User's Manual

11 Event Marker Input and 1PPS Output
98 Trimble R7/R8 GPS Receiver User Guide
Trimble R7 GPS Receiver Operation
Figure 11.1 Time tag relation to 1PPS wave form
The pulse is approximately 8 µsec wide, with rise and fall times of
about 100 nsec. Resolution is approximately 40 nsec, but several
external factors limit accuracy to approximately ±1 µsec:
• Position errors, especially with user-entered reference. Each
meter of error can result in 3 nsec of error in the 1PPS pulse.
• Antenna cable length. Each meter of cable adds a delay of about
2 nsec to satellite signals, and a corresponding delay in the 1PPS
pulse.
111.2 ASCII time tag definition
Each time tag is output about 0.5 second before the corresponding
pulse, as shown in Figure 11.1. Time tags are in ASCII format on a user-
selected serial port. The format of a time tag is:
UTC yy.mm.dd hh:mm:ss ab
Where:
• UTC is fixed text.
• yy.mm.dd is the year, month, and date.
0V
4V
Seconds
Time tag output here Time tag applies here