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I have a raw LAS data that has only one return (no second/ third.. return) and not classified yet. The only information I have is intensity and elevation. Is there any way that I can classify bare earth in ArcGIS? (vendor does not have more info than that). I tried classifying by selection from the profile view, but I know it is impossible to apply to all data.

  • I too wish to do this. It seems this is apart of post processing and there's a principal of mass (assisted heads up classification) that can not be avoided. I'd be happy with a sampling tool that took the lowest z within a tolerance on xy. – GISI Apr 13 '16 at 1:31
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In ArcMap 10.4, there is the ClassifyLASGround tool, from the 3D Analyst toolbox. According to ESRI this tool:

Classifies ground points in lidar data. Only the last return of LAS points with class code values of 0 (never classified), 1 (unassigned), or 2 (ground) will be considered for reclassification as ground.

It has 3 methods for performing the classification: standard, conservative and aggressive. The tool syntax is:

ClassifyLasGround_3d (in_las_dataset, {reuse_ground}, method, {dem_resolution}, {compute_stats}, {extent}, boundary, {process_entire_files})

As alternative, consider using tools from outside ArcGIS if you have difficulties using ClassifyLASGround. Some options are:

  • MCC-LiDAR (MCC algorithm for classification).
  • LAStools (lasground tool).
  • Fusion (groundfilter tool).
  • PDAL (ground and pcl tools).

The following posts from GIS SE have examples about using these tools:

- Determining bare earth DEM from unclassified LAS file?
- Classifying LiDAR data with LAStools?
- Creating DEM from LAS file without using LAStools
- Finding outliers with wrong Z values in LIDAR data

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There are various algorithms developed for classifying a LiDAR point cloud. ArcGIS doesn't have this directly implemented (up to version 10.1 at least), but I recommend lastools. It's a collection of packages for LiDAR processing, including bare earth classification (the module is named lasground). They even have toolboxes developed for import in ArcGIS, so you can do all your processing from there.

Please note that although it's free open software, there is a limitation in the non-commercial version for point clouds of up to 1.5 million points I think...above that the program will generate the output with some no-data bands that traverse it.But you can easily overcome this by splliting your data into tiles and processing them separately. More info here: rapidlasso Lidar processing tutorial

Another interesting tool is MCC-LiDAR. It's a simple command-line executable but I found it gives good results if you take the time to find the best combination of parameters to pass to the program (it uses two: a spacing parameter and a curvature threshold one, more details about how it works in this paper). Unfortunately it appears to be out of active development (last release is from 2013) so it works only with .las format of up to 1.3 or 1.2., but if you have newer version files you can easily convert them to older ones (with a module in lastools for example) since they're all backwards compatible.

You might encounter some problems in densely vegetated areas like shrubery or forests because you only have first returns...but experiment with the data and let us know what you achieve, I'm also actively interested in finding solution for this exact topic.

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