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There are numerous methods for classifying ground and not-ground points from raw LAS point clouds. They all do a great job, depending on local circumstances, but inevitably even when algorithm and terrain are well matched there are some exceptions. How to clean up those outliers? Are there any tools out there in which one can interactively lasso a collection of points and manually change some attributes? E.g. like in a paint program?

3D point cloud with partial building roof classed as ground

Horizontal 3D view of LAS point cloud with all "non-ground" points removed, however some points are mistakenly still classed as "ground".

Viewpoint top down view

Viewpoint top down view

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    Terrascan terrasolid.com/products/terrascanpage.php can do this, it is an extension for MicroStation bentley.com/en/products/brands/microstation - not cheap but effective. QT software (appliedimagery.com) also claims to be able to do this but I cannot attest to this as I have not used it. LASTools has a viewer/editor but I find it clunky at best.
    – Michael Stimson
    Dec 11, 2017 at 23:25
  • What type of terrain and conditions exist in your AOI? Do you know what caused this anomaly? What features are in this screenshot?
    – Aaron ♦
    Dec 12, 2017 at 4:09
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    @Aaron the highlighted anomaly is part of a building on a flat area beside a river and forested slope (binged.it/2BWlsNF), but troubleshooting why the algorithm failed or what would have been a better one to use isn't the point of this question. All algo's fail somewhere, what to do with the stuff they miss?
    – matt wilkie
    Dec 12, 2017 at 18:00

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The LAStools' lasview tool provides GUI functionalities for manual editing points within a scene (including altering class codes and deleting points):

lasview: A simple OpenGL-based viewer for LIDAR in LAS/LAZ/ASCII format that can also edit or delete points as well as compute/display a TIN computed from (a selection of) the points.

Here is a tutorial from Martin Isenburg which explains how to use lasview.

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    Finally got a chance to follow up. Lasview does work for this, though be prepared to set aside some time to get familiar with controls. It's tricky to get the view spun around to the right vantage to select and edit only the points of interest. = and - for growing/shrinking point size is essential. The free version is limited to saving files of less than 1 million points.
    – matt wilkie
    Dec 18, 2017 at 22:26
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In ArcGIS Pro this is done with Interactive LAS point classification

The Classification tab allows you to interactively manipulate the classification conducted on the LAS files of a LAS dataset. You are able to quickly change the class codes and classification flags that are presently set on the selected points.

It works quite well but the view is limited to top down 2D map. You can't spin and rotate to see the elevation of the points. Another significant limitation is that the source file can't be compressed and must be in expanded LAS format, so set aside a lot storage space before starting.

If the Classification >> Select tool is disabled it means the "full resolution" threshold has been exceeded. Adjust the threshold via LAS Dataset Layer >> Appearance tab in the ribbon.

  • Full Resolution: set this value higher (larger) than your Zoom scale. Ex: if Zoom is 1:500, set full res to 1:750
  • Display Limit: set large as possible. Default is 800,000. I use 100,000,000.

If the select tool appears to work but nothing is ever selected make sure there are NO layers in the map that are being projected on the fly. Everything must be in the same coordinate system.

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