// Enforce a minimum span of 1 (nautical) mile of longitude, given the center latitude of the region
// This could very well blow up if you get too close to either pole
- (MKCoordinateSpan)enforceMinimumSpan:(MKCoordinateRegion)region
{
    MKCoordinateSpan    newSpan = region.span;
    CLLocationDegrees   radians = region.center.latitude * M_PI / 180.0;
    CLLocationDegrees   minSpan = (1 / (69.11 * cos(radians)));

    newSpan.longitudeDelta = MAX(newSpan.longitudeDelta, minSpan);

    return newSpan;
}