Where does Open-Streetmap forest data come from?

Question

If you open this url

http://www.openstreetmap.org/?mlat=50.6524658203125&mlon=9.4482421875&zoom=13

you are in a forest in germany. I downloaded the complete Open-Streetmap Data for Germany. I can find the waynodes for the tracks in this area... But not for the forest itself

Cna anyone help? Which way (id) defines the forest under the marker?

Or is it just the Background image for areas where's nothing defined?

Answer 1

You will not find the forest in the ways list because it is build as a multipolygon relation:

http://www.openstreetmap.org/relation/403306

Full text of the xml:

  <relation id='403306' timestamp='2012-01-17T23:33:35Z' uid='302852' user='be-ju' visible='true' version='26' changeset='10423448'>
    <member type='way' ref='132144354' role='outer' />
    <member type='way' ref='145307496' role='outer' />
    <member type='way' ref='145307467' role='outer' />
    <member type='way' ref='132144347' role='outer' />
    <member type='way' ref='132144358' role='outer' />
    <member type='way' ref='30605404' role='inner' />
    <member type='way' ref='31776954' role='inner' />
    <member type='way' ref='34962555' role='inner' />
    <member type='way' ref='45200953' role='inner' />
    <member type='way' ref='45200956' role='inner' />
    <member type='way' ref='47189443' role='inner' />
    <member type='way' ref='49748068' role='inner' />
    <member type='way' ref='49753651' role='inner' />
    <member type='way' ref='52704700' role='inner' />
    <member type='way' ref='52704705' role='inner' />
    <member type='way' ref='52704706' role='inner' />
    <member type='way' ref='55638793' role='inner' />
    <member type='way' ref='55741659' role='inner' />
    <member type='way' ref='55741754' role='inner' />
    <member type='way' ref='55782868' role='inner' />
    <member type='way' ref='59273778' role='inner' />
    <member type='way' ref='60172815' role='inner' />
    <member type='way' ref='60173689' role='inner' />
    <member type='way' ref='60173735' role='inner' />
    <member type='way' ref='70606150' role='inner' />
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    <member type='way' ref='72403561' role='inner' />
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    <member type='way' ref='91066302' role='inner' />
    <member type='way' ref='91321239' role='inner' />
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    <member type='way' ref='91512919' role='inner' />
    <member type='way' ref='91512920' role='inner' />
    <member type='way' ref='91512921' role='inner' />
    <member type='way' ref='91514545' role='inner' />
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    <member type='way' ref='91517921' role='inner' />
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    <member type='way' ref='91517935' role='inner' />
    <member type='way' ref='91518210' role='inner' />
    <member type='way' ref='91518211' role='inner' />
    <member type='way' ref='91577434' role='inner' />
    <member type='way' ref='91577435' role='inner' />
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    <member type='way' ref='91577448' role='inner' />
    <member type='way' ref='91577453' role='inner' />
    <member type='way' ref='91577458' role='inner' />
    <member type='way' ref='91577484' role='inner' />
    <member type='way' ref='91577505' role='inner' />
    <member type='way' ref='91579362' role='inner' />
    <member type='way' ref='91579421' role='inner' />
    <member type='way' ref='91579429' role='inner' />
    <member type='way' ref='91579435' role='inner' />
    <member type='way' ref='91579437' role='inner' />
    <member type='way' ref='93218137' role='inner' />
    <member type='way' ref='91072692' role='inner' />
    <member type='way' ref='91072698' role='inner' />
    <tag k='landuse' v='forest' />
    <tag k='note' v='c' />
    <tag k='type' v='multipolygon' />
  </relation>

If you have a local Postgis database filled with osm2pgsql you will find it in the planet_osm_polygon table with osm_id=-403306.

Most OSM importers still do not handle multipolygon relations correctly. If you need the way nodes, you have to download all ways that are part of the relation, then all nodes of those ways.

The members with role outer form one or several outer rings. You can not rely on the order in the file; the last node of the first member does not have to be the first node of the second. Same goes for the inner members.

As a consequence, you have to re-build the complete import logic of osm2pgsql. It is at least open source: https://github.com/openstreetmap/osm2pgsql

As a reference, you can take the OSM editor JOSM, and download a small part of the area of your interest.

Answer 2

This should be a query in the land use layer.

Run this query.

landuse = forest

and this covers coniferous (pine forest) / deciduous (deciduous forest) / mixed (mixed forest)

This is the info

http://wiki.openstreetmap.org/wiki/DE:Tag:landuse%3Dforest

http://wiki.openstreetmap.org/wiki/Key:landuse