1 - NGA

flret point of Canca-Se e summer
aolstlcs, definition 1.
. . . .
firer polnf of Caprlcornus-S e e winter
eolatlce, definition 1.
first point of Libra-See aut urn nal
equhtox.
flrat.order bench mark-A bench mark
cmwsacled to the datum (usually mean sea
level) by continuous Sirat-omfer leveling.
flrsf-order levellng—Spklt leveling
cordormlng to the specifications of the current
‘Cfassiticalion, Standards of Accuracy and
General Spectlications of Geodetic Control
Survays.- Formerly known as preclaa leveling
and IeVellng of high preclslon.
Recommended for prfmary National Networks,
es a basis for all subordinate elevation
delemrinations, scientific studies such as cruslal
rrxrvemerrt over la~e regions, extensive
engineering projects such as hydroelectric
dams. Such leveling generally includes the
determination of geopotential values through
simukanaoua gravity measurements.
flrat-order lavel—A leveling instrument which
mSats the 10lbwhtg Crftaria: (1) the sensit ivily 01
the level bubble vial must be 10 of arc or less
par dlvbion 012. mm: (2) the instrument must be
mnslrucfed 01 bw expansbn metal to minimize
lhe effeci of unequal heating; (3) the objective
Ians must have an effective opening ot at Ieasl
40 mm and a magnification of 40X.
first.order traveres-A survey traverse which
extends between adjusted positions of other
first-order control surveys and conforms to the
torrent specifications of firai-order traverse, per
‘ClaaeifiiVwn, Standards ot Accuracy and
General Specifications of Geodetic Control
Sunfeys..
flret-order trlssngulatlon-First-order
Viangidatbn was at one time known as primary
trfangutetion; changed in 1921 to precise
triangulation; arkj in 1925 to first-order
trfangutatbn. These surveys contorm to the
rxmenf “Ciaeaifiition, Standards of Accuracy
and Genaral Specifications of Geodetic Conlrol
Surveys. - Recommended for primary National
Networke, as a basis for all subordinate surveys;
metropolitan area surveys, where high value is
attached 10 iend and Its fine of communication
frontage: and in scientific studies, such as
MIL-HDBK-850
crustal movement and space expbralion.
Iirat-ordar wortt-The designation given
survey work of the hlghesl prescribed order of
precision and accuracy. Such surveys were
torrnerly tailed prlma~.
Fischer etilpaold of 1960-A refarence
ellipsoid with two primary uses. In the Merctny
datum it has the approximate dimensions of
semimajor axis-6,378,166.0 melere, and fhe
llattenlng or etlfpticny-11288 .3. In the south
Asia datum the semimajor axfa is 6,378,155.0
meters, and the flattening or eitip’wtty la 1L?98.3.
Fischer ievet-A dumpy iavet capable of firalordar
ievefing.
flxad elava!lon—An elevation which has
been acbpled, either as a result of Me
observatbns or previous adjustment of spirit
leveling, and which is held at its accepted veiue
in any subsequent adjustment.
fixed posltlon—See adjuated poaitlon.
rlxed saleillle—See synchronous
satellite. ..-
Uxed-length recorde-A compuler data
element formal in which all retards have the
same length. These records allow dhecf access
without searching or indices. See also
varlebie-length records.
fixed-ratio pantograph—See pantograph.
fixed-retlo projection printer-A dlaposftive
printer having an optical syalem In which a fens
is placed between the negative and the
diapositive piate, the object and image
distances being set al nominal values according
to the iaws ot optics, but with freedom of
adjustment wilhin narrow iimhs, to produce
dlaposltives whosa acaie Is at a predatennlned
ratie to the negative scale.
tlxer network-(JCS) A comblnallon of radio
or radsr direction finding Inetalietione whfch,
operating in conjunction, are capabie of piotting
the position relative to the ground of an aircratf
In fright.
fixing-The process of rendering a developed
photographic image permanent by removing the
unaffected iight-sensitive materiai.
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