I'm saying that for most everyday situations, Newton's equations provide sufficient accuracy for people to achieve their goals. However, in the case of GPS, the

I'm saying that for most everyday situations, Newton's equations provide sufficient accuracy for people to achieve their goals. However, in the case of GPS, the system wouldn't work reliably if it was only using Newton's equations. Einstein's theory of gravity is much more robust and is highly accurate across a far wider domain. It can be used to implement a reliable GPS system.