[OSM-dev] TIGER field report, Columbia, Maryland

Alex Mauer hawke at hawkesnest.net
Sat Sep 1 05:37:11 BST 2007

Tom Permutt wrote:
> Dave has kindly uploaded Howard County, Maryland. I've had Tiles at Home
> render one tile that I had already partly mapped. You can search for
> zipcode 21044 if you'd like to see it. Here's what I see:
> We'll want some discussion of guidelines for mapping with TIGER data. If
> it's wrong, do we delete it? 

I would certainly say "yes" to this.  That is, if TIGER has a route
which doesn't exist in real life, it should be deleted.

Is it significantly better to try to move
> it to where the street really is? What about if it's right? We won't
> want two versions of the same way, or will we? Which one do we prefer?

I would expect that we prefer the more accurate one, and delete the other.

My current method (since I'm going to be doing the upload for my own
county -- which reminds me, Dave, can you make sure to skip Portage
County, WI on the auto-uploads?  And can you remember to do so in 9
months to a year or so when it gets that far along?) ... is to load the
.osm file as a layer in JOSM, download the existing OSM data as a new
layer, and delete from the TIGER layer where I have my own information.

> TIGER may have a lot of tags, but only some of them may be right. Is
> this better or worse than a verified name and class and nothing more?
> What about road classes? 

Tiger really doesn't have much in the way of tags, and much of what
there is, is inaccurate.  Ordinary residential roads tagged such that
they translate to "service", service-level roads missing entirely, roads
that don't exist and have no evidence of ever existing, that sort of thing.

Tiger pretty much contains the road names, the same broken down into
components (W, Foo, Ln as three tags), and the class (CFCC) which is
very very often wrong.

The only thing TIGER contains beyond the name and class is the postal
code for the area the street is in, whether a road is separated/divided,
and whether it's an underpass (the exact opposite of how OSM does it
with "bridges" -- this is translated to layer=-1 for OSM purposes, which
isn't the best either and will probably end up having to be removed).

TIGER and I disagree about MD 108. Will the
> TIGER classification become the default standard in the US, or should we
> try to apply the existing guidelines (which need better adaptation to US
> English, but that's another issue)?

I certainly hope that the TIGER classification does not become the
standard for the US, because as inadequate as the OSM guidelines are for
describing roads, the TIGER ones are even worse (though in different
ways; they did get some stuff right that we didn't).

> Kudos to Dave and everyone else who has worked to make this import possible.


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