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The Trimble AcutimeTMaccurate event timestamping

Another class was created to interface devices that run the Trimble TSIP Protocol. In particular we interfaced the Trimble AcutimeTM2000 GPS (A2K) receiver and programmed in order to capture and timestamp events such as seismic shots or similar. This task requires accuracies of at least +/- 1ms or better. The A2K system is capable of giving accuracies of few tenths of nanoseconds, by using an overdetermined solution to obtain better time measurements from the highest possible number of SV available.

Figures 15, 16 and 17 show the panels for the instrumental setting. To fill the initialization strings user must press the buttons on the rigth of the white board. The control data bytes are reported in Appendix B. The event timestamp is triggered by pulsing the RTS line (pin 4-7) of the RS-232 port A. The port B is used for the GPS setting. See in Fig.18 the cable roouting and interfacing.

Figure 15: AcutimeTMevent setting, general.
\begin{figure}\centering \epsfig{file=IMG/acutime_event_general.ps, width=12cm} \end{figure}

Figure 16: AcutimeTMevent setting, device. Note also the odd parity setting.
\begin{figure}\centering \epsfig{file=IMG/acutime_event_device.ps,width=12cm} \end{figure}

Figure 17: AcutimeTMevent setting, other.
\begin{figure}\centering \epsfig{file=IMG/acutime_event_other.ps,width=12cm} \end{figure}

Figure 18: EVENT/TIMESTAMP cable routing and interfacing.
\begin{figure}\centering \epsfig{file=IMG/DAPHNE_ACUTIME.eps,width=12cm} \end{figure}


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2004-03-24