Bob, That is simply not accurate - if the solution rate is 1/second, then all parameters are solved in that time frame. There are 4 indpendent variables and minimal processing power is required to solve all four equations. Although I am not very familiar with commercial receivers, that is what happens in the Rockwell, Trimble and IEC military units. If the output is more than once per second it is *usually* an output of the Kalman Filter, not a "true" measurement.
Michael / K7HIL On Fri, Dec 28, 2012 at 6:20 PM, Bob Camp <li...@rtty.us> wrote: > Hi > > …. except… A navigation GPS doesn't care much about the time solution. > Updating the location is a much higher priority than updating the time. The > typical "solution" is to let the time estimate coast for a while and update > it much less often than the location. > > Bob > > On Dec 28, 2012, at 7:18 PM, Magnus Danielson <mag...@rubidium.dyndns.org> > wrote: > > > On 28/12/12 23:35, Bob Camp wrote: > >> Hi > >> > >> The GPS does an estimate against the local crystal frequency. It > generates the PPS off of it's estimate. The less often it updates the > estimate the more odd things you see as the crystal drifts. > > > > A typical GPS off the shelf solves the position solution every second, > having a 1 Hz report rate. This includes clock corrections. Some GPSes is > capable of higher report-rates. > > > >> Of course, the crystal can have trouble all it's own. If the crystal > has a rapid rate of frequency change over a narrow temperature range, the > GPS simply can't keep up with the crystal. > > > > Most GPS receivers only have TCXOs, and even if tossing in an OCXO, > excessive heat can throw the frequency and hence the GPS solution way of > the mark. For many GPS reference stations, rubidiums is used to steer the > internal clock, and the quality of that lock can affect how well it tracks > it and have secondary frequency issues. > > > > So, it comes as no surprise that the GPS module is temperature > sensitive. The metrology labs measure and compare the temperature stability > of various GPS-receivers, > > > > There are also filters that can provide temperature effects, but the > TCXO is where it usually hurts most. > > > > Cheers, > > Magnus > > > > _______________________________________________ > > 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. > _______________________________________________ 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.