December 2011

Volumes

Volumes can only be calculated once you have created a DTM. In simple terms, triangles from the Current DTM are projected to a Reference Surface which could be another DTM or a numeric surface calculated from sample points selected in the model.

But there is more to calculating volumes in n4ce!

Volume options are found at he bottom of the DTM menu and include Prisms and Strings. In both cases you will have to identify the reference Surface, as shown below.

Groups allow you to isolate different areas of your model for independent area and volume calculations. These groups can have Group Depths and allow volumes to be calculated to the underside of the group, or formation level.

December 2011

Volumes using Numeric Reference Surfaces

There are times when you wish to calculate a simple volume, like a spoil heap, and do not have access to another DTM for a reference surface. In this case the option to use is either a datum level or a numeric surface.

The lowest level will be offered to you if you choose to go with a Datum Height.

If you choose Horizontal Plane, Inclined Plane, Saddle Surface or Quadratic Surface you have to select points that will be used in the best fit 3D calculations. These appear as large plus points temporarily so you can see which points have been selected.

Prism Volume Results====================Current DTM : WIT platformSurface Type : Inclined PlanePoint Count : 3

Point 1 : 81247.594 34637.910

112.260 0.000Point 2 : 81258.205 34631.675 112.234 -0.000Point 3 : 81260.839 34642.672 112.237 -0.000

Coeff a : 247.450555813047Coeff b : -0.002009679386 (x)Coeff c : 0.000810992880 (y)

Total Area : 13505.06Not Used Area : 0.00

Cut Volume : 2001.37Fill Volume : 40.53Balance : 1960.85

Cut Area : 11511.48Fill Area : 1993.57Null Area : 0.00

Cut Height : 0.17Fill Height : 0.02

You will be given the option to plot a Table.

A full Report of the calculations performed will be presented. This can be printed, saved or copied to a Word document.

December 2011

Volumes using Groups

Groups are used to separate different parts of a DTM for individual quantities, best described here with heaps. (See Quick Guide on Models first)We will use the base strings of the heaps to create a new model.

Create a new model and call it Base, then used backcloths and select the Heap model. Now select Features Copy and copy the base strings from the Heap model into Base. Now create a DTM from these strings.

Return to Heap model and select DTM Vols Prisms followed by Projected Surface. Then select the model to be projected to.

Reports and Tables present the results of these calculations, isolating quantities.

December 2011

Volumes using Strings

If you don’t wish to go to the extents of creating Groups and want a quick volume, String Volumes may be a solution. It’s important that the base of these heaps are one continuous string.

You will be invited to select the base of the heap(s). The feature will then identify all the triangles encapsulated within that string.

String Volume Results=====================

Current DTM : STEWART_PARKString Cut/Material Fill/Void Balance Cut/Material Fill/Void Null Cut/Material Fill/Void Null Volume Volume Volume Plan Area Plan Area Plan Area Slope Area Slope Area Slope Area==================================================================================================================================BB 864.7 0.5 864.2 603.8 7.8 0.0 644.7 8.6 0.0BB 932.7 1.9 930.8 530.8 19.3 0.0 592.2 21.8 0.0BB 732.1 0.3 731.8 376.1 5.7 0.0 443.5 7.1 0.0==================================================================================================================================

After right clicking on the mouse, the next step is to select the reference surface. Here we will choose a best fit inclined plane. n4ce will use the points in each selected string to calculate this surface and use it for volumes.

Reports and Tables are plotted as before, isolating quantities based on string codes.

December 2011

Complex Volumes

Here we have two DTMs, one being the OGL the other the final Design surface. The design may have groups.

Group Depths should be used when working to the underside or formation levels, else Projected Surface.

SIGN CONVENTION think, what do you have to do the make the Current surface (DTM) into the Reference surface? If the final design surface is the current model then you MUST Swap Cut & Fill, otherwise the signs for cut and fill will be the wrong way round.

Cut is material to be removed (taken away), whilst Fill is the void to be filled (imported material).

December 2011

Isopachytes

Isopachytes are height difference models, calculated between two surfaces. These are created temporarily when calculating volumes between two DTMs. A complex DTM is created between these surfaces, taking into account both sets of triangles and only using common areas of overlap.

You may create this Isopachyte as a separate model which can be used to see a thickness or height difference model.

The zero contour line is the cut/fill line. By fixing the shading interval in DTM Settings to a large value the two colours that will appear show you cut and fill. A Shading key can be plotted, as shown opposite.

Using a Datum value set to zero in volume calculations will also give you cut/fill quantities.