Definition
A data message broadcast by the Wide Area Augmentation System (WAAS) that provides GPS receivers with adjustments for known errors in the GPS signal, such as satellite clock drift, satellite orbit inaccuracies, and ionospheric delays. The receiver applies these corrections to improve the accuracy and integrity of its position solution.
Plain English
A signal sent from WAAS that tells your GPS receiver how to fine-tune its position calculation by accounting for small errors in the raw GPS data.
Context Anchor
Seen in WAAS discussions when explaining how WAAS improves GPS accuracy and reliability for instrument navigation.
Derivation
Correction comes from a Latin idea meaning “to make right” or “to set straight.” In this term, the message does not correct the pilot; it gives the GPS receiver information that helps set its calculated position closer to the truth.
Why Pilots Care
Allows the receiver to support LPV approaches with vertical guidance as low as 200 feet.
Intuition Check
Do not read “correction message” as a spoken instruction to the pilot. Here it means digital information sent to the GPS receiver so the receiver can correct navigation errors.
Example Sentence 1
The WAAS receiver applied the latest correction message to refine its position before commencing the LPV approach.
Example Sentence 2
Loss of correction messages caused the WAAS receiver to downgrade to non-precision GPS navigation.