Why do MLB announcers consider the current stadium for ground rule doubles?

Question

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?

Answer 1

It's common for such a ball to be called a "ground rule double", but as you note, it's not something that is a ground rule.

As of a few years ago, MLB did create some Universal ground rules that should apply in all parks. I suppose it could be combined into the rule book, but it covers things that are traditionally part of ground rules. We can see that the "ground rule double" is not mentioned there either.

This award is defined in the MLB rulebook under 5.05 (a) (6)

5.05 (a) The batter becomes a runner when:

...

(6)  A fair ball, after touching the ground, bounds into the stands, or passes through, over or under a fence, or through or under a scoreboard, or through or under shrubbery, or vines on the fence, in which case the batter and the runners shall be entitled to advance two bases;

I prefer describing this situation as an "automatic double", but I don't announce games.

• Unless the ball does something odd like get deflected by a railing on the way out of the park, there's no ground rule to reference.
• Calling it a "ground rule double" is commonplace, but not strictly correct.