How to pre-render MKMapView from other viewcontroller?

Question

I have a UITabBarController with a MKMapView(added on IB) on the second tab.

I am trying to make it load and render before the user changes switches to that tab.

Concerning the loading it works well (connections triggered and therefore it takes less time to place them) if I do this :

(this forces the viewDidLoad to be called)

LLMapViewController *m = [rootController.viewControllers objectAtIndex:4];
[m view];

I have tried the following without success:

[m.mapView setNeedsDisplay];

Any other ideas on how to do it?