- machine language
-
Instructions coded so that
the computer can recognize and execute them.
- macro
-
A text file containing a
sequence of commands that can be executed as one command. Macros can be
built to perform frequently used, as well as complex, operations. The ARC
Macro Language (AML)
is used to create macros for ArcInfo.
- many-to-one relate
-
A relate in which many
records in one table are related to a single record in another table.
- magnetic media
-
Tape or disks coated with a
magnetic surface used for storing electronic data.
- map
-
An abstract representation
of the physical features of a portion of the Earth's surface graphically
displayed on a planar surface. Maps display signs, symbols, and spatial
relationships among the features. They typically emphasize, generalize,
and omit certain features from the display to meet design objectives
(e.g., railroad features might be included in a transportation map but
omitted from a highway map).
- map algebra
-
Process of adding,
subtracting, multiplying, and dividing maps by applying mathematical
operations to map themes. Map algebra utilities allow the user to specify
mathematical relationships between map layers. For example, a new map can
be generated by determining the difference in elevation between a
topographic map and the corresponding map of the water table.
- Map Analysis Package (MAP)
-
A computer program written
by C. D. Tomlin for analyzing spatial data coded in the form of grid
cells.
- map extent
-
1. The rectangular limits (xmin,ymin
and xmax,ymax) of the area of the Earth's surface displayed using ArcInfo.
Map extent is specified in the coordinate system of the coverage or other
geographic data set used. Typically, the extent of the geographic database
(or a portion of it defined by a zoomed-in view) defines the map extent
for display.
2. The geographic extent of
a geographic data set specified by the minimum bounding rectangle (i.e.,
xmin,ymin and xmax,ymax).
- map generalization
-
The process of reducing
detail on a map as a consequence of reducing the map scale. The process
can be semi-automated for certain kinds of data, such as topographical
features, but requires more insight for thematic maps.
-
An organized, uniformly
defined collection of spatial data partitioned by layers and tiles into
component parts called map sections. A map library
organizes geographic data spatially as a set of tiles and thematically as
a set of layers. The data in a map library are indexed by location for
optimal spatial access. A map library organizes coverages spatially by
tiles and thematically by layer.
- map limits
-
The rectangular area on the
graphics page in which geographic features are displayed. All geographic
data are drawn within the map limits, and none outside the map limits. Map
titles and legends can be drawn outside the map limits.
-
A mathematical model that
transforms the locations of features on the Earth's surface to locations
on a two-dimensional surface. Because the Earth is three-dimensional, some
method must be used to depict a map in two dimensions. Some projections
preserve shape; others preserve accuracy of area, distance, or direction.
See also
coordinate system.
Map projections project the
Earth's surface onto a flat plane. However, any such representation
distorts some parameter of the Earth's surface be it distance, area,
shape, or direction.
-
The process of selecting
information from a GIS by asking spatial or logical questions of the
geographic data. Spatial query is the process of selecting features based
on location or spatial relationship (e.g., select all features within 300
feet of another; point at a set of features to select them). Logical query
is the process of selecting features whose attributes meet specific
logical criteria (e.g., select all polygons whose value for AREA is
greater than 10,000 or select all streets whose name is 'Main St.'). Once
selected, additional operations can be performed, such as drawing them,
listing their attributes or summarizing attribute values.
-
The reduction needed to
display a representation of the Earth's surface on a map. A statement of a
measure on the map and the equivalent measure on the Earth's surface,
often expressed as a representative fraction of distance, such as 1:24,000
(one unit of distance on the map represents 24,000 of the same units of
distance on the Earth). Map scale can also be expressed as a statement of
equivalence using different units; for example, 1 inch = 1 mile or 1 inch
= 2,000 feet.
-
The unit of data storage in
a map library. A map section is the data for one layer in one tile of a
map library. Map sections are implemented as ArcInfo coverages. See also
map library,
layer and
tile.
- map-to-page transformation
-
The process of positioning
and scaling a map on a graphic page. It controls how coverage coordinates
are transformed into graphics on the display screen or plotter page. (Coverages
are not maps; they contain the unscaled coordinates that ArcInfo uses to
draw maps.)
- map units
-
The coordinate units in
which a geographic data set (e.g., a coverage) is stored in ArcInfo. Map
units can be inches, centimeters, feet, meters, or decimal degrees.
-
A symbol used to represent
a point location such as an airport.
- mass point
-
Irregularly distributed
sample points, each with an x,y location and a z value, which are used as
the basic elements to build a
tin.
Each mass point has important, yet equal, significance in terms defining
the tin surface. Ideally, the location of each mass point is intelligently
chosen to capture important variations in the surface's morphology.
- MDI
-
Multiple Document Interface
was developed by Microsoft, with menus, buttons, tools, and windows called
documents. ArcView is based on the MDI standard, including multiple
document types: Project View, Table, Layout, Chart, and Scripts. Documents
can be organized and manipulated in a variety of standard ways: tiled,
cascaded, iconified, resized, or closed.
- menu
-
[CAD/CAM] a set of
preprogrammed areas on the digitizing tablet. By entering a digitizer
signal from one of these areas (squares), the user can choose a particular
set of commands. General interactive computing; a list of available
options displayed on the CRT that the user can choose from by using the
keyboard or a device such as a touch screen.
- merge
-
To take two or more maps or
data sets and combine them together into a single, coherent map or
database without redundant information.
- meridian
-
A line running vertically
from the north pole to the south pole along which all locations have the
same longitude. The Prime Meridian (0) runs through Greenwich, England.
From the Prime Meridian, measures of longitude are negative to the west
and positive to the east up to 180, halfway around the globe.
-
One sample point in the
array of sample points in a
lattice. Each mesh point is located at a constant sampling interval in
the x and y directions relative to a common origin, and contains the z
value for the surface at that location. Mesh points outside the surface,
or which represent holes in the surface, are assigned a
null value.
- metadata
-
Information about data set.
Metadata for geographical data may include the source of the data; its
creation date and format; its projection, scale, resolution, and accuracy;
and its reliability with regards to some standard. See data dictionary.
- minimum bounding rectangle
-
A rectangle, oriented to
the x and y axes, which bounds a geographic feature or a
geographic data set. It is specified by two coordinates: xmin,ymin
and xmax,ymax. For example, the BND defines a minimum
bounding rectangle for a coverage.
- minimum mapping units
-
For a given map scale, the
size or dimension below which a long narrow feature is represented as a
line and a small area as a point. For example, streams and rivers will be
represented as lines if their width is less than .10 inch, and polygons
smaller than .125 inch on a side will be represented as a point.
-
A representation of reality
used to simulate a process, understand a situation, predict an outcome, or
analyze a problem. A model is structured as a set of rules and procedures,
including spatial modeling tools available in a geographic information
system (GIS). See also
spatial modeling,
data model,
analysis and
spatial analysis.
- modeling
-
See model.
- module
-
A separate and distinct
piece of hardware or software that can be connected with other modules to
form a system..
- moment
-
The moment is the time when
all the tasks associated with a
transaction have completed. A feature's creation, deletion or update
date is set to the transaction's moment.
- monument
-
A ground surveyed point of
known x,y,z coordinates that is assumed to be correct for general mapping
purposes.
- morphology
-
The form and structure of a
surface. In tins, the morphology of a surface is defined by the sample
points and
breakline features used to build the tin. Breaklines, when properly
located at locations of significant change in surface behavior, play a
major role in defining surface morphology. In lattices, the morphology of
a surface cannot be directly represented by sample points and linear
features; it must be implied from the mesh point z values.
-
Software used to access
resources on the Internet. The Mosaic project has been conducted by the
National Center for Supercomputing Applications (NCSA) in Illinois to
provide a single front-end or user interface to many information services.
The goal is to present the query to, and results from, each of these
different information resources in a similar way to minimize the number of
"systems" one must be familiar with to successfully navigate the Internet.
Mosaic relies on the existence of servers; it does not serve information
of its own. Mosaic client software exists for X Windows, Macintosh, and
Microsoft Windows. Computers must be connected to the Internet to use
Mosaic.
- mouse
-
A hand-controlled hardware
device for interacting with a computer terminal or entering data from a
digitizer. A mouse is used to make selections and position the cursor to
fields in computer forms when interacting with graphical user interfaces.
A digitizer mouse is used to trace features and enter x,y coordinates of
features.
- MSS
-
Multispectral scanner. An
instrument on some satellites used for imaging the earth. An MSS image
will have data recorded by the scanner from three or more bands of the
electromagnetic spectrum. ArcInfo can read multispectal images in various
formats.
- multispectral
-
Is the ability of a remote
sensing device to detect electromagnetic energy in at least two or more
individual wavelength intervals.
- multispectral photography
-
Photography that creates
imagery from several narrow spectral bands within the visible light region
and the near infrared region. A multispectral image contains two or more
images, each taken from different portions of the spectrum (e.g., blue,
green, red, infrared).
- NAT
-
Arc attribute table. A
table containing attributes for node coverage features. For each node, the
NAT contains a reference to one of the arcs it connects to, an internal
node sequence number and node feature identifier. See also
feature attribute table.
- National Center for Geographic
Information and Analysis (NCGIA)
-
A center funded by the
National Science Foundation that is jointly headquartered at the
University of California, Santa Barbara, the University of Maine, Orono,
and the State University of New York at Buffalo. The Center encourages the
development of quality GIS education programs in universities in the
United States and worldwide. It developed a core curriculum; a set of
teaching materials for a three-course sequence in GIS. It also sponsors
workshops, seminars, and meetings and produces technical publications
related to GIS.
- National Geodetic Vertical Datum of
1929
-
The datum established in
1929 by the U.S. Coast and Geodetic Survey as the surface against which
elevation data in the United States is referenced.
- native mode usage
-
A statement syntax entered
in ArcInfo in the language of an external system. Inclusion of an SQL
WHERE clause in an ArcInfo native mode SQL selection operation, or the
declaration of a DBMSCURSOR are examples of native mode SQL usage.
- NBS
-
National Bureau of
Standards, now known as NIST (see NIST).
- neatline
-
A border line commonly
drawn around the extent of a map.
- needs analysis
-
See user requirements
analysis
- neighborhood analysis
-
Analytical technique to
determine whether a set of areas (polygons) are situated next to each
other and to examine their interrelationships.
- network
-
1. An interconnected set of
arcs representing possible paths for the movement of resources from one
location to another.
2. A coverage representing
linear features containing arcs or a route-system. Also known as
network coverage.
3. When referring to
computer hardware systems, a local area network (LAN)
or a wide area network (WAN).
- NETWORK
-
The ArcInfo software
product that performs address matching/ geocoding, allocation, routing,
and pathfinding across linear networks.
-
In ArcInfo, a line coverage
on which network tools such as PATH and ALLOCATE can operate.
- network element
-
The components of a network
in ArcInfo, including network links and
network nodes, of which there are three types:
stops,
centers, and
turns.
-
Network links are
interconnected linear entities which represent the conduits for
transportation (e.g., vehicles, fluids, electricity) and communication
networks, for example, highways and electrical transmission lines. In
ArcInfo, links are represented as arcs with attributes stored in the AAT.
-
Network nodes are the
endpoints and connecting points of network links, for example,
intersections and interchanges of a road network, the confluence of
streams in a hydrologic network, or switches in a power grid. In ArcInfo,
network nodes are used to model stops, centers, and turns. Network nodes
are represented as nodes, with attributes stored in an NAT.
- networking protocols
-
A networking protocol is
software that provides a communication gateway (link) allowing the
exchange of data between various networking systems. Protocols are a fixed
set of rules used to specify the format of an exchange of data.
-
The Network File System (NFS)
protocol allows a given computer to access a disk on another computer over
a network in a transparent fashion. The hard disk can be accessed just as
easily as if it were local to the user's machine. To get access to a disk
across a network, the disk must be NFS mounted on the user's local
machine. See your system administrator for such operations.
-
National Institute of
Standards & Technology is the agency that produces the Federal Information
Processing Standards (FIPS) for all U.S.A. government agencies except the
Department of Defense.
- NMAS
-
National map accuracy
standards are specifications of accuracy standards for well-defined map
points on published maps that are specified by the U.S. Geological Survey
and revised by the U.S. Bureau of the Budget.
-
1. The beginning and ending
locations of an arc. A node is topologically linked to all arcs that meet
at the node. See also network node.
2. In graph theory, the
location at which three or more lines connect.
3. The three corner points
of each triangle in a tin. Every sample point input to a tin becomes a
node in the triangulation. A triangle node is topologically linked to all
triangles that meet at the node.
- node match tolerance
-
The minimum radial distance
within which two nodes will be joined (matched) to form one node.
-
A conceptual database
design task that involves applying data dependency to a data model to
avoid data inconsistencies by prohibiting redundancy.
- NTF
-
National Transfer Format
(British Standard BS 7567). NTF is an exchange format that permits the
transfer of vector data with five different levels of complexity. NTF is
the format used by the British Ordinance Survey.
-
The absence of a value. If
a particular column of a row in a table is null, that means there is no
value stored. Null is not the same as blank or zero.
- object
-
A single, identifiable unit
or entity. An object can comprise other, smaller objects.
- object oriented
-
The intrinsic
representation and storage of real world entities in a GIS database rather
than the use of cells, points, lines, or polygons to store the object.
- OCR
-
Optical Character
Recognition is the automatic recognition and interpretation of text.
- ODBC
-
Open Database
Communication. A standard API (application program interface) used to
communicate with database management systems, developed by Microsoft, and
incorporated in ArcView Version 2. ArcView supports ODBC for DBMSs on the
Microsoft Windows platform.
- ODYSSEY
-
Computer program developed
at the laboratory for Computer Graphics, Harvard, for overlaying polygon
networks.
- OGC
-
The Open GIS Consortium, a
group composed of software vendors, academics, government agencies,
consultants and software integrators, dedicated to open systems
geoprocessing. Their first project is to develop an open geodata
interoperability specification (OGIS).
- OGIS
-
The Open Geodata
Interoperability Specification being developed by OGC to support
interoperability of GIS systems in a heterogeneous computing environment.
- OLE
-
Object Linking and
Embedding developed by Microsoft. Allows objects from one application to
be embedded within another (e.g., taking an Excel spreadsheet and putting
it into a Word document). ArcView Version 2 does not support the still
evolving OLE standard. Instead, it supports DDE (see
DDE).
OLE support is planned for future releases of ArcView.
- OMG
-
The Object Management Group
is a computing industry collaboration to promote object-oriented
interoperability among heterogeneous computing environments. They continue
to develop specifications which address the many aspects of this problem,
the most popular of which is the Common Object Request Broker Architecture
(CORBA).
- one-to-many
-
A relate in which one
record in a table is related to many records in another table.
- OPEN LOOK
-
A graphical user interface
(GUI) for the X Window system developed by AT&T (Open Look) and Sun
Microsystems (OPEN LOOK). (See also OSF/Motif).
- online access
-
Direct access to data that
does not involve file transfer.
- optical disk
-
A digital data storage
technology that uses optical media to store information. Optical disks are
slower, but store more data and cost less per unit of stored data than
magnetic disks. Several optical platters can be installed in a single
device called a jukebox. Optical disks are used when very large amounts of
data need to be stored.
- optimal estimator
-
An estimator for minimizing
the value of a given criterion function; in kriging this is the estimation
variance.
-
Computer software designed
to allow communication between the computer and the user. The operating
system controls the flow of data, the application of other programs, the
organization and management of files, and the display of information.
- ORACLE
-
A relational database
management system to which ArcInfo has access through the DATABASE
INTEGRATOR.
- orthophoto
-
Are photos that have been
fitted into a standard map projection so that they contain the qualities
of both maps and photographs. Like maps, they have only one scale, which
allows for accurate measurements of distances, angles, and areas to be
made directly from their surface. Like photographs they depict features as
they truly are (without any symbolization).
- OS
-
See operating
system.
- OSF
-
The Open Software
Foundation is an international consortium that promotes the
standardization of the UNIX operating system.
-
An industry-standard
graphical user interface developed by the Open Software Foundation for the
UNIX workstation environment.
-
Open Systems Interconnect,
a seven-layer hierarchical reference interface and communications model
sponsored by ISO, 1984, known as the OSI Reference Model: layer
7--applications, layer 6--presentations, 5--session, 4--transport,
3--network, 2--data link, 1--physical. This model is incorporated at the
operating system level. The OSI model is used to develop interfaces and
integrate two dissimilar systems (i.e., PCs and UNIX or UNIX and
mainframes).
-
1. The reference location
for a planar coordinate system, usually represented by the values 0,0.
2. The place where a trip
starts. This is usually the home for most consumers. For a population
group, an origin could be a census tract or a city. Origins are
represented as nodes in a network coverage, as points in a point coverage,
and as label points in a polygon coverage.
- overlay
-
See
topological overlay.
- overshoot
-
That portion of an arc
digitized past its intersection with another arc. See also
dangling arc.
- page extent
-
Defines a rectangular
portion of the
graphics page to be displayed.
- pan
-
To move the viewing window
up, down, or sideways to display areas in a geographic data set which, at
the current viewing scale, lie outside the viewing window. See also
zoom.
- panchromatic
-
Is the ability of a remote
sensing device to detect electromagnetic energy in only one very broad
band, which includes most of the area of visible light. .
- parallel
-
1. A property of two or
more lines that is separated at all points by the same distance.
2. A horizontal line
encircling the Earth at a constant latitude. The Equator is a parallel
whose latitude is 0. Measures of latitude range from 0 to 90 north of the
Equator and from 0 to -90 to the south.
- parcel
-
See cadastral parcel.
- PASCAL
-
A high-level programming
language that is been used increasingly instead of FORTRAN for scientific
programming.
- passive sensors
-
Passive sensors use only
the naturally available illumination that enters the instrument to record
images. .
-
Point attribute table or
polygon attribute table. A coverage can have either a point attribute
table or a polygon attribute table, but not both. In addition to
user-defined attributes, a PAT contains data on area and perimeter of a
polygon (values are 0 for points), an internal sequence number and feature
identifier.
The PAT is also used for
regions. The same attributes are maintained, however, the name of the
attribute table is PAT<REGION>, where <REGION> is the name of the region
for which attributes are stored. One polygon and many region attribute
tables can be stored in the same coverage. See
feature attribute table.
-
An ordered set of
network links and network
nodes which connects an origin to a destination
(center).
- pathfinding
-
The process of finding a
path between an origin and destination, which usually involves determining
a
least-cost path.
-
The path to a file or
directory located on a disk. Pathnames are always specific to the computer
operating system.
- Paul Revere tour
-
A traveling salesman tour
in which the start is different from the ending stop. The name is derived
from American history, after the famous ride of Paul Revere.
- peak
-
A point around which all
slopes are negative (i.e., downward).
- peripheral device
-
A hardware device not part
of the central computer (e.g., digitizers, plotters, and printers).
-
A long-term
database lock required when users wish to maintain a consistent view
of their data while doing modifications over a
long transaction.
- petabyte
-
A measure of data size. One
petabyte is equivalent to 1,000 terabytes.
- pit
-
A point around which all
slopes are positive (i.e., upward).
- pixel
-
A contraction of the words
picture element. The smallest unit of information in an image or raster
map. Referred to as a cell in an image or grid.
- planimetric data
-
Spatial data that do not
take topographic relief information into account for establishing
position.
- plat
-
A diagram drawn to scale
showing all essential data pertaining to the boundaries and subdivisions
of a tract of land. It is often a legal document.
-
1. A single x,y coordinate
that represents a geographic feature too small to be displayed as a line
or area; for example, the location of a mountain peak or a building
location on a small-scale map.
2. A coverage feature class
used to represent point features or to identify polygons. It is not
possible to have point and polygon features in the same coverage. When
representing point features, the x,y location of the label point describes
the location of the feature. When identifying polygons, the label point
can be located anywhere within the polygon. Attributes for points are
stored in a PAT.
- point-in-polygon
-
A
topological overlay procedure which determines the spatial coincidence
of points and polygons. Points are assigned the attributes of the polygons
within which they fall.
- point event
-
See
event.
-
A coverage feature class
used to represent
areas. A polygon is defined by the arcs that make up its boundary and
a point inside its boundary for identification.
Polygons have attributes (PAT) that describe the
geographic feature they represent.
-
The topological data
structure ArcInfo uses to represent connectivity between arcs to form
polygons. Polygon-arc topology supports the definition of polygons and
analysis functions such as
topological overlay. See also
topology.
- polygon overlay
-
A
topological overlay procedure which determines the spatial coincidence
of two sets of polygon features and creates a new set of polygons based on
identity,
intersect, or
union.
-
POSIX character sets
support languages which only require 7-bit characters (such as US
English). See also
extended character set.
- POSIX 1003.1A
-
A revision to the POSIX
1003.1 standard that defines a set of standard operating system interfaces
and an environment for application programs written in C.
- POSIX 1003.4a
-
Defines thread support to
facilitate writing multitasking operations, particularly server
applications.
- PostScript
-
PostScript is a
page-description computer language developed, marketed, and trademarked by
Adobe Systems, Inc. PostScript is supported on most LaserWriter printers.
PostScript is particularly useful in computerized typesetting applications
and desktop publishing with graphics. PostScript files can be plotted on
non-PostScript plotting devices by means of Raster Image Processor (RIP)
software.
- precision
-
Refers to the number of
significant digits used to store numbers, and in particular, coordinate
values. Precision is important for accurate feature representation,
analysis and mapping. ArcInfo supports
single precision and
double precision.
- preliminary topology
-
Refers to incomplete region
topology. Region topology defines region-arc and region-polygon
relationships. A topological region has both the region-arc relationship
and the region-polygon relationship. A preliminary region has the
region-arc relationship but not the region-polygon relationship. In other
words, preliminary regions have no polygon topology.
-
One or more attributes
whose values uniquely identify a row in a database table. See also
foreign key.
-
A method of analyzing
multivariate data in order to express their variation in a minimum number
of principal components or linear combinations of the original, partially
correlated variables.
-
The property of an
origin which produces a trip for a particular
activity. This is usually a function of the population at the origin. For
example, a household production for two adults and one child might be one
trip per week for groceries, two trips per day for work, three trips per
six months to see a dentist, and so on. Interactions between an origin and
a center are estimated bases on how much of an origin's production will be
attracted to a particular
center.
-
A vertical sectional view
of a
surface derived by sampling surface values along a
section line.
- projection
-
See
map projection.
- projection file
-
1. A coverage file that
stores the parameters for the map projection and coordinate system of a
geographic data set (e.g., a coverage).
2. A text file containing
input and output projection parameters that can be used to convert a
geographic data file from one coordinate system to another.
-
The minimum distance in
ground units separating all point locations on the horizontal plane. If
two or more points are found within the proximal tolerance distance of
each other, only the first point read is passed for further processing.
- proximity analysis
-
Analytical technique used
to determine the relationship between a selected point and its neighbors.
- pseudo node
-
A node where two, and only
two, arcs intersect, or a single arc that connects with itself.
-