SHOUT nano User Guide Version A
Document Number: 451-92681-001A
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Figure 18: Reset Ephemeris Key
The accuracy of the position can be monitored by observing the (Horizontal Accuracy) HACC.
The HACC is measured in meters. HACC is defined as the radius of a circle centered on the true
value that contains the GPS measurement. Thus, a position fix with ten meters’ HACC accuracy
indicates that it is within ten meters of the true position—the higher the HACC value, the less
accurate the GPS measurement.
The Check GPS option is a good indicator of whether or not to initiate a Way Point or a Test
Report when located in a challenging environment, e.g., in dense foliage or around urban
settings with tall buildings. HACC can be monitored in real-time to make sure it converges to a
small and stable value (usually less than 30 meters). At that point, it is certain that a 3D fix can
be obtained with the most current ephemeris data being updated and saved. You can then go
back to the Utilities menu to send a test report. When the GPS receiver cannot acquire a fix,
HACC gradually increases and stops at a value of 4294967.500. This indicates that the
surrounding obstructions prevent the GPS receiver from obtaining a fix and you should move on
to a different location.
7.2
C
HECK
I
RIDIUM
The
Check Iridium
option forces the SHOUT nano to turn on its Iridium transceiver and
continuously update and display signal strength information in real-time. The Iridium
transceiver remains on until you leave this screen by pressing the BACK button. Be careful not
to deplete the battery power by staying on this option for too long.