Satellite Data Collection - Garmin TracPak GPS 30/30 SL Manual

1) 2D exclusively with altitude supplied by the host
system (altitude hold mode)
2) 3D exclusively with altitude computed by the GPS
30/30 SL
3) Automatic mode in which the board set determines
the desired mode based on satellite availability and
geometry considerations
When navigating in the 2D mode (either exclusive or
automatic), the GPS 30/30 SL utilizes the last computed
altitude or the last altitude supplied by the host system,
whichever is newer. The host system must ensure that the
altitude used for 2D navigation is accurate since the
resulting position error may be as large as the altitude error.
See Section 4 for more information on altitude control.
Operation in the exclusive 3D mode may cause undesirable
navigation outages due to satellite shading or limited
satellite availability. However, because the GPS 30/30 SL
tracks up to eight (8) satellites in view, this condition will be
minimal, as the GPS satellite constellation status has
reached initial operational capability.
The GPS 30/30 SL will default to automatic differential
corrections, attempting to apply them to the satellite data,
in order to produce a differential (DGPS) solution. The host
system, at its option, may also command the GPS 30/30 SL
to choose differential only mode. When navigating in the
differential only mode, the GPS 30/30 SL will output a
position only when a differential solution is available.

2.4 SATELLITE DATA COLLECTION

The GPS 30/30 SL will automatically update satellite orbital
data as it operates. The intelligence of the GPS 30/30 SL
combined with its hardware capability allows these data to
be collected and stored without intervention from the host
system. A few key points should be considered regarding
this process:
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