On 2011-03-31, Chris Albertson <albertson.ch...@gmail.com> wrote: > On Thu, Mar 31, 2011 at 9:44 AM, Uwe Klein ><uwe_klein_habertw...@t-online.de> wrote: >> unruh wrote: > >>> My only concern is that the unit places its location 12m away from its >>> actual location on Googleearth-- ie, either googleearth is 12 m out in >>> its alignment to lat/long grid at my house, or the unit is misreporting >>> its position. > > > Another possibility to check is that both are not using the same > system. What spheroid dose Google use? Is it WGS84? The GPS would > need to be set to match whatever Google uses. Errors on the order of > up to 100M are posable. Not everyone uses the same system. > > Better than Google are the USGS topographic maps. These are now > available on-line for free. These are surveyed maps verified by > surveyors on the ground. If you are worried about errors on the order > of a few meters Google is likely not the best source (except to help > you find the USGS.) > > I've got it easy because a while back we did some construction at the > house and the city made us hire a survey team to find the true > location of the lot lines. So now I have a surveyed bronze marker > right on the driveway.
Did they use differential GPS? We have a city survey marker near our house-- the problem is that they charge to give you the information. Did the surveyors tell you what the location of that marker was? _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
