Originally Posted by Silvertate
The known inaccuracies of GNSS is why the WAARS and EGNOS augmentation systems are being developed. Why spend all that money on a new augmentation system, if the original GNS is always 100% accurate? Answer - it is not that accurate, which is why it says 95% accurate on the tin.
For goodness sake! WAAS gives better accuracy: lower minima eg for LP and LPV approaches! That is all!
GLS same: lower minima, no need for expensive ILS gear.
Do you really think someone didn't think of "hey hang on, that satellite is going to drop out of view! What is a crew going to do then?!" That's what RAIM, FD and FDE is all about.