We can think of the transmitted GPS signals as sinusoidal electromagnetic waves. Each satellite broadcasts at two radio frequencies, about 1.2 and 1.6 billion cycles per second (gigahertz). Traveling at the speed of light, these signals have wavelengths of about 24 and 19 cm, or roughly 4 and 5 wavelengths per meter, respectively. Thus over a distance of 100 m, the two signals complete a little more than 400 and 500 cycles. In principle one can measure distance by counting the number of cycles between a transmitter and a receiver.
