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A-16 Lassen-SK8 Embedded GPS Module
Trimble Standard Interface Protocol
A.15 Key Setup Parameters or Packet BB
Selecting the correct operating parameters has significant impact on receiver performance.
Packet 0xBB (set receiver configuration) controls the key setup parameters.
The default operating parameters allow the receiver to perform well in almost any
environment. The user can optimize the receiver to a particular application if the vehicle
dynamics and expected level of obscuration are understood. If the receiver is then taken
out of this environment, the specifically tuned receiver may not operate as well as a
receiver with the default options.
The table below lists suggested parameter selections as a function of obscuration and
whether accuracy or fix density is important. In this table, NA indicates that the operating
parameter is not applicable, DC (don't care) indicates that the user may choose the
operating parameter.
The default values in Table A-15 allow the receiver to operate well under the most varied
and demanding conditions. A user may choose to change the default parameters if the
receiver is only required to perform in a specific or limited environment. The user should
be warned that when the receiver is exposed to operating conditions which are different
from the conditions described by the user setup, then the performance may be degraded.
Initially, the user must consider the environment in which the receiver is expected to
operate. There is a trade-off between how frequently a position fix is output versus the
absolute accuracy of the fix. The user must decide which takes priority and then make the
appropriate selections. This becomes increasingly important when frequent satellite
blockages are expected, as in downtown “urban canyon” environments and heavily
foliated areas.
Following is a description of the key fields in Packet 0xBB.
Table A-14. Setup Parameters
Packet Parameter Accuracy Fixes
Factory
Default
0xBB Fix mode Man 3D AUTO AUTO
0xBB Dynamics code Land Land Land
0xBB Elevation mask 10° 5° 5°
0xBB Signal mask 6.0 4.0 2.0
0xBB DOP mask 6.0 12.0 12.0
0xBB DOP switch NA 8.0 5.0
0xBB DGPS correction age 10 Seconds N/A 30 Seconds