Virtual Surveyor contains a complete toolbox that helps you easily survey roads from drone data. This article provides a step-by-step guide for going from drone data to a CAD road file. The section lines method is inspired by traditional road survey techniques and allows you to deliver lightweight road surface models.


Overview


Draw a Centerline

The drawn centerline is the backbone of the road and the first survey item captured in our workflow. The captured centerline is primarily used as a reference for the section line creation.

  1. Change your data to the 2D View Mode.
  2. On the Home tab, select the Polyline tool and draw your centerline.
    1. You can use the Arc setting to help with road curves.



Create Section Lines

  1. Select your digitized centerline and go to the Create group that is available in the TOOLS for Polyline tab. 
  2. Set the Along and Across values for your project.
    1. Set the Along value to 100 ft or 30 m.
    2. Set the Across value to 100 ft or 30 m.
  3. Click on the Section Lines button to create section lines at the set values. 



Once the section lines are created, notice that a Boundary is automatically created around the section and centerlines.


Model the Topography

Newly created Section Lines are flat when initially created. You'll need to remove any redundant section lines, drape your section lines on the ground, edit the vertices of each section line to make sure they are in a precise location on the terrain, then match your boundary vertices to the section line vertices.


Model and Clean Up the Section Lines

Remove Redundant Section Lines

  1. Remove any redundant section lines using the Project View layer list.
    1. Quickly remove redundant section lines by deleting lines that are numbered in between every 100th foot or 30th meter.
    2. You can select multiple project items by holding Ctrl while selecting them.
    3. You can also select a range of project items by holding Shift and clicking on the first and last item in the list.


Drape the Section Lines to the Terrain

  1. Move the Boundary item to another layer (you'll come back to the boundary later).
    Note: See our Project View article if you'd like more information on how to structure layers.
  2. Select all Section Lines by selecting the Section Lines Layer.
  3. Click on the TOOLS tab. 
  4. In the Densify section, set the Method to Regular and set the Distance to 10 ft or 3 m. 
  5. Click Densify .


Edit the Section Line Vertices

Parts of section lines can appear over surface objects (trees, jerseys, rails, etc.) and require editing to fit with the road topography. The Edit Vertex feature allows you to remove or edit section line vertices that lie over those objects.

  1. Select the section line you want to edit.
  2. In the TOOLS tab, click Edit Vertex to display the vertices.
  3. Select and delete vertices where necessary. 
    1. You can select multiple vertices by holding Ctrl while selecting them.
    2. You can also select a range of vertices by holding Shift and clicking the first and the last vertex of the desired group on the section line.
  4. When all the unwanted vertices are highlighted, press Delete.


A quick way to get vertices from the top of foliage to match ground level vertices is to keep the last vertex of the line and to adapt its Z value according to the surrounding ground elevation. This maintains the section line's horizontal length. You can usually measure the Z vertex value on the terrain with your mouse (or copy the closest Z vertex value) and type it in to the end of line vertex coordinate (Use the Edit Z feature in the TOOLS tab).


Model and Clean Up the Boundary

Drape the Boundary to the Terrain

  1. Select the Boundary in either the Project View or the Viewport.
  2. Click on the TOOLS tab.
  3. In the Transform Group section, click To Terrain.


Edit the Boundary Vertices

For the boundary, you'll likely need to remove a number of redundant boundary vertices from the extra section lines that were deleted. Also, in most situations, using the To Terrain tool matches the boundary vertices with the section line vertices. But in situations where the points drape onto vegetation after using To Terrain, you'll have the extra step of matching the boundary vertices to the ends of the section line vertices. 

  1. With the Boundary selected and while still in the TOOLS tab, click Edit Vertex.
  2. Select and delete vertices where necessary.
    1. You can select multiple vertices by holding Ctrl while selecting them.
    2. You can also select a range of vertices by holding Shift and clicking the first and the last vertex of the desired group on the section line.
  3. When all the unwanted vertices are highlighted, press Delete.


If vegetation places the boundary vertices on top of objects on the terrain (trees, jerseys, rails, etc.), you can edit the Z elevation of your vertex to snap to the ends of the section lines we've already placed at ground level.

  • You can turn on the Transparent Lens in the ANALYSIS tab to see the end of section lines that fall under foliage or other objects on the terrain.
  • You can use Edit Vertex and change the Mode so that only the Z elevation is changed.
  • You can also use Geometry Snapping to get the points to snap together when you move them in close proximity of one another.


Create the Road Surface

Once all the survey items are created and cleaned, you'll want to make sure they are active by ticking the project items "on" in the Project View, then you can create a surface within the survey boundary.

  1. Make sure you turn off the originally drawn centerline (untick in the Project View).
  2. Select the Boundary and click on Triangulate Within in the TOOLS tab. 
    1. The survey displays as triangles (TIN) by default. 
    2. It is possible to change the style of the surface and display the TIN as contour lines as well. 


Export the TIN

When you are satisfied with your results, you can export the results as a CAD file.

  1. Ensure the Surface is checked in the Project View and visible in the Viewport.
  2. Ensure the Surface style is set to display as a TIN.
  3. If you'd like to export any other Project Items (such as the Boundary), ensure they are also checked in the Project View and visible in the Viewport.
  4. Click on the Export tab.
  5. Select your preferred CAD format.
  6. Click on Export Survey.


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