As a microclimatologist I am very aware of the nocturnal inversions that occur in the atmosphere. From ground level to say 1000 feet the air cools at night forming a dense layer. The dielectric properties of this condition must create apparent thickness beneath the satellites. Whereas there is a balanced triangulation of northing and easting in determining lat and long that will null any atmospheric length effects, there is no way of determining the actual altitude from the apparent altitude caused by extra dielectric layering of the atmosphere and ionosphere. So there is little surprise in variable height data. What would be interesting is a correlation between apparent height error and night minimum temperature at ground level (air temperature 2 metres from the ground). cheers, Neville Michie
On 31/08/2008, at 6:15 AM, Mark Sims wrote: > > Besides the wonky geoid, ionospheric delays (which tend to be > poorly modeled and compensated for in single frequency receivers) > tend to affect the altitude reading the most. > > You also need to set the cable delay time for best accuracy. > > Also, for a cheap thrill, run the self survey several times > (preferably at the same and at different times of the day) and see > how much it varies. I set my location to the centroid of about a > dozen surveys done over three days. > ---------------------------------------- > > _________________________________________________________________ > Be the filmmaker you always wanted to be—learn how to burn a DVD > with Windows®. > http://clk.atdmt.com/MRT/go/108588797/direct/01/ > _______________________________________________ > 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. _______________________________________________ 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.
