How to compute a volume in PIX4Dcatch?

Volume can now be computed directly in PIX4Dcatch. Users only need to capture the scene which contains the volume they want to compute. Then after only small manual steps, the volume could be computed in a few minutes allowing the user to save time and to give instant feedback on site.

Compute Volume - Summary

• Capture the scene which contain the volume to be computed

• Select Volume Computation on the project view

• Define the base of the volume by manually adding points

• Compute the volume

• Export the results as a PDF report

Compute Volume - Detailed Description

To compute a volume, first visit the Tools at the bottom and select Volume Computation.

Once selected, a densification process will be launched automatically to facilitate the entire workflow.

To be able to compute the volume, it is necessary to define the base of the volume by simply clicking on the screen to add points.

To remove the previous point, tap on the icon .

To remove all the points created, tap on the icon  

After three points, the computation is possible and could be launched by clicking on the Compute button .

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It is possible to add as many points as it is necessary to well define the base of the volume.

Once the base is correctly defined, to start the volume computation, press Compute.

A progress bar is displayed.

Once the computation is complete, the values of the volume(s) could be found on the dropbox list .

Volume(s) could be deleted with the trash icon 

Mesh volume is displayed on the point cloud.

On each volume, an uncertainty is computed and displayed 

Export the results in a PDF report by clicking on Export PDF.

Select where to store the file.

Volume uncertainty

Volume measurements are reported with an uncertainty that can be read as computed volume +/- uncertainty. This means that the volume is estimated to lie in the [volume-uncertainty, volume+uncertainty] interval with a confidence of about 68%. For confidences of 95% and 99%, the estimated intervals are respectively [volume-2*uncertainty, volume+2*uncertainty] and [volume-3*uncertainty, volume+3*uncertainty].

The uncertainty estimation is based on a theoretical model, which accounts for different sources of uncertainty, such as the point cloud noise, completeness and density. The model does not take scale errors (which can be prevented using an RTK receiver) or errors in the base surface into account. An extensive validation of the theoretical model has been carried out by running experiments on various types of objects.

Volume Confidence with Uncertainty Volume Mesh

Understanding the Uncertainty Volume Mesh

The Uncertainty Volume Mesh provides a visual representation of the confidence levels for each point in the computed 3D volume. These confidence levels indicate the reliability of the volume data, helping users evaluate the accuracy of the measurements. Confidence is expressed as a value between 0 and 1:

• 1 (High Confidence): Highly reliable data.
• 0 (Low Confidence): Data that may lack accuracy.

The confidence values are visually represented using a color-coded legend, which allows for quick identification of areas with varying levels of certainty.

 

Color-Coded Legend for Confidence Levels

The uncertainty mesh uses colors to display the confidence levels:

• Red: Lowest confidence values, representing areas with significant uncertainty.
• Yellow: Somewhat low confidence, indicating moderate reliability.
• Green: Moderate confidence, showing acceptable data quality.
• Blue: Highest confidence values, marking areas of excellent data quality.

PDF Report - Generation

Export the results as a PDF report

Informations which could be editable or entered:

• File’s name: Edit the default name or enter a new one

• Description (optional): Add a description before exporting the report

• Date created: Fixed value of the creation of the report

Press Export

Select the location of the file

Back to the captured point cloud view

PDF Report - Details

The PDF report contained a first page with:

• The file name

• The date created

• The description

• The version of PIX4Dcatch application used for the computation

One or two other pages (depending on the number of volumes computed) are following.

For each type of volume (cut and/or fill volume):

• Value of the volume with his uncertainty

• Value of the 3D area computed with the 3D coordinates of the points defining the base

• Value of the 3D perimeter computed with the 3D coordinates of the points defining the base

• A 3D view image

• A top view image

Best practices

Capture the full dimensions of your object

It is important to capture the full size of your object in order to get the correct volume. 

• Capture both the bottom of your object and its top.

• Do a closed loop

• Remove unwanted objects if possible

Get an accurate 3D model

To get precise volume, it is important to obtain an accurate point cloud.

• To improve the 3D reconstruction of your project, use Autotags.
• To improve the absolute accuracy of your project (and if outdoor), use RTK rovers compatible with PIX4Dcatch

Define the base of your volume precisely

• Use different perspectives to draw the base

• Add many points to define precisely the base

• Remove the point if he seems to be incorrect