GPS itself is a one-way technology. On a basic level, the GPS satellites broadcast their precise location in space, and a very accurate timestamp from an onboard atomic clock. By comparing the difference in timestamps from a few satellites, you can determine how far away you are from each, thus deducing your own position. User devices only receive broadcasts from the GPS constellation; they don’t transmit. This is by design; GPS originated with the US military who wanted a navigation system usable anywhere in the world passively. You can use GPS without giving away your position by transmitting radio waves. The privacy nightmare is when you mix a GPS receiver in with all the other sensors, storage and radios found in a smart phone. How many apps on your phone have GPS privileges? Why does it want that?