[OSM-talk] Coastline errors now updated daily

[Martijn van Oosterhout]

On Nov 22, 2007 2:53 PM, Robert (Jamie) Munro <rjmunro at arjam.net> wrote:
> The problem is that if there is a small island that is correct except
> that it goes clockwise instead of anti-clockwise, then AFAICS, it will
> be rendered blue on blue, i.e. invisible. I think I have found a couple
> because they had incorrect costlines nearby, and I downloaded them together.

Whoops. I do have some code to make lakes blue but I thought it wasn't
working, but evidently I was looking in the wrong place :) Actually,
it can't possibly work so Mapnik must be eliminating negative areas by
itself. Or not. I'll try to work it out...

> If the algorithm could make visible where this has happened somehow,
> that would be a great help. Possibly if you made the sea a
> semi-transparent dark blue, rather than a light blue, that might do the
> trick - water on top of water would show a darker shade. Land on land
> may be harder.

I have considered making the borders stronger, but yes, making lakes a
different colour would be a good idea.

> If you can work out an algorithm to mark those errors with a coloured
> spot, so that you can see it even at low zoom levels, that would be even
> better. Once they are visible, they are easy to fix in JOSM, and you can
> verify that you are fixing the right thing by comparing with Landsat
> imagery.

That would basically be a negative area (lake) that is not surrounded
by land. Tricky, but not impossible... I'll see if I can work
something out.

Have a nice day,
-- 
Martijn van Oosterhout <kleptog at gmail.com> http://svana.org/kleptog/