Hi,
On 22.10.2012 18:45, Igor Brejc wrote:
What does "pre-processed or augmented" data really mean? OSM data has to
be preprocessed to get to the form suitable for rendering. Some examples
of preprocessing:
1. Importing it into PostGIS and flattening the geometries (like Mapnik
does it).
osm2pgsql does that, not Mapnik, and ODbL gives you the option of
specifying the algorithm that produces the data from the source instead
of handing out the data itself.
So in this case, while the osm2pgsql database is clearly a derived
database that falls under ODbL, when someone asks you for the data you
can say: "Get it from OSM, run it through osm2pgsql with the following
options, and you're done."
2. Generalizations: simplifications of roads, polygons etc. for a
certain map scale.
Same process - either you share the generalized data or you share the
algorithm that produces it. If, for example, you were to import with
ImpOSM which does generalisations when importing, that's all you'd have
to say.
3. Finding suitable label placements.
4. Extracting topology from the data (like multipolygon processing,
merging of polygons, road segments etc.).
5. Running other complex algorithms on the OSM data.
This preprocessing can be done "on-the" fly or (in case of Mapnik) as a
separate prerequisite step.
The boundary between what is done as a separate step, leading to a
derived database, and what is done on the fly as part of the rendering
process may sometimes be muddy but I guess in these situations they are
pretty clear.
Another interesting question is how easy the algorithm you specify must
be. It is clear that the algorithm cannot include "buy some Navteq data
and then do this", or "buy ArcGIS and then do that" - but what if the
algorithm includes "run this code, it will take 1000 days", or "make
sure your machine has at least 1 TB of RAM, then continue as follows...".
Bye
Frederik
--
Frederik Ramm ## eMail frede...@remote.org ## N49°00'09" E008°23'33"
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