gistfile1.m

#define MINIMUM_ZOOM_ARC 0.003 //approximately 1 miles (1 degree of arc ~= 69 miles)
#define ANNOTATION_REGION_PAD_FACTOR 1.1
#define MAX_DEGREES_ARC 360

+(MKCoordinateRegion)adjustZoomMapView:(NSArray*) locations {
    
    int count = [locations count];
    MKMapPoint points[count]; //C array of MKMapPoint struct

    for( int i=0; i<count; i++ ) //load points C array by converting coordinates to points
        
    {
        CLLocationCoordinate2D *point = [locations objectAtIndex:i];
        points[i] = MKMapPointForCoordinate(coordinate);
        
    }
    
    MKMapRect mapRect = [[MKPolygon polygonWithPoints:points count:count] boundingMapRect];
    
    MKCoordinateRegion region = MKCoordinateRegionForMapRect(mapRect);
    
    region.span.latitudeDelta  *= ANNOTATION_REGION_PAD_FACTOR;
    
    region.span.longitudeDelta *= ANNOTATION_REGION_PAD_FACTOR;
    
    if( region.span.latitudeDelta > MAX_DEGREES_ARC ) { region.span.latitudeDelta  = MAX_DEGREES_ARC; }
    
    if( region.span.longitudeDelta > MAX_DEGREES_ARC ){ region.span.longitudeDelta = MAX_DEGREES_ARC; }
    
    if( region.span.latitudeDelta  < MINIMUM_ZOOM_ARC ) { region.span.latitudeDelta  = MINIMUM_ZOOM_ARC; }
    
    if( region.span.longitudeDelta < MINIMUM_ZOOM_ARC ) { region.span.longitudeDelta = MINIMUM_ZOOM_ARC; }
    
    
    return region;
   
    
}