Ummm...no. Certain systems do indeed operate as you say, with INS as the primary guidance/navigation mechanism. Submarines for instance, cannot rely on a GPS f

Ummm...no. Certain systems do indeed operate as you say, with INS as the primary guidance/navigation mechanism. Submarines for instance, cannot rely on a GPS fix. Strategic missiles as well. But ground forces do indeed use GPS systems. INS systems are very costly to build and maintain, go GPS is a go-to for missions and requirements where it's a good fit. You simply cannot outfit every ground-pounder with an INS system and then keep it properly operational in their task envelope. Also, parts of the GPS system are quite jam-resistant. Not entirely, but when it was first developed, GPS was pretty secure for it's time, using a cryptographically derived spreading code for the carrier. Here is an example of a system in use today: https://en.m.wikipedia.org/wiki/Defense_Advanced_GPS_Receiver https://en.m.wikipedia.org/wiki/Defense_Advanced_GPS_Receive... Some of you might be interested in an article I wrote on the subject: https://sofrep.com/46818/gps-spoofing-how-iran-tricked-us-patrol-boats-into-capture/ https://sofrep.com/46818/gps-spoofing-how-iran-tricked-us-pa...