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Creating DTMs

To create a DTM, you first need to select sufficient data. There needs to be at least three non-modifying, non-collinear x,y pairs, consisting of points and/or poly vertices. For instance, you could select three points, or one 2-vertex poly and one point, etc. There is no specific limit as to how much data you select, though more data means longer calculation time.

If your selection also contains modifiers, such as polys serving as roads or pads, those items will not be part of the Existing DTM which is calculated. If you are using SimuTerra Pro, those items will be used in calculating a Proposed DTM.

If your selection doesn't contain modifiers, only an Existing DTM will be calculated. If you then add a modifier, such as a poly which serves as a road, to the DTM, you will have to select the DTM and, in the Info Panel, add a checkmark to the Proposed checkbox so as to force the creation of a Proposed DTM. You need SimuTerra Pro in order to have a Proposed DTM.

When you create a DTM, some parameters are taken from the default values for DTMs. You can change the default values by selecting a DTM, setting its values, and choosing Object >: Use as Default Object.

Some parameters, such as contour interval and minimum and maximum elevations, are dependent upon the data. If all of the data is at the same elevation, then the contour interval is set to a small value such as 2. You can always change the values afterwards.

If all the data is at the same elevation, you will not see any contours, other than possibly one around the hull representing elevation 0. If you want to see triangles in a 2D view, you’ll have to indicate your desire in the Info Panel.

See also SketchUp Foam Core Model.

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