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Volume base surface that conforms to actual DSM

Hello,

I have been scanning through the help sections and community posts to see how I’d go about using a DPC or 3-D Mesh from a aerial survey I took to create an accurate base surface.

I shot an area pre-stockpile, and will shoot it again one the crushing operation is complete to calculate a volume of material crushed. Can I not utilize the pre-stockpile survey to create an actual base to the stockpile so the volume analysis is more accurate than any of the base surface options in the volume settings?

Can I export the current model as a shp file and import it into the next survey as a volume? Then when calculating the volume of the material sitting on top of the imported volume it will be a little more accurate by not including the original imported “volume” or surface?

Thank you for your assistance!
Scott

Hi Scott,
Thanks for your interest in Pix4D. You could create a surface in the raycloud and then Export it. You can then import the volume base into the second project just follow the directions in the linked support documents. Please let us know if you encounter issues.
Regards,
Aaron Woods

Hello Aaron, thank you for the input. I have clicked on the 6 vertices that make up my surface boundaries and made sure they were marked on at least 2 images each. I am still getting an error n/a on the enclosed 3D Area (not sure if that matters here).

I should clarify what my expectations are, and maybe you can let me know if I am in fact already generating what I need or if I need to try something else or if it is not possible in Pix4D. When I use Trimble Business Center 5.0 and I create a surface, I see a 3D triangle mesh over the entire surface, contouring to ever bump and dip in the surface. I don’t see that with pix4D. All I am seeing is a 2D surface, with no evidence of it taking into account the topography that was created. The entire purpose of this exercise is to negate the variable topography underneath the stockpile they are about to put on that surface.

TBC 5.0

Pix4D

Does the Pix4D program in fact take the generated point cloud or triangle mesh into account when I create the surface even if it doesn’t look like it on the visual display? I assume it must but I hate to assume.

Thanks again!
Scott

So here is a source of my confusion. In TBC I created a surface and then ran a earthworks report with that surface as the base of the stockpile. Since nothing has changed, obviously there should be no cut/fill.

TBC

I then exported the surface from Pix4D, imported it back in as a .shp file surface, then selected an area within the imported base and ran a volume. Now since nothing had actually changed, shouldn’t there also be no cut/fill?

Pix4D

As I type this it is becoming apparent that the volume calculations do not take into account the triangle mesh and surface of the model. it seems to only create a 2D plane (possibly rudimentary 3D plane) between the vertices the user lays out. It then looks at the cut and fill from that plane to the triangle mesh.

Is this correct?

Hi Scott,

Your findings are correct, the volume is generated based on the DSM and not on the mesh.

It is not possible to overlay more volumes of the same area in Pix4Dmapper. You could compare the volume changes over time by using the exact same base surface. As Aaron mentioned, I would create the base surface in a Pix4Dmapper project, export it as shapefile and then import it in the other Pix4Dmapper project. However, it is a bit cumbersome to compare volumes over time using Pix4Dmapper alone.

This tool might be more suitable for your intentions (due to its timeline functionality): Compare stockpile volumes over time.

An alternative would be to export both the DTM/DSM files from each survey over into another software that is able to compare the two DTM/DSM datasets such as Global Mapper. More info can be found in this community post: Cut and fill software.

Best,
Teodora