[Imports] NYC building + address import - to merge or not to merge?

Elliott Plack elliott.plack at gmail.com
Mon Oct 14 17:42:25 UTC 2013


I like keeping the address separate, since NYC GIS put in the work to give
the spatial locations of the addresses a meaning other than just the
centroid.

Here seems to be an example of where the imports have begun:
http://www.openstreetmap.org/#map=18/40.64105/-73.96687


On Mon, Oct 14, 2013 at 1:01 PM, Serge Wroclawski <emacsen at gmail.com> wrote:

> There's a bit of context missing from this conversation, so I want to
> fill people in on what happened, and then we can discuss the technical
> merits.
>
> Alex made his proposal (with my endorsement) before the import
> happened. Alex suggestebut then modified the data to this alternate
> way before the import event. So now we have both kinds of addresses in
> NYC. You can see some of the pre-import discussion at:
> https://github.com/osmlab/nycbuildings/issues/15
>
> We also have an import event to show what happens with users and the data.
>
> On Mon, Oct 14, 2013 at 12:35 PM, Alex Barth <alex at mapbox.com> wrote:
>
> > Now there's reason to revisit this decision: the data steward (Colin
> Reilly
> > from NYC GIS) told me that NYC GIS took great care to place addresses at
> > about where the entrance of the building sits.
>
> We have a tag "entrance", but when I suggested tagging the entraces as
> entrances,  Alex suggested that many of the points were not entrances,
> but centroids.
>
> If they're addresses, I say tag them as addresses. Then we can
> encourage mappers on the ground to refine the entrances to match
> ground truth, and also to add service entrances, etc.
>
> > This makes me think that there's value in not tossing the address
> location
> > information but keep it in all cases, even if there is only one address
> per
> > building.
> >
> > Here is a comparison of the two options. I'd like to discuss and decide
> at
> > tonight's imports hangout.
> >
> > ## Option 1: Merge addresses into buildings where possible
> >
> > In cases where there is one address point within a building polygon, we
> take
> > address attributes, assign it to the building polygon and toss the
> address
> > point.
> >
> > Pros:
> >
> > a) This is how a lot of buildings are done in OSM
> > b) Not regarding standing practice, merging addresses into buildings is
> an
> > exception from the generally applicable method of doing separate address
> > points.
> >
> > Cons:
> >
> > a) we lose data
>
> If we tag the entrances as entrances, as suggested on the issue 15, we
> lose no data.
>
> > b) makes it harder for NYC GIS to leverage OSM
>
> > ## Option 2: Always keep address points separate
> >
> > In this case we never merge addresses to building polygons, instead
> always
> > keep them as separate entities.
> >
> > Pros:
> >
> > a) this is the NYC GIS way, making it nicer for GIS folks to use OSM
> > b) this is the generally applicable method. No matter whether we have
> one or
> > multiple addresses you can expect to find a separate node carrying
> address
> > information.
> > c) retains useful information
> >
> > Cons:
> >
> > a) Diverges (but does not violate [1]) common OSM practice
>
> b) We see users mistagging addresses
>
> In NYC, at the import, I've seen users tagging the address points with
> building information, such as the type of building it is
> (building=residence).
>
> This confusion is probably going to continue, leading to more problems
> in OSM where the attributes of the building are placed off the
> building.
>
> c) We see multiple addresses
>
> In the NYC import, I've found multiple addresses in/near a building.
> This is from previous data, and needs cleanup. Multiple address points
> aren't wrong when there's a POI and a building, but without a
> building, it's confusing
>
> d) It adds an extra step to data consumers
>
> If you tag the building with an address, you can get the address of it
> by looking at it. And if you have a POI within the geometry of the
> building, you can get it by looking at the building container, if the
> node doesn't have it.
>
> With nodes as points, you have to look at the poi node, then look at
> the building, see that the building has no address, then look for a
> node
>
> If you tag the node as is done here, you have to look at the building,
> see it has no address data, then look for nodes within it, and see if
> they do.
>
> e) It adds no explicit value without entrance tag
>
> Tagging entrances as values with an address is useful. Not only does
> it have value on its own, but you can even add a tag to indicate that
> the entrance is off a certain street (we don't have a tag for this
> now, but it wouldn't be hard to add).
>
> But right now, we don't have the entrance tag, so we lose the benefits of
> both.
>
>
> I think both ways are suboptimal, but they both bear consideration.
>
> - Serge
>
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>



-- 
Elliott Plack
http://about.me/elliottp
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