3 ms·

Gizmodo did some investigating and determined that the icon spacing is consistent with portrait mode.

• roc 15y ago
  Their article ends with: "We tried to match the portrait iPad 2 and iPad 3, but we couldn't. The spacing is wrong no matter how many icons you put on the dock. The reflection intersect the icon's edge in the wrong place no matter where you position it." And after studying my own iPad, I concur. It's definitely closer in portrait than landscape, but there are still enough differences that clearly more variables are in play. (The wallpaper has likely changed, the dock's background image has likely changed, the spacing has changed, etc.)