Setting the Overlap classification flag

LAS v1.4 introduced the concept of the Overlap classification flag. Since this new flag did not previously exist in the classification code byte, the class offsets discussed here do not apply to the Overlap classification flag. A user would need to have both LP360 and TerraScan in order to properly identify and flag overlap points.

  1. If you have the TerraScan trajectories that go with the LIDAR data, and they have they both share the same timestamp format (Adjusted Standard Time), then one can run Deduce Using Time to ensure the flight line number assigned to the point matches that of a trajectory.
  2. Use the Cut Overlap routine in TerraScan to move those overlap points to a single class, Class 12 – Overlap.
    1. If you do not have a “Class 12 – Overlap” you may create one in your point class table (TerraScan General toolbar -> Point Classes).
  3. Use GeoCue or LP360 to up convert the LAS v1.2 file to v1.4 selecting the appropriate options of “Input has Flags and 32 Classes” or “Input has 256 Classes (TerraScan Format)”, ie 256 classes and no flags.
    1. The first option will treat class codes higher than 32 as the corresponding class and flag equivalents.
    2. The second maintains all classes and flags no points.
  4. On the LAS v1.4 file, run a basic filter in LP360, or LP360EQC, to assign the overlap flag to those points and reclassify them as class 1 – Unclassified.

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