IEEE Transactions on Geoscience and Remote Sensing. GE-24(3):400-408. Segmentation of a Thematic Mapper Image Using the Fuzzy C-Means Clustering Algorithm.
Fuzzy tolerance
The fuzzy tolerance is an extremely small distance used to resolve inexact intersection locations due to limited, arthmetic precision of computers. It defines the resolution of a coverage resulting from the clean operation or a topological overlay operations such as UNION, INTERSECT or CLIP.