google "egm96" and "wgs84" to find about the geodetics used in GPS.
there is also an old paper I believe its titled "geodesy for the layman" that will get you are started Your topo map was probably NAVD 1929, a different vertical datum. Brian Kd4FM Michael Baker wrote: > Hello, All-- > > My Thunderbolt seems to be able to determine its > Lat and Lon location coordinates with reasonable accuracy. > > However, after completing its self-survey it thinks > its elevation is 11.2 meters when the actual elevation > of its antenna (on my house roof) is 28.4 meters. > > I arrived at this value by looking at the USGS topo > map of my property, noting the elevation ABMSL where > my house is located and adding the distance from > the ground to the GPS antenna on my roof and coming up > with 28.4 meters. > > Should I store this value into POSITION/ALTITUDE? > > If I enter this value into ALTITUDE, then what? > Should I then SAVE SEGMENT? SET ACCURATE POSITION? > > Thanks, > > Mike Baker > WA4HFR > Micanopy, FL > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.