NavCom SF-2040 Rev.F - Manual (Page 79)

SF-2040 User Guide – Rev. F
Glossary
.yym files see meteorological files (where yy = two
digit year data was collected).
.yyn files see navigation files (where yy = two digit
year data was collected).
.yyo files see observation files (where yy = two digit
year data was collected).
almanac files an almanac file contains orbit
information, clock corrections, and atmospheric delay
parameters for all satellites tracked. It is transmitted
to a receiver from a satellite and is used by mission
planning software.
alt see altitude.
altitude vertical distance above the ellipsoid or geoid.
It is always stored as height above ellipsoid in the
GPS receiver but can be displayed as height above
ellipsoid (HAE) or height above mean sea level
(MSL).
Antenna Phase Center (APC) The point in an
antenna where the GPS signal from the satellites is
received. The height above ground of the APC must
be measured accurately to ensure accurate GPS
readings. The APC height can be calculated by
adding the height to an easily measured point, such
as the base of the antenna mount, to the known
distance between this point and the APC.
APC see antenna phase center or phase center.
Autonomous positioning (GPS) a mode of
operation in which a GPS receiver computes position
fixes in real time from satellite data alone, without
reference to data supplied by a reference station or
orbital clock corrections. Autonomous positioning is
typically the least precise positioning procedure a
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