[OSM-talk] Zero tolerance on imports

john at jfeldredge.com john at jfeldredge.com
Sun Feb 20 01:44:36 GMT 2011

In Nashville, Tennessee, USA, where I live, most of the existing data came from the TIGER import (mapping done by census workers).  In the areas that I have checked, about 60% of the data appears to be correct; about 20% needs tweaking for issues such as one or two streets in a neighborhood being offset by 10 or 15 meters from their actual location, while the rest of the streets in the neighborhood are OK; and about 20% are either seriously obsolete (in some cases, by 30 years or more), or represent new construction.  In a few cases, the TIGER data reflects what was originally planned, as opposed to what was actually built (or not built).

-------Original Email-------
Subject :Re: [OSM-talk] Zero tolerance on imports
From  :mailto:a.errington at lancaster.ac.uk
Date  :Sat Feb 19 19:04:05 America/Chicago 2011

On Sun, 20 Feb 2011 09:40:03 Frederik Ramm wrote:
> Finally, all these warnings must sound hollow to someone who lives in a
> place where 90% of data around him is imported. You will have a hard
> time telling him that imports are bad.

I live in a place where 90% of the data is imported.  Imports are bad.  It's 
bad because I discover errors and start to think 'How many more errors must 
there be?'.  It's mainly bad for two reasons.  Firstly, the data is old, and 
there has been a significant road-building program going on here for a while.  
Secondly, things don't join up because the import processing didn't process 
road junctions properly, so routing doesn't work (until mappers go around and 
join them up).

IMHO imports should exist as 'ghost objects' or 'pencil lines'.  They should 
never render on Mapnik etc. and never be used for routing, but a mapper with 
local knowledge should be able to verify the objects and change them to a 
real object (i.e. 'ink them in').

Of course, if we had one million mappers here they could all take a quick look 
at their local area and fix the mistakes in a couple of days...

Best wishes,


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John F. Eldredge -- john at jfeldredge.com
"Reserve your right to think, for even to think wrongly
is better than not to think at all." -- Hypatia of Alexandria

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