Re: [LAStools] las2dem and las2tin

[Ty Kennedy-Bowdoin]

I think the main difference is that las2tin stops short of making a raster (dem etc.). and gives you a bit more options to choose the parameters for the tin. 

so, las2dems results in a regularly gridded raster, and las2tin results in a trinagulated model (irregular vector), which could be used on its own, or could be gridded later if you so choose. 

If you are after a gridded raster, I would use las2dem unless you want to do the gridding yourself for some reason.

cheers,

Ty

On Fri, Feb 1, 2013 at 5:21 AM, Malgorzata Mendela <malgorzat...@gmail.com> wrote:

Hello,

what is the difference between las2dem and las2tin? I could not find it based on information that are given in README for these tools.

Concerning las2dem there is stated that " This tool reads LIDAR points , triangulates them temporarily into a TIN, and   then rasters the TIN onto a DEM";

whereas for las2tin there is stated " (...) reads LIDAR data in LAS/LAZ/ASCII format and creates a TIN".

Does this mean that both tools are dedicated to create DEM as TIN model?

 

Thank you for your help. 

Malgosia

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Ty Kennedy-Bowdoin
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[Małgorzata Mendela]

Tahnk you for your reply. 

Ok and what about lasgrid tool? What is then the difference between this tool and las2dem? Do both of them are used to create DEM as regularly gridded raster?

cheers,

Malgosia

2013/2/1 Ty Kennedy-Bowdoin <tbow...@stanford.edu>

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Małgorzata Mendela

[Martin Isenburg]

Dear Malgosia,

if you peruse the LAStools group you should find a few prior posts that explain the difference between lasgrid and las2dem.

lasgrid simply puts an x/y grid over all the points and looks which points falls into which grid cell. It then applied to all points of a cell the desired operation: keep the maximum, keep the minimum, compute an average, or compute the stddev. The result is stored in the DEM. Grid cells that have no points falling into them remain empty rasters unless you specify '-fill 1' or '-fill 2' in which case a simple neighbor averaging is done to fill empty rasters from the 1-ring (or if needed  the 2-ring) of filled neighbors.

http://lastools.org/download/lasgrid_README.txt

las2dem computes a triangulation (a TIN) of all the points. It then puts an x/y grid over the TIN and samples the elevation of the TIN triangles at the grid cell. Because the triangles interpolate across voids in the point distribution this should be your tool of choice when you create a DTM (i.e. you will be using only the ground points). if the triangles get too large they do not get "rasterized". this is controlled by the '-kill 500' switch that specifies the edge length at which triangles should get killed. the default is 100.

http://lastools.org/download/las2dem_README.txt

Cheers,

Martin @rapidlasso