MKMapView setRegion "snaps" to predefined zoom levels?

Question

Can anyone confirm that setRegion "snaps" to predefined zoom levels and whether or not this behavior is as designed (although undocumented) or a known bug? Specifically, it appears that setRegion snaps to the same zoom levels that correspond to the zoom levels used when the user double-taps the map.

I'm trying to restore a previously saved region but this behavior makes it impossible if the saved region was set via a pinch zoom and not a double-tap zoom.

A big clue to me that things are broken on the mapkit side is what occurs if I call regionThatFits on the map's current region. It should return the same region (since it obviously fits the map's frame) but it returns the region that corresponds to the next higher predefined zoom level instead.

setVisibleMapRect behaves similarly.

Any further insight or information would be appreciated.

I found these related posts but neither included a solution or definitive confirmation that this is in fact a mapkit bug:

http://stackoverflow.com/questions/1365417/mkmapview-setregion-odd-behavior

http://stackoverflow.com/questions/1383296/why-mkmapview-region-is-different-than-requested

EDIT:

Here is an example that demonstrates the problem. All values are valid for my map view's aspect ratio:

MKCoordinateRegion initialRegion;
initialRegion.center.latitude = 47.700200f;
initialRegion.center.longitude = -122.367109f;
initialRegion.span.latitudeDelta = 0.065189f;
initialRegion.span.longitudeDelta = 0.067318f;
[map setRegion:initialRegion animated:NO];
NSLog(@"DEBUG initialRegion:  %f  %f  %f  %f", initialRegion.center.latitude, initialRegion.center.longitude, initialRegion.span.latitudeDelta, initialRegion.span.longitudeDelta);
NSLog(@"DEBUG map.region:  %f  %f  %f  %f", map.region.center.latitude, map.region.center.longitude, map.region.span.latitudeDelta, map.region.span.longitudeDelta);

OUTPUT:

DEBUG initialRegion:  47.700199  -122.367111  0.065189  0.067318
DEBUG map.region:  47.700289  -122.367096  0.106287  0.109863

Note the discrepancy in the latitude/longitude delta values. The map's values are almost double what I requested. The larger values correspond to one of the zoom levels used when the user double-taps the map.

Answer 1

I restore the region with no problem and with no variance as you describe. It is really impossible to tell what is specifically wrong in your case without some code to look at but here's what works for me:

Save both the center and span values somewhere. When you are restoring them specifically set both the center and span.

Restoring should look like this:

MKCoordinateRegion initialRegion;
initialRegion.center.latitude = Value you've stored
initialRegion.center.longitude = Value you've stored 
initialRegion.span.latitudeDelta = Value you've stored
initialRegion.span.longitudeDelta = Value you've stored
[self.mapView setRegion:initialRegion animated:NO];

Also remember that this method is available in 4.0: `mapRectThatFits:edgePadding: MapRectThatFits helpfully adds a reasonable border to ensure that say a map annotation on the edge is not obscured and the the rect that you're attempting to display is fully visible. If you want to control the border use the call that gives you access to set edgePadding as well.