NorthStar 957, Руководство оператора

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Page 150 957 Operator’s Manual, Rev. B
Chapter 11 - Setting up your 957
•
radiobeacon - the 957 will use radiobeacon differential if
it’s connected to an optional external radiobeacon
receiver
•
WAAS - the 957 will use WAAS differential corrections
Choosing a DGPS
corrections time-out
The DGPS data timeout setting determines how long the 957
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 957 ignore the occasional outage of
differential reception.
Regardless of the setting, if the time-out period ends without
any new corrections, the 957 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 957 receives
valid corrections.
Adjusting satellite
elevation
The
LOWEST SAT ELEVATION
option is used mainly for
technical applications, in which the 957 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°.