Tutorials > Surface Reshaping & Transportation Analysis

Once a design surface exist for the post mining reshaped topography the Transportation Analysis can be performed. Typically the design surface will be created in 3d-Dig in the manner described in the previous exercise, however any design surface which can be loaded or imported into 3d-Dig can be subjected to the Transportation Analysis.

The principles of the Transportation Analysis are explained in the User Manual topic Transportation Analysis. Using the post mining topography and the design surface the system creates a gridded model of the distribution of cut and fill throughout the design area. Each grid point will contain either an excess of material (cut) or a deficit of material (fill). The system allows for the input a cost function that establishes the cost of moving material, per cubic metre, over a given distance.

Using the above information the system conducts an analysis which comes up with a near optimal solution for the movement of material from cut to fill subject to the constraint of minimum cost (cost as defined by the cost function).

The output of the analysis consists of the following:

•a set of transport arcs (arrows) which graphically display the required material movement of material from cut to fill.

•A report of the volume moved and total cost (according to the cost function).

•A set of spreadsheet data which divides the transport of material into bins according to distance moved. This spreadsheet lists each bin (Distance range) and the associated volume. In this manner the total volume is subdivided according to various distance ranges as set up by the user.

The cost function is used primarily to establish the minimum transport distance solution. Although it does produce a dollar value cost, in normal practice it is the spreadsheet containing the bin/volume information which is used to establish the likely cost of implementing the proposed reshaping operation. Hence the cost function is often established with a view to producing the minimum distance solution rather than realistic costs.

The Transport Analysis has a Resolution parameter. This parameter relates to the grid spacing used for the analysis. If the full resolution is selected for every grid point on the terrain surface a data point is created for the Transport Analysis grid, which contains either a cut or fill volume. The default Resolution setting is high which uses every second terrain grid point as a Transport Analysis data point. As volumes are amalgamated this results in no loss of volumetric accuracy but a small loss in spatial accuracy. The High setting generally represents a good compromise between speed and accuracy.

The time of calculation increases exponentially with the size (area and grid points) of the area to be modelled. For large design tasks it is a straightforward matter to subdivide the design area into sub areas which can be modelled with a set of independent but contiguous Transport Analyses. See the user manual topic Subdividing Transport Analysis.

The following exercise conducts a transportation analysis on the reshape surface produced in the previous tutorial exercises. The following steps are used:

1.The 3d-Dig file for the final reshaped surface is loaded.

2.Surface Feature is drawn which encompasses all of the Polygons used for the reshaping. This feature is intended to delineate the area subject to reshaping. The feature is exported as a DXF file.

3.Using the Terrain/Editor Settings/Clip to Work Area command the topography is cropped down to an area just slightly larger than the reshaped area.

4.The topography is saved as a bit file

5.The initial 3d-Dig file, that which has the post mining topography prior to reshaping, is now loaded. The reshaped topography bit file is also loaded as a Inner Surface.

6.The 3d-Dig file now contains both the post mining topography and an inner surface representing the reshaped topography. Using this information to Transportation Analysis is performed.

Load the file:

Reshape_Tut_4.3dd