EM 1110-2-2907
1 October 2003
other parallels of latitude for a given range of longitude. Albers Equal
Area is frequently used in the ellipsoidal form for maps of the United
States in the National Atlas of the United States, for thematic maps,
and for world atlases. It is also used and recommended for equal-area
maps of regions that are predominantly east-west in extent.
Along-track scanner
Scanner with a linear array of detectors oriented normal to flight path.
The IFOV of each detector sweeps a path parallel with the flight
direction.
Alteration
Changes in color and mineralogy of rocks surrounding a mineral
deposit that are caused by the solutions that formed the deposit. Suites
of alteration minerals commonly occur in zones.
Amplitude
For waves, the vertical distance from crest to trough.
Analog display
A form of data display in which values are shown in graphic form, such
as curves. Differs from digital displays in which values are shown as
arrays of numbers.
Analogue image
An image where the continuous variation in the property being sensed
is represented by a continuous variation in image tone. In a
photograph, this is achieved directly by the grains of photosensitive
chemicals in the film; in an electronic scanner, the response in millivolts
is transformed to a display on a cathode-ray tube where it may be
photographed.
Angular beam width
In radar, the angle subtended in the horizontal plane by the radar
beam.
Angular field of view
Angle subtended by lines from a remote sensing system to the outer
margins of the strip of terrain that is viewed by the system.
Angular resolving power
Minimum separation between two resolvable targets, expressed as
angular separation.
Anomaly
An area on an image that differs from the surrounding, normal area. For
example, a concentration of vegetation within a desert scene
constitutes an anomaly.
Device that transmits and receives microwave and radio energy in
radar systems.
Aperture
Opening in a remote sensing system that admits electromagnetic
radiation to the film in radar systems.
APL
Applied Physics Laboratory of John Hopkins University.
Apollo
U.S. lunar exploration program of satellites with crews of three
astronauts.
Apparent thermal inertia
An approximation of thermal inertia calculated as one minus albedo
(ATI)
divided by the difference between daytime and nighttime radiant
temperatures.
ARC Export
EXPORT creates an ARC/INFO interchange file to transfer coverages,
INFO data files, text files, and other ARC/INFO files between various
computer systems. An interchange file contains all coverage
information and appropriate INFO file information in a fixed length,
ASCII format. It can be fully or partially compressed as well as
uncompressed ASCII depending upon the given EXPORT option.
ARC SECOND
1/3600th of a degree (1 second) of latitude or longitude.
ARC/INFO
ARC/INFO is a geographic information system (GIS) used to automate,
manipulate, analyze, and display geographic data in digital form.
ARC/INFO is a proprietary system developed and distributed by the
Environmental Systems Research Institute, Inc., in Redlands, California
ArcUSA
Designed by ESRI, ArcUSA is a general-purpose database used to
generate thematic maps of the conterminous United States at the State
and county levels. The database contains cartographic information,
tabular information, and indices and is designed for a wide range of
applications.
Glossary-2
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