From elements to an orbit
Public orbital elements are a model fitted to observations, rather than a stream of measured positions.
Inclination and eccentricity
Inclination measures the orbit's tilt. Eccentricity distinguishes circular-like trajectories from elongated ones. SGP4 includes perturbations appropriate to the mean elements rather than assuming circular motion.
Frames matter
The propagator returns TEME position and velocity. A GMST rotation gives an approximate Earth-fixed frame for WGS84 latitude, longitude, height and observer look angles. Polar motion and detailed Earth-orientation corrections are excluded.
Ground tracks
The orbit line is transformed into the Earth-fixed frame at one UTC. Ground-track samples rotate Earth at every sample time. Their different shapes reflect Earth's rotation.