[Talk-ca] Address ranges

[Steve Singer]

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
> 
> 
>