GPS is one of the many many component inside modern missile to determine location. An IMU ( https://en.wikipedia.org/wiki/Inertial_measurement_unit https://en.w

GPS is one of the many many component inside modern missile to determine location. An IMU ( https://en.wikipedia.org/wiki/Inertial_measurement_unit https://en.wikipedia.org/wiki/Inertial_measurement_unit ) being usually the main component and GPS being just there for error correction. GPS is too easy to jam, no serious military application would use GPS exclusively.