title: CMAltimeter callback never fires
body: <p>Using my 6+ I've been trying to read the relative altitude and pressure using CoreMotion's new CMAltimeter. However the callback is never firing. I have a very similar setup which instead uses the accelerometers, gyros, and magnetometers. They all seem to work fine. </p>
  
  <p>Was wondering if anyone out there has managed to get a reading? </p>
  
  <pre><code>- (void)viewDidLoad {
      [super viewDidLoad];
  
      if([CMAltimeter isRelativeAltitudeAvailable]){
          CMAltimeter *altimeterManager = [[CMAltimeter alloc]init];
          [altimeterManager startRelativeAltitudeUpdatesToQueue:[NSOperationQueue mainQueue] withHandler:^(CMAltitudeData *altitudeData, NSError *error) {
              // This never fires.
              NSString *data = [NSString stringWithFormat:@"Altitude: %f %f", altitudeData.relativeAltitude.floatValue, altitudeData.pressure.floatValue];
              NSLog(@"%@", data);
              self.altimeterLabel.text = data;
          }];
          NSLog(@"Started altimeter");
          self.altimeterLabel.text = @"-\n-";
      } else {
          NSLog(@"Altimeter not available");
      }
  }
  </code></pre>
  
  <p>I've tried taking this on a quick walk, but there's only one story of altitude to lose/gain around here. </p>