The almanac is not needed. The ephemeris is basically just almanac orbital data plus extra terms to make it accurate enough for meter-level positioning or bette

The almanac is not needed. The ephemeris is basically just almanac orbital data plus extra terms to make it accurate enough for meter-level positioning or better. I'm not sure what you mean by saying the orbital parameters change over days. Ephemerides are updated every ~2 hours to maintain precise positioning.