4 ms·

> crucial to allow GPS systems to accurately convey their positions to orbital satellites. I actually think they may have been referring to the ground stations

• defrost 4y ago
  > Presumably the satellites need to determine their positions based on the positions of the ground stations. The satellites broadcast a rough guide to their collective positions (an almanac) to recievers and a precise guide to their specific exact location (the ephemeris) to ground clients (phones, GPS receivers, etc). Master Ground control stations update the satellites with that information every four hours or so .. strictly speaking the satellites don't do any computation of their own position - they broadcast their weekly lapsed epoch signal and echo data frames from their last Master Ground Station update. Orbital changes can result from solar wind pressure, magnetic forces, passing objects with mass, etc. It's the GPS receivers that do the 'heavy' positional computations for individual fixes .. and the Master Stations that do the somewhat harder work of constellation updates. ( There's a wealth of accuracy processing that can be run in parallel or post - differential base station GPS, forward error correction, post aquisition corrections, et al ) [1] https://gssc.esa.int/navipedia/index.php/GPS_Ground_Segment https://gssc.esa.int/navipedia/index.php/GPS_Ground_Segment [2] https://en.wikipedia.org/wiki/GPS_signals https://en.wikipedia.org/wiki/GPS_signals