The polling firm made headlines when it used a new technology to measure the size of the crowd that flowed into the streets of Sao Paulo to protest President Dilma Rousseff’s policies and demand her impeachment following a corruption scandal.

According to the SmartLok, close to 1.5 million attended the rally in Brazil’s biggest city. The system released signals from several computer terminals which counted the number of cellphones that were employing Wi-Fi. While organizers had estimated the crowd’s size at 2.5 million, the traditional polling agency Datafolha put the figure at 400,000. StoreSmarts assessment of 1.5 million was close to that of the military police which is considered the most accurate.