Curt, I tried it with the online maps this evening and had the same issue. If the error was within 50 meters I would not sweat it but it is off by a mile in some cases. I still think I am not getting the tie points close enough. Based on what I learned on WinAPRS if you take the tie points and use them to draw a box, if it was more rectangular than square, the image would be altered and cause posits to not place correctly on the image file but are on the money with the Tiger files. I could probably do better on the distance of the tie points too. I am not completely to the upper left and lower right as I probably could be. I am trying to use road intersections as reference points to find tie points.
That said, you theory on datums could be right too. I have no idea what Google is using for their datum format on their maps. I know from Geocaching that if the datums differ then the locations are not going to match. I will play with this more this week. Time for shutting down tonight. Message: 2 > Date: Sun, 23 May 2010 09:58:12 -0700 (PDT) > From: "Curt, WE7U" <[email protected]> > To: Xastir - APRS client software discussion <[email protected]> > Subject: Re: [Xastir] Xastir Digest, Vol 54, Issue 27 > Message-ID: <[email protected]> > Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed > > On Sun, 23 May 2010, Guy Story KC5GOI wrote: > > > I got my maps working yesterday evening. There was not much of a > learning > > curve for me on this one since WinAPRS uses the same format with the > > exception of the image size field and that was easy. I am currently > having > > tie point accuracy issues but I can get that taken care of. My maps are > not > > lining up to the Tiger maps, sometimes off by close to a half mile and > > distorted image. > > Which Tiger maps? The online ones? Be aware they use an odd > projection (sine) so they are more accurate at the middle of the > image as far as Xastir is concerned than the edges. > > If you're talking about Tiger Shapefile downloaded maps, it's > possible you're dealing with a datum difference between the two > types of maps. > > -- > Curt, WE7U. > <http://www.eskimo.com/~archer<http://www.eskimo.com/%7Earcher> > > > APRS: Where it's at! <http://www.xastir.org> > Lotto: A tax on people who are bad at math. - unknown > Windows: Microsoft's tax on computer illiterates. - WE7U. > The world DOES revolve around me: I picked the coordinate system!" > > -- 73 Guy Story KC5GOI [email protected] _______________________________________________ Xastir mailing list [email protected] http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir
