1 - NGA

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radm range atatiina. Also called redlo facility
chart.
en:lty node-A primitive used to represent
featurea thal are truly zam dimenabnal. Entity
nodes are Iopobgically linked 10 their containing
face when tecee are praeam.
OnIffy point-Pointe used to represent
teeturee that are zem-ctimeneional (such ae
survey points). Enliy poims may be
topobgicaliy finked 10 a containing face.
.trtlty Set-An attribute table or group of
attributes.
entrance pupil—The image of the aperture
atop formed by all the lens elements on the
object aIda of the aperture stop,
entrance ellt-slit through which energy
emera a spactroec4plc Inswument.
entrance window—The image of me tield
stop formed by all the Iena elements on the
object side of the fietd atop.
Ebtv6s correcrlon-Component of .uncorrected
observed gravity obtained on a
rrwving ptatform thal is attributed to Ihe easlwest
comporram of the velocity that either
increases or decreasee ihe effect of the
centrifugal force caused by the Earth’s rotation,
The formula for the correction usually includes
the term for the secondary vebcity correction,
E6tv6s effect—A vertical torte experienced
by a t=zdy movin~ in an east-west direction on
the rotating Eafth. In gravity measurements, a
posfriie correcfiin is apptied if moving eastward,
and a negatfve correction if moving westward.
E6tv6a unft—The unit of gravitational gradient
10-9 meters par second per second per meter.
ephemerle time-The uniform meaaure of
time defined by the laws of dynamics and
determined in principal fmm the orbital motions
Of the planete, specifically in the orbital motion
of the Earth aa represented by Newcomb’s
Tables of tha Sun.- Ephemaris fima for close-
Earth Salelliles, or more cmrectty the llme
associated wfih satellite ephemerides, Is
observation dependem. For example, It the
observaflona were made In universal lime (UTJ,
the ephemetis time is UT; ff the obsewations
were made in imemafional atomic time (IAT),
MIL-HDBK-850
84
the ephemeris time is in IAT.
ephamerla—(JCS) A publication giving the
computed places of lha celestial bodies lor each
day of the year, or tor olher regutar intervata. [A
publication giving similar krformettin in a iomr
suitable for use by a nevlgator la catted an
almanac. An ephemeris la also a statement,
not necessarily In a pubtiiation, presenting a
correlation of time ard position of caleslial
bodies or man-made satellites. A short
ephemeris of future focation/time of salelfite is
known as a set of alerts.] See also
broadcast ephemarle; precise
ephemerle.
eplpolar plane-( photogrammetry) Any plane
which mntakrs fhe eplpoles, therefore, any
plane comaining the air base. Also called basal
plene.
eplpolar ray —’The tine on the plane 01 a
photograph joining the epipole and the image of
an object. Also expressed as the trace of an
epipolar plane on a photograph.
epfpolee—in tha perspective setup of Iwo
prolographs (IWO perspective projections), I he
points cm the planes o: the photographs whara
they ara cut by the air base (astended line
joining the IWO perspective centers). In the case
of a pair of truly verlical photographs, the
epipoles ara intiniiety distant from the principal
points,
epoch—1. A particular instant for which cerlain
data are given. 2. A given period of time during
which a series of related acts or events takes
place. 3. An arbitrary moment in time to whjch
measurements of position for a body or
orientation for an orbit are referred.
Equel &c Second Baeter Qhart/Map
[ARC)-A rectangular coordinate and
projection system at any scale for the
entire elfipsoid based on the World Geodetic
System 1984 (WGSG4). The ARC syslem
divides the eltipaoid surface into 18 overtapping
latitudinal band acafed zones.
equal energy—Spectral distribution
characterized by equal ftux per untt wavelength
imervai.
equal-altltude obaervatlona of the
Sun—Azimuth Observalbns that consial of
measuring horizontal angles from a southerly
reference ooinf to the Sun’s timbs at an identiial