GPS Relativistic Clock Correction: 2D Orbit Map

This 2D top-down companion to the 3D circular-orbit GPS simulator drives a genuine elliptical Kepler orbit, solved every frame with a real Newton–Raphson Kepler-equation propagator rather than a flattened circular render. Because an ellipse's speed and altitude vary continuously, the special- and general-relativistic clock-rate shifts vary too — and the constant pre-launch clock correction that fully cancels the drift on a circular orbit leaves a real, periodic residual on an eccentric one. That residual is exactly the eccentricity correction term broadcast in every real GPS navigation message; toggle it on alongside the mean frequency offset to watch the displayed clock error collapse back toward zero even on a strongly eccentric orbit. A rate-vs-anomaly strip beneath the orbit map — a genuinely 2D-native view — plots both terms across one full orbit with the satellite's live position marked on it.