Plain English Meaning
When the printed approach or departure chart does not perfectly match what the aircraft's GPS or FMS shows, or what the controller assigns. The two sources should agree, but sometimes they disagree in small but important ways.
Full Definition
Differences between what an instrument procedure chart shows and what is actually loaded in the aircraft's navigation database, or differences in how procedure information is presented across published charts, the navigation database, and ATC clearances. These inconsistencies can include variations in waypoint names, fix sequences, altitude or speed restrictions, course values, or procedure depictions.
Context Anchor
Seen during instrument , procedure , and when comparing an approach chart with the aircraft’s panel navigator or .