NorthStar 958 Operator's Manual page 184

Chapter 12 - Setting Up Your 958
Choosing a DGPS
corrections time-out
Adjusting satellite
elevation
Page 176
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radiobeacon - the 958 will use radiobeacon differential if
it's connected to an optional external radiobeacon
receiver
•
WAAS - the 958 will use WAAS differential corrections
The DGPS data timeout setting determines how long the 958
will continue to use old DGPS corrections if no new
corrections are received due to bad weather, extreme distance
from beacon, etc.
Under normal operating conditions, you should set the
time-out to one minute (the factory default) to guarantee the
best accuracy. A time-out of 30 seconds or less is often too
short and can cause intermittent problems. Generally, one
minute provides good navigation accuracy, and is best left
unchanged.
In bad weather—and if you can tolerate a minor loss of
accuracy—you can increase the value up to a maximum of four
minutes, which lets the 958 ignore the occasional outage of
differential reception.
Regardless of the setting, if the time-out period ends without
any new corrections, the 958 goes back to standard GPS
navigation; displays the OLD CORRECTIONS status message
on the DGPS STATUS screen; and displays the DGPS LOST
alarm. DGPS will automatically resume when the 958 receives
valid corrections.
The LOWEST SAT ELEVATION option is used mainly for
technical applications, in which the 958 must track all visible
satellites regardless of how low they are on the horizon. In
other instances where high-precision fixes are necessary, you
can change this setting to "hide" any low satellites, thereby
preventing their use as sources of GPS position information,
and avoiding potential errors.
This option is adjustable from 0° to 25°, in 5° increments, but
Northstar recommends leaving this option at the factory
setting of 10°.
958 Operator's Manual, Rev. A