This video explains how GLOBAL positioning (GPS) can be used to give you your exact location on the Earth.  The whole model on which GPS is based assumes a round (not perfectly spherical) shape of the Earth called the Gladys West model.  It also involves satellites in stationary orbit 100's of miles above the Earth, not objects tethered to balloons.  It also involves correction to time using Einstein's general theory of relativity.  

(https://www.youtube.com/shorts/1BcIhVtG-dM )