NavCom RT-3010 Rev.E - Manual (Page 53)

RT-3010 User Guide - Rev. E
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 .
GMT see Greenwich Mean Time
GPS see
Global Positioning System .
GPS time a measure of time.
GPS time is based on
UTC , but does not add periodic ‘leap seconds’ to
correct for changes in the earth’s period of rotation. As
of September 2002
GPS time is 13 seconds ahead of
UTC .
Greenwich Mean Time (
GMT ) the local time of the 0°
meridian passing through Greenwich, England.
HAE see
altitude , and ellipsoid .
JPL Jet Propulsion Laboratory.
Kbps kilobits per second.
L-Band the group of radio frequencies
extending from approximately 400 MHz to
approximately 1600 MHz. The
GPS carrier
frequencies L1 (1575.4 MHz) and L2 (1227.6
MHz) are in the
L-Band range.
L1 carrier frequency the primary
L-Band carrier used
by GPS satellites to transmit satellite data. The
frequency is 1575.42MHz. It is modulated by C/A code ,
P-code or Y-code, and a 50 bit/second navigation
message.
Glossary-51