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of the bOffOM, and the location of coral reefs,
mokfl shoals, and man-made obstacles.
hydrographic sextanl—See surveying
Saxtallt.
hydrographlc 8oundlng-See sounding,
defintfions 1 and 2.
trydrogrephlc survey-A survey made in
retetbn to any mnsiderable body of water, such
as a bay, harbor, lake, or river for the purposes
of determination of channel depths for
navigetbn, Ioca!ion of rocks, sand bars, lights,
and tx.keys; and In the case of rivers, made for
flood comrol, power development, navigation,
water auppfy, and weter storage.
hydrogrrsphy-1. (JCS) The science which
deals with tha measurements and description ot
the physical features of the oceans, seas, lakes,
rivers, and their adjoining coastal areas, with
particular referenca 10 their use for navigational
fxmses. 2. Thai part of topography pertaining
to water and drainage features.
hydrology+ydrology in IIS broadest extem
deals with the properties, iaws, and phenomena
of water of ifs physical, chemical, and
physiolo@cal relations; of its distribution
throughout Ihe habilable Earth; snd of the
eff8d Of lhIS CirCUfalien on human lives and
interests.
hydrophore-An electroacoustic transducer
that canvefis sound energy into electrical
energy. Sea also transducer.
hydrosphere-That pafl 01 the Earth that
consists of the oceans, seas, lakes, and rivers; a
M7?ilaf par7 of any other spatial body il such a
body eXiStS. Dkwinguistred trOM lh8 atMOSfJhere
and lithosphere.
..,” ---.,- .,-m .. . ---- ,.. . . .. . . .. . .
nB,”n”48, m,** -q”m, m”,,— u,, Sau,,,u,,bcl,
eqixafione, the term assumed by the verlical
mmponenf of the vector equation of motion
when all Coriolls force, Earth curvalure, Iricfional,
and ~efiiml ac@er81i0n tarms are considered
negllgfbte compared with those involving the
vertiial pressure force and the force of gravity.
hydrostatic equlllbrlum-The stale ot a fluid
whose surfaces of cansfanf pressure and
conetam maas (or density) coincide and are
horfzonfaf throughout. Complete bafance exists
between the torte of gravity and the pressure
force. The relation between fhe pressure and
._. ——— _
MIL-HDBK-850
fhe geomefric heighl is given by fhe hydrosfelic
equation.
hygromatrlc—Relaf in~ to the retetlve humldlfy
or wmparafive amounf of moisture frr the
atrrme.phera. SInca the atrmsphare penetrates
the pores or cells of maferfal bodiis in vsrying
degrees depending upon fhe aubefances of
which fhey are cmmposad, fhe amount of
moistura which it comaine wili effeci the shepaa
and dimensions of certain inaftumems and
equipmenf used In surveying and maPpfng. For
this reason 11is necessary to sefecf metartats
which are not a.enaflive to hygromafrfc urnditione
for the construction of fevefing rods, pfenetafrie
sheels, efc., and for the construction and
priming of maps.
h yg roscopjc—The prope!ly of malerials such
as paper and films to absorb or reiease moisture
and, in so doing, to expand or contract.
hyperbolic Ilne of poslflorI-A fine of
position in the shape of a hyperbola,
determined by measuring the difference In
distsnce to two fixad points. Loran lines ot
position are an example.
hypariocal diatanca-The distance from the
camera lens to me nearest object in tocus whan
the camera lens is focused at infinity.
hyperatereoscopy—( JCS) Stereoscopic
viewing in which Ihe relief effect is nodceabty
exaggerated, caused by the esfenslon ot fha
camera basa. Afso called appearance ratfo;
axaggeratad etereo; relief etrefchlng;
stereoscopic sxaggeratlon. See also
verlfcal exaggerelion, definition 1.
hypsographlc detail-The feafures
pertaining 10 relief or elevafion of terrain.
hypsographlc map (or chari)-A map or
chart showing land or wbmarine bottom ralief in
terms of height above, or below, a datum by
any me!hod, such as contours, hachuras,
shading, or finfing. Also called hypsomatrlc
map (or chars).
hypsography—1. The science or art of
describing alavations of land surfaces wilh
reference to a dalum, usually sea level. 2. That
part of fopogrephy dealing with rafief or
elevation of terrain.
hypaograph-An instrument of fhe slide rule
type used fo comp,ute elevations from veflical
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