Having a built-in GPS in a emergency, one push of the Distress button, transmits the distress signal containing your MMSI# and location Lat/Lon information to USCG and all other DSC capable receivers within your broadcast range. Should (you) the operator become incapacitated, the radio will continue to send the mayday signal.
If your DSC radio does not have a built-in GPS, the Coast Guard urges, in the strongest terms possible, that you take the time to interconnect your DSC-equipped radio to an external GPS. Doing so may save your life in a distress situation! Here is a link to an external GPS available from Cobra https://www.cobra.com/collections/marine-accessories/products/cm300005cobrapositioningsystem