The data set in question was made using .las and .zlas files from respectable sources.
Data set 1 was collected in the Fall of 2014. The RAW flight line swath data was processed to create classified LAS 1.2 files formatted to 742 individual 1500m x 1500m tiles. The vertical accuracy is 18.3cm at the 95 percent confidence level. The horizontal accuracy is 1.04m at the 95 percent confidence level. The comprehensive metadata files will be made available.
Data set 2 was collected January 25, 2012 through April 11, 2012. The tiles were formatted to 5,000m x 5,000m in ASPRS ver 1.2 format. The vertical accuracy is 0.36m at the 95 percent confidence level. The horizontal accuracy is 1.04m at the 95 percent confidence level. The comprehensive metadata files will be made available.
The data was processed using Arcmap 10.5.
The two datasets had different sized tiles that overlapped in several areas. The larger tiles below are from the NRCS 2012 dataset and the smaller tiles are the SDGS 2014 dataset.
The Tile LAS tool in the 3D Analyst toolbox was used to create a new LAS dataset with uniform tiles. Rearrange_Points option was checked under LAS options. This orders LAS points according to their spatial clustering. The target file size was set at 250MB.
The result was a new LAS dataset with uniform tiles 250 MB in size. This took about 7 hours of processing time.
The filter settings underneath the layer properties menu were changed to show ground points only.
After the LASD layer was changed to show ground points only, the LAS Dataset to Raster tool from the conversion toolbox was used create a raster dataset. This required a new file geodatabase to be created for storing the new output files. The interpolation type was set to triangulation and the method was set to natural neighbor. The grid cell size used was 10 x 10m. This took about 4 hours of processing time.
The resulting raster dataset is below and is now a bare earth DEM. The dataset came out as expected however there are some areas on the eastern part of the river that appear as white specs. I think these are most likely areas where there were no ground points.
Can this be fixed by using the Binning interpolation type?
My main question was to ask the forum if there is a better way to combine LAS files like this. I'd like to make another data set of the same DEM but use .las files from a third data set with higher vertical accuracy. I have reserves about this because I am not sure what the Tile LAS tool does to the data points. Like I don't know how using this tool affects the accuracy of the final DEM and if there is a way to keep track or recalculate vertical and horizontal accuracies for the final DEM. I have limited processing power and the final DEM will be used for stream geomorphology analysis.