i have two Lidar las files, one is original let's say with X points. And the other is copy of the first las file but with Y points, where Y is less than X. Now, i wanted to compare how the Digital Elevation Models of these two las files vary... I wanted to get information like RMSE, standard deviation, etc... I would appreciate, if anyone could tell me what softwares, or ways to get the comparison info... Thanks!
You can do this through the ESRI ArcGIS Geostatistical Analysis Extension - there is a section in the help on performing validation on subsets.
You could do the same through GRASS through the R interface. Tomislav Hengl describes in some detail how to do so in his book A Practical Guide to Geostatistical Mapping. It's open access, so the PDF is free to download.
This answer was edited based on an attempt to incorporate @JeffreyEvans's suggestions.
Part 1: solution using the software R.
See @whuber's answer on comparing two TINs for a theoretical insight about this issue.
Part 2: Constructing lidar DEMs using R + software Fusion + Multiscale Curvature Classification (MCC) algorithm.
Fusion is a free software for lidar processing and visualization developed by the United States of America forest service (McGoughey, 2013).
"MCC-LIDAR is a command-line tool for processing discrete-return LIDAR data in forested environments" (Evans & Hudak, 2007).
Firstly, let's create a hypothetical situation to illustrate the below code example:
i) Fusion and MCC-LiDAR are installed under the following directories, respectively:
ii) the 2 lidar clouds (".las" files) are stored in the below directory with the following names:
iii) the outputs which are going to be the DEMs will be stored as it follows:
iv) other intermediate files will be stored under C:\lidar\project
Read: How to Run MCC-LiDAR link and Evans & Hudak (2007) work (see "References" section below),
For more ground algorithm options see Meng et al. (2010).
This point goes back to part 1 of this answer.
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.
McGaughey, R. J. (2013). FUSION / LDV : Software for LIDAR Data Analysis and Visualization. Seatlle, WA.
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.
As far as I know, RMSE is only stated during the making of the DEM, and not as an attribute for further refrence, so you'de have to "catch it" manually during the making of the DEM (that said, I never made a DEM from Lidar, only from other data).
If you want to see the differences between the DATA inside the two DEMS, I'd use cut/fill which is in the Spatial Analyst extension of ArcGIS (under "Surface Analysis"). The cut/fill shows you in a simple thematic map the changes between the DEM's.
I would do a simple DEM of difference. DEM2-DEM1. This will show all areas that are different and by how much.
Theres an image to a high res dem of difference on my website homepage. thadwester.com