Conor Calahane provided this information concerning the issue of point density required by a human to recognize an object vs. an algorithm. It’s a EuroSDR study on applying automated algorithms to point clouds gathered from Aerial Systems. It demonstrates the effect of point density on accuracy and also on the importance of point density to automation. He says it’s for an aerial system rather than MMS, but that it’s a good example and one he uses a lot.
Kaartinen, H., Hyyppa, J., Gulch, E., Vosselman, G., Hyyppa, H., Matikainen, L., Hofmann, A.D., Mader, U. And Persson, A. Accuracy of 3D City Models : EuroSDR comparison. In International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences 36 (Part 3/W19), pages 227-232, 2005.