CSD - Computing Volumes

Volume Calculation

Note

To learn more about the inner workings of the Volume Calculation, please refer to 'How the volume calculation works' in the Help pages.
To visualize the volumetric differences in the 2D Plan View pane, refer to Visualizing volumes

Select

from the Grid Tools ribbon which opens the Volume Calculation Wizard Page#1.

Be patient as it may take quite some time to open!
Here select the area(s) to use as boundaries to the volume calculation.

The options are to use Multiple Boundaries or Current Selection, the latter referring to the area defined using the Selection button in the Home ribbon tab.

When set to Current Selection the extents defined using the Selection button are used.
When no selection is made, or when a different selection is needed, click on the

button.
The Wizard is then hidden until a valid selection is made with the Selection tool.

When set to Multiple boundaries, select from the pull-down list of Line and CAD/GIS files.

Then choose the layer and polygon(s) to use. Any checked areas are used for the volume calculation. Use Ctrl+A to select all areas listed.

Press Next to advance to the wizard's second page.

Choose the active and reference layers to use in the volume calculation based on the differences between these two layers.

There are three different layer Types to use for the Active Layer in the volume calculation: survey, design model, and sounding grid.

Active Layer

Layer Type

Survey

Select a survey file and the data source. The data source is either/or:

Grid - The calculation uses the gridded survey data as source for the calculation
Points - Uses the footprints as source for the calculation

Sounding Grid

Select a Sounding Grid file, Layer and Attribute to use as source for the volume calculation.
Only attributes representing a depth are supported (Mean, Minimum and Maximum).

Design Model

Select a CAD / GIS file and layer to use as a design model.

A fourth Type is added when defining the Reference Layer.

Reference Layer
Layer Type	Reference	Specify a single depth to use in the volume calculation.

Enter Upper and Lower tolerances if required as part of the volume calculation.

Enter values for link settings. These are used to optimize the TIN (Triangulated Irregular Network) models used for the Volume Calculation.

Link Angle

This angle control lets you enter the maximum edge angle to use in creating link lines between points. Where the angle between three points along the outside edge of the DTM is greater than the maximum value you enter here, a link line along the opposite side is excluded. The default value of 160° is usually adequate (the maximum value is 179°). With larger angles, undesirable link lines can be created around the exterior of the project. You can correct this situation by reducing the edge angle.

Link Distance

This distance control establishes the longest distance between triangle points along the edge of a DTM. The value is used to trim the edge of the DTM after all of the points have been linked. If the distance between two edge points is greater than the distance entered here, the link is deleted. Try to set this distance at a value that is a little larger than the longest distance between your exterior points.

Note: If there is a "lone" point or an island of points which are farther from the main group of points by a distance that is greater than the maximum edge distance, links will still be drawn so that a single DTM is formed. All 3-D points on a layer are included in the DTM, regardless of the linking parameters.

Decide which Grid calculation method to use.

Square Columns Method

The square columns method enumerates over all sounding grid cells in the area of interest. For each cell the necessary attribute (mean, deepest or shallowest) is read. At the same location one sample is taken on the reference layer.
The difference between these two values is multiplied by the area of the cell, resulting in a small volume. All these volumes are added up to form a final volume calculation result.

In the case that a grid cell is partially in the area of interest, the exact area within the area of interest is calculated and used.

The square columns method is a fast and memory friendly approach.

Triangulated Method

For the triangulated method, both the active and reference layers are triangulated. The resulting triangulated layers are then compared to calculate the volumes.
This method is slower and has (depending on the data and area) a significant memory load.

For a full explanation, also refer to How the volume calculation works.

Click Next. This initiates the calculation resulting in display of the final page of the wizard when the volume calculation is finished.

A summary of the volume calculation is shown.

Click on the Print and Export button to open the Volume Calculation Report.

Volume Calculation Report

Most of the parameters on the Volume Results page relate to configuring the report and are self-explanatory.

Which columns to show under Volume Results is a configurable item; press the Columns button:

Use the Export button to save the columns configuration to a *.vcrconfig file. Use the Import button to import an existing configuration file. Files are stored in the \Export folder.

Adjust the size of the image shown in the report.

Export results to a third party format using the Export tool located in the ribbon. Various formats are available:

Print a hard copy.

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Return to: CSD - Dredging Results.

Return to: Dredge Reporting.