Augmented Reality Sandbox
AR sandboxes are the most hands-on, intuitive models of topography i have come across. Here is a video of my nephews using the sandbox:
The set-up consists of an xbox kinect pointing down towards the sand measuring depth values across the sand. As the sand is moved, these measurements are recorded and used to project contour lines along with a color map representing different levels of elevation back onto the sand.
I have one of these built and want to find it a good home. If anyone in Toronto is interested in borrowing it or displaying it, get in touch.
The full instructions/community forum can be found here. Full credit to Oliver Kreylos on sharing his work.