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Comment by hylaride

12 hours ago

My understanding is that the encrypted military-level GPS is much more robust against jamming and spoofing. There's probably a lot of capabilities we don't know that's classified, too.

Called M-Code.

Has a fascinating history.

https://odimpact.org/case-united-states-opening-gps-data-for...

  • M-Code is a new encrypted signal that is not fully operational yet. OCX was supposed to enable it.

    GPS has always had the P(Y) code, which is an encrypted signal, at a higher chip rate than the C/A code that has been broadcast on L1 forever. The P(Y) code has its own interesting history of (semi-)codeless processing. If the US military is lucky, the history books will close on that by 2030: https://www.gps.gov/codelesssemi-codeless-gps-access-commitm... . (Currently, 21 GPS satellites broadcast L5.)

I think the new US GPS satellites have ability to do a spot beam of increased strength in a region of interest.

That is my understanding as well. But having another band allows for error correction as a side benefit.