A Japanese team of researchers are working on a positioning system using muons, which could be used in places where GPS signals can’t be received (such as underwater or underground).
The article discusses many of the challenges and reasons why it currently isn’t ready for practical applications. But it certainly is a very interesting technology.
It would make sense that eventually you could do both real-time and after-the-fact calculations depending on whether real-time communications is available. Presumably it will depend on the specific application