Modifying the Minimum Plane Length

About the Min. Plane Length

The Min. Plane Length value is best input as the maximum point spacing or ground sample distance found in point cloud data. This distance is used to construct a moving window where the moving window will have a length and width of twice the Min. Plane Length value. A window sized with the dimensions as previously described, is fit around each point and an equation of a plane will be fit to these points. If the plane is a good fit based on the plane fit parameter, a surface growing process begins adding new points that are within a threshold orthogonal distance to the plane. In general, planar surfaces with an area less than the dimensions of the moving window described above will not be classified.

Effects of Increasing or Decreasing the Min. Plane Length
This parameter has the most complex effect when increasing or decreasing the value from the maximum post spacing or ground sample distance of the point cloud. Results are dependent on the amount of overlap, geometric characteristics of the planes (e.g., buildings) under consideration, amount and type of vegetation present, proximity of vegetation and other man-made objects to the planes, and the magnitude of the change.

• Decreasing Value
  The effect of decreasing the Min. Plane Edge is as follows:
  
  
  1. A decrease in the value will likely increase the number of vegetation points misclassified.
     
     
  2. A decrease in the Min. Plane Length may capture smaller planes that do not represent the objects of interest but were missed when the Min. Plane Length was larger.
     
     
  3. A decrease in the Min. Plane Length will reduce the number of points classified during the surface growing. This occurs because the surface growing expansion factor is based on the Min. Plane Length with a smaller value reducing the likelihood of growing the surface into nearby vegetation or disconnected man-made objects. Decreasing the Min. Plane Length beyond a certain point will eventually result in fewer points classified because the window size will be too small to find the minimum number of points required for a plane (i.e., 3).
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• Increasing Value
  The effect of increasing the Min. Plane Edge is as follows:
  
  
  1. An increase in the value will likely decrease the number of vegetation points misclassified for isolated vegetation patches.
     
     
  2. An increase in Min. Plane Length might not classify smaller planes that do represent the objects of interest that were classified when the Min. Plane Length was smaller but are missed at larger window sizes.
     
     
  3. An increase in Min. Plane Length will increase the number of points classified during the surface growing. This occurs because the surface growing expansion factor is based on the window size with a larger window size increasing the likelihood of growing the surface into nearby vegetation or disconnected man-made objects.