On Sun, Sep 13, 2009 at 9:39 AM, Habib Habib <[email protected]> wrote:
> I am starting to edit maps by using Yahoo images. The area that I'm mapping > has already many buildings layed out. However, they seem displaced a bit and > do not match the map correctly. My question is, should I trust Yahoo and > correct the positions of all buildings, or instead trust OSM? The aerial photos can be displaced slightly. Potlatch has a built in facility for moving the background photo to align it to the real world. The word is to trust the GPS traces over the aerial photography. Consumer grade GPS units do still have a margin of error, but it usually is not very much if you have a good view of the sky. The way that I would look at getting an accurate alignment of a photo would be to find a survey monument that has a highly accurate lat/long associated with it, and align that spot on the photo to the lat/long provided. The issue with doing that is that the information for the survey marker may not fit within the bounds of legal requirements for use in the OSM project. In the real world, I have located survey markers as part of a Geocaching hunt, and my consumer grade GPS was never more than a couple feet off from where the survey monument was located. I'm happy with having a map that "may" have a margin of error of a couple feet. James VE6SRV _______________________________________________ newbies mailing list [email protected] http://lists.openstreetmap.org/listinfo/newbies
