Ah, I see what you mean. It does make more sense that GPS updates only around 1Hz.
I’m not sure I can go with the ultrasound however, since obstacles could mess up the timing, especially in dynamic environments. As for radio, I don’t know if it’d be possible to be used to track a cellphone-is it?
stevec talked about using multilateration, which basically uses more than one receiver. Apparently the more receiver used the more accurate the timing is. I’m fine with having more receivers, but are there any way of keeping nanosecond precision timing without GPS? Ideally I’d like something that I could just attach with some development board and microcontroller. I have a feeling that there aren’t any…
Alternative I can just go down the signal strength path…maybe if I have numerous bluetooth antennas that checks for the signal strength from the cellphone and since I know the positions of the antennas I could somehow come up with a fairly accurate average of the cellphone’s location. Is this a possibility?