Here is a part of photosynth blog:
New Feature: Overhead View: Have you ever wanted to look down on Mt Rushmore from directly above the Presidents? What about seeing the exact layout of Stonehenge from above? If you’ve used Photosynth you know that it automatically calculates a “cloud” of 3D points representing the features matched between photos. Our new overhead view lets you turn the photos off, and puts your point of view immediately above the scene.
Cant understand??Enjoy the video…Its uber Cool..