here’s how GPS works
there’s a clock involved..the satellite sending out GPS signal has it..and satellite is orbiting the Earth about 20000 Km above surface with 14000 Km/Hr. So there’s a very precise clock on-board a very fast moving satellite..what da hell/..?
Satellite sends a signal consisting of its orbital data and current timing. so with knowing exact timings of the signal was sent and then received by the GPS receiver on your phone. You multiply that small time dT with speed of light and you get the shortest distance b/w satellite and your phone.
An object moving very fast or travelling near a very heavy object experiences slower time. So for a satellite with nice clock moving very fast around Earth..Relativity is a real bitch..so our clock is kinda screwed but we still work around the math and still GPS works.
that was relativity screwing with the clock..clouds or physical changes in weather mess with the signal it self..they slow it down..and no way possible to know how much it got slowed down..again math involved..GPS still works gives workable accuracy of around 5-8m.
so the green bars in the back are satellites of the Rover and Grey ones are for Base.
what is it..? its an Real time Kinematic GPS..the one in Yellow and Green.
Any signal transmitted has a carrier and some data..carrier is like a package in which data is carried. So RTK ignores what the package is carrying. It uses phase of the signal(physical property of the signal) to figure out the information it needs..it uses statistical algorithms which require quite powerful processing..at the receivers end.
and the above data is from Emlid’s Reach RTK..uses Intel Galileo.
here’s a fun instance..a while ago while working on the co-axial octocopter..we were testing out it RC failsafe in the Rig( metal frame we tie the drone to..before its first flight or testing)..and I set it to RTL which is Return to Launch..being a noob with Pixhawk back then..we tested RC failsafe and the instant the RC turned off..a second after..everyone ran for their life..as the beast almost touched the roof…drone wasn’t even above 1m but it still RTL’ed..throttle value touched all the way top..it was fun