Definition
A combined notation used on instrument approach charts and in flight planning to indicate an approach or navigation procedure that may be flown using either GPS guidance or guidance from a ground-based Non-Directional Beacon. GPS is a satellite-based navigation system that provides precise position information worldwide. An NDB is a low or medium frequency ground transmitter that broadcasts a non-directional signal an aircraft's Automatic Direction Finder (ADF) receiver uses to point toward the station. When an approach is published as GPS/NDB, a suitably equipped aircraft may use GPS in lieu of the NDB to fly the procedure.
Plain English
A label showing that an approach can be flown using satellite navigation (GPS) or by tracking a ground radio beacon (NDB). Either method gets you to the same runway, but GPS is more accurate and is what most pilots use today.
Context Anchor
Seen on electronic flight displays when selecting or identifying the source for navigation information during instrument flying.
Why Pilots Care
Allows pilots to transition from legacy NDB procedures to GPS while maintaining a backup reference and verifying position accuracy.
Intuition Check
The slash does not mean GPS and NDB are the same system. It means the display label is referring to one source or the other, depending on what is selected or installed.
Example Sentence 1
The chart was titled GPS/NDB Runway 24, so we briefed the approach using the GPS overlay rather than tuning the beacon.
Example Sentence 2
During the approach, GPS/NDB data on the display helped maintain course alignment when the NDB signal weakened.