FOSS4G North America Conference 2013 Preliminary Program

Concurrent Session Presentations
Open Source Geospatial Technology
Analysis and Big Data
Foursquare's Open Geo Stack: Geocoders, Reverse Geocoders and more
Reverse Geocoders
David Blackman, Foursquare
Almost all data at Foursquare is tagged with geographic coordinates ­­ from our tens of millions
of places to our billions of check­ins. To make sense of this data, we've developed and open
sourced a number of tools on top of a mostly open set of geographic data.
Foursquare needs to be able to geocode (and split) incoming queries to our local search engine..
To solve this, we've created Twofishes, a coarse, splitting geocoder that combines geonames
data with other sources of polygon and ranking data. It ingests all geographic data at foursquare
and outputs a standardized thrift representation that we use both as a wire format and as the
basis of our other geographic tools.
That canonicalized geographic data repository is further processed into an in­memory reverse
geocoder used in the mapreduces that build the data that powers our local search ranking. This
allows us to both normalize ranking signals and provide listings curated around intuitive, human
boundaries such as neighborhoods and cities. Additionally we can provide more context to our
users around the requests generated by their sometimes unreliable phone GPS readings.
The tools to power this that we will demo are a country/timezone polygon simplifier, a geographic
data ingestion pipeline, a coarse splitting geocoder and reverse geocoder, a blazing fast
in­memory reverse geocoder designed to keep up with mapreduces, a slower but still awesome
shapefile based reverse geocoder and a visualization tool for the s2 spherical geometry library.
Additionally, we'll show integration with the Quattroshapes project, a set of unencumbered
locality and admin2 polygons we're developing for many countries in the world without open
government data.