Hi,
I think an automatic fix of the problem is possible, however it would be
a good idea to try and find out what the root cause of the problem is -
bad software, bad imports, bad instructions?
To get an idea of how big the issue is, I did this on a standard
rendering database:
create table buildings as (select way,osm_id from planet_osm_polygon
where building is not null)
select a.osm_id, b.osm_id into duplicates from buildings a, buildings b
where a.osm_id < b.osm_id and a.way ~= b.way and st_equals(a.way,b.way);
This took a few days - probably it could have been done more efficiently
- and resulted in a list of about 70k buldings world-wide that are exact
duplicates (geoetry-wise) of other buildings. The list is here:
http://www.remote.org/frederik/tmp/duplicatebuildings.csv
Some buildings are in OSM three or four times (contained i nthe above in
the form of "a is duplicate of b, b is duplicate of c") but I've
extracted them in extra files:
http://www.remote.org/frederik/tmp/triplcatebuildings.csv and
http://www.remote.org/frederik/tmp/quadruplicatebuildings.csv)
I don't have the time to analyse the situation in more detail at present
so if anyone wants to take the above lists as a basis for deeper analysis...
Cheers
Frederik
--
Frederik Ramm ## eMail frede...@remote.org ## N49°00'09" E008°23'33"
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