Re: Getting a bit ridiculous
Not that difficuly on account of space being really big. So the space between satellites being high. Give or take dodging space junk, which may increase if the SHTF in any big way.
But we're meant to be technologists. So there are 6 competing satnav systems. The original being GPS, which had it's SA mode to degrade accuracy. Geeks being geeks, and accurate navigation being really useful, came up with a variety of solutions to improve accuracy. So differential GPS, WAAS, A-GPS etc. So having 6 different satnav systems means you should be able to come up with something that can use multiple sources + INS to figure out how precisely lost you are. Which also means you've got more resilience if one or more signal sources is lost, and could probably also detect/prevent spoofing.
That would probably cost a lot less than designing & launching our own satellite. Especially as we'd also need to design, build and fit suitable navigation systems to use the signal(s) as well. Plus to be really secure, we'd need an independent way to launch LEO navsats for coverage or replace any that have been kinetically degraded. I'm guessing that trying to install a UK navigation system into say, an F-35 and integrate that would be.. expensive.