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haza-The radiance of the atmosphere.
heading-(JCS) (navigation) The diretilon in
whfch the fongtfudinsl azis of an aircralt or ship
Ie pointed, usually expressed in degrees
cicrckwise from mrffr (true, magnetic, compass,
or grid).
height rsnomaly-T?re difference between the
height of a terrain point above the reference
spheroid and the corresponding rwrmal height,
rrSSaSUred along the normal piumb he.
height difterantirN-Tfre difference In height
between predominant height grouplnge In a
homogeneous sutlace area.
trelgfrt displacement—See roller
dlsplacemant.
halght !lndar—A stereoscopic range finder so
constructed as 10 indicale vertical heights rather
than slant rarge. See also stereometer.
helgtrt of Instrument-l. (spirit leveling) The
height 01 the line of sight 01 a leveling
instrumem above the adopted datum, 2. (sladia
surveying) The height o! the center oi the
Ielescope (horizontal axis) of transit or telescopic
afidade above Ihe ground or station mark. 3.
(trigonomatrfc leveling) The nelgtd of tne cenler
Of the thaodollfe (horizontal axis) above the
ground or station mark.
MIL-HDBK-850
Sun as origin.
ttellotropa-A device used in geodetic
surveying Ior reflecting the Sun’s rays to a
distanl point, to ati in bng-dbtams
observations. Sae also aalOnOtrOpSr.
hellpad-(JCS) A prepared area dssfgnated
and used for take off and Iancthg ot heficoprars.
(Inctudas iouchdown or hovefpoint.]
hellport-(JCS) A facility designated for
operating, basing, setvicing, and malnlalnlng
helicopters.
Helmert’8 gravity tormula of 1901—A
formula for theoretical gravity developed from
the gravity observations available al the lime
(1901), but not ,fitted to any preassigned value
of Use Earths elfipticity,
Halmart’a gravity formula of 1915-A
Iormula for theoreibsl gravtty based on a triasial
ellipsoid and therefore includes a bngitude
term. See also Iongltuda term gravity
formula.
hemispherical map—A map of one-haff of
the Earths surface, tounded by the Equator, or
by meridians.
hidden finee-Line segments obscured from
view in a projected image of a threa+imansional
object.
height of fhe tk4a-The vertical distance hferarchy-(digital) A system of cfaesitying
from charl datum to the surlace water level al features acmrding 10 feature type and
any stage of the t“de usually measured in feat. signifbance. For exampla, in some cases
features with lower numbem are mesked out by
halght-of-eye CorrectIon—That correction to higher numbared features occupying the same
sextant aftiiude due to dip of the horizon. Also posit ion.
called dlD COrraCtlOn.
height-(JCS) The vertical distance of an
object, poim, of level above the ground or other
eatabfiehed referance plane. Height may be
Irxfbated as follows: very /ow-bslow 500 feet
but above ground level; /Ow-SOO to 2,000
feet; mediu*2 ,000 1025,000 feet; frigh-
25,0001050,000 feet: very high-above 50,000
feet. See also altltuda; elevallon;
ellipsoidal height; geoldal hefgnt.
heliocentric paraflax-See annual
parallax.
heliocentric—Relative to the center of the
High Speed Digital Chart (fiSDC)-. vector
digifal chart of selected and generalized coestai,
and harbor and approach charl inforrnafion in
supgwt of navigation and colliiion-avoidance
display systems, HSDC davebpmem waa
coordinated. with the National Ocean Senrica
and Is produmd using Committee on the
Exchange of Digital Data formal feature
encoding. HSDC is no longer supported by
OMA.
high altltude-(JCS) Conventionality, an
attitude above 10,000 reelers (33,000 feet). See
also altitude.
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