TIN volume surface method

[Anonymous]

Hi,

I am currently working on a project where i am required to measure the volume of a mound of demolition waste. I have created two surfaces ('Existing ground' and the 'mound') and used them to create a TIN Volume surface. This has produced a volume for me. QED.

I have been asked to provide a methodology of how the volume is generated to go into a report. I am talking about the maths behind how C3D gets it's results. I've come across posts regarding 'end area method' & 'composite method' etc methods when creating volumes from corridors. But this is not the case here (I am calculating mound volumes).

I found this on the Autodesk website but it doesn't go far enough:

"A TIN volume surface provides an exact difference between the base and comparison surfaces. Therefore, the Z-value of any point in the volume surface is precisely the difference between the Z of the comparison surface at that point and the base surface at that point"

Does anybody know what calculation method is used by C3D when calculating a basic TIN volume surface?

Thanks.

[M_c3d]

In simple English, it compares the difference between two surfaces to the exact point of a millimeter (or inch for our imperial cousins). It will calculate it to the nth degree were the slightest change can make a sizeable difference.

Be careful when giving quantities of volumes, it must be heavily caveated. The software measures the volumetric difference between two surfaces, it does not take into consideration items such as sequence of works, bulking factors (these can be applied), top soil strip & depth of construction (these can be applied), method of construction, over excavating etc, excavations for drainage, foundations etc.

When I issues volumes I send it with a whole list of caveats.

[Anonymous]

Hi mmcgovern,

Thanks for the reply.  So if i am correct it calculates millions of vertical distances between to surfaces. Presumably using (x1,y1)(x2,y2) formula or something similar. 

How do we get from there to a final volume in m3?

Thnaks,

[M_c3d · Accepted solution]

It works out any location where triangulation intersects  in plan between the two surfaces and calculates the depth at each triangulation point to work out the volume. This will give you more information http://help.autodesk.com/view/CIV3D/2017/ENG/index.html?guid=GUID-A3C76CEC-EE1F-45D4-8D34-E819EB51BD...

[Anonymous]

Ah i see. So it is the composite method that C3D uses when a TIN volume surface is created using the volumes dashboard.

That is what i need to put in the report.

Many Thanks.