Humans can leave traces of information through GPS and other location based services. Without the right privacy settings, we can be almost constantly transmitting location data sometimes unwittingly through apps on smart phones or embedded in image data, and in more overt ways such as tagging live locations. This can become an issue where others can draw conclusions from that data about patterns of movement, habits and behaviours. For example (and arguably less nefarious) advertising can be tailored according to your habits, but at the other extreme thieves could  use such information to determine when you’re not home, or routes you might travel. A famous example is when heat map and route data from the health/fitness app Strava all but identified and mapped locations of military assets in active areas of conflict.