[OSM-dev] Getting POI nodes deleted by user

[Michael Reichert]

Hi Michał,

Am 12.12.2017 um 01:11 schrieb Michał Brzozowski:
> Hi all, so I have a problem with user rowers2 who has been tracing
> buildings (with Tracer2) quite carelessly. After doing this (which he does
> in quite high volume) he then merges address nodes with building outlines.
> E.g. https://nrenner.github.io/achavi/?changeset=53993885
> JOSM has an option to merge (by copying tags and deleting the node) address
> nodes into building outlines. However, it can also merge POI whenever they
> have address tags, which isn't always appropriate, e.g. for ATMs or
> anything that doesn't occupy the whole building (quite easy to tell by
> common sense, but not really automatically).
> 
> I stumbled into this ATM shenanigans purely by chance in PostGIS when
> searching for nodes inside areas which both have same amenity value. But
> this pertains also to other POI like tourism=information.
> 
> How can I, having a full history dump for an area, find all POI nodes
> (having shop/amenity/office...) that were deleted by user rowers2?
> 
> Or, which DB schema can deal with history reasonably?

You don't need a database, just a regional extract of the full history
dump. You can download full history extracts from Geofabrik Downloads
(history extracts are updated weekly).

You can process them using the Osmium C++ library or Pyosmium. These
files are ordered by type, ID and version. If you want to use C++, write
a handler class (derived from osmium::handler::Handler). Osmium will
call the methods node(), way(), relation() etc. for each
node/way/relation while reading the input file. If
osmium::OSMObject::deleted() returns true for an OSM object, it is a
deleted version.

You could start with
https://github.com/osmcode/libosmium/blob/master/examples/osmium_count.cpp
as a base. You might also have a look at the Osmium Manual at
http://osmcode.org/libosmium/manual.html

Using the Python bindings might be easier to start but probably slower
to process.
http://docs.osmcode.org/pyosmium/latest/intro.html#reading-osm-data

Best regards

Michael

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