Hi Neville > When you think of time specifications from GPS, the GPS system is a > poor way to find north.
I do not understand. Please elaborate. A baseline of 10 meter will often give better than 1mrad accuracy. > Even with a base line of 1000 metres you only have a fraction of a > degree. This is just not true. > The GPS system may be useful to get accurate time to simplify a star > observation, from a known (GPS) > position on this planet, but finding north is still a problem because > of the accuracy of a small > number of observations from a star fix. > Gyrocompasses take some time to get a measurement > ( one hour) but even their estimate of North cannot match the > precision that the GPS system can get us with time. While legacy mechanical gyrocompasses on a ship, might take time to converge - it does not take a modern strapdown INS more than about 4 minutes to find north while stationary. But having 4 minutes at hand with some decent GPS-receivers its easy to get a north-measurement that will be much better than the best available intertial systems. > cheers, Neville Michie -- Björn _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
