C
C
A high-level programming language.
CAD
Computer Aided Design. An automated system for the design, drafting and display of graphically oriented information.
cadastre
"An official register of the ownership, extent, and value of real property in a given area, used as a basis of taxation" (Random House).
CADkey
A popular commercial microcomputer Computer Aided Design (CAD) software package from CADkey, Inc.
CAD object
A CAD object, in RVC format, like a vector object, is composed of coordinate data, but uses a different data structure. A CAD object has a free-form topology, so it may be useful for applications that do not require an exact description of the relationships between the elements in the object. CAD object topology does not reconcile things like line intersections, polygon overlap, and polygon islands.
A CAD object also allows for descriptions of geometric shapes. For example, in a vector object, a circle is always stored as a polygon, and at a high enough magnification, the discrete point and line elements become visible. By contrast, a CAD object stores a circle by its center point and radius. Thus, at any magnification, it looks circular.
Since they have reduced topological constraints, CAD objects generally require less storage than their vector object counterparts. [See also: element (CAD).]
calibrate or cell size calibration
To establish scale or cell size (for a raster) for an object in a project file. Once a raster, vector, or CAD object has been calibrated, accurate measurements can be determined and displayed. (See also:georeference)
calibrated image map
An image that has been processed to be like a map in appearance, scale, geometry, boundary, and projection with a degree of precision that satisfies the user. Measurements made from an image map yield results equal to those made from the corresponding planimetric, topographic, or other map. Similarly, either the image map or the conventional map can be overlaid and matched with the other.
calibration
The process of choosing attribute values and computational parameters so that a model properly represents the real world situation being analysed. For eg. in pathfinding & allocation, calibration generally refers to asigning or calculating appropriate value to be entered in impedance and demand items.
capture
To freeze and digitize a standard video input signal (such as VHS tape or broadcast video). Some microcomputer display boards offer video capture. (See also: frame-grabbing)
cartesian co-ordinate system
A two dimensional, planar co-ordinate system in which X measures horizontal distance and y measures verticle distance. Each point on the plane is defined by an x,y coordinate. Relative measures of distance, area and direction are constant throughout the cartesian co-ordinate plane.
cartography
The art or science of making maps.
cartridge
erasable optical cartridge - A two-sided removable storage unit that typically holds between 300 and 500 megabytes per side. Data on EO cartridges can be erased so the cartridge can be updated or re-used.
WORM cartridge - Write Once, Read Many drive. A type of drive that reads and writes to non-erasable optical disks, which are used for permanent, high-capacity file storage. WORM disks are empty when purchased, and the user can write files to them until they are full. Data is recorded with reflective pits in the coating laid on the surface of a glass or metal disk. Once the pits have been burned into the coating, they cannot be removed, which makes this medium non-erasable. (See also: erasable optical cartridge, erasable optical drive, optical disk)
cascade button
A type of button that displays a cascading menu. A cascade button is typically a selection on a parent pulldown menu. It includes an arrow graphic that points in the direction the cascading menu appears.
cascading menu
A submenu that opens from a selection on a parent pulldown or popup menu that provides selections that amplify or supplement the parent selection.
categorical data
Data in a raster object is said to be categorical if it cannot be represented by a continuous surface, since intermediate terms cannot be derived with meaningful results. Example 1: soil type data cannot be interpolated, since a soil type 14 and a soil type 15 cannot sensibly be averaged to derive a soil type 14.5. Example 2: feature classification data cannot be interpolated, since a cell assigned membership in the feature "corn" cannot sensibly be used in any process that averages it with a cell assigned membership in the feature "wheat."
Do not confuse the terms "categorical data" and "category"-they have different and distinct meanings.
category
(in Feature Mapping) A subdivision within a region of interest (which also has a particular meaning in reference to Feature Mapping) that lets you divide the study site so that the measurement data in the output text file will be organized geographically. So, if you have defined a region of interest as the wetland duck habitat along a river floodplain, you might want to divide the wetlands into categories: perhaps ownership areas (like refuge lands, private ownership, and easement areas). Then the text output file would break down the wetland feature measurements by ownership area.
CAT scan
A medical diagnostic image produced by Computer Aided Tomography.
CD-ROM
Compact Disk, Read-Only Memory. A 5" optical disk containing prerecorded data sets that may be read and used as DOS files.
cell
One value in a raster that corresponds to a specific area on the ground. A raster cell may contain a value that describes the elevation above sea level at one position in a survey site or the intensity of red radiation for a pixel in a video image. For convenience, a raster cell is usually thought of as square or rectangular, although many image collection devices actually measure circular or elliptical areas. If a raster object is created from a screen image, each cell value represents one pixel.
cell size
The dimensions of the area on the ground to which a raster cell value applies. A cell size of 30 meters signifies that the value in each cell of the raster object applies to a 30 x 30 meter area in the study site.
cell size calibration
The transfer of cell size information to a raster.
central meridian
The north-south meridian of a map projection around which the map is centered.
centroid
"The point that may be considered as the center of a one- or two-dimensional figure, the sum of the displacements of all points in the figure from such a point being zero" (Random House).
CGA
Color Graphics Adapter. An early microcomputer graphics subsystem developed for the IBM PC. The CGA was hampered by low resolution and limited color selection. It has been largely superseded by the EGA and the newer VGA. (See also: EGA, VGA)
CGM
Computer Graphics Metafile is a graphic image exchange standard ANSI:x3.122-1986, ISO:8632-1986 for graphic output file format. ARC/INFO, Arc VFiew Version 2, and PC ARC/INFO Support CGM.
change image
An image produced using raster algebra that shows change over time between coregistered images.
character
An element used for the graphic representation of data (such as a letter, numeral, or symbol) or control of data (such as a tab, space, return, or enter). Each element has a corresponding character code in the Unicode table.
check button
A square button in a pop-in window that presents one selection in a group of on/off options. When a check button is "on," it appears "pushed in". Clicking on one check button does not effect any other check buttons in the group. (See also: radio button.)
chip
Commonly, any integrated circuit logic component of a computer. The two broadest categories of chips are memory chips and processor chips. Most DOS microcomputers use main processor chips developed by Intel Corporation (the 8088, 8086, 80286, 80386, 80486 series).
choropleth map
A map consisting of areas of equal value separated by abrupt boundaries.
CIR image
Color-infrared image. Color-infrared images may be collected by an electronic scanner or a camera that uses special film with sensitivity from green through infrared. The photographic infrared radiation just beyond the range of human vision is then displayed as red. Normal red from the scene becomes green, and green becomes blue. Normal blue in the scene is filtered out and not recorded. CIR images are used to show the vigor of plant life. Healthy vegetation appears red, while distressed or damaged vegetation may look pink, tan, or yellow. (See also: color-infrared image)
class
(raster) A set of all image features of the same type. As part of the interpretive process, the user names a class to identify the type of material it contains, like "corn," "bare soil," "wetland," or "urban." In a set of coregistered raster objects, a grouping of cells with similar sets of values. A class normally corresponds to a specific land cover type with a restricted set of biophysical properties.
class center
The set of raster values that define the mean vector for the class in feature space.
classification
Grouping cells (often by color characteristics) from coregistered rasters to map the location and type of image features (like type of crop, surface cover, and map line type).
class list
A subobject containing a list of classes associated with a vector or CAD object.
client/server
A software system is said to have client server architecture when there is a central process (server) which accepts requests from multiple user processes. (clients)
clip
The spatial extraction of those features from one coverage that reside entirely within a boundary defined by features in another coverage.
clip art
Icons, symbols, and drawings distributed in computer-readable format. Computer clip art was popularized by the Apple Macintosh, which can use published clip art for electronic cutting and pasting into drawings or pages of text.
cliping
A graphic process of cutting lines and symbols off the edge of a display area.
clump
A set of contiguous line, node, and polygon elements in a vector object.
clustering
A process in which multiple, registered, overlapping, rasters are reduced to a single raster, which is referred to as a cluster map. The rasters used in clustering represent analytical data (such as images and elevations). Different clustering methods (such as K-means, Fuzzy C-means, and Isoclass) use varying logic to accomplish this mapping and dimensional reduction. In general, all of the methods use the concept of testing multiple values for each cell against all other cell values to determine which subpopulation each cell is most similar to and should be grouped with. All clustering methods first make a preliminary set of groups by testing all cells or a sample of them. They then proceed by various methods to test individual cells and dynamically redefine the clusters until every cell is satisfactorily assigned a cluster membership in a single cluster, which is recorded at that cell's position in the cluster map. The maximum number of clusters to form and the number of refinement iterations is
usually controlled during setup. (See also: labeling, unsupervised classification)
cluster labeling
Identifying and grouping the clusters in the cluster map raster object that result from any kind of automated image interpretation. The user chooses labels (names for types of features) based upon his or her knowledge of the areas or materials in the image.
cluster map
The output raster created by clustering or by unsupervised classification. The clusters are usually identified or labeled as some useful type of material (for example, an agricultural crop, a body tissue type, or a soil type). It is important to note that this raster does not contain values that can be subjected to further mathematical analysis because the clusters and their reidentification as material or area types do not represent data values that are mathematically continuous. For example, cells in a cluster arbitrarily assigned the value of 4 by the clustering process does not necessarily represent twice as much of something as a cell assigned to a cluster that was given a value of 2.
CMY or Cyan-Magenta-Yellow
The standard set of subtractive, processing colors used in printing. Color printing devices use discrete dots of cyan, magenta and yellow to present the appearance of a full-color image to the human eye. The combination of cyan, magenta and yellow produces black. However, some printers include black ink along with the above three colors, which is properly called CMYK.
coextensive
Covering the same ground area exactly. If two raster objects are both coregistered and coextensive, there is a 1:1 cell correspondence for ground area coverage in each cell of the rasters.
COGO
The Coordinate Geometry (COGO) process includes COGO commands that when executed accomplish meaningful functions for professional surveying and civil engineering applications. COGO by definition is a command structured problem oriented language and computer program for the solution of geometric problems. COGO tools are useful for creating or editing vector or CAD objects with land surveying, global positioning system, and other precision data. The COGO approach has been used by surveying and civil engineers since approximately the early 1960's. COGO is relates to the LOGO language used in early computing and permits the creation of precise control and descriptive data entry into new or existing objects tied to the ground surface, projection, and datum. COGO points and the objects defined by those points, can be determined in 3D space within the interior of an object (for example rooms and hallways in a building; adits, shafts, and various tunnels in an underground mine; locations in a timber stand; or areas in a hydro-geologic environment) and can be used to define interior surfaces in vector applications and solid objects in vector and CAD applications.
color balancing
Adjusting the intensities and distribution of red, green, and blue to create an image with a particular color appearance for display or printing.
color compression
Removing duplicate (in some cases near-duplicate) colors from a color map to make room for new colors.
color depth or pixel depth
The number of data bits each pixel represents. In 8-bit contexts, the pixel depth is 8, and each display pixel can be one of 256 possible colors or shades of gray. With a 24-bit raster (or with three coregistered 8-bit rasters) the pixel depth is 24, and 16,777,216 colors are possible.
color-infrared (CIR)
Color-infrared images may be collected by an electronic scanner or a camera that uses special film. Infrared film records the photographic infrared radiation just beyond the range of human vision as red. Normal red from the scene becomes green, and green becomes blue. Normal blue in the scene is usually filtered out and not recorded.
Any physical or biological damage to growing plants which begins to cause a deterioration in their vigor (their water and/or chlorophyll content) causes a rapid decrease in their reflectance of photo-infrared radiation, and increases in their red reflectance. CIR photographs show these changes much sooner and more dramatically than normal photographs or human eyesight. Healthy, green vegetation appears in bright red, while damaged, diseased, or dying vegetation appears in shades of pink, tan, and yellow.
This knowledge was first used during the Second World War when color-infrared film was called camouflage detection film. It provided pre-visual detection of the changes in vegetation cut or damaged by military activity and could very easily separate color-camouflage materials (like olive drab canvas) from live foliage.
color map or color table
A color map is the table, or map, used by a computer system to assign display colors to digital values. A color map for an 8-bit raster object can contain a total of 256 colors. A gray scale image may have a color map with 256 shades of gray, ranging from black (0) to white (255). The first 64 places in a color map are normally assigned to the "standard 64" annotation colors. Additionally, certain processes may use the following 16 values for standard shades of gray. The remaining 176 or 192 colors are then available for the image colors used in the display..
color separation
Manipulating a full-color image in order to extract features of one color or range of colors. The color separation process can be used to create a binary raster object from a composite color raster object (or a set of three RGB raster objects) to lift out blue line images, for example, leaving behind background colors and lines images of other colors. Printers use related color separation techniques to prepare process color separates from full-color originals.
column
A vertical list of data values or display cells in a raster object or display.
command
A specific instruction to a computer programs issued by the user to perform a desired action.
COMMAND.COM
A file that contains the internal DOS commands required at PC startup. This file is transferred when a disk is formatted as a startup disk.
command line interface
software product that allows the user to type in command at a promt.
commit
to make permanent any changes made during a database transaction.
component
Any single element in a window, including buttons, fields, scroll bars, sashes, panels, menus, panes, frames, dialog boxes, or separators.
compose sequence
A sequence of two or more keystrokes used to create a single character, as in the case of European languages that have characters with various diacritical marks.
composite color raster object
A raster object in which each cell contains a data value representing one of the colors into which all available color data for that cell has been compressed. For 8-bit raster objects, there are 256 possible colors for each cell; for 16-bit raster objects there are 32,768. Composite color rasters are usually compressed from a red/green/blue raster set that retains a wider range of color information. The composite raster still produces near photographic quality color displays.
composite color video
The standard color video output of a VCR or video camera that adheres to the NTSC video standard. All the color information is contained in one signal (instead of in the three RGB color signals).
computed field
A field in a database table with a value calculated from the values of other fields in the same or different tables of a single database. You define the expression used to generate the values for a computed field using the same language and syntax employed for database queries. The appropriate record values for use in a computed field are determined through primary and foreign key relationships or by element attachment.
Concurrency management
A database management process for maintaining consistency of the data while supporting simultaneous access by more than one user. A typical technique is to allow any number of users read access but to allow only one user to have write access. A second user wanting write will have to wait until the first person completes their transaction.
Conformal Projection
A projection that can accurately preserve the shape of mapped entities with the drawback of scalar and area distortion All projections introduce same distortion into the cartesian results, to a certain degree, however, the mathematics chosen to perform the transformation can reduce certain types of distortion while introducing other types of distortion. A conformal projection preserves the proper angles between connected line segments and therefore tends to preserve the shape of geographic objects better than other types of projections.
conic projections
This group includes projections that are constructed by placing a cone tangent to the globe along a standard parallel in the mid latitudes, or in the case of a polyconic projection, placing a cone secant to two (or more) standard parallels. Conic projections are commonly used to depict hemispheres or smaller portions of the earth's surface.
connectivity
A topological identification of connected arcs by recording the from-and to -node for each arc. Arcs that share a common node are connected. see also arc-node topology
contiguity
The topographical identification of adjacent polygon by recording the left and right polygons of each arc. Also see polygon-arc topology.
continuous data
A surface for which each location has a specified or derivable value. Typically represented by a tin or lattice. (eg. - Surface elevation).
contour map
A line connecting points of equal surface value.
contour interval
The difference in surface values between contours.
contour map
A topographic map that uses contour lines to portray relief. Contour lines join points of equal elevation.
contours
Lines on a contour map or other isomorphic map that identify levels of a parameter at specified, discrete intervals.
contrast
The difference between bright and dark values in the display or printout of a continuous tone (usually grayscale) image. The stronger the contrast, the more difference between the brightest and darkest values. Most images benefit from a process of contrast enhancement, which artificially increases the contrast.
contrast table
A contrast table assigns display intensity values to raster object cell values using a specified translation method, such as linear or normalized translation. The type of translation chosen and the limits defined will change the display values but, in general, the result is to increase the apparent differences between the majority of cell values, which usually fall within a narrow range.
control panel or panel
An area of a window that holds related buttons, sliders, fields, and other components used to govern the behavior of a process.
control point
Points and/or cells which are used to establish map coordinate control for ungeoreferenced objects. In the manual mosaic process, a control point is a feature in a piece of the mosaic (such as a road intersection) for which the map coordinates are known. In the raster-to-vector calibration process, a control point is a feature that is co-located between the ungeoreferenced raster object, and the georeferenced vector object overlay. A control point may be something like a bend in a river or a road intersection that shows on both a raster object and an overlying vector object.
control point list
One type of map registration subobject (Regist) that contains a paired list of map coordinates and cell coordinates.
convergence angle
The angle between y axis and true north on a map. This is often used as a measure of azimuthal distortion on a map; and it often varies from one position to another.
convolution
Mathematically determining the data value for a new cell in an m x n neighborhood of cells. Raster filtering, resampling, and other raster processes use convolution. Convolution processes should never be applied to raster objects that contain categorical data. Convolution is only appropriate for continuous data.
coordinate system
A reference system for defining precise locations on the earth's surface. Coordinate systems may be independent of or tied to a particular map projection.
coprocessor
Microcomputers used for heavy computational tasks often have a second microprocessor, called a math coprocessor. To speed things up, the main CPU assigns its tedious arithmetic to this helpful specialist in much the same way that modern accountants use calculators for the computations their grandfathers did by hand. In the Intel CPU series, the main processor's chip number ends with the digit 6 and the coprocessor's chip number is the same except for the final digit 7: 80286 / 80287; 80386 / 80387. With the 80486, Intel included the math coprocessor in the basic design. (Thus there is no 80487).
coregistration
The condition in which associated raster and/or vector objects overlay each other with correct orientation and geometry so that corresponding internal features align.
correlation
The degree of relatedness between two objects; more specifically, the degree to which one value in a set of values can be used to predict the corresponding value in another set of values.
correlation points
(also "tie points"). A pair of points collocated on a common feature, such as a road intersection, in a pair of images. A set of correlation points defines the mutual spatial relationship of a pair of overlapping images without regard for their real position in a map coordinate system.
cover#
A unique sequence number automatically generated by ARC/INFO for each coverage feature. This internal number is used to directly access features and to describe topographical relationships between coverage features. It is often referred to as the 'record number'.
Cover ID
An integer identifier assigned by the user to relate geographic features and correspondic attribute data. Cover ID is an item found in feature attribute tables, with 'cores' replaced by the coverage name (eg for soil coverage, the cover-ID would be SOIL-ID). Feature - ID and user ID arc synonymos terms to cover-ID.
Coverage
1. A digital version of a map forming the basic unit of vector data storage in ARC/INFO. A coverage stores geographic features as primary features (such as arcs, nodes, polygons, and label points) and secondary features (such as ties, mapextent, links, and annotation) Associated feature attrubute tables describe abnd store attributes of the geographic features.
2. A set of thematically associated data considered as a unit. A coverage usually represents a single theme such as soil streams, roads or land use.
coverage extent
The coordinates defining the minimum boundary rectangle i.e. (x min, y min and x max, y max) of a coverage or grid. All coordinates for the coverage or the grid fall within this boundary. In ARCPLOT and ARCEDIT; map extent is often set from the coverage extent.
coverage file
See: pcARC/INFO coverage file.
coverage unit
The units (eg. feet, meter, inches) of the co-ordinate systems in which a coverage is stored.
CPU
Central Processing Unit. The main computing engine of a computer.
CRT
Cathode ray tube.
CSSM
The content standard for Spatial Metdata. A document produced by Fedral Geographic Data Committee (FGDC) that describes Spatial meta data.
cubic convolution or cubic interpolation
A computationally intense interpolation method used in raster resampling. This method determines a new cell value to produce a smoother result by fitting a cubic polynomial surface to a 4 x 4 neighborhood of cells. Bilinear interpolation normally produces results which are almost as good. Cubic convolution should not be applied where the mean data value for a group of cells is undefined as in categorical data (like an 8-bit color raster object, a classification map, or any raster object containing similar category-type data).
cursor
1. A graphic pointer used with a mouse to point to a location on a terminal screen.
2. An internal pointer to a record in a table which provide a mechanism for proessinga selected set of records. The cursor is moved one by one through the set while operations such as display, query and update are performed.
cursor hot spot
The pixel location on a cursor shape at which the cursor activity takes place. For example, the hot spot on an arrow cursor is at the point of the arrow, while the hot spot for a cross-hair cursor is at the intersection of the crosshairs.
cycle
1. In Patrhfinding, a cycle is a path or tour beginning and ending at the same node.
2. In tracking, a cycle is a set of arcs forming a closed polygon. Upstream and downstream directionality are undefinable in a cycly
cylindrical projections
This group of projections includes all projections constructed by placing a cylinder tangent to the globe along a standard parallel-usually the equator, or secant to the same standard parallels in opposite hemispheres, respectively.
Cyrillic
An alphabet widely applied to the Slavic languages, as in the case of the thirty-three-letter Russian alphabet. Since the 1930's it has been used for most of the languages of the former Soviet Union. (Attributed to Saint Cyril, a ninth-century Christian apostle of the Slavs.)