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geometry changes. This may be as soon as a new satellite comes into view, or, in the
worst case, when the satellites move by a few degrees in the sky, which can take from
one to more than 10 minutes.
You can control the reliability that the receiver provides, this indirectly controls the
speed of carrier phase initialization. The higher the reliability the longer it takes to fix
integers.
The receiver offers three modes for ambiguity fixing:
a.
b.
c.
The command $PASHS,CPD,AFP controls the ambiguity fix parameter.
The two choices of formal reliability for fixed solution are provided to allow you to
trade off speed with reliability. The AFP setting controls the internal thresholds of the
receiver so that the expected statistical reliability of getting correctly fixed integers is
99% or 99.9% respectively. The receiver fixes integers two to three times faster with
AFP=99 than with AFP=99.9. The actual achieved reliability has been tested under
different conditions in different locations, and using two different test techniques.
Under the first technique, the receiver is reset at regular intervals (every 10 minutes).
Under the second technique the receiver is reset every time it has fixed integers.
Results vary according to location, environmental conditions (multipath and
blockage), and test method. Best and worst case results of all tests are listed in the
Table 5.9.
Table 5.9: Actual achieved reliability results with AFP settings of 99 and 99.9
AFP
Setting
99
99.9
1
Time to fix integers varies with number of satellites in view, and baseline length. The more
satellites in view, the faster integers are fixed. The longer the baseline, the slower the integers
are fixed. Values shown are typical for tests over baselines of 3.5km to 7km. Most tests last more
than 24 hours, during this time there are periods of high satellite visibility when time to fix
integers is much shorter than the typical times shown
Differential and RTK Operations
Float solution only
Fixed solution, formal reliability = 99%
Fixed solution, formal reliability = 99.9% (default)
Worst Achieved
Reliabilty
96%
99.97%
(3.5km baseline,
(3.5km baseline,
800 resets over 5 days)
3826 resets over 1 day)
99.6%
100%
(3.5km baseline,
(7km baseline,
800 resets over 5 days)
829 resets over 5 days)
Median Time
Best Achieved
to Fix
Reliability
(50% of resets)
< 1 minute
3 minutes
90% Time to
Fix
(90% of resets)
1
1
10 minutes
1
1
> 10 minutes
61
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