Laser line profiling is a common technique for measuring the topography of a surface, with many systems based on this idea commercially available. In the case highlighted here we needed to accomplish this over a large deposition experiment in real-time as the material accumulated, slumped, and flowed.
No commercially available solutions allowed us to profile the ~1 by 6 meter flume fast enough, so we built our own. An array of 5 cameras and 250 laser lines with custom programmable timing electronics to trigger them allowed us to profile the entire deposition experiment every 2 seconds. We wrote image analysis software to transform the resulting sets of images into a 3D model of the deposition topography for each timestep using geometry, and followed the surface velocity using the cross-correlation of the surface texture between subsequent images (projected onto the 3D model, of course!).