1 - NGA

inequality—A systematic deparfure VDM the
mean value 01 a quamny. See also annual
Inequality; diurnal Inaqunllty; lunar
Inaquallty; parallactlc Inequality;
parallax Inaquallty; phase Inequality;
varlatlonsrl Inaquallty.
MIL-HDBK-850
Inarrlal ●zlmulh-An azlmufh which
approximates the value which mulct be obtained
from asfmnomic obsewafions, but which is
derived from direct obeewations along the fine
of sfghl with an inertial azimuth measurfrrg
davfca conelafing of a north-seakkrg gymsmpe
ootilned with a iheodollle. See also
gyrotfreodoli.te.
Inertial coordinate system—A coordinate
system (n whch the axes do not rotate with
respect fo the Wed sfars. and in which dynamic
behavbr can be deacrbed using Newlon’s laws
ot motbn.
Iner?lal guidance eystem—A system in
which gukjance IS parmlffed by means of the
maaaurement and in!egrsfion of acceleration
from wilhin the craft.
Inortlal measurement unl! (lMU)—(missile
guidance) A wmpacf componen! of an inertial
guidance ayslem which fsas three
accaleromefers mounted cm a gyrostabifized
plafform. See also accelerometer.
ine~lal nsvlgatlon ●ystam—A ayslem which
is not dependent on man-made elecfmmagnatic
signals. Newion$e sacond law of molbn is
ufilized wffh a syatom conakllng of
amelemmetera mounfad on gyroelabllized
plaffonme, each for measuring bngifudinal,
lateral, and verlkal amelerations. The double
Infegratbn of ali accelerations in lhree mutually
perpendicular directions pmvkfes distance
traveled (Imm a known starting point) in three
mutually perpendicular dlracfions. Navigation is
by a highty refined form of dead rackoning with
system posfficm t9ing updated fmm other
navigational references In the more
sophisticated ayateme.
lnarflal navlQatlon-The process of
meaeuring a craft% velocity, attitude (in the
aubmaflne missile Iaunchlng appficalions), and
displacement (incfuding changes in altitude in
Ihe aircraft a@catbn) from a known etarfing
poinf through sensing the acceleration acting
on ff In known directions by means of devices
that mechanfze Newton’s laws of motion,
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Inefllal referance photography—
Cartographic aerial photography obtained
simultaneously with rnagnatlc tapa recordad
inertial retererwe positioning data.
Inferior conjuncrlon-l%o mnjuncfbn of an
Inferior planet and the Sun when the planol is
between the Eanh and the Sun.
Inferior planeta-The planets with orblfe
smatier than thaf of the Earth, i.e., Mercury and
Venus.
Inferior traneH-See Iowar tranelt.
lnflnity—~e poinI, line, or region beyond
measurable fimfis. An unaltered source of figM Is
regarded as at infinity if if is a! such a great
distance that rays from If can be considered
parallel.
Infrared dlstsnce measurement-A
distance determined by measuring the phase
delay 01 rnedulation algnats on a li@f beam
(infrared) traveling ot a known vebcify between
a dwlsnce reeler and reflector.
Intrared film-(JCS) Film carrying an omukbn
especially sensitive to ‘near-infrared.. Used to
photograph through haze, because of the
penetrating power ot inlrared fighl, and in
camouflage delection to distinguish between
tfving vegatathn and dead vegetalbn or artificial
green pigment.
Infrared—Pertaining to or designating the
portion of the electromagnetic spectrum with
wavelangfhs ]usf beyond the red end of the
visible spectrum, such as radiatkm emitted by a
hof body. Invisible to the eye, infrared rays are
detected by their thermal end phefographic
eHects. Their wavelength are longer fhan those
of visible light and shorter Ihan thOSa Ot radio
waves,
h’thorlted error—The error In iniflal values
used In a amputation: especially the error
irrfmduced from the previous steps In a step-by.
step imagration.
inltlal Graptrlc Exchange Speclflcetlon
(lGES)—An interim efandard tormet devebpad
by the Naltonal Bureau of Standards (NIST) for
exchanging graphics data between computer
systems IGES Is the most wldafy used
exchange formal in the world.