Sample Line Volume Report and Suface Volume give different Quantities

[seskinner]

Hi.

I'm working with TIN surfaces, doing cut/fill comparisons for a surface mine.

My volume surface statistics show a cut volume of 5167.22 cy and fill volume of 8456.18 cy.

The sample line group volume report show cumulative cut of 5527.67 cy and fill of 8465.56 cy.

What could be some causes of this disparity. All reference surfaces are built from points and use a non-destructive boundary.

Any help would be greatly appreciated. Thank you.

Scott

[KirkNoonan · Accepted solution]

It is hard to say for sure without seeing the data, but I think that the accuracy of the sample line group method depends on the number of sample lines that you are using for the calculation. Try to increase the frequency of the sample lines and see if your numbers come more into line with each other. Is the proposed surface completely covered by the length of the alignment and the width of the sample lines? Does the proposed surface daylight fairly well into the existing? That could also cause some discrepancy.

[seskinner]

Try to increase the frequency of the sample lines and see if your numbers come more into line with each other.

I increased the sample lines from 50' to 5' and the accuracy improved greatly. This makes sense because C3D is only taking the values from each station and averaging them with the next.

Is the proposed surface completely covered by the length of the alignment and the width of the sample lines?

Yes.

Does the proposed surface daylight fairly well into the existing?

Yes.

Thank you.