1 - NGA

Outputs include digital elevation data and
rectified and orthorecfified imagery. See also
Dlgltal Production System; MARK 85.
hardcopy—Producfs which are primed on
papar, photograph materials or other media,
and can be interpreted dlreclfy by the human
user.
hmnonlc coefflclente-lhe coefficients of
t@OltOMStriC terms Of an infinite series used 10
approximate an Irregutsr ckmed surface. See
8180 spherical harmonics.
harmonic component—Any of the simple
sinusoidal components into which a periodic
quantify may be resolved.
hermonlc constents—Tha amplitude snd
epochs 01 the harmonic constituents of the tide
or tidal current at any place.
harmonic constituent—See constltuerrf.
harmonic axpreaalone—Trigonometric terms
of an infinite series used to approximate
irregular curves in two or three dimensions.
harmonic tunctlon—Any real function Ihsl
satisfies Laplace’s equation,
hamronlc mollon—The projection of circular
motion on a diameter of the circle Of such
motion.
harmonic—A sinusoidal quantity heving a
hequency that is an integrel multiple of the
frequency of s periodic quantily to which ii is
relatel See also compound harmonic
motion; gravitational hsrmonlcs;
sactorlal harmonics; almple harmonic
motion; apherlcal harmonics: tesseral
lSSrMOnlCS; zonal harmonica.
Hassler baae-llna measurlrrg
aPParatuS-~ Optical base-llne measurkrff
apparatus consisting of tour rectangular iron
bars mounted end to and In a wooden box.
Each bar h 2 metara long. The combined length
of tire apparatus being 8 me!ers.
tiaylord dallectlon templsts—Templels
used In mnneclbn with studies for the figure of
Ihe Earth and ieostasy. In obtaining elevation
raadings hmm maps in connection with
topographic and Isostalic reductions, femplets of
plastic are used, The templets used in
MIL-HDBK-850
connection with defleci”bn of the varlical studies
have circles and radial tines drawn u~n them,
S0 proportioned wilfl refereme to scale of map
and azimuth thal land elevations and ocean
depths within each compartment formed by
adjacent arcs ard radii can be easily averaged
and the effect of the mass therein on a plumb
liIIS at the station (center O! Circles), under
various hypotheses, can be computed. See also
Hayford gravity templeta.
Heyford elfact-The direci aftacf on gravity of
masses of unit deneity extending to various
distances abova and bsbw sea level; it nagleds
the differences of elevat”mn batwaen tha
relerertce spharoid and the gaoid.
Hayford gravity anomalles/Hayford
anamalles—lsostatic anomalies obtained by
computing the isoalatic compensation according
to the Pratt theory of isostasy es developed by
Hayford, using various depths tor purposes 01
comparative analysis,
Hayford gravity templeta—Tamplets used
in connection with gravity aludies whtch are
similar 10 Haytord deflection templets excapt
thal no account is taken ot ~im~h, aII
compartments bounded by a given pair of
circles being of the same eize and shape. A
given templei can be used only on maps of the
scale and projection for which it is constructed.
See also Hayford deflection templata.
Hsytord epherold (elllpaold)-A rafsrance
ellipsoid having the fOlloWirIg approximate
dimensions: semimajor axis 6,378,3S8.0
meters: semi minor axis-6,356,909,0 meters;
and the flattening or ellipticity 1/297.00,
l+ayford-Bowle method of Iaoatatlc
reduction—A method of rmmputing tha effacf
of topography and isostatk compansatiorr on
grsvity by which the effact of topography IS
compuled dirsctiy and then corracfed for the
effaCl of isostatic compansalion. Tha mechani~
of this method invoive the use of the Haylord
gravity iamplets.
Hay ford-Bullard (or Bullard) mathod of
lsostatic reduction—A method by which the
topographic effect of an infinita slab of density
2.67 and a thicknass equal to the elavation of
the gravity atalion is first computad, and then
corrected for curvature of the aea Iavai surface
and, fOr difference of eievation between the
station and the to~graphy.
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