It’s a view-based refresh network link, which fetches the Digital Globe data 2 seconds after your motion over New Orleans stops. What’s innovative here is that the data consists of tiles, just as in Maps, and is delivered via a PHP script, with URL http://dev.keyhole.com/katrina/dg/tileserver.php
I’d love to know what that PHP does:-) It looks like it accesses the exact same tiles as Google Maps does, depending on what level you are zoomed in, no doubt determined by the bounding box of your view, which the PHP script receives. As those tiles are all just small jpegs, the script would need to decide how many to fetch and how to arrange them.
Indeed, if you look at what the network link delivers, it is a list of overlays, each containing one tile, and each one being independently adjustable on/off and for transparency. Very nifty.
Do read the whole thread. It contains interesting feedback.
PS. This of course means that the Google Earth team, should it want to, could now deliver the original Google Map tiles to Google Earth via such a network link/server solution. Unlike with Google Maps, however, Google Earth is able to drape these tiles over height information, which would definitely be worth a look just to see if it results in something cool and/or useful.
[Update 2005-09-05: This network link is now also available from Google Earth’s main Katrina page.]