I believe, in earlier days of professional baseball, each stadium had their own set of ground rules. This is true today and can be seen in Tropicana Stadium, as there are specific guidelines for when balls enter the catwalk.
However, what we all understand to be the ground rule double does not vary from stadium. That is, a ball bounces in fair play, then enters above the yellow line into the area defined to be home run territory.
My question focuses on the TV announcers that call any given game. When a ground rule double occurs, the TV announcers are sure to confer with each other before asserting that it is a 2 base award. Is their caution before asserting the 2 base award really necessary?