Specifications

VP ONCORE COMMAND REFERENCE
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6 CHANNEL POSITION/STATUS/DATA OUTPUT
MESSAGE (@@Ba)
The input command sets the rate at which the 6-Channel
Position/Status/Data Message is output by the VP receiver. The mode
parameter (m) in the input message instructs the GPS receiver to either
output this message one time (polled), or to output this message at the
indicated update rate (continuously). Once the GPS receiver is set to
continuous output, the continuous message flow can be stopped by
sending a one-time output (poll) request. The GPS receiver will output
the message one more time, then terminate any further message
outputs. If the VP receiver has been placed in Idle Mode with the
@@Cg command, it outputs the last known valid Position/Status/Data
message once when polled.
The state of the mode bit is stored in nonvolatile memory. If the VP was
continuously outputting the 6 Channel Position/Status/Data message
when turned off, it will begin to output this message continuously (at the
selected update rate) again when power is reapplied.
The 6 Channel Position/Status/Data output is explained in the response
message section. Refer to the Date, Time of Day, Latitude, Longitude,
and Height commands for more details on the formats of these
parameters.
The number of satellites visible is computed using the current date, time,
position, almanac, and a default mask angle of ten degrees. If no
almanac is available, this number will be zero. This condition will not
prevent satellites from being tracked.
In order for a satellite to be used for positioning, the satellite mode must
reach eight, indicating that the ephemeris for that satellite has been
acquired. Once the ephemeris is available, the satellite can be used for
positioning in modes five through eight. Refer to the Response Message
section for definition of channel tracking modes. The signal strength
value is meaningless when the channel tracking mode is zero.
The VP Oncore GPS receiver has a “Position Propagate” mode that is
used to extend coverage when satellite dropouts occur. When a 2D fix
can no longer be computed, the last known velocity vector is used to
propagate the position solution ahead for up to five seconds. This
condition is indicated in the receiver status message byte.
NOTE: United States export laws prohibit commercial GPS receivers
from outputting valid data if the altitude is greater than 18,000
meters and the velocity is greater than 514 meters per second.
If the GPS receiver is used above both these limits, the height
and velocity outputs are clamped to the maximum values. In
addition, the latitude and longitude data will be incorrect.
70 Synergy Systems, LLC 05OCT01