We have a lot of images of landscapes and we are interested in finding the volumes of the rocks and forest located on them. The volume tools don’t seem to do a very accurate job, many of the measurements have a large margin of error because of the human error of clicking the points around the object to be the base surface. I noticed all the different volume options, which is best for calculating volume on a sloping hill? Is it the change in elevation that is making these measurements inaccurate? Is there anything to be done to make the measurements more accurate or to edit the volume once you have calculated it?
The accuracy of a volume measurement depends on the quality of the reconstruction and on how well the base surface is defined.
This means that I would first make sure that the project itself is well reconstructed by checking the quality report and the point cloud. The point cloud can be checked directly in the rayCloud view: is there noise? are there more than a single layer? how is the reprojection of a point in the images?
The volume measurement accuracy can also be increased by adding Ground Control Points (GCPs) in the area you measure or by adding a scale constraint as reference to the project:
How to scale a project
If you have made sure that the project is well reconstructed, you can have a look at these articles for more information:
How Pix4Dmapper calculates the Volume?
Accuracy of Pix4Dmapper Outputs
As for the definition of the base surface, the “Triangulated (default)” or “Fit plane” surface option seems most adapted for your use case, as the other options will not keep the angle of the slope in the base surface. As you noted, the base surfaces will still need to be clicked carefully so that the right area will be measured.
Hi, Pierangelo
I have the similar question, as shown in my picture,
I want to measure the volume the seaweed deposited on the beach zone, and the beach base is sloping and not flat. Under the ‘triangulated base’, the volume can be acquired. However, I am not sure which volume value (i.e. cut volume, fill volume, and total volume) is my target volume, should I plus the cut and fill volume together (25.84+1.14=26.98 m3)? Or just use the cut volume as the volume of seaweed pile? Could you give me a brief explanation, please?
You could select the one that you need but please note that fill volume has a negative value so if you put it together, it should be 25.84 - 1.14 = 24.7, which is the same as the total volume in the attached image. Total volume is often used as a result of a volume calculation.
- Cut Volume [units3]: Volume that is above the volume base. The volume is measured between the volume’s base and the surface defined by the DSM.
- Fill Volume [units3] : Volume that is below the volume base. The volume is measured between the volume base and the surface defined by the DSM.
- Total Volume [units3] : Total volume, Total Volume = Cut volume + Fill volume.
Please visit the link below for more information.
Menu View > Volumes > Sidebar > Objects.
Volume Difference of an Area Surveyed over different Time Periods
Warm regards,
Thanks a lot for your kind reply. However, still, I am not very sure which volume value (cut volume or total volume) is better to show the true volume of seaweed pile on the beach. Could you give me more explanation, please, based on your experience?
I don’t have the data so I cannot confirm it, but in general, the total volume could be used. The total volume is calculated using both areas below the base (Fill) and above the base (cut).
Cut and total volume could be the same if there are no areas below the base.
Kind regards,
Hi, Yuka
Now, I know that clearly. Thanks very much for your detailed explanation!
Wish you a happy day!
Thank you for your comment! Have a wonderful day!