Definition
An FAA Technical Standard Order that sets the minimum performance standards a GPS sensor must meet when it relies on WAAS augmentation to provide position data to other avionics. Equipment built and approved to TSO-C145A is a GPS/WAAS sensor — it produces position information for use by a separate navigation system (such as a flight management system or integrated avionics suite), rather than functioning as a standalone navigator with its own pilot interface.
Plain English
It is the FAA rulebook that a GPS-with-WAAS sensor has to pass to be approved for use in aircraft. A TSO-C145A unit is the position-finding part that feeds another system in the cockpit — it does not have its own controls and display for the pilot to fly the GPS directly.
Context Anchor
Seen in discussions of approved GPS/WAAS equipment, especially when deciding whether installed navigation equipment can be used for instrument procedures.
Derivation
TSO stands for Technical Standard Order — an FAA performance standard for a piece of equipment. The 'C145' is just the FAA's catalog number for this particular standard, and 'A' marks the first revision. Knowing it is a TSO tells you the document is about minimum equipment performance, not about how to fly with it.
Why Pilots Care
Equipment meeting this standard provides the accuracy and integrity needed for GPS-based instrument approaches.
Analogy
Think of TSO-C145A like a required approval label for the GPS sensor. It does not tell you how to fly the procedure, but it tells you the sensor was built to a recognized FAA standard.
Intuition Check
TSO-C145A is not an approach type, a chart note, or a button on the panel. It is an FAA equipment standard; the aircraft installation and operating approval still matter.
Example Sentence 1
The aircraft's flight management system gets its position from a TSO-C145A GPS/WAAS sensor mounted in the avionics bay.
Example Sentence 2
Only units meeting TSO-C145A or later are approved for certain GPS approaches.