My guess is that they use the referrer only as a point of origin on the map. Each subsequent user to hit that referrer id plots on the map in sequence from the

My guess is that they use the referrer only as a point of origin on the map. Each subsequent user to hit that referrer id plots on the map in sequence from the original, based on their geolocation. They probably do not plot users who do not share their locale. Just a guess.