NavCom SF-3040 Rev.F - Manual (Page 208)

SF-3040 Product User Guide
– Rev. F
Glossary-206
GAGAN (GPS Aided Geo Augmented Navigation)
is an Indian satellite system that provides a set of
corrections for the GPS satellites, which are valid for
the Indian region. They incorporate satellite orbit and
clock corrections.
geoid is the gravity-equipotential surface that best
approximates mean sea level over the entire surface
of the earth. The surface of a geoid is too irregular to
use for GNSS readings, which are measured relative
to an ellipsoid. Conventionally surveyed positions
reference a geoid. More accurate GNSS readings can
be obtained by calculating the distance between the
geoid and ellipsoid at each position and subtracting
this from the GNSS altitude measurement.
GIS (Geographical Information Systems) is a
computer system capable of assembling, storing,
manipulating, updating, analyzing, and displaying
geographically referenced information, i.e., data
identified according to their locations. GIS technology
can be used for scientific investigations, resource
management, and development planning. GIS
software is used to display, edit, query, and analyze
all of the graphical objects and their associated
information.
Global Navigation Satellite System (GNSS) is the
standard generic term for satellite navigation systems
that provide autonomous geo-spatial positioning with
global coverage.
Global Positioning System (GPS) geometrically,
there can only be one point in space, which is the
correct distance from each of four known points. GPS
measures the distance from a point to at least four
satellites from a constellation of 24 NAVSTAR
satellites orbiting the earth at a very high altitude.
These distances are used to calculate the point’s
position.