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MIL-HDBK-850
dlffefunce of Iafftude-1. The shorler arc 01I
any meridian between tha psrallals of hvo
places, expressed in angular measura. 2.
(plane surveying) The diierence of latitude o!
the two ends of a tine is fraquenlly called
tetltuda 01 tha Ilna, and deflnad as the
orlftogrephic projection 01 Iha kina on a
raferenca merldlan. The Iatltude (as ebovs
defined) of tha middle of a Iina is also rererred to
as Iatltude of the Ilna.
dlfterence of longlWde-The smaller smgla
at the POlS or lha shorter am of a parallal
betwean the maridians of hvo places, expressed
in angular maaaure.
dlfterentlel abarratlon-The difference
between the aberration of stare and that of a
moving objacf (e.g., a satalfile). Also called
parallactlc aberration.
dlfferantlal dlstorfion-The resultant
dimensbnal changes in length and width in any
medium. See also differential aftrlnkage.
dlfterantlal levallng—The process 01
measuring the difference of alevation between
any two ~ints by spirit leveling. See also dlracf
Iavaling.
dlftetentlel atwlnkage—The difference in
unit contracfbn abng the grain structure of the
matadal as mmpared to the unit conlractkm
acmes the grain sdructure; fraquenlly refers to
photographic film and papers and 10 map
maferiafe in general.
differential temperature-A natural error in
surveying whereby temperahsre variations in the
instnsmant cause reading errors that cannot be
detecled. It is usually caused by direct sunlight
on the inslrumsnf which can be minimized by
ehading the Instrument during survey
operations.
cllflractlon--(oplice) The bsnding of light rays
around the edgea of opaque objects. Dua to
diiraclbn, a point of Iiiht scan or pmjactetf
through a circular apetlure will always be imaged
as a bright center surrounded by light rings of
gradually diminishing Intanslty. Such a pattern is
called a diffraction dlek, elry dlek, or
centric.
diffuse reflection-Any reflection process in
which ma reflected radialion is sent out In many
directions usually baarlng no simple relationship
fo the angle of Incldance. See also cliff ufslon;
●pecular reflection.
dlffuelon-The scattering of fight rays either
when reflected tram a rough surface or during
tfl#~~#mlssion of light through a Translucent
Dlgltal Aeronautlcel Fllght Information
Flla (DAFIF)-A DMA flight fnforrnetiin data
basa confalnksf airport, runway, navigafiinal
aid, and enroute data. Both the high affttuda
(18,000 feet and abova) and bw attitude (bebw
18,000 fae!) enroule structures ara included.
Dlgltal Bathymatrlc Deta Sass! (DSDB)—
A grtided bathymetric data besa portraying
depths in uncorrected meters for each 5
minutes of latitude and Iongftude. Available on
magnatic tape.
Digital Chert of tha World (DCW)
Project—A DMA R&D project designed to
develop, ratina, and establish a suite of
standards to support future Defense Mapping
Agency digtfal data products and enhanca the
utility of digital inlormatlon in vector Iormat. See
also Vactor Product Format.
Dlgltal Chan of the World (DCW)-D C W
Is the firsl DMA product employing the Vector
Product Standard (VPS). It provides global
soveraga of the earth’s land surtecs at a
1:1,000,000 scale information content wtrbh
includes all the information found on tha baee
map tor tha Operational Navigational Chart
Series. Appticafion SOftwara is provided to albw
data baae queries by feature/aftribute or epefial
selection. Data output is 10 hard disk, tazf tile,
or ploI tile. Sea afeo Vector Product
Format.
yDlgltal Cltlaa Data Baae (DCDB)—A DMA
standard product consialing of the outfinea of
cities digitized from Operational Navigation
Charts [ONC).
Dlgltal Comparator Segment (DC/S)-A
segment of DMAs MARK 85 modemizatiirr
process. The Digital Comparator is a dignal
phologrammetric system used to measure mint
Iocalions on digtial imagary. Points may be
measured infaractively by the operator or
automatically using d~ital correlation
techniques. This segment also has the
capabilny to estract elavation dafa in soft copy.
Sea also MARK 85.
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