Originally Posted by jim202
One thing that wasn't said in the article is that in order to use these other signals, you need to know exactly where they are located. Sure you can put together a receiver to use these existing signals, but they are useless for triangulation unless their location is known to use for the location calculation of where you are.
Big problem I see is trying to identify the exact location of all these signals that they say can be used. That's the advantage of the GPS now. The exact location of each of the satellites is a known and from that you can calculate where you are.
If I'm reading the article right, the system doesn't need to know the location of the transmitter(s) it is using. I don't know how this system could possible figure out it's location without either timing pulses (as with GPS) or Tx location (for triangulation). There is a system, similar to radar, that uses unknown transmitters to plot the location of signal disturbances caused by the target aircraft but that wouldn't work for figuring out the location of the receiver.