Specifications

VP ONCORE COMMAND REFERENCE
Back to Index
DIFFERENTIAL TIME-OUT SELECT (@@AJ)
The differential time-out select message allows the user to determine
how long the receiver will stay in differential mode in the absence of valid
updated corrections. The GPS receiver will stay in differential mode as
long as it has a current and valid differential correction message.
The user should note that excessive differential correction latencies
could lead to significant error growth. As a rough guideline, an
acceleration error of 1cm/sec
2
due to Selective Availability can be
assumed producing the following (one-sigma) error component values in
the differentially corrected solution:
Correction Latency (s) Induced Position Error (m)
30 4.5
60 18.0
90 40.5
120 72.0
150 112.5
180 162.0
Range: 5 to 180 seconds
Default: 90 seconds
Resolution: 1 second
NOTES: Since Selective Availability (S/A) was discontinued by the U.S.
Government in May of 2000, autonomous position errors have dropped
markedly. Likewise, the time induced position errors of differential
systems are currently much lower than the values shown in the table
above.
Later receivers such as the GT+ and M12 do not support the @@AJ
command and utilize a fixed differential time-out of 90 seconds.
35 Synergy Systems, LLC 05OCT01