title: iPhone MKMapView: set map region to show all pins on map
body: <p>I'm trying to set the map region (center and span) so that the map shows all pin-annotations at the same time.</p>
  <p>I'm having trouble converting the long/lat coordinates from NSString to double, resp. make calculations with them. Here is the code I'm using:</p>
  <pre><code>- (void)updateMemberPins{
  
  //calculate new region to show on map
  double center_long = 0.0f;
  double center_lat = 0.0f;
  double max_long = 0.0f;
  double min_long = 0.0f;
  double max_lat = 0.0f;
  double min_lat = 0.0f;
  
  for (Member *member in members) {
      
      //find min and max values
      if ([member.locLat doubleValue] &gt; max_lat) {max_lat = [member.locLat doubleValue];}
      if ([member.locLat doubleValue] &lt; min_lat) {min_lat = [member.locLat doubleValue];}
      if ([member.locLong doubleValue] &gt; max_long) {max_long = [member.locLong doubleValue];}
      if ([member.locLong doubleValue] &lt; min_long) {min_long = [member.locLong doubleValue];}
      
      //sum up long and lang to get average later
      center_lat = center_lat + [member.locLat doubleValue];
      center_long = center_long + [member.locLong doubleValue];
  }
  
  //calculate average long / lat
  center_lat = center_lat / [members count];
  center_long = center_long / [members count];
  
  NSLog(@&quot;center long: %d, center lat: %d&quot;, center_long, center_lat);
  NSLog(@&quot;max_long: %d, min_long: %d, max_lat: %d, min_lat: %d&quot;, max_long, min_long, max_lat, min_lat);
      
  //create new region and set map
  CLLocationCoordinate2D coord = {latitude: center_lat, longitude: center_long};
  MKCoordinateSpan span = MKCoordinateSpanMake(abs(max_lat) + abs(min_lat), abs(max_long) + abs(min_long));
  MKCoordinateRegion region = {coord, span};
  [resultMapView setRegion:region];
  
  //remove all pins from map
  [resultMapView removeAnnotations:resultMapView.annotations];
  
  //show member pins
  for (id member in members) {
      [resultMapView addAnnotation:(Member *) member];
  }
  </code></pre>
  <p>}</p>
  <p>The result of the log-output is:</p>
  <blockquote>
  <p>center long: -1946827116, center lat: 1075651472</p>
  <p>max_long: -6267216, min_long: 1076018553, max_lat: 0, min_lat: 0</p>
  </blockquote>
  <p>I think the problem comes from (wrongly) converting values from NSString to double, however I cannot find a way to make it work... The format of the location-strings is like '43.5686473'.</p>
  <p>Any hints? Cheerz</p>