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Reply to "GPS Sync and Ski Racing"

The usefulness of the GPS synch feature is lost on me. I guess it might be useful for something like rally-raid timing, where the Stage Start and Stage Finish timing crews are 600 km apart? I can't imagine a situation where it would be of much use, but I guess it's nice to know it's there.

On the other hand, the "Johnny Appleseed" feature of the Timy (impulse on channel 0 at Top Dead Center when holding down green & red OK) is *extremely* useful. Once you get a "reference Timy" going, it doesn't matter whether the reference is synched in any semblance to UTC or local time, as long as all your time bases match the reference, and therefore each other.

In any event, looking through the Garmin docs, the contents of the $GPRMC packet is dangerously misleading. Param #1 is the UTC time, and Param #2 is the Status Tag. You would think a Status Tag of "V" (as in Mike's example above) means "Valid", but the opposite is true. "V" is a "validity warning". "A" means the GPS is synched up.

Most GPSs have some non-volatile memory, so they "remember" the UTC time - but with substantial drift. Until that $GPRMC param #2 turns from "V" to "A", the GPS time is going from memory, not from the satellite, and may be off substantially. If the GPS has been moved or reset, then the UTC may start from 000000. The Garmin docs state that a full satellite synch from scratch takes about 5 minutes from the time the GPS is powered up and has a view of the sky.
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