Glympse allows you to pan and zoom the map to get a better idea of your surroundings, or those of your friends.
The lock icon in the upper left corner of the map allows you to "lock" the view onto the user(s) currently in focus. If the map is not focused on anyone, then tapping the lock icon will zoom out so that everyone currently sharing is visible. You can also tap the user bar at the bottom of the map screen to quickly center the map view on them and their destination.