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Under GNU General Public License
2012-05-24 05:04 @38.107.179.238 Crawled by CCBot/1.0 (+http://www.commoncrawl.org/bot.html)
US(3pm) User Contributed Perl Documentation US(3pm)
NAME
Geo::Coder::US - Geocode (estimate latitude and longitude for) any US address
SYNOPSIS
use Geo::Coder::US;
Geo::Coder::US->set_db( "geocoder.db" );
my @matches = Geo::Coder::US->geocode(
"1600 Pennsylvania Ave., Washington, DC" );
my @matches = Geo::Coder::US->geocode(
"42nd & Broadway New York NY" )
my ($ora) = Geo::Coder::US->geocode(
"1005 Gravenstein Hwy N, 95472" );
print "O'Reilly is located at $ora->{lat} degrees north, "
"$ora->{long} degrees east.\n";
DESCRIPTION
Geo::Coder::US provides a complete facility for geocoding US addresses, that is,
estimating the latitude and longitude of any street address or intersection in the United
States, using the TIGER/Line data set from the US Census Bureau. Geo::Coder::US uses
Geo::TigerLine to parse this data, and DB_File to store a highly compressed distillation
of it, and Geo::StreetAddress::US to parse addresses into normalized components suitable
for looking up in its database.
You can find a live demo of this code at <http://geocoder.us/>. The demo.cgi script is
included in eg/ directory distributed with this module, along with a whole bunch of other
goodies. See Geo::Coder::US::Import for how to build your own Geo::Coder::US database.
Consider using a web service to access this geocoder over the Internet, rather than going
to all the trouble of building a database yourself. See eg/soap-client.pl,
eg/xmlrpc-client.pl, and eg/rest-client.pl for different examples of working clients for
the rpc.geocoder.us geocoder web service.
METHODS
In general, the only methods you are likely to need to call on Geo::Coder::US are set_db()
and geocode(). The following documentation is included for completeness's sake, and for
the benefit of developers interested in using bits of the module's internals.
Note: Calling conventions for address and intersection specifiers are discussed in the
following section on CALLING CONVENTIONS.
Geo::Coder::US->geocode( $string )
Given a string containing a street address or intersection, return a list of
specifiers including latitude and longitude for all matching entities in the database.
To keep from churning over the entire database, the given address string must contain
either a city and state, or a ZIP code (or both), or geocode() will return undef.
geocode() will attempt to normalize directional prefixes and suffixes, street types,
and state abbreviations, as well as substitute TIGER/Line's idea of the "primary
street name", if an alternate street name was provided instead.
If geocode() can parse the address, but not find a match in the database, it will
return a hashref containing the parsed and normalized address or intersection, but
without the "lat" and "long" keys specifying the location. If geocode() cannot even
parse the address, it will return undef. Be sure to check for the existence of "lat"
and "long" keys in the hashes returned from geocode() before attempting to use the
values! This serves to distinguish between addresses that cannot be found versus
addresses that are completely unparseable.
geocode() attempts to be as forgiving as possible when geocoding an address. If you
say "Mission Ave" and all it knows about is "Mission St", then "Mission St" is what
you'll get back. If you leave off directional identifiers, geocode() will return
address geocoded in all the variants it can find, i.e. both "N Main St" and "S Main
St".
Don't be surprised if geocoding an intersection returns more than one lat/long pair
for a single intersection. If one of the streets curves greatly or doglegs even
slightly, this will be the likely outcome.
geocode() is probably the method you want to use. See more in the following section on
the structure of the returned address and intersection specifiers.
Geo::Coder::US->geocode_address( $string )
Works exactly like geocode(), but only parses addresses.
Geo::Coder::US->geocode_intersection( $string )
Works exactly like geocode(), but only parses intersections.
Geo::Coder::US->filter_ranges( $spec, @candidates )
Filters a list of address specifiers (presumably from the database) against a query
specifier, filtering by prefix, type, suffix, or primary name if possible. Returns a
list of matching specifiers. filter_ranges() will ignore a filtering step if it would
result in no specifiers being returned. You probably won't need to use this.
Geo::Coder::US->find_ranges( $address_spec )
Given a normalized address specifier, return all the address ranges in the database
that appear to cover that address. find_ranges() ignores prefix, suffix, and type
fields in the specifier for search purposes, and then filters against them ex post
facto. The intention for find_ranges() to find the closest match possible in
preference to returning nothing. You probably want to use lookup_ranges() instead,
which will call find_ranges() for you.
Geo::Coder::US->lookup_ranges( $address_spec, @ranges )
Given an address specifier and (optionally) some address ranges from the database,
interpolate the street address into the street segment referred to by the address
range, and return a latitude and longitude for the given address within each of the
given ranges. If @ranges is not given, lookup_ranges() calls find_ranges() with the
given address specifier, and uses those returned. You probably want to just use
geocode() instead, which also parses an address string and determines whether it's a
proper address or an intersection automatically.
Geo::Coder::US->find_segments( $intersection_spec )
Given a normalized intersection specifier, find all of the street segments in the
database matching the two given streets in the given locale or ZIP code.
find_segments() ignores prefix, suffix, and type fields in the specifier for search
purposes, and then filters against them ex post facto. The intention for
find_segments() to find the closest match possible in preference to returning nothing.
You probably want to use lookup_intersection() instead, which will call
find_segments() for you.
Geo::Coder::US->lookup_intersection( $intersection_spec )
Given an intersection specifier, return all of the intersections in the database
between the two streets specified, plus a latitude and longitude for each
intersection. You probably want to just use geocode() instead, which also parses an
address string and determines whether it's a proper address or an intersection
automatically.
CALLING CONVENTIONS
Most Geo::Coder::US methods take a reference to a hash containing address or intersection
information as one of their arguments. This "address specifier" hash may contain any of
the following fields for a given address:
ADDRESS SPECIFIER
number
House or street number.
prefix
Directional prefix for the street, such as N, NE, E, etc. A given prefix should be
one to two characters long.
street
Name of the street, without directional or type qualifiers.
type
Abbreviated street type, e.g. Rd, St, Ave, etc. See the USPS official type
abbreviations at <http://www.usps.com/ncsc/lookups/abbr_suffix.txt> for a list of
abbreviations used.
suffix
Directional suffix for the street, as above.
city
Name of the city, town, or other locale that the address is situated in.
state
The state which the address is situated in, given as its two-letter postal
abbreviation. See <http://www.usps.com/ncsc/lookups/abbr_state.txt> for a list of
abbreviations used.
zip Five digit ZIP postal code for the address, including leading zero, if needed.
lat The latitude of the address, as returned by geocode() et al. If you provide this to as
part of an argument to a Geo::Coder::US method, it will be ignored.
long
The longitude of the address, as returned by geocode() et al. If you provide this to
as part of an argument to a Geo::Coder::US method, it will be ignored.
INTERSECTION SPECIFIER
prefix1, prefix2
Directional prefixes for the streets in question.
street1, street2
Names of the streets in question.
type1, type2
Street types for the streets in question.
suffix1, suffix2
Directional suffixes for the streets in question.
city
City or locale containing the intersection, as above.
state
State abbreviation, as above.
zip Five digit ZIP code, as above.
lat, long
A single latitude and longitude for the intersection, as specified above. If you
provide these values as part of an argument to a Geo::Coder::US method, they will be
ignored.
BUGS, CAVEATS, MISCELLANY
The TIGER/Line data is notoriously buggy and inaccurate, but it seems to work reasonably
well for urban areas. Geo::Coder::US uses interpolation to estimate the position of a
particular address within a block, which means that it will necessarily be slightly
inaccurate. Hey, it's only 14 meters off for my house, which is better than the 300 meter
error given by another prominent geocoder, and definitely close enough for navigation.
In rural areas, TIGER/Line doesn't give names for lots of putative roads, even if the
roads have names. Maybe the sign blew down the day before the Census agents got there,
assuming there was ever a sign. What can you do? Similarly, lots of rural areas have
official county subdivision names that an ordinary user would never think to give.
Probably the right thing to do is map in names from a ZIP code database, but that data's
not in TIGER/Line. What can you do? In general, you should expect the geocoder to be a lot
more accurate in urban versus rural areas.
There may be many kinds of US street addresses which Geo::Coder::US can't parse. In
particular, Geo::Coder::US strips out letters and dashes from house numbers, which may
cause ambiguous results in certain parts of the country (particularly rural Michigan and
Illinois, I think). Mea culpa. Send patches.
The full TIGER/Line data set is one heck of a lot of data -- about four gigabytes
compressed, and over 24 gigs uncompressed. The BerkeleyDB database covering the whole US
runs to 750+ megabytes uncompressed, or about 305 megs compressed. Unfortunately, I am not
at present able to offer copies for download.
It would be nice to see a version of this for other countries, e.g. Geo::Coder::CA,
Geo::Coder::DK, Geo::Coder::UK, with the same methods. Contact your local legislator about
why the public geographic data for your country isn't freely available like it is in the
US. If street address data is freely available for your country of choice, what are you
waiting for?
TODO
Reverse geocoding methods, to retrieve the nearest street address from a given lat/long.
This would probably necessitate using a R-tree or some other spatial indexing algorithm.
A metaphone index, for doing fuzzy matching on misspelled street and place names.
SEE ALSO
DB_File(3pm), Geo::TigerLine(3pm), Geo::Coder::US::Import(3pm)
TIGER/Line is a registered trademark of the US Census Bureau. Find out more, and get the
latest TIGER/Line files from <http://www.census.gov/geo/www/tiger/>. Actually, the best
place to download the data from is <http://www2.census.gov/geo/tiger/tiger2004fe/>.
You can find a live demo of this code at <http://geocoder.us/>. Our consultancy, Locative
Technologies, offers service and support for this software on a contractual basis.
AUTHORS
Schuyler Erle <schuyler AT nocat.net>
Jo Walsh <jo AT frot.org>
Geo::Coder::US incorporates a patch submitted by John P. Linderman. Submit a useful patch
and get your name added here, too!
COPYRIGHT AND LICENSE
Copyright (C) 2004 by Schuyler Erle and Jo Walsh
This library is free software; you can redistribute it and/or modify it under the same
terms as Perl itself, either Perl version 5.8.3 or, at your option, any later version of
Perl 5 you may have available.
perl v5.10.0 2005-05-17 US(3pm)
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On Apache
Under GNU General Public License
2012-05-24 05:04 @38.107.179.238 Crawled by CCBot/1.0 (+http://www.commoncrawl.org/bot.html)