Using Crowdsourcing and Machine Learning to locate swimming pools in Australia · Tomnod

As part of a recent campaign, we asked our crowd to classify 693802 property parcels in Adelaide, Australia, in parcels that contain a swimming pool ('yes') and parcels that do not ('no'). The campaign was sponsored by a private company that compiles public and private sector data for a variety of markets including education, public safety, government, telecommunications, and insurance. Sounds like a simple task for our crowd, right? A pool is pretty easy to see in our imagery. In order to reduce the average number of user votes required per parcel to classify all the parcels in the data set with sufficient confidence, we decided to deploy a supervised machine learning algorithm to help direct the crowd to the parcels where the presence of the pool was likely, and remove from consideration the parcels which most likely did not contain a pool.