Hi
> On Mar 28, 2018, at 12:10 AM, Mark Sims <hol...@hotmail.com> wrote: > > Lady Heather's automatic rollover fixer works by looking at the year in any > time message that it sees. If it sees 10 consecutive year values less than > 2016, it assumes the receiver has rollover issues and then adds 1024 weeks > worth of seconds to the Julian date/time calculated from the receiver > time/date message until the resulting year is past 2016. > > One problem with this is when a receiver is first powered up... most of them > send dates in the 1980s to 1990s until they start tracking satellites. Once > Heather detects a rollover condition, the code does not currently undo it if > the receiver starts sending good dates. > > Heather keeps all times as a double precision Julian date. Using Heather's > code can be a problem on Arduinos since their "double" precision numbers are > actually 32 bit single precision, so you would need to do some more > complicated math. > > Heather's rollover compensation value is actually in double precision > seconds. You can manually specify a rollover correction to sub-second > resolution and tweak the displayed time/date to anything you want... comes > in handy for testing calendar/eclipse/sunrise/sunset/etc code. > > Speaking of rollovers, the GPS system has a 1024 week rollover next year > (April 6th-7th). A lot of older receivers had code that could handle the > first system rollover in 1999, but might have issues this time. There are a surprising number of GPS modules that really don’t handle the rollover very well. That includes a significant number of designs that came out after 1999. Bob > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
