[Tagging] Housenumber interpolation with regularlyskippednumbers

Randy Thomson rwtnospam-osm at yahoo.com
Sun Oct 11 06:12:42 BST 2009

Anthony wrote:

> I didn't say I don't know anything.  I said I don't know the number of
> houses.  The way interpolations work, everywhere except for OSM, is
> that you record the address of the first house on the block and the
> last house of the block (possibly on each side), and you assume that
> the houses in between have numbers in between, roughly evenly spaced.
> That's not exact, and if you have more information it's certainly
> better.  But it's good enough to allow routing software to get you to
> the right block, and approximately to the right section of the right
> block.
> I'm not saying it's wrong to give the extra detail, but I am saying
> it's wrong for data users to assume that an interpolation from 1-11
> necessarily has a 1, 3, 5, 7, 9, and 11.  Not that I can think of any
> reason a data user would make that assumption in the first place.

That is certainly one way to do it, and I grant that is the way most
commercial map companies do it. In fact they often interpolate for many
blocks at a time. I'm in the user group for a GPS system that uses
TeleAtlas data. You'd be surprised, well probably not, how many users
complain that "it doesn't even have my address in the right block!" My
understanding was that OSM was attempting to be something better than

If I know that a set of street addresses is numbered in a particular
way, wouldn't it be better to have the capability to tag it that way
than to only have the option to knowingly tag it incorrectly or to tag
each address individually? I thought the answer to that question was
obvious. Apparently it is far from that.

Regarding your question of how I'll get the data, it doesn't relate to
my issue. My issue is "I have this data that shows the houses skip
every other number. I want a way to correctly interpolate those
addresses rather than putting a node at each address."

I think you would be surprised at the number of OSM data users, and
certainly mappers, who make the assumption that the data is being
entered as accurately and completely as possible. Especially if they
read the various tag pages.

However, I'm beginning to wonder if we are arguing the same question.

I'm arguing for the capability to use interpolation to tag housenumbers
relatively accurately, at least not knowingly tagging them incorrectly,
using interpolation.

I think maybe that you are arguing that you personally should not be
required to map accurately if you don't feel its necessary to do so. I
say this because I haven't really heard an objection from you to having
the capability, only the objection to your having to use it. (Well,
maybe a slight suggestion that I shouldn't do it either.) And, if the
capability to do what I want to do is added to renders, routers, etc.,
I am certainly not saying that you should be required to use it. That
would be anti-OSM, or anti-anarchist or some other terrible anti that I
don't even want to think of. If that's the case then maybe we agree and
don't know it.

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