TerraScan Ground Parameters

The TerraScan Ground Routine is designed to classify a ground surface from point data. There are multiple parameters within the filter. The following chart is a summary and general guidelines for setting the parameters.

Max Building Size Grid size for initial seed surface Smaller is more aggressive, higher fidelity, but more false ground points in initial surface
Terrain Angle Max terrain angle Maximum slope plus 10 – 15°; 88° in areas of near vertical features (cliffs, retaining walls)
Iteration Angle Maximum value at which a point will be added to the ground surface Higher is more aggressive; typical is 4 – 10°
Iteration Distance Maximum height above surface at which a point will be added to the ground surface Higher is more aggressive; typical is 0.5 – 1.5 m
Reduce Iteration Angle Soft stop; adds less points in areas with greater point density ½ of desired grid spacing
Stop Triangulation Hard stop; ensures no triangles with an edge smaller than the specified value ¼ of desired grid spacing

The TerraScan Ground Routine algorithm is implemented based on the widely used Axelsson algorithm.

Axelsson, P., 2000, “DEM GENERATION FROM LASER SCANNER DATA USING ADAPTIVE TIN MODELS”, International Archives of Photogrammetry and Remote Sensing, Vol. 33, part B4/1, ISPRS, Amsterdam 2000, pp. 110–117.

Additional Articles for Consideration

Tips for Classifying High Frequency Ground Features


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3 thoughts on “TerraScan Ground Parameters

  1. Saxon says:

    Thanks very much for answering the question. Just when I thought I had read the entire manual, the code section I skipped over. I will tackle the issue of out of memory when running Terradispatcher.

  2. Saxon says:

    Running a ground routine through terra dispatcher results in a number of blocks failing (9 out of 93). The report shows:
    Block Central_Coast_2020-C1-ELL_3406302_56_0002_0002.las
    Loaded 42729704 points from active block.
    Loaded 2783873 points from neighbouring blocks
    FnScanClassifyGround(“1″,2,”2”,1,600.0,88.00,6.00,1.40,1,1.0,0,2.0,0,0) returned -4

    All of the returned points in this routine are -4. Is this an error code?
    Thanks Saxon

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