> For the complete documentation index, see [llms.txt](https://docs.ceruleansonar.com/c/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ceruleansonar.com/c/ceruleantracker/overview/output-messages/gpdbt-gphdt-gpgga-messages.md).

# GPDBT, GPHDT, GPGGA messages

If the appropriate output boxed is checked, CeruleanTracker emulates a “GPS” mounted on the ROV by outputting $GPDBT, $GPHDT, or $GPGGA messages with the ROV location and other data. $GPDBT and $GPHDT messages are never valid if a DVL is not present.

The $GPDBT numeric fields will be blank if a DVL-75 is not present or is present but not locked.

The $GPHDT fields will be blank if a DVL-75 is not attached.

The $GGA latitude and longitude fields will be blank if there is no lat/long calculated. The fix quality field of $GPGGA will be either ”0” (no fix) or “6” (dead reckoning fix). All other fields of the $GPGGA message are always dummy values.