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

[Rick Collins]

At 12:56 AM 10/9/2007, you wrote:
>The only thing you have in this situation, though, is two sets of data
>that don't quite match. It is possible that both sets are also skewed
>several meters east of reality - without calibrating the GPS or the
>images to known positions, we cannot know if only one is skewed, or if
>both sets are skewed.
>
>You own the copyrights to your personal knowledge, and you can assign
>those rights to OSM. The same cannot be said of Yahoo's data. Therefore,
>it is better to use your own data - your GPS tracks and your personal
>knowledge - instead of Yahoo's.

Looking at a map and observing that your data has an error and making 
that correction is not the same as violating copyright by directly 
copying the data.  I can read a source and then use that information 
in my term paper.  That is what learning is all about.  I just can't 
copy someone else's work.  Using their work to correct my paper is 
legitimate.

But there are many other sources of information for this.  Yahoo is 
only one source of good data.  Terraserver is another and I know that 
data is freely available as it was provided by USGS.

My point is that it is silly to think that you should let uncorrected 
data enter a database or that all GPS receivers work the same.  All 
data should be verified as accurate using whatever means is available 
and appropriate.

BTW, if Yahoo photo data is truly not freely available, perhaps the 
Potlatch primer page should be changed.