# Stage Curves - How do you calculate the cut volumes between two surfaces

Hi there. I have two surfaces of a Tailings Storage Facility, the fist surface is the existing TSF and the second surface is the new area that will be added on top of the existing TSF. I want to calculate the volumes in 0.5 meter intervals between these two surfaces. Please can you advise me on how to go about doing this?

As a reference value, I have calculated the volume between the two surfaces. I have used this volume to compare my cut and fill results to.

I have tried to run the cut and fill tool on the two surface collectively, where I used the "Perform multiple calculations over a range of base heights" option. Here I used the min elevation as the min elevation of the existing surface, and the max elevation as the max elevation of the new surface. However, the total cut volume did not equal the volume between the two surfaces.

I have also tried to combine the two surfaces, however this was still unsuccessful.

Any assistance would be appreciated. Thank you!

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## Best Answers

• Accepted Answer

Hi Nakela,

I'd direct you to this excellent workflow from AlienYouth: https://www.globalmapperforum.com/discussion/15921/tools-for-calculating-volume#latest

And also this excellent webinar (a bit dated now, but workflow is exactly the same): "Analyzing Terrain in Global Mapper" https://www.youtube.com/watch?v=2kLAEtExNFk

If those don't help, suggest you upload a couple of screen grabs of what you are trying to do to this forum and we'll help.

Cheers,

/al

• Accepted Answer

Check out the reply to this post.

Measure Volume Between Surface of Waste Rock Dump and Uneven Topo at Incremental Intervals? — Global Mapper Forum

The problem with GM here is similar to the problem with the STAGESTORAGE command in AutoCAD. They work fine for comparison between a flat surface and uneven surface such as ponds, but not between two uneven surfaces like what you are analysing. In a nutshell you have to run the volume analysis twice against a common 'comparison surface'. So in essence you are computing the volume between the Existing TSF and the comparison plane; and then the Proposed TSF surface and the plane. You then subtract one from the other.

I included a video and an excel spreadsheet to paste the results to calculate the stage storage. The total volume cross check is reasonably close to the volume results from Civil 3D and Deswik.CAD. FYI I now use Deswik.CAD to compute my stage storage for TSF/DSF designs. It's much quicker and more accurate as it works with the original wireframe/mesh.

## Answers

• Thank you both for your answers, I will try out these methods and see what answers I get to. Much appreciated!

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