Discussing everything from Time Servers to GPS's.
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1) What accuracy can be expected using a GPS as the reference time?
2) This GPS I am using has a PPS pin. Does PTS take advantage of this?
3) Also, I know NTP works via a handshaking protocol in which timestamps are exchanged between a client and the server. How does this work with the GPS?
Last edited by jeremy (2009-08-10 14:01:03)
1. This depends on the GPS. If you take a cheap USB GPS with associated virtual com port driver, it can be as bad as 100ms. If you take a Rockwell Collins GBGRAM and remove all the unnecessary parts of Windows then you can achieve microsecond accuracy. The key is to have a good GPS clock, use serial port rather than USB and trim Windows until you get the accuracy you need.
3. Your GPS will likely have a serial port which will, or can be configured to output NMEA text strings. These are used to set the date, time. If your GPS allows it, configure GGA substrings only with once per second updates.