QS BHD - Volume Calculation

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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 learn more about terminology used, refer to Volume Results Terminology.

Visualize Layer Differences

Open the Processing Manager (PM) and double click on the sounding grid used during dredging.

Click on the Grid Tools tab to access the grid tools.

Select one or more Layers which modifies what is seen in the 2D Plan View.

Hiding or showing individual layers is done in the Project Explorer pane by ticking the check boxes in the 2D column (shown in the image above)..

Click on Color Settings to open the Plan View Settings dialog.

Click on Sounding Grid Settings.

Selections for the various General settings depend on the objective. Typically you want to know:

To be dredged PAID
1. Total
  1. Min
  2. Design
  3. Max
2. To be done
Dredged NOT paid

This requires you to:

Compute volume between the in-survey layer and the design layer.
Compute volume between an interim dredged layer and the design layer.
Compute volume between the final dredged layer and the design layer.
Compute volume between the final dredged layer and the design layer.
Compute volumes for all the above but using the upper and lower tolerances.

A reference layer is used to graphically illustrate the differences between two layers and to compute volumes.

Usually volumes are computed using the attribute 'Mean'.

Insurvey bathymetry layer (Max = -5.0, Min = -10.0)	Design bathymetry layer (Max = -5.0, Min = -10.0)
Dredged bathymetry layer (Max = -5.0, Min = -10.0)	Difference between Insurvey and Dredged bathymetry layers (Max = +1.0 Min = -5.0). Red indicates no difference.

So far only a visualization of the dredging results has been presented. The next step is to produce volumes.

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Calculation Procedure

Select

from the grid tools bar which opens the Volume Calculation Wizard Page#1.

Be patient as it can 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 refers 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.

Select one of three different layer Types: survey, design model, and sounding grid.

The selection is used for the Active Layer in the volume calculation.

A fourth Type is added when defining the Reference Layer.

This allows you to 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.
Typically a link angle of 160 degrees is used. Link distance depends on spacing of depth points.

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.

On completion results are displayed in the final page of the wizard.
A summary of the volume calculation is shown below.

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

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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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