Statistical Point Reduction

In this section:

Introduction

This command will reduce the amount of points from one or more input data sets. The selection method can for instance be priority of the Minimum or Maximum depth values. The selection area can be by looking at points inside a Rectangle or Circle. The selected points are always with the original position and not snapped into any grid structure. 

The output will be a new point data set which in Geocap will have a schema of type Pointcloud.

The command is a folder command and is implemented for folders with schema types Charts, Multibeam, Soundings and Generic.

Selection of shallowest point within 250 m radii.

   
The Statistical Points Reduction dialogs

The content of the menu

The upper part of the menu contains the project name and the name of the active folder.

The Selection Area part

Set parameters for the geometry of the area to select points within.

• Rectangle: Divide the area into cells and analyse the points which ara inside the cell. Normally the cell size will be a square.
• Circle: First collect all points into cells with half the size as the circle radius. Then sort on increasing or decreasing values and then start removing points within the given radius. 

The Rectangle definition part

Set parameters for the rectangle to select points within.

The Width (X size) (m) and the Height (Y size) (m) are the definitions of the selection cell size.
Use Height=Width means that the value of the Height should be the same as the Width.

The Circle definition part

Set parameters for the circle to select points within.

The Radius (m) is the definition of the selection circle size.

The Point selection method part:

Set parameters for the method for selecting the points. Several options can be selected for each run, but be aware of possible memory capacity problems.

• Minimum means the shallowest (smallest) value inside the cell or circle.
• Maximum means the deepest (largest) value inside the cell or circle.

The next options are implemented for the Rectangle method only:

• Shallower than Mean means the first point shallower (smaller) than the mean value in the cell.
• Deeper than Mean means select the first point deeper (larger) than the mean value in the cell.
• Closest to Mean means the point with depth value closest to the mean values of the points in the cell.
• Minimum number of points in cell: If the cell has less points than the minimum number, the cell will not contribute with a point to the result data set.

The Dataset part or Survey Line part

Select in the list which datasets to do the point reduction from. The area for the selection is taken from the extension of the input files. The corner points are justified to fit the selected increments for the rectangles.

The Chart Name part

Select in the list for which charts to do the point reduction from. The area for the section is taken from the extension of the input file, and the input data is the Soundings data set. The corner points are justified to fit the selected increments for the rectangles.

The Results

After executing the statistical point reduction a dialog will pop up showing the result from the selection. The report is saved in the project structure in the folder named Reports located in the same folder as the command. The report itself is named as YYYYMMDD Statistical Point Reduction (the name of the executed command).
All reports from all runs will be saved in the Reports folder.

The resulting points file will be a combination of the inut file name, the selection area and selection parameters.

For the Rectangle method the file name will be: 'filename'_'selectionType'_'width'_'height'_'minimumPoints'.
For the Circle method the file name will be: 'filename'_'selectionType'_Radius_'radius'.