1 - NGA

of features having the same general surface
composition.
homoloaouri Images-The images o{ a
single object point Shal appears on each of two
or more overleppimg pholograpfm having
dittarant perepecuve c%nters.
homologous photographa—Two or more
ovartapplng photographs having ditferam
camera stations.
hotnolooous reye-The two perspective rays
corresponding to a pair 01 homobgous image
pdsts.
homologous—Ttre condilion whera an Image
of a given object pokrt or series of such polnls is
common 10 two or mora projections having
diffarenl perspective centers.
tsomolographlc (homafograph[c) map
proJsrctlon-An equal-area map projection.
This term ia found in the designations givan
Some particular map projections, such as lhe
Mollweide homalographic projection.
horizon camera—-A camera used in
conjunction with another aerial camera 10
photograph the horizon simultaneously with Ihe
olher photographs. The horizon photographs
indicate the tilts of the othar photographs.
horizon closure—See error of closure,
definffion 6.
horizon coordinate system—See horizon
system of coordinates.
horizon photograph—1. A photograph of
the horizon takan simullansously with anolher
photograph for the sole purpose o! obtaining an
Itiicafion of the orientation of the other
pho!o~raph at the time of exposure. 2.
(surveying) A corwlnuous matched Sal 01 horizon
photograph defining obstructions 360°around
a given station.
horizon prkzm—A prism which can be Insenerl
In the optical path of an instrument, such as a
bubble saxtant, to permit obsewation of Iha
visible horizon.
hortzon profile-A pfot of vertical angles
agahtst Ihe norlzomal anglas taken 360” around
a point wtth annotation. See also horizon
photograph; frorlzon aweep.
MIL-HDBK-850
horizon sweep-( surveying) A preliminary
reconnaissance technique where the Instrument
is pointad inH\ally al the farthest v’biilde known
poim and recording clockvrba anglas to tarka,
spiras, buitdtigs, signals, etc., tor purposes of
idenllflcat”km and eubsequem use. Sea ateo
horizon profile.
horizon system of coordlnatee-A aet 01
celestial coordhates, usually altiiude and
azimuth or azimuth angle, basad on Ihe
celestial horizon as tha primary graat clrcte. Also
called horizon coordinate system.
horizon traca-An imaginary fine, In the plane
of a photograph, which represents the image of
the true horizon tt corresponds to the
intersection of the plane ot a photograph and
!he horizontal plane containing tha internal
perspective cemer or rear nodal point of the
lens. See also true horizon.
horizontal angle-Angle in a horizontal
plane.
horizontal axis—The axis about which the
[alescope of a theotilie or transit rotates when
moved vertically,
horizontal bridging—See brldglng.
horizontal circle-A graduated circle affixed
to lhe lower plate of a transtf by which horizontal
angtes can be measured.
horizontal closure error—See srror of
closure, definition 8.
horizontal control dstum—A geodetic
reference point which is the basis for horizontal
control surveys, and of wttiih tiia quamifies ara
known: latitude, longitude, azimuth of a tine
trom this pint, and two constanta which arc the
parameters of the reference ellipsoid. Tfre
horizontal conlrol dstum may extend ovar a
continent or be limited to a small area. Also
called horizontal datum; horizontal
gsodstlc datum.
horizontal Controf point—Sae horizontal
control station.
horizontal control staflon—A station whose
position haS been accurately determined in xand
~grid Coordinates, or Iatituda snd longitude.
Also called horizontal control point.
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