Classify Ground

Classify Ground classifies ground points using a progressive TIN densification algorithm. Initially, the lowest elevation points in the cloud are assigned as ground points. From there, the algorithm attempts to add points to the ground class (i.e. densify the ground class) that are within the specified Iteration Angle and Iteration Distance. Essentially, for a point to be classified as ground, it cannot be too high above one of the starting ground points:

Iteration Angle and Iteration Distance are visualized:

As mentioned above, the filter initializes using the lowest elevation points (the ground is presumed to be the lowest most feature). Thus it is important to Classify Noise prior to running the Classify Ground tool, otherwise, isolated points located far below the true ground surface will be initiated into the ground class, and from there it is unlikely that points in that region satisfy the Iteration Angle or Iteration Distance parameter. This common issue is visualized below: