Updating Roads in Chattanooga TN in OSM

Jan 8, 2017 | Chattanooga, Open Street Map, postgis

I’ve been attempting to get better with PostGIS. I’ve also been trying to take baby steps back into the world of OpenStreetMap. I’ve also been trying to take baby steps back into my City’s Open Data Initiative.

Why? I’ve been away for long enough – plus – never quit learning.

I’ve only so many hours in a day. To be honest with my attempts at getting back outdoors and doing things that interest me, I’ve more or less stopped a lot of side projects. With the weather currently being disagreeable to most things outdoors I’ve decided to start diving back into a few things I’ve left hanging.

The OpenStreetMap group here in town is a bit hit or miss. We have a high school that maps. We have a few people diving in here and there. There’s no coordination to the madness and I tried, as did a few of us, to coordinate some of it. I finally gave up. So I do a *few* things in OpenStreetMap here locally but not much.

I made a decision to:

  • Map as many Churches as I can (more on that later).
  • Fix the Roads

Fixing roads is a bit of a chore. I hate touching interstates because I don’t understand the relations involved. There’s probably some “OSM Roads” email list but I just don’t want to get that committed. I’m happier working by myself for a bit or in smaller groups. I’ve also never took a look at the road names in OSM – I’ve worried with alignment but never “names”.  About the time I was moving back into Chattanooga mom called, “They changed two road names in the neighborhood!”. I actually think road names had been changing for a while in the county as the County GIS department did their best to clean up confusing road names for 911 purposes. I *think* this data is then fed to the city or maybe the city is changing road names at the same time. Whatever the case – names are changing and it’s already fixed in Google Maps.

Chattanooga has an open data portal.  I’ve been randomly mucking around looking at data and found the Chattanooga city addresses. I also found that they’ve already been donated to the openaddresses project. I downloaded them and loaded them into PostGIS. There are 102761 points. Each has a street address. I grabbed the roads from OSM and the city boundary from the open data portal. Through  series of maneuvers in SQL that would horrify the more well educated – I actually compared the two and built some foreign keys and other things to make joins easier. Through that my favorite color scheme in the world – Red Green. Green is right as far as I can tell and Red isn’t.

What I did find:

  • my join was a bit sloppier than I wanted but overall I can pick out the problems between the Chattanooga’s address data and the OSM data.
  • I spent more time than I should have reading the FGDC Address standard – BUT – it helped (plus SQL examples).
  • There aren’t a lot of errors but enough. In some cases there was a completely new name applied by the city to a street. In many cases the road in misspelled in OSM (which is probably a holdover from the days of TIGER Data).  Some are from the high school. They are great at editing but not so much at cleaning up. I need to work on that.
  • The cities address data extends into the county by about 1000 feet. Which means when I clipped my roads I lost some data I need and will need to fill back in. Thanks to the power of scripts and me being anal retentive – not that big of a deal and I’ll deal with it as it becomes an issue.

Of course the big question is “Is the cities address data correct?”. As a GIS person I say Yes. As a guy that has worked in GIS for 25 years now I’ll say “probably because I’ve talked to no one over addressing”. So I’ve making a list and print it out and over the coarse of the next few months I’m going to inspect many of the things I’m seeing as wrong. There are three on the way to my parent’s house. I’ll probably even hassle the city/county a bit for information. I’d like to get them more involved if at all possible.

Why fix it? Why not. OSM is enough of a force that it should get fixed – BUT – as GIS people our attention is diverted by what the clients use. You never hear someone say “Well I was using OSM to find my way to the mall…..” it’s usually “Google It” or “what does Google/Waze/Something else say”. It’s not that hard to fix problems once you have a list.

Anyway – more on this as the months progress. This will most likely occur “as time permits”.

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