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Grading a Platform

Updated March 08, 2021

This article applies to:
  • Terrain 3D
  • Terrain Forestry
  • RoadEng Civil
  • RoadEng Forestry

The Grading option projects a feature at user specified cut/fill angles to a 'Target surface'. Slope lines are created at each feature point and at user specified interpolated points. The daylight line is also calculated as shown in the figure below.

Figure 1: Grading a Polygon to a Target Surface

In this platform design example, we will assume the platform is in a good plan location (if this is not the case, the pad can be easily dragged to a new location using Ctrl + M). We will grade the platform top to a topo surface.

  1. With the rectangle selected. Open the Grading Dialogue box: Terrain Modeling | Grading.

  2. Within the Grading Dialog box press the Browse button and select file <Terrain>\Grading\OriginalGroundGrading.terx. Press Open. Change the other fields to match those shown in the figure below. Press OK.

  3. Still within the Grading Dialog box, check boxes Interpolate; Spacing: 5.0; Set breakline property. Check all the boxes under TIN / Volumes: Set Daylight to TIN boundary; Calculate TIN; Calculate Volumes.

Figure 2: Grading Dialogue Box

The Grading Dialogue box controls how the slope is projected (Orientation), the elevation or surface (Target Surface) the Slopes from the pad to the surface, and the spacing (Slope line interpolation spacing) of the projected slope lines. The dialogue also allows you to calculate the TIN model as well as volumes after the grading calculation operation is complete.

After a few seconds, the grading calculation will complete and the Volume / Surf. Properties Reporting dialogue box will appear. Notice that there is a considerable amount of fill indicated in the Volume / Surf. Properties Reporting dialogue box.

  1. Press Close.

Note: Ensure that the OriginalGroundGrading.ter file is designated as “Original” and the Untitled.ter file is designated as “Final” otherwise the cut and fills will be reversed. (Refer to the figure below).

Figure 3: Volume/Surf. Properties Reporting Dialogue Box

To balance the cut and fills, let’s try dropping the pad by 1-meter increments.

  1. First, select the pad if it is not already selected. Select the pad top by using the selection cursor . It is not necessary to select the slope and daylight lines. (Refer to the figure below)

Figure 4: Screen Shoot with Pad Top Selected

  1. Feature Tools | Transform. You may get a Terrain warning dialogue box as shown in the figure below. Press OK. Select the Rotate/Translate/Scale tab.

Figure 5: Terrain Warning Dialogue Box

  1. Uncheck Disable (no coordinate adjustment) box. Change the Shift Offset Z to –1 as shown below. Press OK.

Figure 6: Coordinate Transformation Dialogue Box

  1. Terrain Modeling | Grading button. Press OK.

Figure 7: Volumes After Dropping the Pad by 1-meter

  1. Open the Feature Properties panel. You should see the elevation of the platform decreased from 1175 to 1174 in the status portion.

  2. Transform the elevation down 1m again. Repeat the above transform, grading, TIN and volume calculation as in Steps 11 through 13. Press OK. Once the grading calculation has completed you will notice that there is still too much fill.

  3. Now select Feature Tools | Shift. Change Z to 1172.5 as shown in the figure below. Press OK.

Figure 8: Using Shift to change elevation of “Platform”

  1. Terrain Modeling | Grading button. Press OK.

Figure 9: Screen Shot of Final Cut and Fill Slopes

The cut and fill is close to being balanced. (Refer to figure above).

  1. File | New. Do not save changes.