1 - NGA

MIL-HDBK-B50
splwre formed by the inleraaction cd the
calsdsl sphere end a pfwre fangsnf to the s6e
fawel mxfsca of fhs Earth at the zenith nadir fine
geoldel separation-See gaoldal halght.
gaold-The equipomntial surface in the gravity
field of the Earth MA appmximaIrrs tha
undktwbad mean see fcwel extanded
ccmlinueusfy Ihmugh the confinerrls. The gaoid
is the surfa~ d raferanrx for asfroncarric
ObCONti .8rd fOr @OdOfb k?dl~. .%tr dk3
companaated goold; ●qulllbrlum theory;
●qulpotantlal ●urfaea; gaoldal horizon;
gravlmotrlc gaoid; Ieoatatlc gaold;
rafarenca apharold.
gooklnatlcs-imcsl and globel rnetion of the
Earth ar sea, its -umrnem: iadetion from,
arxl etl=t upcm pracisii equ~mant and
maaauring instrumnt.x. Usually applied to the
design and teat of inertial instruments and
sydems and sfabis pisffonna.
gecrloglc survey-A surwey or investigation of
the Earth, of the phye”~l changas whwh ths
Earth’s crust has undergone w is undargaing.
end of the muses producing those changes,
Geological Long Ranga Incllnad Asdlc
(GLORIA)-A low ramlution side scan sonar
used for racennaicsanm surveys ef the ocean
floor.
gaologkal msp-A map showing the
structure and rnmposit”mn of the Earths cruet.
gaomagnatlc coordinates—A system of
spherical cc.ardinsles baaed on the best fm of a
centered d@fa to the actual magnetic field of
the Earth.
gaomagnatlc ●quator-The terrestrial great
cimia aerywhara 9@ fmrn the gaerra~Ic
poles. Geomagnetic aquator should not be
confused with magnetic aquator, Iha iina
connecting all pdnls of zem magnetic dip.
gaomagnetlc latltude-Angular distance
from the geomagnetic equator, msasurad
rrorlhward or southward through 90° and labeled
“N” w ‘S to indicate the duaction ~
measurement. Goomagnetlc latitude
should not be confused with magnetic
Iatltudo. Sae also dip.
goomagnotlc morldlan—Tha meridional
lines of n gmrnegnetb coordinafa system. Not
106
to be csmfuwd with magnatlc meridian.
fraomapetlc Pole-Either of fwe ant@edal
poima rrwking the inraraaction d tha Earth’s
surface with the exlsrdsd axis of ●powadul bar
msmet SSSti to be bested at the canter of
the Earth arxt Sppmximeting the eourca d the
actual msgnetic fiefd of the Earth. The
expresskm geomagrtetk polo sheutd rmf be
mrdusad with magnetic pole, whtch ralates
to the dual magnetic fisfd of the Eatth.
goomagnetiam—1. The magnetic
phanomanen, collectively cortsidared, exh~sd
by the Earth and ite atmosphere, and by
extension fha magnatic phenomena in
interpisnsfnry apace. 2. The etudy of the
~9netic fii~ d the Earth, Abe @IIsd
Wrroatrlai msgnatlsm.
geometric latltude-See parametric
Iatituda.
goomatric map pro)actiOn-Saa
parepectiva map projection.
geometric nonlinearity-Any dktoriion
irrkducad by digitization snd subsaqusnt
pmcesaing d a mathamaticdy-cerract reference
system or grid, other than aimpk mtatian,
tranatstion, or scale change,
geomatric primitive-one of the three basic
geometric units of re+mraenlatien: nede, edga,
❑nd face. Equivalent with gaagraphc prim~we.
geometrical dl~The verfiil engla, at the
eye et an absatver, between the Froriiontai and
a straighf fine tangent to tha surface of the
Earth. It is larger than dip by the amount of
terraeliiel refrsdion.
gaomatrlcal horizon-riginally, the ceiestiel
horizon; now more mrmnonly the irrtersedion of
the caiestial sphere and an infinite number of
straight finaa tangent to the Earth% surface, and
radiating from the aye of the obaervar. If there
ware no terrestrial refrscfiorr: geematricai and
visible horizons would rmincide.
geomorphic dats-A sat of model
coordinates defining the tram of a geomorphk
feature. Thsce consist of ridgeiinas, valleys,
drairwge and lnkea whwh are uaad to refine the
elevation data grcqr during tha production
process.
goomorphlc-Patleining to iand forma.