I've noticed a curious odditity on a Motorola M12 GPS module, when started up completely from cold with no stored almanac data:  When the module eventually 'appears'  to lock up and show the correct lat /long and the NMEA data showing satellite staus 'Valid', the NMEA reported time is 15 (ish) seconds out.   Which means it hasn't downloaded the leap-second correction yet and is still working on GPS time - the NMEA report gets corrected after a minute or two longer wait.

 

BUT... Why does it decide that it has enough info for location calculation when it clearly hasn't yet downloaded all the almanac data ?

It's lying.    Has anyone met this?

Only the M12 behaves like this out of those tested.  All other modules I've used, including the older Motorola. Oncore,. give the correct time immediately they show lock.   Of course, if the internal battery is alive the almanac data is already stored and it jumps into life immediately with a warm start, but after several months of storage - sometimes just weeks -  this battery goes flat. 

Andy
www.g4jnt.com