Mapping Hacks

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Chapter 7, Names and Places

#79 Geocode a U.S. Street Address

HACK

This street segment goes from (38.390313, –122.816102) to (38.389814,

–122.81515686); one side of the street includes addresses from 1001

through 1019, and the other covers addresses from 1000 to 1018. We can

interpolate that “1005” is about a fifth of the way from 1001 to 1019 and,

assuming the street is straight, that it will be about a fifth of the way

between the ends of the blocks.

There is a lot of other information in this line, and in the other files that

make up the data set for a county. TIGER/Line comprises some 24 gigabytes

of data for the whole country. Including information on curves in the road

that are not the ends of street segments, but in the interests of compressing

that 24 GB into something searchable, we will simplify away that extra

information.

Fortunately for us, Schuyler Erle has stripped away all of that complexity at

http://geocoder.us/, a free geocoding web site and web service for U.S.

addresses based on the U.S. Census TIGER/Line data.

You may use the web site to geocode individual addresses or use one of

three web-service interfaces to geocode via code, as illustrated in “Automati-

cally Geocode U.S. Addresses”

[Hack #80]. You can even download the source

code from CPAN, the Perl code repository at http://cpan.org, and the

TIGER/Line data from the census and create your own geocoding service.

The