I've worked in mapping software and GPS in some capacity for 20 or so years, and Null Island is always my go-to example of why it's bad to use an actual valid value for a variable as a default-initializer, as a sentinel value, or as a signal for "invalid". 0,0 is a real location and should not mean anything special besides "that exact location in the Atlantic" to your code. There are an infinite number of actually invalid lat/lon pairs, if you really, really need some constant that gets interpreted as "an invalid lat/lon". 0,0 is not one of them.
I always joke that if nuclear war ever broke out, that spot in the Atlantic is going to bear the brunt of the explosions from all of the poorly-coded computer systems firing the missiles.
I always joke that if nuclear war ever broke out, that spot in the Atlantic is going to bear the brunt of the explosions from all of the poorly-coded computer systems firing the missiles.