Nearly ever GPS chipset on the market will use some sort of Kalman/State space filtering. At it's most basic level this means that the GPS will know (via a mathematical model) what it expects it's next location value to be based on current velocity vector, if the calculated value (based on radio signals) is different then an error 'weighting' (Kalman gain) is applied to that calculated value to indicate that it might be erroneus and it is not used in the mathematical model of the current location.
In short, if your aircraft GPS detects a sudden step change in location data your GPS system /should/ detect that it is erroneus. If the change is small and progressive, that is more difficult to handle.