[Tagging] Housenumber interpolation with regularly skipped numbers

Richard Bullock rb357 at cantab.net
Sun Oct 11 12:53:22 BST 2009

> In an interpolation, the number of houses is unknown.

The wiki page for the Karlsruhe Schema on interpolation has said this since 
the day it was created;

"For missing house-numbers (e.g. missing "12") two ways need to be drawn 
(e.g. "1-11" and "13-25"). "

I.e. if you have the first house #1 and last house #25, but there is no #12, 
then you should have two interpolation ways - 1-11 and 13-25. Something 
similar would apply if you only had even numbers or odd numbers. That's how 
I've been using it and I thought others were. This makes it explicit exactly 
how many houses are present.
Interpolation allows editors to edit large quantities of address data 
without needing to add many hundreds of POIs - or indeed needing to take 
waypoints for every single building (yet). The wiki for the Karlsruhe Schema 
suggests that interpolation is intended as a temporary feature - with 
eventually house numbers being tagged explicitly as individual nodes or 
building outlines.

You still have to do the survey to find any missing numbers (or as is quite 
common here to find extra numbers i.e. those with A or B etc. suffixes which 
are quite common here) - but interpolation allows a huge speed up of the 
process of entering data and surveying, without actually losing much 
information (you lose the exact position of each building - which is not so 
important if buildings are roughly regularly spaced). Where there is a big 
gap between houses, I tend to use two separate interpolation ways.

You mention about commercial maps just interpolating between first and last; 
If you go to G**gle maps and type in a house number with street name which 
doesn't exist - it takes you to a location somewhere near the middle of the 
street. If you type in a house number on the same street that does exist, it 
takes you to the interpolated position of that house.

E.g. one I entered on OSM the other day; 8 Lindow Fold Drive

But there is no 18 or 20 Lindow Fold Drive (despite every other even number 
being present between 2 and 32)
Try typing 18 or 20 in and it just takes you to the street, not a specific 
part of the street.

(OSM location http://osm.org/go/eu15MCjuj--)

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