Recent advances allow us to mine GPS data to understand actual shopper journeys. The new technology even lets us detect visits and trigger mobile surveys to shoppers when they are inside specific stores. But how are these technologies relevant for real business needs? And what is the right way to invite shoppers to participate, given privacy concerns around location-sharing on mobile? This talk will discuss lessons learned when Locately and a retailer client implemented this methodology in the USA to deeply understand shopper journeys during Holiday 2012. We used GPS analytics to detect visits to 7 key retailers of interest: Best Buy, JCPenney, Kohls, Macys, Target, ToysRUs, and Walmart. Visit-triggered in-store mobile surveys allowed us to evaluate the impact of marketing activations.