[OSM-newbies] coastline and mangrove forests

[Ævar Arnfjörð Bjarmason]

2009/3/19 doug brown <dougcb68 at hotmail.com>:
> I am working on mapping San Blas, Nayarit, Mexico
>
> http://www.openstreetmap.org/?lat=21.542&lon=-105.2876&zoom=14&layers=B000FTF
>
> and encountered an issue that I feel requires some discussion.
>
> San Blas is surrounded by extensive mangrove forests.  The original
> coastlines that were drawn, obviously using the Yahoo imagery as a source,
> has placed the coastlines on the landward side of these mangrove forests.
>
> My opinion is that this is inappropriate for two reasons.  1) I think of
> coastline as the boundary of the ocean--mangrove forests, though wet, are
> clearly not part of the ocean, and 2) anthropomorphically, the use of the
> mangroves is completely different than the use of the use of the
> ocean--mangroves are exploited on foot and the ocean requires boats.
>
> My opinion about the estuaries that penetrate the mangrove forests is less
> clear, though I tend toward classifying them as inland water features with
> the coastline boundary being placed at the  sandbars at their mouths.
>
> Is there any existing discussion related to this topic that somebody could
> point me to?  If not, how to proceed?

You should correct the coastline as you suggest, mangrove forests are
not part of the ocean but coastal wetland habitats. And the coastline
in question was not drawn by hand from Yahoo data but is rather the
result of the automated PGS import, which frequently messes up coastal
saline habitats (as they are often dark enough to be wrongly
classified as ocean).

Once you've fixed the coastline you can tag the mangrove forest with a
natural=wetland wetland=mangrove area:

http://wiki.openstreetmap.org/wiki/Tag:natural%3Dwetland

The estuaries should be tagged with waterway=river and waterway=riverbank areas:

http://wiki.openstreetmap.org/wiki/Tag:waterway%3Driver
http://wiki.openstreetmap.org/wiki/Tag:waterway%3Driverbank