[Talk-ca] Address ranges
Steve Singer
ssinger_pg at sympatico.ca
Sun Mar 22 16:02:54 GMT 2009
On Sat, 21 Mar 2009, Richard Weait wrote:
>
> My understanding of Karlsruhe schema is imperfect, but I believe that
> interpolated addresses require a way rather than two nodes? If so, and
> if we address a "curvy" block, then the address-interpolation-way may
> cross the block twice or more. I don't know if that is fatal to
> addressing, but it would look suboptimal. Given this situation, is it
> possible to add the interpolated way by:
>
> duplicating the road / block
> clip four meters from each end
> offset from the road by two meters
> apply address interpolation data as appropriate.
Having the interpolation way follow the shape of the road seems to have
precedent. See
http://www.openstreetmap.org/?lat=49.028355&lon=8.361898&zoom=18&layers=B000FTTT
> This does triple the db size (node and way count) for each road with
> address info. But it's just Canadian road data, it's not like we're
> tripling the size of the US data....
Tripling the number of nodes+ways in the DB isn't something we want to do
lightly. The Canadian DB will be a lot larger once all of the NRN roads are
imported, tripling that number might mean a difference of hundreds of
megabytes. It also isn't just Canada, recent TIGER updates have included
address information (I suspect block face based).
If we know the coordinates of a house/building I don't have a problem with
creating a separate node for it. If all we are doing is offsetting the road
geometry by 4 meters I'm not convinced of the value of storing all those fake
nodes the renders can apply a 4 meter offset just as easily as the import
scripts can and we don't triple the database size.
Another thing to consider is what happens when some adjusts/alters the road. If
they are doing it based on GPS trace from driving the road the won't have a
direct basis for shifting the address nodes, but if the address nodes are
derived solely from the road then they probably should move as well.
Part of me prefers a scheme that adds address tags directly to the nodes that
make up the road.
The downside of that is
* It isn't karlsruhe (I don't see a lot of objection to karlsruhe and its being
used; that kind of is like consensus)
* The renders might not support rendering the house numbers to the to the side
of the road
* An import script that adds tags to existing nodes is harder to write than one
that creates new nodes
* Intersection nodes would have multiple addresses
But it would mean a lot fewer nodes+ways in the database.
>
> Wonderful news that you are looking at this.
I haven't yet decided what I'll work on next, it might be this, or it might be
trying to match up roadnames from statscan.
>
> Best regards,
> Richard
>
>
>
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