[OSM-talk] Bing maps is misplaced

Jacek Konieczny jajcus at jajcus.net
Wed Dec 8 10:09:58 GMT 2010


On Wed, Dec 08, 2010 at 11:32:39AM +1100, Steve Bennett wrote:
> On Wed, Dec 8, 2010 at 4:51 AM, Jo <winfixit at gmail.com> wrote:
> > Jaak, do you know that you can change the offset in most editors? Potlatch2
> > and JOSM. I suppose in Merkaartor too, but I don't know for sure.
> 
> But how do you know which direction to offset and by how much? Is the
> Bing imagery really offset so uniformly, over large areas?

You should not map from the Bing imagery area you know nothing more
about. Usually there is already something mapped in the interesting
area, there should be some GPS traces over important roads. That should
be enough to align the imagery. 

And even when the imagery is only what you have and there is no other
data in that are, the shift won't matter much. Someone with GPS or
even better equipment will come there and move everything to the right
place. This way the incomplete data will be completed. And that is why
'source' tags and right changeset comments are important – they give
some information about what accuracy we may expect.

The real problem appears when someone traces the misaligned imagery over 
existing correct OSM data.

As far as the uniformity of the offset is concerned, it seems it is not
very uniform even on small areas. I try to align it to the closes known
data.

Please remember, that the imagery is only some aid, not exact geodetic
data.

Greets,
        Jacek



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