I think I know enough about optimization problems for what I need, but GNSS seems like a step up. I guess my though is that optimization clearly works fine with

I think I know enough about optimization problems for what I need, but GNSS seems like a step up. I guess my though is that optimization clearly works fine within a single constellation because all of your information is definitely good, but across constellations are you guaranteed that they will necessarily agree? Or maybe more concretely - are my position and time in a theoretical "perfect" fix the same on GPS vs Galileo vs GLONASS etc exactly the same?If not, is splitting the difference closer to ground truth? I think that depends on what reference datums they use, and they're not the same [0]. Regarding the political aspect - you're right, and it's easy to forget about. I could say something cynical about that but I'll leave it. [0] https://gssc.esa.int/navipedia/index.php/Reference_Frames_in_GNSS https://gssc.esa.int/navipedia/index.php/Reference_Frames_in...