Statistical Noise Point Filter

*This feature is available in the Advanced license level of LP360.

About the Statistical Noise Point Filter

The Statistical Noise Points classifier is an automated algorithm that is used to find points that fit a "noise" criterion. These points are then moved to the specified Destination Class.

The Statistical Noise Point Cloud Task is intended to be used for smoothing near-horizontal surfaces such as ground. It could be applied following ground classification where the resultant ground is "noisy" as a result of laser range precision ("noisy" range) or surface characteristics. A common approach is to iteratively apply this algorithm. This classifier has the effect of thinning data in the Source class so be sure to monitor point density if iteratively applying this classifier.

Note that this is not the appropriate classifier for finding "low" points. Use instead the Low/Isolated Point Cloud Task.

Basic Algorithm Description: A "virtual" grid of cells of spacing (Sample Distance) X (Sample Distance) is superimposed over the task area. For each cell the statistical mean Z and standard deviation of mean Z are computed. All points with a Z value more than "Max Standard Deviation" above the mean Z or with Z value more than "Max Standard Deviation" below the mean Z are moved to the specified Destination Class (depending on selected options). If the "Use separate high point class" is checked, the points above the upper threshold are moved to the separately specified High Points Class.

How to use the Statistical Noise Point Filter

1. Use the Add Files command to open the LAS files that contain the data you want to use.  

2. Use the Add Task command to create a new point cloud task. When you are selecting a Task Type in the Add Point Cloud Task dialog, select Statistical Noise Point Filter. Once you click OK, you should see the unique name that you gave your task selected in the list and the Statistical Noise Point Filter property page displayed on the Point Cloud Task tab.

3. Specify the settings for the Statistical Noise Point Filter operation in the Properties page that displays.

Overview of the Statistical Noise Point Filter

Source Points Button
The set of points that will be used in the filter. If a classification is not turned on or is a part of the filter, then those points will not be used in the filter nor will they be classified or edited.

Filter Low Points
Checking this box enables the low points classifier.

Filter High Points
Checking this box enables the high points classifier.

Destination Class
The class that points passing the selected test(s) will be moved to. Note: If "Use separate high points class" is checked, the high points are moved to a different class.

Units
Convert to the Map Units if this unit setting is different (e.g. if the Map Units are set to meters and the units of this dialog are set to feet, the input units of the dialog will be converted to meters).

Sample Distance
The virtual grid size (in the X, Y plane) used for determining the sample for each statistical test. Note: In undulating terrain, this will need to be smaller than in flat terrain. The trade-off, of course, is that a larger sample size considers more points in computing the standard deviation.

Max Standard Deviation
The deviation used as the threshold for classifying points.