David Crandall (https://www.cs.indiana.edu/~djcran/), on the faculty at Indiana University introduced a Hidden Markov Method based  Layer Finding based on new approach reported in P. Felzenszwalb, O. Veksler, Tiered Scene Labeling with Dynamic Programming, IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2010. Current results are sufficiently encouraging that the new tool will be used in some production work.