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chart in ffs varbus stages of preparation to
Insure eccssracy, corrgrlelenasa, and correct
preparation fmm and interpretation of the
sources used, and to assure legible and precise
reproduction. Edns are usually relermcf to by a
parfidar produdion phase, such as cnmpifatbn
Scfii, acdbhlg edit, etc.
effsctlve arsa-For any aerial photograph
Ihal la one of a series in a ffiiht strip, that mntral
part of fhe photograph delimited by the
bmactors of overfs~ with adjacent photograph.
On a vertical photograph, all imagea wifhin the
effective area hava lass dlspfacemenl than their
mrjugale Images on adjacent phonographs.
●ffsotlvo Earth rsdlue--$ee ●ftectlve
radius 01 the Eanfr.
atfec!lve focal length (EFL)-See
prhrclpsl dlatance, definition 1.
effective radlua of the Eanh—A fictilious
value for the radius of the Earfh, used in place
o! lhe geometrical radius 10 correcf for
atmospheric rehacfbn when lhe index of
refraction In the atmosphere changea linearly
with height.
Egault laval-A French tnslrurnent having the
spirit level attached to a level bar which also
carries wyes in which the telescope rests.
electrical dlstencs-LengttI measured in
terms of the distanca traveled by radio waves in
unit fima.
elactrlcal survey net edjueter (ESNA)— A
device used for obtaining least squarea
adjustments of level, traverse, and veriical angla
nets through fhe medium of an analogous
electrical net.
electromagnetic spectrum—Tha entire
mnge of wavelengths or frequencies of
elacfromagnatic ratilatlon extendhtg from
gamma rays to the bngeaf radio waves and
including visible fighl. Moat remofe aenshrg
aystema are desfgrred to oparate within the
elecfmmagnetlc spesfrum,
Elactronlc Chart Dlapley end
Inforrnatlon Sysfam (ECDIS)—A system
whkh In Ifs mosf mmptete design integrates all
essential alda to nav~afion into one system
krclucflng charl Informstbn, posirlonal
Information amf ships’ parameters such as
came and speed. Echosounder, readings,
MIL-JiDBK-850
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radar, compieta or selective and other inputs
may also be included.
Electronic Chart Lfpdata Manual
(ECfiUM)-The elesfrurric version of the Chari
Update Manual (CHUM). See Chsrf Update
Manual.
elecfronlc bsrarlng-A bearing obtained by
means of eledronic equipment.
elscfronlc confrol-fhr!tol obtained by
elecfmnic devices.
electronic dlatence-meaaurlng (EDM)
equipment—Devkes that measure the phase
difference behvean irsnsmfftad and retumad
(i.e., reflected or retransmfffad) elacfromagnaflc
waves, ot known frequency and speed, or the
round trip transil time of a pulsed signal, fmm
which distance is computed. A wlda range of
such equipment Is available for surveying and
navigational use. Also sailed dlalance
measurhtg equipment (DME). See also
eiaclronlc poaltlon Indicator;
Elactrotape; Geodlmeter; Iaaer; sonar;
Telluromeler.
electronic Ilna of po$ltlon-A line of
position established by means of electronk
equipment,
alectronlc map data (EMD)—Se e
etectrontc map.
electronic map-Consisfs of fhe information
of a map or chart, fhat is captured, stored, and
displayed by electronic means. See akO
raster: rasfer data structure; Raster
Product Standard(s) (RPS); vector;
vector Osta; vector Product Format
(VPF); Vector Product Standsrd (VPS).
electronic poeltlon fndlcator (EPI)- A
type of elecfmnlc distance measuring
e@PmeM used primarily in hydmgraphic
surveying. Tha offshore range has been
esfendsd from the fimita of shoran diafancas to
more than 500 miles by use of EPi.
electronic refraction—The refraction due to
the elfects of the atmosphere and fhe
ionosphere, which infrdma appreciable
changes in the quantities measured by means
of alactronk devices, such aa in the phase
dtiferences measured with interfemmefara, in
Ihe rale of change of phase measured with fhe
Doppler systems, and in the change in phase