Volumetric Analysis Properties

How To Define a Volumetric Analysis Task

1. Use the Add Files command to open the LAS files that contain the data you want to analyze with the Volumetric task.
2. Use the Add Task command to create a new task. When you are selecting a Task Type in the Add Point Cloud Task dialog, select Volumetric Analysis. On the Point Cloud Task tab again, you should see the unique name that you gave your task selected in the list and the Volumetric Analysis properties displayed.
   
   

   Defining Hull Properties

3. Click the Hull tab in the Point Cloud Task window. This set of steps will define the circumscribing polygon and determine how the hull surface is to be generated.
4. To use the Base Polygon as the Hull, check Use Base Polygon. Otherwise, deselect this option and then select the browse button next to the 3D Polygon Boundary field. This will display the I/O Manager.
5. In the available drop-down menu under Type, select the method that will define the hull polygon boundary. The available options are:
   
   • Tool Geometry - allows you to specify the circumscribing polygon via the Feature Layer or Feature Layer indirect tools (the 2D drawing tools will be disabled for a Volumetric task).
   • SHP Layer - a shapefile defining the polygon to use.
   • File - other file that contains the polygon definition to use.
6. On the Hull tab again, in the Surface Generation Method drop-down menu, select the method to use for generating the hull surface.
   
   • Use LAS Points - builds a TIN model from the specified Input LAS Points Layer using the specified Input Points Filter and Breakline Enforcement. Note that the TIN model includes and is bounded by the specified Hull perimeter (specified in the 3D Polygon Boundary).
   • Use Polygon Only - builds a TIN model using only the specified hull perimeter polygon vertices and Breakline Enforcement.
   • Constant Z - a constant (flat) elevation specified by the Constant Z value.
7. If you selected LAS Points as the surface generation method, click the browse button next to the Input LAS Points Layer field to open the I/O Manager. In the Map Layer dropdown menu, select the layer to use.
8. On the Hull tab, if you selected Constant Z as the surface generation method, enter an elevation value in the Constant Z field.
9. To use Breakline Enforcement, select the Breakline Enforcement button. In the dialog that opens, specify Breakline Enforcement properties to use and select OK. See Breakline Enforcement Property Page for more information.
10.  Select Apply at the bottom of the window to continue.
    
    

    Defining Base Properties

11. Select the Base tab. The properties are mostly the same as the Hull tab.
12. Repeat the same steps that were necessary to create the hull surface for creating the base surface.
    
    

    Defining the Volume Properties

13. Click the Volume tab. This set of steps will specify the shapefile to which the Volumetrics output polygon is written.
14. Click the browse button next to the Output Polygon File field. The I/O Manager will display again.
15. In the available dropdown menu under File/Folder, select the folder button and then type a filename for the output polygon file and then browse to a location in which to save the output SHP file that will contain the volume properties. Press Save.
16. In the Output Mode list, select Append to combine the new file with an existing file or Overwrite to replace an existing file.
17. Click the Add to Map checkbox (also in the Volumetrics Output Polygon row) if you want to add the output file as a layer to the map.
18. Click Apply at the bottom of the Point Cloud Tasks window to continue.
    
    

    Defining the Optional Cut/Fill Image Properties

19. To generate an optional Cut/Fill image, select the Cut/Fill tab and enable the Output Cut and Fill Image checkbox. This set of steps will create a color-indexed GeoTIFF image representing positive or negative elevation differences between the hull and base surfaces.
20. Select the browse button next to the Cut and Fill Output Image File field. The I/O Manager will display.
21. In the available dropdown menu under File/Folder, select the folder button and then type a filename and browse to a location in which to save the Cut/Fill image file. Press Save.
22. Enable the Add to Map checkbox (in the Volumetric Output Cut and Fill Map row) if you want to add the Cut/Fill image as a layer to the map.
23. On the Cut/Fill Image tab, press the color button next to Cut Color and select a color to use to represent the cut values in the image file. The cut will represent a positive elevation difference between the hull and base surfaces.
24. Press the color button next to the Fill Color and select a different color to use to represent the fill values in the image file. The fill will represent a negative elevation difference between the hull and base surfaces.
25. Press Apply at the bottom of the window to continue.
    
    

    Defining the Optional LAS Output Properties

26. Select the LAS Output tab. This set of steps will set up the generation of a volumetrics LAS output file.
27. Enable the Output LAS File(s) checkbox.
28. Under LAS Point Source, select either the Hull or Base to use as the source of points for the LAS output file. The layer used to generate the interior surface of the option chosen here is the layer used in the generation of the output file. The points from the LAS Point Source determine the XY coordinates of the output points, while the Z value is computed as the difference in elevation between the hull and base surface at the point XY coordinate. The layer chosen here will also determine which output LAS version, point format, etc. will be used.
    
    

    Note If only one operand used LAS Points to generate its interior surface, that LAS Point Source will be used regardless of what is picked here. If neither operand used LAS Points to generate its interior surface, no LAS File output will be generated.

29. Select the Negate Output Z Value to flip the sign of the output Z value. The default is hull - base. Clicking this option will compute the Z value as base - hull instead.
30. Select the class to use for the output points in the Destination Class drop-down menu.
31. Select how the attributes are set up on the output points using any of the available options: Synthetic, Key-point, Withheld, Overlap.
32. Select Cookie Cut into Regular Tiles to break the output LAS file into tiles. This may be desirable if you have dense data and/or are covering large areas.
33. If you selected Cookie Cut into Regular Tiles, do one of the following:
    
    • Select By Size to specify the output tile size. Then specify the tile Width and Height in map units.
    • Select By Number of Tiles to specify how many tiles (files) wide and high the output should be. This will auto-compute the tile size for you at run time. Then specify the number of tiles in each row in the Rows field (number of tiles in vertical position) and the number of tiles in each column in the Columns field (number of tiles in horizontal position).
34. Specify a File Naming Method. See Specifying a File Naming Method for descriptions of each available method.
35. Select the browse button next to the LAS Output Folder field. The I/O Manager will display.
36. Select the folder button in the available File/Folder cell and type a filename if you are not tiling the output. If you have specified that tiles be created, then select the folder in which to store the output files. Press OK.
37. Enable the Add to Map checkbox (in the Volumetric Output LAS row) if you want to add the LAS file as a layer to the map.
38. Close the I/O Manager.
39. Press Apply at the bottom of the window to save your changes.