# The Schwarzschild Metric: Part 1, GPS Satellites - Comments

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fresh_42
Mentor
Just a little remark. It is Johannes Kepler, not Keplar.

PeterDonis
Mentor
2019 Award
Nice Insight? I have one comment, though: it might be worth mentioning that in the calculation of ##\Delta \tau_R## (for the Earth observer), you are assuming the Earth is non-rotating. That turns out to be OK for the particular calculation you are doing because the time dilation correction due to this is roughly two orders of magnitude smaller than the effects you compute; but rotation also introduces other complications, such as correctly defining clock synchronization, which can't be ignored (the excellent Ashby paper you refer to goes into all this).