title: Display only overlay map without Google Maps
body: <p>I have a ImageMapType which overlays the Google Map (v3 API). This is the default view for my web application and the user can decide to hide the overlay pressing a button.</p>
  
  <p>Can I avoid to load the Google Map tiles untill the overlay is shown?</p>
  
  <p>I have seen in documentation that there's a parameter called <em>mapTypeId</em> which can be set to specific values, but it seems it's not possible something like: mapTypeId: NULL</p>
  
  <p>Thanks,
     Riccardo</p>