[postgis-users] TIGER geocoder with Census 2009 shapefiles
Stephen Woodbridge
woodbri at swoodbridge.com
Tue Mar 2 10:33:57 PST 2010
Mark Vantzelfde wrote:
> Can anyone comment on the accuracy of the Tiger geocoder vs MapMarker?
I can't comment specifically on these, but in general I have done a lot
of geocoder analysis and I have found that the best way seems to be to
get a large list of addresses that are typical for your needs. The
typical for your needs, is the important part because address lists can
be notoriously bad in my experience. So having typical addresses of what
you will be feeding it are important to get reasonable measurements.
Large is in 20K range for quick checks and 100-250K records for a more
through test.
Then run this list to make a baseline and verify the results, either via
random samples, or whatever makes sense for your needs. Now you can run
this list against other geocoders and get stats.
One way to do this is to have each record already geocoded like:
address, city, state, postalcode, lat, long
When you use this record as input you can compare the distance of the
result to this location and use that as a measure of accuracy. Then just
compute some statistics on the results to access if the new geocoder is
better or worse. You can also slice and dice the results by state or
region, because I have seen that some areas have significantly more
problems than other area depending on the data set being used.
It is just as important to look at the failures as the successful
geocodes and to understand if a success is really that and why a given
address failed, bad input, bad data, algorithm limitation or bug, etc.
-Steve
> Thanks
> Mark
>
> On Tue, Mar 2, 2010 at 11:40 AM, Stephen Woodbridge
> <woodbri at swoodbridge.com <mailto:woodbri at swoodbridge.com>> wrote:
>
> 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> <mailto: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>>
> [mailto: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/>
> <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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> --
> Mark Vantzelfde
> NetMasters, Inc.
>
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