In a message dated 12/11/2007 22:00:37 Pacific Standard Time, [EMAIL PROTECTED] writes:
>I am surprised surveying mode is needed anymore. In a SA environment it >makes sense, but for me its hard to understand with the current accuracy >given by the GPS system. -- > Björn Hi Bjoern, even with a very good M12M or M12+ receiver we will typically see some variation of the averaged position over it's ~3 hour (default) auto-survey interval. I've seen altitude change by a meter or two for example. Those couple of nanoseconds may be insignificant when compared to older GPS receiver performance (VP Oncore etc), but if one has the time, why not get the best position average possible. I did also note that it does make a difference if the Auto Survey is done during the day, at dawn, or during the night etc. Might be caused by multipath etc. A 12 hour or 24 hour Auto Survey may reduce the Diurnal effects. We recently added a command to our Fury firmware that allows the user to set any time from 1s to 10,000s for the Auto Survey process to finish. This was done because the differences are so small between any given single-second position, and an auto-surveyed position (less than 5 meters or so). The error due to this is much less than 100ns which is more than adequate for a lot of applications. We have some customers that want the unit to do only 3 to 5 minutes of Auto Surveying for a particular mobile military application, and the resulting <<100ns UTC accuracy is way better than their requirement. In that case the Auto Survey time is insignificant when compared to the OCXO warmup time. It all depends on your particular accuracy requirement. bye, Said **************************************See AOL's top rated recipes (http://food.aol.com/top-rated-recipes?NCID=aoltop00030000000004) _______________________________________________ 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.
