The researchers built the cropland database by combining information from several sources, such as satellite images, regional maps, video and geotagged photos, which were shared with them by groups around the world. Combining all that information would be an almost-impossible task for a handful of scientists to take on, so the team turned the project into a crowdsourced, online game. Volunteers logged into "Cropland Capture" on a computer or a phone and determined whether an image contained cropland or not. Participants were entered into weekly prize drawings.