[postgis-users] TIGER geocoder with Census 2009 shapefiles

Stephen Woodbridge woodbri at swoodbridge.com
Tue Mar 2 08:40:55 PST 2010 

Hi Kevin,

I have worked with the Tiger data for about 10 years now. The recent 
improvements in tiger are really great to see, but not without their own 
set of issues. Tiger has a lot of known limitations based on the rules, 
regs and requirements of the US Census. The recent work has georectified 
the street data and added lots of new streets based on digitizing 
high-res satellite imagery. but that does not let you read the street 
names so they are added after the fact. There are a lot of street 
segments that do not have names. We can only hope that these will be 
added over time. Because of non-disclosure, address ranges can be weird 
also. Many small streets have address ranges 1-100 encoded on them, in 
spite of the fact that the real address ranges only run from 1-20. This 
has the effect of skewing all the locations to the front end of the street.

Because language is ambiguous and typos and sounds-like errors, fuzzy 
searching is employed. Most geocoders do some form of fuzzy searching so 
you often run into the Main St vs Main Ln issue or you find W Main St 
when you are search for E Main St.

When a geocoder says "Found it!", you need to be prepared to say Found 
What? or be tolerant to mis-geocodes. I like geocoders the score the 
results and return them in ranked order.

In general a geocoder can never be better than its data and can in fact 
be much worse than its data. Fuzzy searching lets you find possible 
candidates in the data that might not have been encoded correctly in 
either the input address or the data address, but with the uncertainty 
that this is the actual location wanted or not.

You might also want to look at PAGC Geocoder. It is written in C and 
uses some statistical matching techniques which are very good, There are 
some change in one of the branches that let you load all the Tiger data 
for the US.

http://www.pagcgeo.org/


-Steve


Kevin Galligan wrote:
> I actually bought an early access copy of the book.  I work in linux and 
> have been playing around with different geocoders and the tiger files. 
>  Most recently with a ruby geocoder, for no other reason than I'm trying 
> to find one that is fairly complete and functional.
> 
> Any idea how "production quality" this particular one is?  If its fairly 
> high, I'll probably put some time in to get it working on linux.  I have 
> the full 2009 tiger dataset on an EC2 block drive, waiting to import 
> into a different database.
> 
> Right now I'm using zip+4 data to get a rough geocode, which is good 
> enough for what we're doing, but it only gets 92% of our non-PO Box 
> data.  From my experience with the tiger data, it only adds a couple 
> percent at most above that, but the geocoders I've used have been pretty 
> hacky, so its possible that was the issue.  Also, some of them seem to 
> not be concerned with stuff like matching "Main St" when you're looking 
> for "Main Ln", which is pretty terrible.
> 
> On the plus side, if there is major work going on with this geocoder (or 
> any tiger geocoder), I have a huge national data volume that will help 
> stress test the system.
> 
> Recently I've been toying with USC's free geocoder project.  In some 
> areas it actually gets about half of the data I previously could not, 
> which is impressive.
> 
> The really frustrating thing is, in general, the first 90% is 
> cheap/free.  The next 3-4% is marginally expensive.  The rest is really 
> pricey.
> 
> Is there any idea how complete the tiger data is, and why there is this 
> apparent lack of data in there?  I find it strange.  Some streets are 
> just missing.  Stuff like that.
> 
> Rambling.  Anyway, will take a look later.  Thoughts on the quality of 
> the geocoder appreciated.
> 
> -Kevin
> 
> On Fri, Feb 26, 2010 at 11:52 PM, Paragon Corporation <lr at pcorp.us 
> <mailto:lr at pcorp.us>> wrote:
> 
>     David,
> 
>     As a matter of fact we've been working on that for chapter 10 of our
>     upcoming book and think we have it all working.  As a part of the
>     example
>     generation process for our chapter 10, we had to come up with a way
>     to load
>     the tables that works on both windows and Linux.  Unfortunately we
>     haven't
>     had a chance to test the Linux loading approach, but is pretty much a
>     parallel of the windows approach.
> 
>     To do so we started out with Steve's code, added some additional
>     skeleton
>     tables and a database function that generates a command line script
>     for the
>     respective OS.  Hopefully it all makes sense from the readme file we
>     have
>     packaged.
> 
>     We also changed one of the functions because there was an error in
>     it and
>     revised slightly to work with Tiger 2009 data.  You can dowload our
>     slightly
>     hacked version of Steve's code from our chapter 10 page.
> 
>     Steve -- if you are listening we are hoping to remerge your version
>     with our
>     loader part and bring back into the PostGIS distribution as part of
>     PostGIS
>     1.5.1 or 2.0 release.
> 
>     http://www.postgis.us/chapter_10
> 
> 
>     Leo and Regina
>     http://www.postgis.us/
> 
> 
>     -----Original Message-----
>     From: postgis-users-bounces at postgis.refractions.net
>     <mailto:postgis-users-bounces at postgis.refractions.net>
>     [mailto:postgis-users-bounces at postgis.refractions.net
>     <mailto:postgis-users-bounces at postgis.refractions.net>] On Behalf Of
>     Dave
>     Fuhry
>     Sent: Friday, February 26, 2010 3:04 PM
>     To: PostGIS Users Discussion
>     Subject: [postgis-users] TIGER geocoder with Census 2009 shapefiles
> 
>     I'm trying to set up the TIGER geocoder from
>     http://www.snowman.net/git/tiger_geocoder/ which is new and aims to work
>     with the new TIGER shapefiles.  I'm trying with the 2009 shapefiles from
>     www2.census.gov/geo/tiger/TIGER2009/
>     <http://www2.census.gov/geo/tiger/TIGER2009/>.
> 
>     I'm not sure how to create the roads_local table (derived closely from
>     completechain in the old version).  A join between edges and addr?
> 
>     Wondering if anyone can offer any direction.  A relevant ticket is
>     http://trac.osgeo.org/postgis/ticket/135.  The out-of-date file
>     which used
>     to create the roads_local table is tables/roads_local.sql, in the above
>     repository.
> 
>     -Dave
> 
>                                           Table "tiger.edges"
>       Column   |          Type          |                         Modifiers
>     ------------+------------------------+----------------------------------
>     ------------+------------------------+--------------------------
>      gid        | integer                | not null default
>     nextval('public.edges_gid_seq'::regclass)
>      statefp    | character varying(2)   |
>      countyfp   | character varying(3)   |
>      tlid       | bigint                 |
>      tfidl      | bigint                 |
>      tfidr      | bigint                 |
>      mtfcc      | character varying(5)   |
>      fullname   | character varying(100) |
>      smid       | character varying(22)  |
>      lfromadd   | character varying(12)  |
>      ltoadd     | character varying(12)  |
>      rfromadd   | character varying(12)  |
>      rtoadd     | character varying(12)  |
>      zipl       | character varying(5)   |
>      zipr       | character varying(5)   |
>      featcat    | character varying(1)   |
>      hydroflg   | character varying(1)   |
>      railflg    | character varying(1)   |
>      roadflg    | character varying(1)   |
>      olfflg     | character varying(1)   |
>      passflg    | character varying(1)   |
>      divroad    | character varying(1)   |
>      exttyp     | character varying(1)   |
>      ttyp       | character varying(1)   |
>      deckedroad | character varying(1)   |
>      artpath    | character varying(1)   |
>      persist    | character varying(1)   |
>      gcseflg    | character varying(1)   |
>      offsetl    | character varying(1)   |
>      offsetr    | character varying(1)   |
>      tnidf      | bigint                 |
>      tnidt      | bigint                 |
>      the_geom   | public.geometry        |
> 
> 
>                                          Table "tiger.addr"
>      Column   |         Type          |                         Modifiers
>     -----------+-----------------------+------------------------------------
>     -----------+-----------------------+-----------------------
>      gid       | integer               | not null default
>     nextval('public.addr_gid_seq'::regclass)
>      tlid      | bigint                |
>      fromhn    | character varying(12) |
>      tohn      | character varying(12) |
>      side      | character varying(1)  |
>      zip       | character varying(5)  |
>      plus4     | character varying(4)  |
>      fromtyp   | character varying(1)  |
>      totyp     | character varying(1)  |
>      fromarmid | integer               |
>      toarmid   | integer               |
>      arid      | character varying(22) |
>      mtfcc     | character varying(5)  |
>      statefp   | character varying(2)  | not null
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