Identifying Triangulation Problems

AutoCAD Land Desktop Tutorial

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Identifying Triangulation Problems

First-hand knowledge of the site is indispensable for identifying problems with the surface model, and comparing your drawing to site photographs is useful even if you have access to the site.

One way to identify triangulation problems is to look at contours and see where features such as ridgelines or streambeds are improperly represented. Unnecessarily jagged contours can also be indicative of triangulation problems. A second way to identify triangulation problems is to look at sections cut through critical areas to verify expected surface behavior.

  1. On the View menu, click Named Views to display the View dialog box, under Name, select 2, click Set Current, and then click OK.

  2. On the Terrain menu, click Set Current Surface to display the Select Surface dialog box, from the Selection list, select Area1b, and then click OK.

    To see the triangulation pattern that causes problems without adding any objects to the drawing, generate a Quick View.

  3. On the Terrain menu, click Surface Display Quick View.

Quick View entities are drawn with temporary vectors and cannot be edited.

In the circled area, the TIN lines triangulate between contours at the same elevation, thus creating a flat area. In most cases, flat surfaces like this are minimized. Occasionally, manual editing is necessary to correct these situations when they occur. Also, in the accompanying existing ground cross section, the slope to the left is flat, and then drops off steeply. This does not reflect the actual slope condition.

4On the command line, enter REDRAW to erase the Quick View temporary vectors.