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How can I delete duplicate LiDAR points? I incorrectly read the same las twice and saved as a one file resulting in duplicate XY points. How should I delete these duplicate points?

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    What software and/or tools are you using and what format is your data in (.las for example)? In ArcGIS there's a Delete Identical tool at the Advanced License level... but I don't know if that would work on a LIDAR point cloud. – Chris W Mar 11 '15 at 21:12
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You can delete all duplicate points from a las, laz or ascii file using lasduplicate in LAStools.

Finds and removes all duplicate points from a LAS/LAZ/ASCII file. In the default mode those are xy-duplicate points that have identical x and y coordinates. The first point survives, all subsequent duplicates are removed. It is also possible to keep the lowest points amongst all xy-duplicates via ‘-lowest_z’.

It is also possible to remove only xyz-duplicates points that have all x, y and z coordinates identical via ‘-unique_xyz’.

Also, lasfilterduplicates in the lidR package (documentation p. 51):

lasfilterduplicates(las)

Filter points that appear more than once in the point cloud according to their X Y Z coordinates

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You can also try a tool in WhiteboxTools - LidarRemoveDuplicates. You can run it separately through CMD line or as QGIS 3.4 plugin. Instruction on how to use and install WhiteboxTools in on their webpage

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If you consider to remove duplicated points on X, Y coordinates (with different Z), after using lasfilterduplicates function from lidR package, you may use lasfilter function.

las <- lasfilter(las, !duplicated(las@data, by = c("X", "Y"))

I think it will retain the first return points (from that duplicated points).

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