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I'm looking into geocoding U.S. locations without using Google or Bing. I found a service that geocodes according to the Tiger Census data of 2013. I have little knowledge about this Census and didn't get extremely far poking it around. When I use the api of the service that geolocates based on that census, I get several possibilities for the same full address in some cases. E.g. I got that one address in San Francisco is related to 3 different zip codes (that address, randomly picked, is "1354 Market St, San Francisco, CA")

Is that at all possible in the U.S. zip code system?

Do you think the Tiger Census data of 2013, is a very good source for geocoding?

Thanks, Matan

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    Geocoders vary in accuracy and data varies widely in urban and rural locations. Paid for services do provide better verification and accuracy can save headaches later... – Mapperz Sep 16 '13 at 16:56
  • Any paid service recommendations @Mapperz ? – Matan Sep 17 '13 at 21:48
  • tomtom geocoder.tomtom.com/app/view/index – Mapperz Sep 18 '13 at 1:25
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As far as I know, the TIGER data has address ranges only. Hypothetically, if there is North Market St and South Market St, there could be address ranges that include 1354, even if there is not an actual building with that number.

  • @mkennnedy, not sure how this comes to answer my question, or you may assume I have knowledge about U.S. addressing that I don't :( but thanks for trying! – Matan Sep 16 '13 at 17:28
  • Informative comment anyway. – Matan Sep 17 '13 at 21:52
  • Here's an example, do a Google search for 6912 church st, Highland, CA. If you look, there are no houses or buildings there. Google is extrapolating the location based on the from/to addresses listed for the block. Highland (which has one zip code) also has a Church Ave and Google will extrapolate a 6912 address on that street too. – mkennedy Sep 17 '13 at 22:10
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One of the problems here is that a city can have more than one of the exact same street address (e.g. 1354 Market St, San Francisco, CA). On the flip side, all addresses within a zip code must be unique.

I know that TIGER shapefiles have information on zip codes in the edges shapefiles (which also have address ranges). I also know that TIGER is based on the MAF, which is a database of addresses updated by the USPS. I've also seen some of the same geocoding errors with TIGER that I've seen with google maps (an apartment with a street number can be extremely inaccurate because geocoders assume it is along the street instead of inside a complex).

  • are you saying there are really several places in San Francisco that bear this address, each one in a different zip code? – Matan Sep 17 '13 at 21:50

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