Mapping All the Swimming Pools in Los Angeles

Caitlin Dempsey


Los Angeles is known for its nearly constant sunshine and warm climate so it’s no surprise that the region contains a whole lot of swimming pools.  How many?  Benedikt Groß (or Gross since ß is a long s), a German graphic designing completing his master’s thesis at London’s Royal College of Art while working at Senseable City Lab at MIT teamed up with Joseph Lee, a research assistant at MIT to figure out that answer.

The two wanted to see if they could access publicly available aerial imagery in order to digitize every pool in the Los Angeles Basin from the Hollywood Hills to San Pedro.  Groß and Lee accessed both natural color (RGB) and Near Infrared bands of the imagery provided by the National Agriculture Imagery Program (NAIP) for the year 2010.  The NAIP captures aerial imagery every three years across the United States, which it makes freely available to the public for downloading. According to an article in the LA Times, the researchers sent a set of aerials to India where workers were paid $300 to digitize every pool they could find.  The second set was uploaded to Amazon’s Mechanical Turk crowdsourcing service, where for $350, participants in the program verified the pool outlines and determine when a pool outline was actually a roof or another object.  The final count?  Groß and Lee determine that there are 43,123 pools in the area.

Groß and Lee pulled other GIS data including LA County Assessor parcel data, crime data, Megan’s law sex offender locations, and campaign donations for and against Proposition 8, which sought to ban gay marriage.  The end result of all this geospatial data is an enormous gallery of all the pools in the region accompanied by maps such as the one showing where sex offenders live in relation to swimming pools.  The completed effort takes up an astounding 6,000 pages organized in 74 volumes.  Only one set has been published at a cost of $3,700 and resides with Groß.

Both personal sites for Benedikt Groß and Joseph Lee offer more detail about the atlas included a a 22-minute video of the pools on Vimeo created using Google Street View images and Google Street View Hyperlapse.

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The Big Atlas of L.A. Pools takes up 74 volumes.
The Big Atlas of L.A. Pools takes up 74 volumes.
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About the author
Caitlin Dempsey
Caitlin Dempsey is the editor of Geography Realm and holds a master's degree in Geography from UCLA as well as a Master of Library and Information Science (MLIS) from SJSU.