Monitoring dirt volume on construction sites can be challenging. Thanks to drone surveying, it is easier to get better insights into your earthwork's projects. However, you still need to efficiently analyze the drone data for it to be useful for project monitoring. This article is a step-by-step guide teaching you how to create a relevant Cut/Fill analysis to measure volume between Timesteps. 

Overview

• Clean Each Terrain
• Cut/Fill Analysis Between Two Timesteps
  • Manage Timesteps
  • Draw Your Boundary or Boundaries
  • Use Cut/Fill Maps for Volume Calculations
  • Cut/Fill Maps Visualization Settings
  • Extract Cut/Fill Areas
• Cut/Fill Analysis Between Timestep and Design
  • Create/Import Designs
  • Cut/Fill Maps
• Monitor Your Project Over Time 
  • Video

Clean Each Terrain

Drone data collected from construction sites commonly include machines (bulldozers, excavators, dump trucks, etc.) and other items or materials. You do not want to include these objects in your earthworks volume or cut/fill calculations and need to clean them off of each timestep you make. To clean your terrain:

• Use the one-click Remove Object tool (or the Replace Terrain tool for more control) to remove unwanted objects from the terrain. 
• To help you detect objects that need to be removed, you can use the Slope Steepness Terrain Lens. 
• Cleaning the terrain must be done for each drone survey. 

Cut/Fill Analysis Between Two Timesteps

Let's compare a drone survey with another drone survey obtained earlier to analyze the work that was done between those two dates.

Manage Timesteps

To manage multiple drone surveys, you need to use the Timeline. 

1. Create a Timestep for each date the site has been flown.  
2. Each drone survey data package (DSM and orthomosaic) must be imported into the dedicated Timestep. 
3. Switch between Timesteps and make sure both are fully cleaned of surface features. 
4. Go back to the earliest drone survey to start your work. 

Draw Your Boundary or Boundaries

Before going further, you need a boundary that defines the limits of the construction site or the area of interest. 

• Use the Boundary tool available in the Home tab to draw that item or import a DXF file that contains a boundary. 
  • See our article about Updating an Existing Boundary for more details. 

Use Cut/Fill Maps for Volume Calculations

When you select the boundary, you can access the Volumes tools group in the Tools for Boundary tab. 

1. Set the Reference Type to Timestep
2. Select the Reference State (most recent) in the box and click on Cut/Fill button to create the Cut/Fill map. 
3. Cut areas appear in warm colors (yellow to red) and fill areas appear in cool colors (cyan to blue). 
4. Cut/Fill values for the entire area are available in the volume box. 

When the Cut/Fill map is selected, you can change the reference Timestep in the Reference box and the Cut/Fill map is automatically updated. 

• The quantity values still need to be recalculated using the Recalculate Volume button in the Volumes section.

Cut/Fill Maps Visualization Settings

Now that the Cut/Fill map is available, let's make it easier to analyze. 

1. Select your Cut/Fill map within the Viewport or through the Project View to get access to Tools for Cut/Fill. 
2. Set the Min. Cut/Fill value to highlight only significant earthwork areas. 
   1. Using a 0.3ft or 10cm value typically clears noisy areas. 
3. Reduce the stretch value a little to enhance the color appearance. 
4. Enable the Cut/Fill annotations to get a better understanding of the dirt movement. 
   1. You can adjust color, size, and spacing of the spotted height labels in the Annotate section of the TOOLS ribbon.

Extract Cut/Fill Areas

To go deeper in the earthwork analysis, break down the Cut/Fill map into smaller areas. 

1. Enable the Extract Cut/Fill Area tool and click on any cut or fill area. 
   1. This area is available as a separate cut/fill item in the Project View. 
   2. By selecting it, you can view quantities related to that specific area in the Volumes section. 
2. Enable the Volume annotations to get a better understanding of the dirt movement. 
3. After breaking down all the relevant areas, you can export Cut/Fill values as a text file and create a more detailed report. 

Cut/Fill Analysis Between Timestep and Design

Now, we will compare a timestep to the design to assess how much dirt needs to move in order to complete the project. This can also be done to compare your "as built to design" when you finish the field grading.

Create/Import Designs

First, let's create a new timestep for the design. Then we can import a DXF design file and convert the surface to a terrain. However, sometimes design files come in 2D and don't contain any surface, in that case: 

1. Import the 2D design file and edit contour lines and other elevation items to set Z values according to 2D plan annotations.  
2. When all geometries are available in 3D, triangulate to create a surface and convert it to a terrain. 

Cut/Fill Maps

Come back to your drone survey timestep and use the construction site boundary to create a new Cut/Fill map. This time, use the Design timestep as a reference.

Monitor Your Project Over Time 

If you have multiple drone surveys, the Cut/Fill map can be pinned to stay available on all the timesteps. In that way, you can switch from one drone survey to another within the Timeline and monitor work progress through a clean and simple to use time-lapse. 

• To pin a Cut/Fill map, enable the pin icon related to that map within the Project View.

Video

• Construction Site Earthwork Monitoring