I have used the lidR package (https://github.com/Jean-Romain/lidR) to produce a normalized point cloud. I then filter out the points tagged with the overlap bit using:

opt_filter(ctg) <- "-drop_overlap"

The resulting point cloud appears to have a directional pattern, where points are present in somewhat uniform strips. It seems the unfiltered point cloud has a similar pattern but much it is much less pronounced. Is this a normal feature of lidar data?

Here is a 3d representation of the normalized and filtered point cloud with the pattern I have described: enter image description here

  • 1
    Now I know that your dataset is sample with two beam this image makes even more sense.
    – JRR
    Commented Mar 23, 2020 at 1:15

1 Answer 1


ALS data are usually sampled with an oscillating mirror carried on a moving platform. The point pattern is thus a zigzag. Here you only have a very tiny region of the flightline so you are seeing near parallel lines. Everything looks ok to me. I'm only questioning the relevance of using -drop_overlap because its meaning is often misunderstood

  • Thanks for your answer. The area is indeed quite small - it is a ~1000 square meter circle. I'm using -drop_overlap to achieve a single coverage point cloud. I will be extracting statistical moments (e.g. 90th percentile height...) from the point clouds to be used as predictor variables in an Above Ground Biomass model. I don't want the distribution of returns to be influenced by double coverage in areas of overlap.
    – Lucas
    Commented Mar 11, 2020 at 18:32
  • You are assuming that the overlap bit tags the points in overlaps. I might be true... or not. Just sayin'
    – JRR
    Commented Mar 11, 2020 at 18:35
  • You are suggesting that the flag could have been inappropriately set by the data producer. The metadata associated with the las tiles includes the following information - "Swath overage points were identified in these files using the standard LAS overlap bit." - "the nominal swath overlap, as a Percentage: 20" I feel like I should go by what is indicated in the xml metadata...
    – Lucas
    Commented Mar 11, 2020 at 18:41
  • 1
    If it is documented by the provider it is ok!
    – JRR
    Commented Mar 11, 2020 at 18:48

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