Q:

Totally different views on iPad for portrait Vs landscape ... is this acceptable user interface design?

I'm refactoring one of my apps from the iPhone to the iPad and this has resulted in the removal of tabs as I've been able to combine functionality onto 1 screen and use popovers to enable the user to select stuff that previously required a new tab.
I'm basically left with 2 tabs now. One (which is best viewed landscape) shows a map of the world with some overlays drawn on it plus an indication of where you are. The second is a data display with a few graphs which is best viewed portrait.
I note what Apple say about requiring apps to run in all orientations on the iPad, and of course I could do this, and keep my 2 tab bar buttons to switch views.
HOWEVER
In this case, there is 1 view that is best suited to landscape view and 1 view that is best suited to portrait view. Would be be appropriate (or even Apple permissible) UX design to drop the tab bar and switch views on an orientation change instead?
From a user perspective, you wouldn't need to be switching back and forth much, you tend to use the landscape view to change location (if you need to) and then work mainly in the portrait view - so I don't think it would be frustrating and dropping the tabs seems to make more sense to me.
What do you think? Any best practice in these situations?
Roger
London

A:

I would say that the best practice is not to restrict the orientation of views. 
The central idea here is not to force the user to hold the device a certain way. For example, a lot of people use iPads in a stand or holder and input with a keyboard. Do you want to force your users to stop and physically adjust the device in the holder/stand before they can read the view in the other orientation? Other people simple prefer holding the device one way or the other and lock the orientation (I do that a lot.) Forcing users to change from their preferred device orientation won't win you happy customers. 
Apple will not penalize you for a non-standard UI unless it reflects badly on the device itself. As long as the end users can tell it's your apps non-standard behavior, Apple does not care. However, in my experience, end users tend to interpret non-standard interfaces as flawed or broken because they don't understand them. 
In this case, if I launch your app for the first time, how am going to know that changing orientation changes to another view altogether and another data set? Nothing in the standard UI teaches me to expect that. I will have to discover it by trial and error. If I have the orientation locked, not even trial or error will help. At that point, I might well conclude that the app is broken. 
You could try adding instructions but just the thought that they might be necessary is a red flag for a potentially poor UI. 

