EM 1110-2-2907
1 October 2003
Doppler radar
The weather radar system that uses the Doppler shift of radio waves to
detect air motion that can result in tornadoes and precipitation, as
previously-developed weather radar systems do. It can also measure
the speed and direction of rain and ice, as well as detect the formation
of tornadoes sooner than older radars.
Doppler shift
A change in the observed frequency of EM or other waves caused by
the relative motion between source and detector. Used principally in the
generation of synthetic-aperture radar images.
DOQQ
Digital ortho-quarter quadrangle
Drainage Basin
Geographic area or region containing one or more drainage areas that
discharge run-off to a single point.
DTM--Digital Terrain
A DTM is a land surface represented in digital form by an elevation grid
Model
or lists of three-dimensional coordinates.
Dwell time
Time required for a detector IFOV to sweep across a ground resolution
cell.
E
Earth Observing System
A series of small- to intermediate-sized spacecraft that is the
(EOS)
centerpiece of NASA's Mission to Planet Earth (MTPE). Planned for
launch beginning in 1998, each of each of the EOS spacecraft will carry
a suite of instruments designed to study global climate change. MTPE
will use space-, aircraft-, and ground-based measurements to study our
environment as an integrated system. Designing and implementing the
MTPE is, of necessity, an international effort. The MTPE program
involves the cooperation of the U.S., the European Space Agency
(ESA), and the Japanese National Space Development Agency
(NASDA). The MTPE program is part of the U.S. interagency effort, the
Global Change Research Program.
EDAC--Earth Data
EDAC, also known as the Technology Applications Center (TAC), has
Analysis Center
served as a NASA center since 1964. EDAC operates under the
objective of transferring Earth-observing technologies to the user
community. It supports and works directly with industries developing
technologies related to space science and collaborating with them to
enhance and encourage the user community to adopt the new
technologies. EDAC also supports and works with public agencies,
private citizens, educational organizations, and volunteer groups to
ensure ready accessibility to NASA generated space imagery.
EDC
EROS Data Center.
Edge
A boundary in an image between areas with different tones.
Edge enhancement
Image-processing technique that emphasizes the appearance of edges
and lines.
Ektachrome
A Kodak color positive film.
Electromagnetic radiation
Energy propagated in the form of and advancing interaction between
electric and magnetic fields. All electromagnetic radiation moves at the
speed of light.
Electromagnetic spectrum
Continuous sequence of electromagnetic energy arranged according to
wavelength or frequency.
Glossary-9
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