Glocom GX-9 (FB250 Class) Operating Manual
33
TTTT
ECHNOLOGY
ECHNOLOGY
ECHNOLOGY
ECHNOLOGY
O
O
O
O
VERVIEW
VERVIEW
VERVIEW
VERVIEW
GPS
The Global Positioning System (GPS) uses 24 orbital satellites to determine the position of the Terminal
anywhere on the globe.
O
O
O
O
BTAINING A
BTAINING A
BTAINING A
BTAINING A
GPS
GPS
GPS
GPS
F
F
F
F
IX
IX
IX
IX
In normal operation, a GPS receiver, such as that built in to the Tracking Antenna, needs to be able to
receive signals from at least four satellites so that it can then calculate a latitude, a longitude and an
altitude – this position fix is referred to as a 3-dimensional or 3-D fix. If only three GPS satellites can be
seen by the GPS receiver, then the last available altitude measurement is assumed and the GPS receiver
calculates a position fix based on latitude and longitude only. This simpler position fix is referred to as a 2-
dimensional or 2-D fix and is quicker and easier to obtain than a 3-D fix, but may be less accurate.
The GPS receiver may take between a few seconds and 20 minutes to obtain a GPS fix, depending on
how frequently the GPS receiver is being used. The frequency of use determines the how quickly the
GPS Terminal is able to start.
Hot start
Hot start
Hot start
Hot start
−
if the GPS receiver is being used frequently, (that is, in the last two hours), it is regularly
updated with data from the GPS satellites, and so only takes a few seconds to obtain a GPS fix after
being switched on.
Warm start
Warm start
Warm start
Warm start
−
if a GPS receiver has not been used for more than two hours, then it will take up to 45
seconds to obtain a GPS fix.
Cold start
Cold start
Cold start
Cold start
−
if the GPS receiver has not been used for some time or is 300 km or more from where it was
last used, it can take as long as 15 minutes to obtain a valid position fix.
The time taken to obtain a valid GPS fix can also be affected by the visibility that the GPS receiver has of
the GPS satellites. The GPS system is relatively tolerant of atmospheric conditions such as heavy cloud
or rainfall. However, physical blockages, such as tall buildings or terrain can significantly degrade the
ability of the GPS receiver to obtain a fix. For this reason, ensure that the GPS receiver has a clear view
of as much open sky as possible.
GPS
GPS
GPS
GPS
AND
AND
AND
AND
BGAN
BGAN
BGAN
BGAN
R
R
R
R
EGISTRATION
EGISTRATION
EGISTRATION
EGISTRATION
BGAN uses the accurate position and timing information obtained from GPS to help ensure efficient
registration of a BGAN Terminal with the BGAN network.
Following successful registration and providing the Terminal is left switched on and remains stationary,
the GPS is no longer needed. Periodically, the BGAN Terminal contacts the BGAN network to inform the
