[OSM-talk] Is *just* tracing useful?

[Dave Stubbs]

I was out mapping today in London, and came across a few roads which I
thought were mapped, but actually it looks like they were just traced off of
the Yahoo imagery.

I was interested as to just how much of London had actually been mapped, and
how much is simple tracing... so after applying a few incredibly simple
metrics to determine what's a traced road and what's a mapped road, I came
up with the following:

All data 2007-09-05:
http://dev.openstreetmap.org/~random/progress/london/london-070905-mapnik.png<http://dev.openstreetmap.org/%7Erandom/progress/london/london-070905-mapnik.png>

Just the mapped data:
http://dev.openstreetmap.org/~random/progress/london-070905-mapped-only-mapnik.png<http://dev.openstreetmap.org/%7Erandom/progress/london-070905-mapped-only-mapnik.png>

The traced streets:
http://dev.openstreetmap.org/~random/progress/london-070905-traced.png<http://dev.openstreetmap.org/%7Erandom/progress/london-070905-traced.png>


So there's a reasonable amount of traced stuff there. Also, some of it has
been there a while, so there doesn't seem to be any effort to properly map
it.

Now my question is this: is this tracing actually useful?

>From my mapping perspective:
 - it makes it much harder to see what needs doing
 - when loaded onto my GPS the traced stuff becomes very difficult to
distinguish, so it takes me longer and I also miss stuff because I assume
it's been done.
 - entering the data takes longer because I have to fix all the oneway
streets, and the ways that don't follow the roads, the ways that aren't
roads, and all the bits that were missed anyway... it's much quicker to
generate from scratch correctly

In other words, I'd rather people didn't do it! In fact, I'd love it if
anyone tracing off of the imagery had to sign a legally binding declaration
saying they'd actually been to the place first ;-)
But maybe it fills some purpose I'm not aware of?
I'm also interested about the people doing this... are you all just
incredibly bored, or is there a goal here?

Any thoughts?

Dave
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