Constructing lidar DEMs from unclassified point clouds with:
- MCC-LiDAR using the Multiscale Curvature Classification (MCC) algorithm.
MCC-LIDAR is a command-line tool for processing discrete-return LIDAR data in forested environments" (Evans & Hudak, 2007).
Workflow illustration (gross cloud --> ground returns classified --> bare-earth DEM):
Firstly, let's create a hypothetical situation to illustrate the below code example:
MCC-LiDAR is installed under the following directory:
C:\MCC
The lidar cloud (".las" file) is stored in the below directory with the following name:
C:\lidar\project\cloud.las
The output which are going to be the bare-earth DEM will be stored as the following:
C:\lidar\project\dem.asc
Now, let's provide an example about how to classify ground returns with the MCC algorithm and create a bare-earth DEM with 1 meter resolution.
#MCC syntax: #command #input_file #output_file #output_DEM
C:\MCC\bin\mcc-lidar.exe -s 0.5 -t 0.07 C:\lidar\project\cloud.las C:\lidar\project\mcc_ground_cloud.las -c 1 C:\lidar\project\dem.asc
Read: How to Run MCC-LiDAR link and Evans & Hudak (2007) work (see "References" section below),
to understand better how the scale (s) parameter and the curvature threshold parameter (t) works.
They need to be calibrated to avoid the commission/labeling errors (when a point is classified as belonging to the ground but actually it belongs to vegetation or buildings). See picture bellow.
For more ground algorithm options see Meng et al. (2010).
The MCC-LiDAR uses the interpolation technique of Thin Plate Spline (TPS) to generate the bare-earth DEM from the classified (ground returns) lidar cloud.
References:
Evans, Jeffrey S.; Hudak, Andrew T. 2007. A multiscale curvature algorithm for classifying discrete return LiDAR in forested environments. IEEE Transactions on Geoscience and Remote Sensing. 45(4): 1029-1038.
Meng, X., Currit, N., & Zhao, K. (2010). Ground Filtering Algorithms for Airborne LiDAR Data: A Review of Critical Issues. Remote Sensing, 2(3), 833–860. doi:10.3390/rs2030833
Silva, A. G. P. da, Gorgens, E. B., Rodriguez, L. C. E., Silva, C. A., Alvares, C. A., Campoe, O. C., & Stape, J. L. (2012). Influência da janela do filtro de terreno em dados LiDAR sob duas coberturas florestais. In C. Lingnau, J. R. dos Santos, & E. da S. Lopes (Eds.), X Seminário de Atualização em Sensoriamento Remoto e SIG Aplicados à Engenharia Florestal (Vol. 10, pp. 65–72). Curitiba, Brazil: 10seminarioflorestal.com.br.
*abstract and pictures' caption are available in English.