An on-screen display turns flight-controller data into readable status on a live camera image.

Where does the text on an FPV image come from? Understanding OSD

Voltage, current, flight mode and direction indicators on an FPV picture do not originate in the camera lens. On-screen display (OSD) combines a live image with status information supplied by the flight controller and other sensors.

Follow the data path

The flight controller collects measurements and state such as battery voltage, current, GPS information, warnings and flight mode. It sends relevant values to an OSD processor or to a digital-video system that draws text and symbols over the image. The video transmitter then sends the combined picture. Some receiver or ground-station overlays may be drawn at the receiving end instead; the location depends on the system.

This separation matters when troubleshooting. If the camera image is clear but a status value is wrong, inspect the data source, protocol and OSD configuration. If both image and overlay freeze together, look at the video path. If only the overlay disappears, check the telemetry connection and layout settings before replacing the camera.

Which fields help?

Battery voltage and current indicate remaining power and load. Flight mode and arming state explain how controls will behave. Link-status or signal indicators help distinguish an aircraft issue from a video issue. GPS-related direction and distance fields are meaningful only when their sensors have a valid fix and are configured correctly. Units, alarms and field positions should be checked during setup rather than trusted from their mere appearance on screen.

The original illustration has Chinese labels; this article describes the same data path in English. A useful setup check is to compare on-screen values with the flight controller's own readout while the aircraft is safely stationary.