Most quarry survey specifications require a survey of breaklines. Virtual Surveyor allows you to create a lightweight line survey from your drone data that you can export to a common CAD format and load it into mining software. In this article, we'll show you an efficient method for drawing breaklines and some options you have to enhance your line survey.

Overview

• Step 1: Load Your Drone Data from Terrain Creator
• Step 2: Create a Line Survey as Breaklines
  • Optional: Generate a Surface for the Quarry from the Breaklines
• Step 3: Add Points for a More Regular Surface
  • Optional: Create a TIN of the Points and Breaklines
• Step 4: Export Your Line Survey
  • Load Your Line (and Points) Survey into CAD
  • Load Your TIN Results into CAD
• Use Q-Points Instead of Breaklines
• Tips & Tricks

Step 1: Load Your Drone Data from Terrain Creator

After processing your drone photos in the Terrain Creator app, click on Open in Virtual Surveyor to load your resulting orthophoto and elevation model in the Virtual Surveyor app.

Step 2: Create a Line Survey as Breaklines

Use the polyline tool to capture the tops and toes of the slopes as breaklines. You simply left-click along the top of the slope and right-click when you are done drawing the line.

Use the Guided Breakline Tool to Draw Faster: Among the many features of Virtual Surveyor, the Guided Breakline tool combines fast computer calculations with the human mind that is better at interpreting the terrain. It works by creating a line of evenly spaced points along a slope's top or bottom. With minimal input, the tool extends the breakline for you. Your first click sets the starting elevation, and the second click defines the spacing and direction for additional points along the breakline of the slope.

With the Polyline tool active, click on the Guided Breakline drawing mode and go to the bottom of the slope and give it one click to start, and another click in the direction you want it to go. The breakline systematically draws along the lowest part of the slope. 

Enable the Slope Steepness lens to help you manually draw the breaklines: You can get a different visual to help you draw the breaklines by activating the Slope Steepness lens found in the Analysis tab. You can always use this lens to make it easier for finding the tops and toes of the slopes when drawing them with the Polyline tool, as it visualizes the terrain in a color palette. The contrasting color change helps identify the breaks (top or bottom) of the slope.

Correcting the Guided Breakline: For areas that are a bit tricky to draw, if you're using the Guided Breakline tool and your line goes off course, it is easy to fix. Just press the Backspace button on your keyboard to delete points that went off course, then give it a new break to follow. You can always switch back to the Free drawing mode and manually place the breaklines if the break isn't defined enough for the computer to recognize. 

Edit your breakline vertices: Once you're done drawing the tops and toes, you may find vertices that aren't optimally placed on the breaks of the slopes. You can edit any of the vertices on the polylines you drew by right clicking a drawn polyline from the Viewport and selecting Edit Vertex from the quick access menu. You can now easily add, delete, or move points to get the most precise representation of the breaks. If you turn the Slope Steepness lens on and off for reference (you can quickly do this using the keyboard shortcut Alt+S), it is often easier to see the highs and lows of the slope and where best to place your vertices.

When you've finished creating all the breaklines for your site, it should look something like the image below:

At this point in the project, you can skip forward and export your breaklines to create a CAD file (.dxf, .xml, or .shp file), but you do have the option of generating a surface to assess and check your breaklines for quality. We'll also show how you can go one step further in Step 3 of this article to make a more regular representation of the surface by adding points around your breaklines. 

Optional: Generate a Surface for the Quarry from the Breaklines

You can take an additional step here and quickly generate a lightweight surface model from your quarry drone data to check your line survey and validate the quality of your model before you export and deliver it. A TIN (Triangulated Irregular Network) is a vector-based representation of a land surface. It models the surface in three dimensions using a network of connected triangles. TINs accurately capture peaks and breaks, which are missed when representing a land surface with contour lines.

To generate the surface: 

1. Ensure all your breaklines are visible and click on Triangulate All to generate the surface.
2. Use Edit Surface to remove unnecessary triangle edges.

You can preview the TIN by itself in the Viewport by turning off the Elevation and Image Terrains from the Project View.

Step 3: Add Points for a More Regular Surface

You can quickly add points along with your breaklines for a more regular surface. You will need to create a boundary in order to create a grid of points, and you can create a boundary from a surface you created using the breaklines.  

Create a boundary: The easiest way to create a boundary in this situation is to extract the boundary from the created surface (TIN). To extract the boundary from a surface:

1. Select the surface generated from the breaklines (as shown in the optional step above).
2. Go to the TOOLS tab.
3. Click on Extract Boundary.

You can then delete or disable the TIN you created from the breaklines as you will create another regular surface after adding your point grid. You can now use the extracted boundary to create your point grid. 

Create a Point Grid: You can create a point grid to get more regularity in the surface. Setting the grid to 10 meters is a good choice as it keeps the surface lightweight. To create a point grid:

1. Select the boundary.
2. On the Home tab, set the point grid Type to Rectangular.
3. Set the Grid Size to 10.00 m.
4. Click Point Grid to create your points within the drawn boundary.

Remove unwanted points: Now you'll want to remove points using the Erase tool to remove points as necessary. Some of the points added from the point grid may be created on surface objects like bulldozers or conveyors and they'll need to be removed in order to create a surface at ground level.

Optional: Create a TIN of the Points and Breaklines

To assess your work and ensure a good surface creation, ensure both your Point Grid and all your Breaklines are enabled. Then select the boundary and click on Triangulate Within (in the HOME tab) to create a new surface. Creating a TIN within a boundary prevents you from needing to remove any triangle edges.  

When you include a point grid (in this case with 10-meter spacing), you'll get a more regular surface over the one you create only using breaklines, and it can still be used as a light-weight CAD model.

Step 4: Export Your Line Survey

To use your survey in mining or quarrying software, export it as a .dxf, .xml, or .shp file. The Export feature works as "what you see is what you get" or "WYSIWYG", so you'll only enable what you want to export.

1. Ensure the boundary is disabled if you just want points and lines in your export.
2. Go to the EXPORT tab and select your desired format.
3. Click Export Survey and save the file with the desired name and location.

Load Your Line (and Points) Survey into CAD

Export lines and points as a .dxf and open it in a CAD program.

Load Your TIN Results into CAD

You can also export the TIN as an .xml and open it in CAD program. Just make sure the TIN is enabled and visible in Virtual Surveyor when you click Export Survey. Then load the .xml file into CAD. In Civil3D, the .xml file will automatically be recognized as a surface. 

All the options we've shown you are just to expand your tool belt and help you decide the best way to create a surface model. You can try using these digital surveying concepts on your own dataset and very quickly create lightweight surface models with precise and accurate details.

Use Q-Points Instead of Breaklines

Another option for creating a quarry survey is by using Virtual Surveyor's Q-Points tool. The Q-Points tool is an intelligent tool that uses an algorithm to model your topography with precisely placed points along the breaks of slopes within a boundary area you create. This tool is made for bare-earth terrain.  

Q-Points is an automated process that produces points instead of breaklines, but still gives you an accurate topo surface. The Q-Point process can take some time to generate points, but requires no other work than drawing a boundary, setting elasticity for points, and clicking a button to completely survey the terrain.

You can read more about how to do this in our Create a Surface for a Quarry article.

Tips & Tricks

Display the topography as different kinds of surfaces: You can display your surface as either a Triangulated Irregular Network (TIN) for a 3D model or as contour lines in 2D mode to help you assess your survey.

• Create and manage layers in the Project View.
• Rename and renumber Project Items or move them from one layer to another. 
  • For example, you can create layers to group crest, top of bank, bottom of bank, etc:

Use the styling options in the HOME tab to set the shape, size, and color of your survey items.