What is the carrier frequency used by commercial GPS satellites?

The correct response highlights the function of the L1 carrier frequency used by commercial GPS satellites. The L1 frequency transmits a civilian signal (known as the Coarse/Acquisition or C/A code) that allows non-military users to access GPS functionality. This frequency operates at 1575.42 MHz and is fundamental for consumer GPS devices, enabling users to determine location, speed, and direction.

The mention of it being 'coarse' refers to the accuracy level compared to military signals. While the military also utilizes the L1 frequency for encrypted signals (precise and classified), the focus here is on the commercial application of the L1 frequency which provides basic positioning services accessible to the general public.