My 2 living grandparents when I was younger lived more than 800 miles from us when we were growing up. We referred to them as grandma and granddaddy. My great-great grandmother lived next door to us until she passed when I was 9 years old and we called her Big Ma or Big Mama. Funny thing was that she was about 4'10" and weighed about 90lbs, but her presence was always known when she came in the room.
My kids and my sisters kids all call our parents (their grandparents) Ma and Da, just like we do. We call my brother-in-law's father Paw-Paw.