EM 1110-2-2907
1 October 2003
Density slicing
Process of converting the continuous gray tones of an image into a
series of density intervals, or slices, each corresponding to a specific
digital range. The density slices are then displayed either as uniform
gray tones or as colors.
Depolarized
Refers to a change in polarization of a transmitted radar pulse as a
result of various interactions with the terrain surface.
Depression angle (y)
In radar, the angle between the imaginary horizontal plane passing
through the antenna and the line connecting the antenna and the
target.
Descending Node
Direction satellite is traveling relative to the Equator. A descending
node would imply a southbound Equatorial crossing.
Detectability
Measure of the smallest object that can be discerned on an image.
Detector
Component of a remote sensing system that converts electromagnetic
radiation into a recorded signal.
Developing
Chemical processing of an exposed photographic emulsion to produce
an image.
Dielectric constant
Electrical property of matter that influences radar returns. Also referred
to as complex dielectric constant.
Difference image
Image prepared by subtracting the digital values of pixels in one image
from those in a second image to produce a third set of pixels. This third
set is used to form the difference image.
Diffuse reflector
Surface that reflects incident radiation nearly equally in all directions.
Digital display
A form of data display in which values are shown as arrays of numbers.
Digital image
An image where the property being measured has been converted from
a continuous range of analogue values to a range expressed by a finite
number of integers, usually recorded as binary codes from 0 to 255, or
as one byte.
Digital image processing
Computer manipulation of the digital-number values of an image.
Digital number (DN)
Value assigned to a pixel in a digital image.
Digitization
Process of converting an analog display into a digital display.
Digitizer
Device for scanning an image and converting it into numerical format.
Directional filter
Mathematical filter designed to enhance on an image those linear
features oriented in a particular direction.
Distortion
On an image, changes in shape and position of objects with respect to
their true shape and position.
Diurnal
Daily.
DLG--Digital Line Graph
A DLG is line map information in digital form. The DLG data files
include information about planimetric base categories, such as
transportation, hydrography, and boundaries.
DMA--Defense Mapping
The DMA was established in 1972, when mapping, charting, and
Agency
geodesy functions of the Defense Community were combined into this
joint Department of Defense agency. The mission of the Agency is to:
produce and distribute to the Joint Chiefs of Staff, unified and specified
commands, military departments, and other department of defense
users, timely and uniquely tailored mapping, charting, and geodetic
products, services, and training; provide nautical charts and marine
navigational data to worldwide merchant marine and private vessel
operators; and maintain liaison with civil agencies and other national
and international scientific and other organizations engaged in
mapping, charting, and geodetic activities.
The above activities were handled by the DMA Combat Support Center
until the Center was disbanded in 1995 and responsibilities were
transferred to the National Imagery Mapping Agency (NIMA)
Doppler principle
Describes the change in observed frequency that electromagnetic or
other waves undergo as a result of the movement of the source of
waves relative to the observer.
Glossary-8
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