Hello Peter, that's a good question. Some users of our Fury use rented/borrowed survey equipment (Leica, Javad, etc) to get a very precise position of their antenna, or they call in a surveyor. It is also possible to let the receiver do the auto survey multiple times, preferably during different times of the day, then manually average the position fixes, and enter them into our Fury unit as the new position-hold position. I described this method some time ago. Position error should be reduced by this type of averaging. One could also use the Fury NMEA GPGGA output command to send NMEA position data to a PC over a long time, say a week or more, then crunch all that data down to one averaged position fix and manually enter it into the Fury. And your idea of trial and error is not bad either, but I would think height errors of <10 feet, and position errors of less than 5 feet would be sufficient to try. This requires a good reference to compare against though, and LOT'S of patience I would think. >From what I can see, all commercial GPS receivers have a really tough time generating an accurate antenna height measurement due to the way GPS works. They don't seem to have a problem generating good long/lat coordinates. But in timing, all three axis need to be precise unfortunately. bye, Said In a message dated 1/6/2009 03:23:53 Pacific Standard Time, [email protected] writes:
Said wrote: >When we say units typically have 25ns unit-to-unit variation on the 1PPS on >un-calibrated units, then I believe most of this is caused by the auto-survey >position errors of the GPS receiver. One could get much better performance by > manually entering the exact position-hold position of the antenna, and then >calibrating for antenna cable delay (in 1ns steps). A naive question, if I may: how do I go about doing a precise manual position survey? Is it simply a case of letting the unit self survey, then manually entering different co-ordinates (say +/- 10 metres) in each of the three directions in turn, watch the signal output, and try to tune for minimum wobble? Thanks, Peter _______________________________________________ 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.
