1 - NGA

’
lnvswhsble ponduium—A pendulum so
desQned and equipped wiih means 01 support
Ihsl ii can be ueed In only one position.
MIL-HDBK-850
lnvar—An alloy of nickel and steel having a
very bw meffiifsnf of thermal expansion. Invar
is used in the construction of Jaderin wires
(base-line fnaasurfng apparatus), subtense bars,
precise Iavelirrg rods, tepes, and pendulums.
See also Lovar.
lnventoW sufvey-A survey for the purpose
01 mllecfkrg and mrrelaling engineering data of
a particular type, or types, over a gfven area. An
invenfo~ survey may be recorded on a base
map.
Inventory-Existing wurce matarials,
intermediate and final products ‘kfentiiied by
type of geographic mverage, and currency.
Inverse chswf-See transverse cherf.
Inverse computation—See Inveree
position computation.
Inverse cylindrical orfhomorphlc charl—
See transverse Mercator chart.
Inverse cylindrical orfhomorphlc map
projection-See Iraneverae Mercator
map projection.
Inversa equator—See transverse
equetor.
Inverse latitude—See transverse
Iatltude.
Inveree IongltudeAee trenaverae
longitude.
Inverse Marcator chart-See transverse
Mercator chart.
Inverse Mercator map projection—Se e
traneverssr Mercator map projection.
Inveraa merldlan—Sea transferee
merldlan.
Inveree parallal-See tranaverea
parellel.
Inversa poeltlon computation—The
derivation of Iha length, and the forward and
back azimuths of a line by mmputstfon baaed
on Ifre known positions of Ma ends of the fine.
Also tailed Invarea; Inveree computation;
Inverse posltlon problem.
Inverse poeltlon problem—See Invaree
position computation.
Inverse rhumb llne-See Iranaverae
rhumb Ilna.
lnverae—See Inverse poaltlon
computation; trsnaverae.
Invereora-(photography) Me&hankal devices
used to maintain Wrrecf conjugate distances
and collinearity 01 negative, lens, and easel
planea in autofocusing optical instruments, such
as copy cameras and rati(fiera. See also
Carpantler inversor; Peeucelller
Cerpentlar invarsor; Pesucelller
Inveraor; Pythagorean right angle
Inversor.
Inverted lmsge-An image thal appears
upside down in relation to Ihe object.
Inverted atere%See psaudoscoplc
stereo.
Inverting telescopsr-An instrument wifn the
optics so arranged that the Itghl rsys entering
me objective of the lens meet al tha cress hairs
and appear inverted when viewed through the
eyepiece without allering the orfentafion ot the
image. See also arectlrrg telescope.
lnvertlng—See trensli, definition 3.
lonoephere—(JCS) That part of the
atmosphere, extending from aboul 70 to 500
kilometers, in which ions and free electrons exfat
in sulficiem quamitles to reflect elecfromagnatic
waves. See also atmosphere.
Ionospheric correction—The mrretiton
made to electromagnetic measurements
between sateltiies and ground stations to
compensate for the effect of the ionosphere.
lrradlanceRadiant flux incident per unit area.
Irregular error—See random error.
Irregufar llne-A complex line which cannof
be easily described by a mathematical
polynomial.
12