anonymous FTP: Ability to connect with
another site on the Internet without a user account, and to download files.
FTP is the file transfer protocol, available on a large number of computer
systems. Login is usually under the name anonymous with the password set to
your own user ID on the Internet.
AVHRR (Advanced Very High Resolution Radiometer):
An instrument on the NOAA orbiting polar satellites that returns 1- and 4-km
resolution data about the earth in four wavelengths. Used extensively for
large-area land-cover and vegetation mapping and weather prediction.
background image: A satellite image
or air photo that serves as a backdrop for display and registration purposes
only rather than as a layer for analysis with the GIS.
base layer or map: A GIS data layer
of reference information, such as topography, road network, or streams, to
which all other layers are referenced geometrically.
CD-ROM: Compact disk read-only memory,
a hardware storage device capable of making extensive data and software available
for distribution on removable CDs or as off-line storage for a microcomputer.
Corona: Originally a secret satellite-based
remote sensing system carrying the early- generation Keyhole cameras for the
period 196274. Very high resolution monochrome data from Corona, some covering
the United States, are now available on-line through the USGS's EROS data center.
data mining: Revisiting existing data
to explore for new relationships using new and more powerful tools for analysis
DIGEST: A U.S. military and NATO data
transfer standard, best known as the format for the digital chart of the world,
which is in the Defense Mapping Agency's vector product format (DIGEST-A).
digital orthophoto quad (DOQ): One
element of a national mapping effort to cover the lower 48 United States at
a 1-meter ground resolution with monochrome air photos in digital format with
a 1:12,000 equivalent ground extent. Collections of DOQs are distributed compressed
distributed network: A network-connected
set of locations, each storing one element of a system. A distributed GIS
may have the GIS software running on a workstation but use data dispersed
at many computer storage locations over a local or wide area network.
download: To move a file across a network
for eventual residence locally.
DX-90: A data transfer standard in
use among the members of the International Hydrographic Organization, primarily
to assure standardization and free exchange of digital nautical charts.
EOS (NASA's Earth Observation System):
A multisatellite 15-year program to increase the available data about the
earth's land, water, clouds, ice, and air.
EOSDIS: The information distribution,
dissemination, and storage section of the EOS program, which eventually will
provide full network access to the data collected by all the various EOS instruments
file server: A computer whose primary
function is to store data and make them available on a network as part of
a distributed system.
FIPS 173: The federal information processing
standard maintained by the USGS and the National Institute of Standards and
Technology, which specified a standard organization and mechanism for the
transfer of GIS data between dissimilar computer systems. FIPS 173 specifies
terminology, features types, and accuracy specifications, as well as a formal
file transfer method.
fix: A solution to a software problem
or bug. Usually, a section of a computer program or a file to be overwritten
to correct the problem, called a patch.
freeware: Software and data made available
on the networks to any user at zero cost. Immense amounts of freeware, including
entire operating systems and GIS packages, are available on the Internet.
geographic information science: The
scientific use and study of methods and tools for the capture, storage, distribution,
analysis, display, and exploitation of geocoded information.
GRID: A United Nations program to assemble,
use, and disseminate data sets of global extent of use to the United Nations and
GUI (Graphical User Interface): The
set of visual and mechanical tools through which a user interacts with a computer,
consisting of windows, menus, icons, and pointers.
hypertext: Textual information in which
direct links can be made between related text through "hot links,"
where pointing to a highlighted term moves the user to the text context for
that term in the same or a different document.
interoperability: The extent to which
users, software, and data can move between computer environments without change
or retraining. In a fully interoperable GIS, the user interface will look
and feel the same in two different environments (say, a microcomputer and
a Unix workstation), and the same set of functions will have the same effect
on the same data.
in-vehicle navigation system: A navigation
aid allowing the driver of a car, pilot of a plane, or navigator of a boat
direct assistance during operation. Combinations of GPS, on-board digital
maps, GIS functions such as routing, and voice information are common in these
systems. Most use outside aids. Those using the sensed motion of the vehicle
are called inertial.
Landsat: A U.S. government satellite
program collecting data about the earth's surface in the visible and infrared
parts of the spectrum. Two instruments, the multi-spectral scanner (79-meter
resolution) and the thematic mapper (30-meter resolution), have been used.
Landsat 7 is the next to be launched, for which the data will return to the
metadata: Data about data. Index-type
information pertaining to the entire data set rather than the objects within
the data set. Metadata usually includes the date, source, map projection,
scale, resolution, accuracy, and reliability of the information, as well as
data about the format and structure of the data set.
metaphor: For a GUI, the physical analogy
for the elements with which the user will interact. Many computer GUIs use
the desktop as a metaphor, with the elements of a calendar, clock, files, and
file cabinets, and so on.
microcomputer: A stand-alone computer
containing at least a microchip, a keyboard, a display, and some sort of memory,
running under an operating system. Typically, microcomputers have separate
elements, and extensions such as network links, graphical pointers, and storage
are added to a core system.
multimedia: The use of multiple simultaneous
means of communication in a single "document," normally including
sound, graphics, animation, and hypertext.
multispectral scanner: An instrument
carried on the Landsat series of satellites capable of capturing four parts
of the spectrum simultaneously for pixels 79 meters on a side.
multitask: The ability of a computer's
operating system or GIS to handle more than one process at once: for example,
editing and running a command sequence while extracting data from the database
and displaying a map.
National Spatial Data Clearinghouse: A
World Wide Web resource that serves as a cross-reference point for the distributed
database of all U. S. government public-domain and other geographic information.
national spatial data infrastructure: The
set of base geographic data necessary for effective operation of the federal
government and its suppliers, made accessible as a distributed database.
network conference group (also
network news group, usenet group, List): An Internet resource on which
users with similar interests can share broadcast exchanges of information.
Several major GIS groups exist, including comp.infosystems.gis;
also called GIS-L.
object-oriented: Computer programming
languages and databases that support "objects." Objects are standard
"classes" that contain all the properties of an object. As a simple
example, an object class could be a point and will contain the latitude and
longitude of the point, a feature code for the point, such as "radar
beacon", and any necessary text to describe the object.
Open/GIS: An active effort to assure
interoperability among GIS software packages by specifying a standard set
of functions and a common user interface.
OpenLook: A set of GUI specifications
agreed upon by several software vendors for an interoperable graphical user
interface. Sun's Open Windows is an example of an implementation of OpenLook.
operating system: The suite of software
programs and utilities necessary for the control and use of a computer, including
as a minimum the management of files and the use of the computer's processor.
OS/2: A microcomputer operating system
produced by the IBM Corporation.
parallel processing: A computer or
workstation configured with multiple microcircuits, each functioning as a
separate computer but usable in tandem. Either each computer can handle a
separate task or each computer can hold data to which a uniform process is
patch: A fix to a program or data set
involving a sequence of data that are to be overwritten onto an older version.
Pathfinder: A U.S. government prototype
effort to use data mining of older Landsat and other data to provide complete
GIS coverages of the United States at different time periods.
PCMCIA: A credit-card-like device interface
for microcomputers and other devices, such as GPS receivers, that meets the
standards of the Personal Computer Memory Card International Association.
PCMCIA cards can act as memory, connectors to disk drives, and links to other
types of devices, perform many other functions, and are interoperable across
public domain: Information that has
been made available to the general public and is distributed and redistributed
without copyright or patent.
radar mapping system: An active form
of remote sensing in which a radar beam is transmitted to earth and the reflected
signals are detected and stored. These systems have the distinct advantage
of being operable at night, through clouds, and through vegetation and therefore
are used extensively for mapping in the tropics and for mapping terrain.
remote login: The ability of a computer
user to log directly into another computer through a network connection or
remotely sensed data: Data collected
by a sensor that is not in direct contact with the area being mapped. Active
remote sensing involves transmitting a beam that is detected after reflection;
passive remote sensing simply measures light from the sun being reflected
by objects being sensed. Similar instruments for remote sensing can operate
from aircraft or satellites.
scientific visualization: Use of the
human visual processing system assisted by computer graphics, as a means for
the direct analysis and interpretation of information.
shareware: Data or software placed
in the public domain for distribution, whose use or support involves the payment
of a (usually token) fee to the author.
spatial data transfer standard (SDTS):
The formal standard specifying the organization and mechanism for the
transfer of GIS data between dissimilar computer systems. Adopted as FIPS
173 in 1992, SDTS specifies terminology, feature types, and accuracy specifications
as well as a formal file transfer method for any generic geographic data.
Subsets for the standard for specific types of data, vector, and raster, for
example, are called profiles.
SPOT (Systeme Proprietaire pour l'Observation
de la Terre): A French remote sensing satellite system with 10- and 20-meter
resolution and stereo capability.
TCP/IP: A network communications protocol
that forms the basis of most communications on the Internet.
Unix: A computer operating system that
has been made workable on virtually every possible computer and has become
the operating system of choice for workstations and science and engineering
user interface: The physical means
of communication between a person and a software program or operating system.
At its most basic, this is the exchange of typed statements in English or
a program-like set of commands.
WIMP: A GUI term reflecting the primary
user interface tools available: windows, icons, menus, and pointers.
workstation: A computing device that
includes as a minimum a microprocessor, input and output devices, a display,
and hardware and software for connecting to a network. Workstations are designed
to be used together on local area networks, and to share data, software, and
World Wide Web (WWW or W3): A distributed
database of information connected by the Internet and special-purpose software
for browsing, searching, and downloading.
X-Windows: A public-domain GUI built
on the Unix operating system and computer graphics capabilities, written and
supported by the Massachusetts Institute of Technology and the basis of most
workstation shareware on the Internet.