Purpose: Global Positioning System (GPS) satellites broadcast microwave signals to enable GPS receivers on or near the Earth's surface to determine location, velocity, and time. The GPS system itself is operated by the U.S. Department of Defense (DoD) for use by both the military and the general public.
GPS signals include ranging signals, used to measure the distance to the satellite, and navigation messages. The navigation messages include ephemeris data, used to calculate the position of each satellite in orbit, and information about the time and status of the entire satellite constellation, called the almanac.
Issues: These devices use microwave frequencies. They are usually used in close proximity to the body. This can increase the EMF exposure from these devices. See the cell phone information for more data.
Frequency Range: For the ranging codes and navigation message to travel from the satellite to the receiver, they must be modulated onto a carrier wave. In the case of the original GPS design, two frequencies are utilized; one at 1575.42 MHz (10.23 MHz × 154) called L1; and a second at 1227.60 MHz (10.23 MHz × 120), called L2.
The C/A code is transmitted on the L1 frequency as a 1.023 MHz signal using a bi-phase shift keying (BPSK) modulation technique. The P(Y)-code is transmitted on both the L1 and L2 frequencies as a 10.23 MHz signal using the same BPSK modulation, however the P(Y)-code carrier is in quadrature with the C/A carrier (meaning it is 90° out of phase).
Better Option: As ubiquitous as the use of GPS has become, paper maps are a better option from an EMF standpoint. A more reasonable solution is to download your maps when conected to a wired network, and, when using your GPS, affix it to the dash to get it as far away from your body as possible (this also gives it a better line of sight connection with the satellites). When not using the GPS maps feature, you can turn off the GPS antenna on your phone and further limit your exposure.
Source:
https://en.wikipedia.org/wiki/GPS_signals