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

[Dave Clark]

"I don't know for sure, but I expect that Yahoo is using USGS supplied 
photos which would mean Yahoo does not have a copyright on them. "

Using Yahoo maps directly,  the "satellite" images have various 
copyright attributions. Images for my area indicate copyrights 
attributed to Aerials Express and i-cubed. Images in the UK are 
attributed to i-cubed and GeoEye. There's a generic attribution to 
Yahoo! Inc. on all of them. Yahoo has a personal-use only caveat in 
their terms of service, I am unaware of the license agreements as to the 
images themselves.

"That would say that I should not correct any of the deviations from the 
true road which does not seem obvious to me.  The point is to create 
accurate maps, not to document the aberrations of the particular GPS 
receiver you are using.  GPS technology continues to improve and today's 
errors may not be there tomorrow. "

A few skewed points when your satellite signal is erratic or you took a 
small detour is not the same as a consistent, 2-3 meter northerly skew 
in your track points. You have personal knowledge of your route and can 
remember that your reception was fluky over on North Avenue,  that you 
stopped at a gas station that took you off of Main Street for 20 meters, 
that you changed lanes on Market Street, or swerved to miss a dog on 
Seventh Avenue.

If you have independently verified that your GPS returns a position 
consistently skewed by several meters, (do you cross a USGS survey 
marker regularly?) then you would have personal knowledge that your data 
points are skewed and you can adjust them appropriately.

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.

Dave



> At 07:11 PM 10/8/2007, you wrote:
>> I can think of two reasons why you'd want to use your data instead of
>> Yahoo's:
>>
>> 1. Yahoo's images are copyrighted: If we consistently used their images
>> instead of our data, they could be considered a derivative work, and
>> possibly subject to copyright issues.
>
> From the OSM wiki on using Potlatch...
>
> /Because OpenStreetMap exists to create open maps, not copyrighted 
> ones, you can't just copy from someone else's map. Instead, you should 
> draw the ways using your own knowledge; using tracklogs of journeys 
> you have made with a GPS receiver; or by tracing from the satellite 
> photo background ( Yahoo! Aerial Imagery 
> <http://wiki.openstreetmap.org/index.php/Yahoo%21_Aerial_Imagery>)./
>
> I don't know for sure, but I expect that Yahoo is using USGS supplied 
> photos which would mean Yahoo does not have a copyright on them.
>
>
>> 2. A second GPS would likely follow your track: your data is likely more
>> accurate for the end-user of the data.
>
> I don't agree with that at all.  That would say that I should not 
> correct any of the deviations from the true road which does not seem 
> obvious to me.  The point is to create accurate maps, not to document 
> the aberrations of the particular GPS receiver you are using.  GPS 
> technology continues to improve and today's errors may not be there 
> tomorrow.
>
> Rick Collins
> ------------------------------------------------------------------------
>
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