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I want to visualize OpenSeaMap data on an Android device using Mapsforge. Since I need to do this in a disconnected manner (think boat out to sea) I need to generate a .map file using the Mapsforge Osmosis plugin, however to be able to do that I need a .osm file of the OpenSeaMap data.

Can anyone point to where I might find one or some other way to proceed?

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There is already and Android SeaMap App - not saying you shouldn't create your own app - but worth looking at. – Mapperz Jun 13 '12 at 17:00
That app does look nice, but it's online only; not much use when you're off-shore :) – MerseyViking Jun 13 '12 at 21:12
Have a look at Oruxmaps or Oruxmaps Blue for android. – user40503 Nov 12 '14 at 16:27
up vote 4 down vote accepted

Looking at the main OSM website, all the data you need is there, but isn't rendered in any of the standard styles. The tag you are looking for is seamark.

For instance, zooming in on a part of the Solent reveals nothing. But if you choose Edit|Browse (you'll need an OSM login), a few spots show up in the water. Clicking on one of these gives us the goodies.

Downloading the data for this area as OSM XML, I can find data such as this:

<node id="672436827" lat="50.8070813" lon="-1.2841124" user="malcolmh" uid="128186" visible="true" version="11" changeset="9107813" timestamp="2011-08-23T21:22:36Z">
  <tag k="seamark:buoy_cardinal:category" v="north"/>
  <tag k="seamark:buoy_cardinal:colour" v="black;yellow"/>
  <tag k="seamark:buoy_cardinal:colour_pattern" v="horizontal"/>
  <tag k="seamark:buoy_cardinal:shape" v="pillar"/>
  <tag k="seamark:light:character" v="VQ"/>
  <tag k="seamark:light:colour" v="white"/>
  <tag k="seamark:name" v="Calshot"/>
  <tag k="seamark:topmark:colour" v="black"/>
  <tag k="seamark:topmark:shape" v="2 cones up"/>
  <tag k="seamark:type" v="buoy_cardinal"/>

Knowing this, you can download either one of the country, continental, or world datasets, and filter out just nodes with at least one seamark tag.

The biggest issue is one of styling; OpenSeaMap has a bunch of different symbols that are extra to the standard OSM lot, but I'm sure they're all available with a bit of asking around, although I'm sure Ian that you're capable of creating your own!

share|improve this answer
If you don't have a OSM login - go to Edit on… and click 'Browse Map Data' reveals the 'goodies' points info – Mapperz Jun 13 '12 at 16:56
I stand corrected! For some reason it didn't let me browse until I had logged in; maybe I wasn't zoomed in far enough... – MerseyViking Jun 13 '12 at 17:06
*recommend all GISse users to have a OSM login... – Mapperz Jun 13 '12 at 17:10
thanks - I should have thought to look in the data file :-) – iant Jun 14 '12 at 7:42
:) I'd be interested in what you come up with, if you're able to post the data somewhere. – MerseyViking Jun 14 '12 at 9:14

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