3.2 Landform Design Parameters

Overview: This dialog box sets the design parameters or design inputs for the area within the boundary zone (typically the whole survey area but can be a portion of it).  These settings tell the OptiSurface Calculation Engine what characteristics or properties the proposed design surface should have.

Every design file (osd) will have one boundary zone and zero or more subzones. The Boundary Zone is displayed as a black line around all or part of the surveyed area. This boundary defines the area in which designs surface will be calculated. You can modify this boundary or redefine its extents from scratch by clicking the menu: Tools>Design Zones then clicking the: Draw Extents or Modify Extents buttons.

Displayed by:
Menu:  Tools> OptiSurface Design….
Toolbar: 
      

Or


Appearance:

3.2.1 General

Zone Name: Set to “Boundary Zone”. You cannot change this. 

Zone Perimeter Colour: Colour of the boundary zone as displayed in the 3D scene. Click the colour to select another colour if required. 

Surface Type: Select the surface type required:

  • Plane: Single Plane of Best Fit

  • OptiSurface1D™: Optimised surface incorporating Infinitely Variable Grades™ (IVG™) which drains in one direction (1D). This suits crops grown with furrows where the water needs to drain in one direction along the furrow to exit the field. All furrows will have positive slope to one end.  An example application is furrow irrigated cotton where water is added at the top end of the furrowed row and must drain out the other end.

  • OptiSurface2D™: Optimised surface incorporating Infinitely Variable Grades™ (IVG™) which can drain in two direction (2D). This suits crops grown with furrows where the water needs to drain in along the furrow but it can drain out either end of the furrow and even some distance along the furrow using a cross drain. The location of a cross drain is defined using a Subzone with a Subzone Type setting of ‘Valley’.  All furrows will have positive slope to either end or a ‘Valley’ Subzone.  An example application is liner move  irrigated sugar cane where water can drain out either end of the furrowed row.

  • OptiSurface4D™: Optimised surface incorporating Infinitely Variable Grades™ (IVG™) which can drain in any direction (4D) as long as it is continually falling to some location on the boundary. This suits crops grown WITHOUT furrows where the water can drain in any direction. All locations on the field have positive slope towards the boundary (i.e no depression areas to hold water).  An example application is rainfed wheat where it is planted on a flat soil surface (no furrow) and water can drain in any direction. Note: it is called OptiSurface4D because in actual fact the calculated surface falls in only 4 directions of the calculation grid (eg North, South, East or West or similar depending on grid rotation setting). This can produce jagged flow paths which can be smoothed using the slope smoothing (Slope max change) and breaklines.  
Main Slope Bearings (deg): This defines the direction of the main slope or downslope in Surface Types: Plane, OptiSurface 1D and 2D. It also defines the calculation grid rotation which OptiSurface4D uses but the concept of a downslope direction is not relevant for this surface type. 

Use the ‘Pick’ tool to click two points to define the direction. After clicking the ‘Pick’ button, click the higher end of the field first then the lower end (ie the direction you want the furrows to flow). 

Calculation Grid Spacing (m): Defines how far apart in metres, the calculation points for the design surface are. A larger grid spacing will calculate quicker but the earthworks estimates will not be as accurate. When designing it is a good idea to adjust this setting to be larger (e.g. 20m) when doing initial design calculations a get a feel for the workable slopes etc. Then when you’re happy with the initial design, adjust this setting to be smaller (e.g. 5m) and redo the calculation to get a more accurate earthworks estimate and design surface.

Mass Haul Optimisation Weighting (%): Not working yet. It is coming in a future release.


Cut/Fill Ratio
: The cut/fill ratio is defined as: cut/fill ratio = Volume of Cut / Volume of Fill; and should be in the range of 1.1 to 1.5 depending on the soil type and its condition. The necessity of having cut/fill ratios greater than one for land levelling operations stems from the fact that in disturbing the soil, the density is changed (the fill soil is more dense because its structure has been destroyed). Selecting a cut/fill ratio remains a matter of judgement. 

Fill To Import (m3): Defines the volume of soil to bring into the field boundary area from an external area. This volume is taken into account when balancing earthworks to the cut fill ratio.

Fill To Export (m3): Defines the volume of soil to remove from the field boundary area to an external area. This volume is taken into account when balancing earthworks to the cut fill ratio.

 

3.2.2  Constraints

These are the design setting that constrain the design surface to the user requirements. i.e. the design surface must meet these constraints to be acceptable. Each constraint has a tickbox. This tickbox must be ticked on if the user wants this constraint applied. Whenever you apply a constraint or tighten it (eg make minimum slope higher or maximum slope lower) you earthworks will either be unaffected (if the constraint is not limiting) or increase. The earthworks will never go lower. So the more constraints you apply and the tighter you make them, the more earth you will need to shift. It is a trade off between achieving your desired design objectives versus the additional cost to move the earth.

Main Slope: Defines acceptable slopes in the main slope direction:

  • Minimum(%): Minimum acceptable slope in %. Enter a positive slope for falling in the direction of the main slope bearing. Typically 0.1% for good drainage but can use 0.01% if limited by topography.  Note: You need to tick the tickbox ‘on’ to adjust the value and use this constraint in the calculations.

  • Maximum(%): Maximum acceptable slope in %. Enter a positive slope for falling in the direction of the main slope bearing. Usually defined by erosion risk. Note: You need to tick the tickbox ‘on’ to adjust the value and use this constraint in the calculations.

  • Max. Change (%/m): Maximum acceptable change in slope in % per meter. This effectively smooths the surface so the grade changes do not change too rapidly e.g. from minimum slope to maximum slope in a short distance. A typical value is 0.01%/m but depends on how much soil you want to shift versus how smooth you want the finished design.  The grade changes are calculated at every grid point. For example, if the calculation grid spacing is set to 10m, and Max Change is set to 0.01%/m, then at each grid point the slope can change a maximum of 0.1% (10 x 0.01). Eg from 0.1% to 0.2% at one grid point, then the next grid point it could go from 0.2% to 0.3%, etc  Note: You need to tick the tickbox ‘on’ to adjust the value and use this constraint in the calculations.

Cross Slope: Defines acceptable slopes in the cross slope direction. Does not apply to OptiSurface4D as the main slope constraints apply only.  The cross slope is defined to run perpendicular to the main slope direction, with negative and positive direction defined as per the Figure 1 below. Also see Figure 2 for more explanation.  

  • Minimum(%): Minimum acceptable cross slope in %. Enter a positive or negative slope depending on direction of cross slope as per Figure 1. Typically it will be negative eg -1%.  Note: You need to tick the tickbox ‘on’ to adjust the value and use this constraint in the calculations.

  • Maximum(%): Minimum acceptable cross slope in %. Enter a positive or negative slope depending on direction of cross slope as per Figure 1. Typically it will be positive, restricting the fall in the  eg +1%. Note: You need to tick the tickbox ‘on’ to adjust the value and use this constraint in the calculations.

  • Max. Change (%/m): Maximum acceptable change in slope in % per meter. This effectively smooths the surface so the grade changes do not change too rapidly e.g. from minimum slope to maximum slope in a short distance. A typical value is 0.01%/m but depends on how much soil you want to shift versus how smooth you want the finished design.  The grade changes are calculated at every grid point. For example, if the calculation grid spacing is set to 10m, and Max Change is set to 0.01%/m, then at each grid point the slope can change a maximum of 0.1% (10 x 0.01). Eg from 0.1% to 0.2% at one grid point, then the next grid point it could go from 0.2% to 0.3%, etc  Note: You need to tick the tickbox ‘on’ to adjust the value and use this constraint in the calculations.

 

Figure 1. Definition of the direction of positive and negative cross slope relative to the main slope bearing. When looking into the main slope bearing (up the field), positive cross slope is to the right and negative cross slope is to the left.

 
Figure
2
. Typical Cross Slope minimum and maximum settings to achieve different cross section profiles (indicated in brown). 

Tip - You would typically use Scenario B and C with Subzones to force a tail drain or head ditch to fall in one direction.

 
Max. Allowable Elevation (m): Defines the maximum elevation of any calculation grid point over the field.

Min. Allowable Elevation (m): Defines the minimum elevation of any calculation grid point over the field. 


Max. Allowable Cut (m)
: Defines the maximum depth of soil that can be removed (cut) from any grid point over the field.

Max. Allowable Fill (m): Defines the maximum depth of soil that can be added (filled) on any grid point over the field.


Special
: This is for passing special commands to the OptiSurface Calculation engine. There are no special commends defined at present.

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