Iridium utilizes 66 LEO satellites to support cell phone communications “anywhere, anytime.” The system relies on the Earth being a sphere in order to function: 6 polar orbital planes each with 11 satellites. Every spot on the earth is covered by one or two Satellites, each orbiting at an altitude of 400 nautical miles with an orbital period of 90 minutes
Mission data takes the following path: Individual subscriber unit (cell phone) to Satellite (L-Band), routed from Satellite to Satellite (K-Band), down to ISU (or GS/TS destined for ground-based infrastructure).
All this unimpresses the Flat Earther. They will respond: “I can just use my cell phone.”
Stuck on stupid.
Forget about GPS. Just try sailing across any ocean with a compass, a chart, and a chronometer (technical name for a marine clock), the way everybody did it before GPS was invented. The whole thing was, and is, based on spherical trigonometry and wouldn’t work if the earth wasn’t an oblate spheroid.