Cool, je tombe par hasard sur cette page. En 2001-2 j'ai passé un an à Saint Martin d'Hères, dans la rue Louise Michel. (c'est tout)

Brilliant stuff. Presumably if they're using open source tools, any new software they write (interface, rendering etc) will also be open source? The more of these things around, the easier it gets for local governments that aren't quite so cutting edge...

This is a big problem that needs addressing. I'm a one-week newbie, and fell into the trap myself. Suggestions:
1) WARN PEOPLE IN BIG SHOUTY LETTERS wherever there is discussion of how to use imagery. Perhaps even in Potlatch itself. In my case it's Nearmap, not Yahoo.
2) Alert people to the fact you can align the imagery to the existing maps (space+drag in potlatch).
3) Add mechanisms to lock nodes?
4) Add warnings whenever a newbie tries to move existing nodes.
5) Store local imagery offsets? For example, if it's known that in the local area, the yahoo images are off by (3.5, -2.0) metres, then display them that way?

It's a serious problem because it's so hard to correct, and once the newbie discovers what they're doing wrong, they're going to be seriously discouraged from any further fiddling in case they mess up again.

The problem I find is when you're adding new stuff in a mapped area...you can't ignore the imagery, and you can't ignore the existing stuff. I tried just ignoring a mapped bike path, and tracing a building...but the bike path then goes through the building. What can you do? (Other than slide the imagery around as mentioned...but you have to be careful not to let it slide too far)

Several times I've caused duplicate ways/nodes. The reason is Potlatch occasionally failing to retrieve data from the server. Unfortunately, there is no visual distinction between "this area is unmapped" and "this area is mapped, but the data hasn't been downloaded yet". So you end up mapping the area, then some time later (maybe after browser refresh), the real data comes through...and now you have two sets.

(Though come to think of it, you're talking about real duplicates, not near-duplicates. Hmm.)