Processes and tools

Volume measurement - PIX4Dsurvey

PIX4Dsurvey's volume measurement tool measures the volume between a base surface (defined by a volume polygon) and the active point clouds. As a default, this method connects all the vertices and triangulates the volume above and below the base surface. It is possible to move the vertices vertically to a different altitude.

Video: PIX4Dsurvey tutorial: Create volume measurements in PIX4Dsurvey

Video: Do you want to measure the volume of an object, even against a wall or in a corner? Try volume measurement in PIX4Dsurvey and get your data with fast, simple steps!

How to create a new volume

    1. On the tools bar, select the Volume measurement tool by clicking volume_icon.png.

      PIX4Dsurvey_volume_measurement_selection.png

    2. To draw a volume, left-click on points in the 3D view. Right-click or press enter to complete the volume base polygon.
    3. (Optional) To accurately mark the vertices, select the volume using the simple selection tool ic_cursor_black.png. The position of each vertex can be corrected in the 3D view, on the images, or using the vertex editor.
    4. (Optional) To assign a common elevation to the vertices of the volume base surface, first select the volume using the simple selection tool ic_cursor_black.png. Then, in the volume panel, click align vertices vertex_align.png to choose how to align the vertices.
Tip: Aligning the vertices to the lowest base elevation simplifies the volume measurement for stockpiles leaning on walls or in a bay. More information can be found in the align vertices article.

After drawing the volume, details about the volume measurement are displayed. More specifically:

  • Name of the volume and name of the layer the volume belongs to. The name of the volume layer and color of visualization can be edited.
  • 3D perimeter, 3D area, minimum and maximum elevation are displayed according to the drawn polygon.

    PIX4Dsurvey_volume_measurement.png

Note: A new volume layer can be added by selecting the add.png icon of the volume layers on the left sidebar. The volume can be moved to another volume or vector layer by right-clicking on it.
Tip: It is possible to use the Stockpile Detection tool to easily detect and create volume polygon around stockpiles.

How to compute the volume

Once the volume is drawn, in the Measurements section of the volume panel, click Compute to trigger the volume computation.

PIX4Dsurvey_compute_volume_measurement.png

After completing the volume measurements, the cut/fill volumes and errors are displayed.

PIX4Dsurvey_computed_volume.png

More specifically:

  • Cut volume [units3]: Volume above the volume base. The volume is measured between the volume base and the surface.
  • Fill volume [units3]: Volume below the volume base. The volume is measured between the volume base and the surface.
  • Total volume [units3]: The total volume (cut + fill volume).
Important: If the polygon defining a volume is modified (adding/removing/moving vertices), a warning appears in the Volume layers list and the Export tab, indicating that the volume measurement is now outdated.
It is needed to compute the volume again to take the modifications of the volume polygon into account in the volume measurement.
WarningVolumeLayers.jpg
WarningExportVolumes.jpg
Tip: Only the displayed point cloud points are used in the volume calculation. This means that, for example, in the case where the terrain filter classified a stockpile to be terrain, and a conveyor above it to be non-terrain, it is just needed to turn off the non-terrain layer before calculating the volume to get the right results. No need to delete points that should be excluded.

How to export a volume or volume report

After computing the (cut/fill) volume measurements, the Volume report, the volume polygon and the 3d volume are available to be exported.

PIX4Dsurvey Volume export.jpg

To export the Volume report:

  1. On the Menu bar, click File, then Export. Alternatively, on the top right, click export.jpg Export. The Export panel opens on the right.
  2. In the Export panel, select the output format (PDF, HTML, or CSV for volume reports. LandXML for the 3d volume. DXF, ZIP SHP, SHP, or GeoJSON for the volume polygon).
  3. (Optional) Unselect the output Volume layers that do not need export.
  4. In the Destination section, navigate to the path where the files should be saved.
  5. Click Export.
Video: The following video shows how to generate a volume report with PIX4Dsurvey.

How PIX4Dsurvey calculates the Volume measurement

PIX4Dsurvey calculates the volume as follows:

1. A new volume is drawn. For more information on how to draw a volume: How to create a new volume. volume

Note: PIX4Dsurvey creates the base taking into account the altitude of each vertex.

volume_base

2. PIX4Dsurvey projects a grid with GSD spacing on the base.

volume_base_grid_white

3. For each cell i of the grid, its volume (Vi) is given by:

Vi = Li * Wi * Hi

Where:

Li = the length of the cell.
Wi = the width of the cell.
Hi = the height of the cell.

The Length (Li) and Width (Wi) are equal to the project's GSD.

Li =Wi = GSD

The Height (Hi) is given by:

Hi = ZTi - ZBi

Where:

ZTi = the terrain altitude of each cell at the center of the cell.
ZBi = the base altitude of each cell at the center of the cell.

Therefore, the volume Vi of cell i is given by:

Vi = GSD*GSD* (ZTi - ZBi)

Note:
  • ZTi is the altitude of the 3D terrain corresponding to the center of the cell i.
  • ZBi is the altitude of the base surface of the volume corresponding to the center of the cell i .
volume_pixel_3d.jpg
volume_pixel_element_dimensions.jpg

4. PIX4Dsurvey calculates 2 volumes:

    • The Cut volume Vc is the volume between the base and the 3D terrain when the terrain is higher than the base.

Cut volume = VC = VC1 + VC2 +...VCN

Where:

VC1...N = Cut volume for cell i..N

    • The Fill volume VF is the volume between the base and the terrain when the terrain is lower than the base.

Fill volume = VF = VF1 + VF2 +...VFN

Where:

VF1...N = Fill volume for cell i...N.

Note: The Fill Volume is given with negative value/sign.

5. The Total volume is given by:

Total Volume = VT =VC+ VF