It does appear to be a datum issue. Although I never got the two GPS to match exactly, they are still a few meters apart. I did find an older thread on the topic from March also. Thanks for the replies!
Jamie --- On Sat, 12/27/08, Ed, k1ggi <[email protected]> wrote: > From: Ed, k1ggi <[email protected]> > Subject: Re: [time-nuts] altitude difference between two gps > To: "'Discussion of precise time and frequency measurement'" > <[email protected]> > Date: Saturday, December 27, 2008, 11:12 PM > On the thunderbolt, what datum do you have selected in Setup > > Packet Masks > and Options? If it is 0 (WGS-84), try 2 (NAD-27). > -30m is about right for the geoid height around Las Vegas. > Ed, k1ggi > > -----Original Message----- > From: James R. Gorr [mailto:[email protected]] > Sent: Saturday, December 27, 2008 9:26 PM > To: [email protected] > Subject: [time-nuts] altitude difference between two gps > > Hello everyone! > > I have a tbolt that I am monitoring with tboltmon.exe and > some off-brand 12 > channel GPS (I bought from Sure Electronics on eBay) that I > am monitoring > with VisualGPS. Both are fed from the same GPS antenna > through a > symmetricom splitter. There is a 30 meter difference in > the altitude > readings between the two. My tbolt says my altitude (after > a self-survey) > is ~761 meters and the 12 channel Sure Electronics GPS says > my altitude is > ~791 meters after 7,500+ readings. I took my hand held > Garmin 12XL outside > and it says my altitude is ~790 meters at street level. > > Anyone have an idea why my tbolt might be reading different > from the other > two devices? I am assuming the tbolt is reading low. > > Jamie > > > > > _______________________________________________ > 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. _______________________________________________ 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.
