You could try it with SAGA GIS. The program is open source, very efficient and runs as a GUI, command line, through API calls, or even through an Arc Toolbox. I’ve had great success with it. SAGA - System for Automated Geoscientific Analyses https://sourceforge.net/projects/saga-gis/ Module: Import LAS Files http://www.saga-gis.org/saga_tool_doc/2.1.4/io_shapes_las_1.html Library: Spline Interpolation http:// http://www.saga-gis.org/saga_tool_doc/2.1.3/grid_spline.html