Ephemeris

Modern GNSS signals transmit "broadcast ephemeris" data. This contains precise orbital parameters that your phone or car's GPS receiver uses to calculate the satellite’s exact position, allowing it to determine your location on Earth.

An ephemeris provides more than just a location in the sky. Scientific versions often include: Ephemeris

Astrologers use these tables to track planetary "transits" (the movement of planets through zodiac signs) and generate birth charts. Scientific and Technical Data Modern GNSS signals transmit "broadcast ephemeris" data

Calculations have evolved from using Earth’s variable rotation (Universal Time) to highly uniform scales like Ephemeris Time (ET) and its successors, Terrestrial Time (TT) and Barycentric Dynamical Time (TDB), which incorporate relativistic corrections. Leading Sources and Software Ephemeris