[OSM-talk] Keeping imported data updated with source changes

[Wiktor Niesiobedzki]

2015-01-10 16:44 GMT+01:00 Jason Remillard <remillard.jason at gmail.com>:
>  Hi Wiktor,
>
> I don't think an address tag is needed or desirable.
>
> The best way of doing this is to compare versions of the official data
> (perhaps every 6 months), making a list of things that have changed so
> that they can be examined in OSM.

To compare only changes in the source, I need to know, what was
imported to OSM first. And without any reference in OSM, how do I
guess the baseline? I could just check what's new for last 6 months
(for example - previous half of calendar year), but then - we still
need some tooling to verify, if someone actually did it during this
time and present backlog for specific areas. We have very uneven
distribution of mappers between geographic areas.

And this way, I may fail to identify nodes, that were deleted in the
source (not all sources report deleted nodes).

>
> Of coarse the big issue is that the matching is not trivial. First
> devise a matching score combining of distance to address, and edit
> distance in the address name and number. These scores are the weights.
> Then use one of the weighted bipartite graph matching algorithm
> (augmented path) that works well on sparse data. If you keep the
> search radius down, the graph will be very sparse, so should be
> manageable. Using the match, you can get a list of nodes that have
> been moved, deleted, and edited in the official data set.

But how should I handle such real scenario:
- address is created in municipality
- mapper adds it on a map
- the script runs, sees a new address, finds a nearby address, but if
there are some difference (different street or something like that) -
should it update, or skip it? According to the rules so far, when I
have a change in source, I should update the OSM, but this might not
be the case here.

And - from algoritmic point of view it looks exactly the same as scenario:
- address is created in municipality
- address is imported to OSM
- street change in address by municipiality
- the script runs


Cheers,

Wiktor