title: how to calculate field of view of the camera from camera intrinsic matrix?
body: <p>I got camera intrinsic matrix and distortion parameters using camera calibration. </p>
  
  <p>The unit of the focal length is pixels, i guess. </p>
  
  <p>Then, how can i calculate field of view (along y) ?</p>
  
  <p>Is this formula right?</p>
  
  <pre><code>double fov_y = 2*atan(height/2/fy)*180/CV_PI;
  </code></pre>
  
  <p>I'll use it to parameters of </p>
  
  <pre><code>gluPerspective()
  </code></pre>