Methods and systems are presented for updating assistance data in an indoor navigation system. In some embodiments, a method includes receiving ranging measurements from a reference positioning terminal, computing an estimated location of the reference positioning terminal based on the received ranging measurements, receiving information associated with a high-confidence location of the reference positioning terminal, determining that a difference between the estimated location and the high-confidence location of the reference positioning terminal is greater than a predetermined threshold, and sending an assistance data update to a server associated with the indoor navigation system, the assistance data update including an update to assistance data based on the received ranging measurements of the reference positioning terminal.