There are two stationary satellites above the equator, one over the Atlantic and one over the Pacific oceans, which are dedicated to the Wide Area Augmentation System (WAAS). Their function is to transmit corrections to the position of the other satellites, and to the time signals used by them.

A GPS receiver that is WAAS capable or “has WAAS”, will have its accuracy improved from 10 meters to 7, although many manufacturers report an improvement to 3 meters. These values are subject to some variation due to ionospheric changes.

Reception of the WAAS signals can be affected by location or intervening structures. A WAAS capable receiver will indicate proper reception to the user on its satellite data display screen. Due to this uncertainty navigators should not rely on WAAS, but rather enjoy it when it is being received.