[Imports] Cleaning up an old import

[David Schneider]

Hi List!

I searched an address in the eastern parts of Cape Town, and I was
suprised that nomatim didn't report it as residential. I checked the
data, and found that vast parts of Cape Town's residential areas are
made up from unclassified roads instead of residential!
>From the metadata, this seems to be the result of an import some
years ago.

I feel this should be fixed. I don't know if this can be done auto-
matically, or a manual community effort is required. My proposal would
be to select "user=Firefishy  maxspeed=60 highway=unclassified" in JOSM
and change all to residential. Now, a few roads that should be
unclassified will be residential, but the ratio seems to be 99% wrong
now vs. 1% wrong after this change. Of course, roads that have been
touched since the import will missed by this, but there will be an
improvement for sure.

Another thing that I noticed is that the roads are massively over-noded.
http://www.openstreetmap.org/browse/way/32216567 demonstrates both. It
should be residential, and if you compare to aerial images, the straight
section is represented with 6 nodes, 3 of them within 5m. I presume this
comes from calculating the centerline of a full shape, as the road widens
towards the east, where the many nodes are.
(I would map that road with 3 nodes, with the two on the eastern sides
interfacing between the NW-SE road, going away at 90° from there. I.e.
making a slight right turn when going east. The data is just the opposite,
going to the left, which gives an odd angle that is not there in reality
when you come from the south and turn east.)

I downloaded a section of Cape Town, exported to GPX and used gpsbabel
to apply the Douglas-Pecker algorithm with 1m max deviation. The number
of nodes went down to less than half! So maybe removing some excess nodes
could be performed during any update.

Best,
David