1 - NGA

Frosnsd larr-A lens which corsslsls of a Ifrin
stepped disc with each slep having the
curvature 01 a rruch thiier lens. A similar
design wwld be the roof o! a factory that boka
like the teeth of a saw. This pattern, embossed
in ptaet’c, la used to dtstribufe image (or light)
brightness over a given area.
frllllng-The separation, along the edges, of
the photographic ernufaion from its base.
front ●lement—Sea lens elemant.
MIL-HDBK-850
front focal dlafance-The distance
measured trom the vertex of the fronl surface of
tha lane to the fmnf focal point.
front nodaf point—See nodel point,
definition 1,
front eurface mirror—An optical mimer on
whkh the reflecting surface is applied to the
frxrnt surface of the mirror instaad of to the back;
i.e., to the first aurlace of Incidence.
Fulcrum—A videodisc-based electronic map
display system tor the presentation arw analysis
of muniam.rrce data including maps, da!a bases,
imagefy, gazetteers, and graphic symbols.
Developed by Interactive Television Company.
fundamental circle-See prlmery great
cfrcle.
fundamental etar pfaces—The apparent
rfght ascensions and declinations of standard
Cm’Parkon stare obtained by faadkrg
observatories and published annualiy.
fundamental tablea, deformation of the
geoid end Ite effect on grevity—Tables
gtimg the deformation of the gaoti and its
effect on gravity, computed for masees of unit
densfry extending to various dstances almve
and below the surface of the geoid.
Fundamental tablaa sarve aa the basia for the
preparation of special tablas cxmrasporrding to
particular assumptions respecting dansfry,
Iaostasy, etc.
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