Point Count by Cell

I am relatively new to creating terrain models using LiDAR data and using GM, so please forgive me for my very basic questions.  I am working on a project where we need to create the "best" DTM of coastal dune systems in our area to support the analysis of habitat for an endangered species.  Since I am new to creating DTM's I am unsure about what resolution DTM to create in order to generate the "best" terrain based on my data.  Therefore, I want to run some explanatory analyses on my data to help determine what resolution I should settle on.  The average density of my data is approx 2.5 pts/m^2.  In testing, I've generated a 2m DTM and a 5m DTM (GM's default value) for a sample area.  Qualitatively I can see a difference, but that doesn't really help me in really understanding which is "better".  So I ran the "Combine/Compare Terrain Layers" tool to see how the two differed.  This was informative, but now I want to see how many LiDAR points went into calculating the elevations for each of the cell in my two DTMs.  My thinking is that this will help me really to see if the elevations generated for my higher resolution DTM are based on a whole lot of cells that have only one or two points within them (I really don't want this, but suspect this is happening for the 2m DTM).

That being said, my first question is ...within GM how do I create a lattice (vector) of each of the DTMs and then secondly how do I then take each lattice and do an overlay to count the number of LiDAR points that fall within each of the lattice cells?  ...Or, is there a way I can do this directly in the raster world of GM?

Thank you very much in advance.
paul

Here is the 2m DTM (produces a rougher, more detailed terrain (as you would suspect), but not sure if that is a lot due to sample size per cell).


This is the 5m DTM (more smooth terrain (as you would suspect), but verging on too course for capturing fine scale dune structure)

Sign In or Register to comment.