Interface Builder Scaling?

I've noticed in two different projects over the past few day开发者_如何学运维s that distances aren't lining up between IB and the actual app. For example, in one application I have a MKMapView. In IB, it is aligned with the bottom of a UIImageView, however when deployed on device it overlaps by about 20pts.

What's the issue? Elements are getting pushed up and down the screen. Using a tab bar interface. The tab bar is present on the bottom of the NIB, so I don't think it's a resizing issue. Help?

The tab bar should be a "simulated metric", not an actual tab bar on the screen. Select the main view itself (click the border), and open the attributes inspector (Command-Option-4). Under Simulated Metrics, select Tab Bar from the popup for Bottom bar.

The other possibility is when rotating—set your structs and springs correctly. You haven't mentioned rotation though, so I think it's the first answer.