I tried doing this:
<pre><code>var currentHeight = Math.max(frustum.right - frustum.left, frustum.top - frustum.bottom);
var ellipsoid = frameState.scene2D.projection.getEllipsoid();
var destinationHeight = ellipsoid.cartesianToCartographic(destination).height;</code></pre>
but i'm getting different values for `currentHeight` and `destinationHeight` when the camera hasn't moved.  Am I missing something?