As the value for the smoothing factor is set to Linear in the Digital terrain model area of the Terrain options, the contour lines are drawn linearly between the individual grid lines. If you want the contour lines to be displayed more exactly, you need to increase the smoothing factor in the Terrain options before you create the DTM. Alternatively, use the Modify DTM tool.
To increase the smoothing factor and the number of decimal places for contour lines
1 Click Modify DTM (Digital Terrain Model flyout).
2 Click the DTM you want to modify.
3 On the context toolbar, click Factor and set the smoothing factor to 10.
4 Click Point and set the point label type to H + No (height + number).
5 Click Decim. and set the decimal places in contour line labels to 1.
6 Click OK to confirm the settings.
Tip: The smoothing factor only affects contour lines, elevation points and interpolations, and not cut and fill, slope and surface calculations, etc. The higher the factor, the more time is required for large models.
The contour lines adapt accordingly. Your drawing should now look like this:
As you can see, the contour line labels also update automatically.
7 Press ESC to quit the Modify DTM tool.
Geodesy Unit 2: Digital Terrain Model module 69
Exercise 4: raising a 3D element
In the last exercise of this unit, you will create a simple 3D element (consisting of two boxes) and raise it to the height of the terrain.
Before you do this, however, you need to assign the same group number to these two boxes to ensure correct results.
Finally, you will check the position of the building in the terrain by creating a cutaway around the 3D element.
To create a 3D element
1 In the Tools palette, select the Bonus Tools family and open the 3D Modeling module.
2 On the Window menu, click 3 Viewports.
3 Click Box (Tools palette, Create area), open the Point snap options and clear the Grid point check box.
4 In plan view, specify the corner of the first box (see below).
5 Enter the following values:
X coordinate: 6 Y coordinate: 4 Z coordinate: 3
6 In isometric view, define the start point of the second box (see below).
7 Enter the following values:
X coordinate: 2 Y coordinate: 2 Z coordinate: 1
8 Press ESC to quit the Box tool.
Your drawing should now look like this:
3D elements are always raised segment by segment; in other words, every individual segment is raised to the height given. The two boxes need to be combined into one entity group to ensure that their height settings are retained. Otherwise, the position of the two boxes relative to one another would change.
To assign the same group number to 3D elements
1 Click Modify Format Properties (Edit toolbar).
2 Click Match parameters at bottom left in the Modify Format Properties dialog box.
3 Click one of the two boxes.
Tip: The two boxes can be grouped automatically. To do this, click Assign Group Number on the Format menu before you create them.
Geodesy Unit 2: Digital Terrain Model module 71 The group number of the box clicked appears in the Group number line.
4 Clear all the check boxes in the dialog box with the exception of Group number and Line color, select line color 5 and click OK to confirm.
5 Click the two boxes in plan view.
Now both boxes have the same group number.
6 Press ESC to quit Modify Format Properties.
3D elements can be raised to the minimum, maximum or mean height. You can also enter a constant height. This exercise uses the mean height. To determine this value, Allplan calculates the height of the element in all its corners.
To raise 3D elements
1 In the Tools palette, select the Terrain family and open the Digital Terrain Model module.
2 Click Raise 3D Elements (Tools palette, Change area).
3 Click the DTM.
4 Select the two boxes by clicking them with the middle and then left mouse button. This selects the entire group.
Make sure that plan view is active when you click the two boxes.
5 In the input options, click Mean to raise the 3D element to a mean height.
The following illustration shows the effects of the Min, Max and Mean options.
Min Max Mean
6 Press ESC twice to quit the Raise 3D Elements tool.
Geodesy Unit 2: Digital Terrain Model module 73 Although you have raised the 3D element to the mean height of the terrain, it is still not possible to see how the height calculated by Allplan and the actual terrain heights behave in the building area. To achieve this, you will create a cutaway around the 3D element.
Before you do this, however, you need to mesh the corners of the element with the DTM.
To mesh elements with the DTM
1 Click Mesh Element with DTM (Digital Terrain Model flyout).
2 Click the DTM.
3 Click Polyline in the Input options.
4 Click the 3D element.
Points are meshed with the DTM and interpolated to terrain height at the corners of the element.
The DTM should now look like this in plan view:
5 Press ESC to quit Mesh Element with DTM.
To create a cutaway around the 3D element
1 Click Cutaway (Digital Terrain Model flyout).
2 Click the DTM.
3 Click the four corners of the 3D element one after the other and press ESC to finish.
To finish, click the first point again.
The cutaway is created.
In isometric view, you can see how the terrain behaves around the 3D element.
You can see, for example, that the building corner at top left is above the height of the terrain. You can use Raise 3D Elements to lower it.
4 Press ESC to quit the Cutaway tool.
5 Set the view to 1 Viewport (Window menu).
Cutaway Building edge