NavCom SF-3050 Rev.B - Manual (Page 190)

SF-3050 User Guide – Rev B
surface closely, so GPS altitude measurements can
contain a large vertical error component.
Conventionally surveyed positions usually reference a
geoid, which has an undulating surface and
approximates the earth’s surface more closely to
minimize altitude errors.
epoch literally a period of time. This period of time is
defined by the length of the said period.
G1 carrier frequency the primary L-Band carrier
used by GLONASS satellites to transmit satellite
data. The frequency is 1603.00MHz.
G2 carrier frequency the secondary L-Band carrier
used by GLONASS satellites to transmit satellite
data. The frequency is 1247.00MHz.
GAGAN (GPS Aided Geo Augmented Navigation)
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.
Galileo a GNSS system currently being built by the
European Union (EU) and the European Space
Agency (ESA). Galileo uses the same concepts for
positioning as GPS.
geoid 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 GPS readings, which are measured relative to
an ellipsoid. Conventionally surveyed positions
reference a geoid. More accurate GPS readings can
be obtained by calculating the distance between the
geoid and ellipsoid at each position and subtracting
this from the GPS altitude measurement.
GIS (Geographical Information Systems) a
computer system capable of assembling, storing,
manipulating, updating, analyzing and displaying
Glossary-188