There are also ground based systems at airports which increase reliability / integrity for things like simultaneous parallel approaches. [1] says to within +/-

There are also ground based systems at airports which increase reliability / integrity for things like simultaneous parallel approaches. [1] says to within +/- 1m horizontal and vertical. [1] https://www.skybrary.aero/index.php/Ground_Based_Augmentation_System_(GBAS) https://www.skybrary.aero/index.php/Ground_Based_Augmentatio...