[Imports] Starting Szczecin building outlines import (similar to French cadaste?)

andrzej zaborowski balrogg at gmail.com
Mon Mar 1 00:51:25 GMT 2010


I have performed a test import of a fragment of auto-traced building
outlines data for Szczecin, Poland and am looking for comments before
continuing with the rest of the city and perhaps other cities,
http://osm.org/go/0NgiAGiak--.  This contains addresses, heights (in
storeys count) and primary usage for each building.  I made an analogy
to French cadastre because this data is based on the city's website
running a map server that only provides raster images and is
auto-traced using a program, I'm not sure if this has been done before
but the result is similar to the manual tracing.

The full story:
In Wroclaw, Poland user "lms" asked the city administration if he
could use their 8cm aerial imagery for tracing map features for OSM to
which the city responded that he was permitted to use all of their
website, which also has about 10 other data layers accessible through
the web interface.  With lots of hard work he has traced many
buildings in his district with similar tools and similar results to
the French cadastre users in OSM.  Later user "antblant" obtained a
similar permit with regards to the Szczecin city's GIS website
(gis.um.szczecin.pl).  Since both websites let you zoom in as much as
you like on the data layers, you can in theory reproduce the full
vector layer, either manually or using some smart algorithm.  I have
asked the mappers to also ask the city councils if they allowed
automatic tracing of the features from their data layers and so far
the Szczecin point of contact has replied that they had nothing
against automatic tracing and indeed were interested in knowing how
this worked.

I'm using a modified potrace (subproject of Inkscape I think?) as the
"brain" of a python script that later spends 10 times longer than
potrace in fixing the result of the tracing to get usable quality and
I'm quite happy with the results now.  It still requires manual fixes
here and there, but there's some space for improvement in the script
still.  The housenumbers and heights are obtained from different

I have also asked my city's (Warsaw) "geodesy and cadastre bureau" the
same question about using their website but they're much less willing
to allow any use under any free license and I have heard at least two
different answers so far, maybe that's because I'm talking to a
contact person there who is not a lawyer and has to go and ask their
lawyer about every detail and I have even heard complaints from him
about the lawyer guy's attitude and how it isn't easy to catch him at
work much less ask him something.  One thing he made clear is that
there's some law that prevents the cities in Poland from releasing the
actual vector data to anyone under any license allowing redistribution
or commercial use, and even for private use the access to the building
outlines for all of Warsaw for example costs about EUR 75000 and this
is also fixed by that law... :(


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