GPS model animation

A function to create an animation of the GPS constellation and working principle (pedagogic purpose).

For pedagogic / scientific diffusion purposes.

F5 to run and create the animation file named 'GPS_constellation &_working_principle_model.gif' that will appear in the same directory as you registered this .m file.

Dashed green lines links show visible spacecrafts (white dots) at a certain time on a certain place on the planet.

Theoritically minimum satellites vsible in the sky to give position and time is 4 (three for position, one for time)

Orbital angle values may be different from reality.

Old piece of code, still suboptimal cause not maximum factorized.

Please don't forget to rate this code if it helped you ;-)