Modifying Global Optimisation Settings

At the project level, you can specify global grading constraints and project objectives that must be considered for your Grading Optimization project. These are the default settings for your grading project that will take effect unless overridden by grading objects. To set these global properties, click Optimisation Options on the Optimisation Toolbar.

In the Optimisation Options dialog, there are three areas to consider.

Global Constraints

Global Constraints defines your base slope gradient limitations. Zones with different Min Drain Slope and Max Slope settings can and will override these settings.

Max Slope specifies the maximum allowed slope value for any surface triangle. Min Drain Slope, on the other hand, specifies the minimum required drainage slope for any surface triangle. The direction of the drainage is determined by Drain Lines and Low Points.

Cut and Fill Constraints define how to handle cut and fill balancing. You can specify None, Cut or Fill. Then, in the Cut-Fill field, you can specify target net volumes.

Optimisation

You can define the iterations that the optimisation will attempt before it stops. If a solution is found within the tolerance parameter, it will stop before it reaches the maximum iterations. The Convergence Plots dialog graphs the progress and errors at each iteration.

Note: You can stop the optimisation and reset the surface before the maximum number of iterations is achieved.

Objective Weights

Objectives are not constraints so much as they are targets. Along with the surface grading, these three factors are considered during optimisation depending on the weight assigned to them.

Balance Cut and Fill is how much to consider minimising the difference between total cut and total fill. You can also specify a net earthwork volume as defined by the Cut and Fill Constraint. The selected constraint affects the specified balance as follows (cut minus fill).

None: Specifies the target net earthwork volume from zero to a specific volume amount.
Cut: Specifies the target net cut volume. This must be a negative number.
Fill: Specifies the target net fill volume. This must be a positive number.

Minimise Earthwork attempts to minimise the total amount of earthwork (the sum of total cut and total fill). This will try not to change elevations unless constraints or other objectives require it.

Smooth Surface attempts to minimise the gradient change between adjacent triangles on the surface, smoothing the surface.