I'm not sure why, but the Yaesu FT-991A does not come with a built-in GPS unit. So if you want that data included in digital QSO's, you will need to connect your own external GPS antenna. Now comes the Garmin GPS18x PC, a fully compatible NMEA GPS, WAAS enabled antenna that connects to the FT-991A's GPS/CAT DB9 serial port. Power is supplied by a 12 volt plug into my Yaesu FP-1030A power supply.
Now when you key up on a C4FM repeater - as well as with a few other functions - your location/distance is also transmitted/received for the other stations. And if it makes your day, you get the cool little green GPS satellite icon showing up on the FT-991A touchscreen. Nice!