[OSM-newbies] Trust GPS or Yahoo aerial imagery?

[Rick Collins]

At 05:26 PM 10/8/2007, you wrote:
>I just did a GPS track of some roads, and uploaded it. Now I see it on
>the main map, it seems that the roads are consistently few metres north
>of where they are on the Yahoo aerial imagery. Do I move them to match,
>or do I trust the GPS over Yahoo (i.e. are the Yahoo images offset a bit)?

If your data deviates from the Yahoo images only for part of the 
track, then I would say to correct the data.  But if it is 
consistently off you might want to verify against a different image source.

I have read that Google maps can be off by some distance.  I don't 
know about Yahoo maps.  If you are in the USA, you can download a 
free program for Windows (assuming you use Windows) and view your 
track data from a GPX file as an overlay to USGS topo maps, photo 
data or higher resolution photo data which is only available for the 
largest cities.  I have done a little comparison of my collected data 
to the USGS images and the correlation seems to be pretty good.


Regards,

Rick Collins