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@nocat.net>

    Jo Walsh <jo@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.

