[OSM-newbies] mapping islands of a salt flat

[Craig Wallace]

On 24/11/2011 15:33, Alexandros Papadopoulos wrote:
> Hello.
>
> I am mapping the islands of the Salar de Uyuni
> (http://osm.org/go/NK_7Jv--) as I found it particularly annoying they
> were not on the map when I needed this information.
>
> The one island that *was* already mapped
> (http://www.openstreetmap.org/browse/way/43540410) was tagged with
> natural=land which seems to be deprecated.
>
> For this case (a salt flat), I have been using natural=coastline and
> place=island/islet. Is this OK?

No - islands within the sea should be tagged with natural=coastline, but 
not islands within inland water, eg lakes/ponds/rivers.
That Salar de Uyuni is tagged as natural=water, so it counts as inland 
water, and is equivalent to a lake or pond.

Islands in inland water need to mapped with multipolygon relations. ie 
map the island as an area, and add it to a multipolygon relation with 
role "inner", and add the outline of the lake to the relation with role 
"outer".
I see that Isla Incahuasi is already mapped with a multipolygon 
relation, so you can add all of the other islands to the same relation, 
with role inner for each.

There is no need to tag the islands with natural=land. It is more useful 
to tag what is actually there. eg if the island is covered with trees 
then tag it with natural=wood, or if its a beach tag it as natural=beach 
etc.

> And is it still true that it may take months for the changes in
> coastline to render on the map and thus the newly mapped islands to
> appear?

Yes, coastline can take months to update on Mapnik. But this does not 
apply to inland water - it should update more or less immediately.

Craig