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 <l...@pcorp.us
<mailto:l...@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-boun...@postgis.refractions.net
<mailto:postgis-users-boun...@postgis.refractions.net>
[mailto:postgis-users-boun...@postgis.refractions.net
<mailto:postgis-users-boun...@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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