At a high enough altitude a line-of-sight can be established with multiple cellular towers. Can such information be used to accurately correct INS drift (assuming GNSS is not available)?
No, for several reasons:
- There is no receiver onboard (granted, this could be remedied easily)
- Cells are very small, their antennas are directional privileging ground. Detection from an aircraft is difficult. For an aircraft in cruise, the distance is at least 10 km, only a large cells found in rural areas would be received. In populated area cell radius is much smaller.
- Aircraft switch from a cell to the other, most of the time before being able to create a stable link. This may be a problem or not, depending on the distance measurement principle. If the principle is based on measuring radio trip time rather than azimuth, a synchronization with the cell controller is required.
- On the other hand, if angles are used to determine distance, triangulation is not really accurate as the angles are small, less than 60° by design. In addition receiving antennas must be phased arrays (or rotating antennas) to determine the transmitter azimuth and elevation.
Last but not least, this would interfere with the cell network working. This reason is among the critical ones cell phones must be powered off while flying on a fast aircraft like an airliner. Cell phones on US aircraft are not prohibited by FAA but by FCC (its scope of interest is frequency protection, not aircraft safety). When a cellular network is available in flight, then there is a tiny cell in the cabin,connected by satellite link to the ground telephone network. Same for WiFi. There is no connection with a ground cellular network.