There are plenty of real errors in a system like this but the main effect of orbital speed and the presence of the Earth's mass is surely not an error but a main feature of the whole system - and would have been included in the very first, idealised 'back of a fag packet' system concept.I'm not going over the same stuff unless I have to. Error is the wrong word but who's nitpicking? You need to do the project because time dilation effects are not apparent. IE relative time and distance intervals are real natural phenomena. Since you intend to introduce that 'nonsense' catch you later.
I used the word 'nonsense' because I can see no reason how a measured position could possibly be regarded as drifting off at the rate of c. Can you?