What are a few real-world examples for ECF and ECI (with more focus on an ECI example).
I have read several articles and it only presents these concepts through physics and trig, lacking real-world examples. The same description is repeated for ECF -- when the axes and Earth rotates together while for ECI -- when axes is fixed while only the Earth rotates, which incorporates Newton's laws as true.
Only the real-world applications referring to ECF/ECI that I read from sources are ECI can be used for satellites and projectiles while ECF is for position on the Earth. This is weak real-world reference when trying to understand the real-world usage of ECF/ECI.