User`s guide

Chapter 3 - Receiver Descriptions
DATA LATENCY
The receiver can output position, velocity, and time data on the serial port at a maximum rate of
once each second. The start of the output data is timed to closely correspond with the receiver
measurement epoch. The measurement epoch is the point in time at which the receiver makes
satellite range measurements for the purpose of computing position. The first byte of serial data
in the position message is output between 0 and 50ms after the most recent receiver
measurement epoch. Refer to Figure 3.7 for the discussions that follow.
Let T
k
be the most recent measurement epoch. The receiver takes about one second to compute
data from the satellite range measurements. Consequently, the data that is output 0 to 50 ms
after T
k
represents the best estimate of the position, velocity, and time based on the
measurements taken one second in the past, at time T
k -1
. Position data (latitude, longitude, and
height) is computed from the most recent measurement epoch data, and is output immediately
after the next measurement epoch, which is 1.0 to 1.05 seconds after the original measurements
were taken.
Figure 3.7: Position/Status/Data Output Message Latency
Motorola GPS Products - M12+ User's Guide Revision 6.X 09FEB05
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