You can create a volume difference between 2 drone surveys with a cut/fill map. This video explains 7 best practices when working with cut/fill maps.
1) Cut/Fill Maps
You can create a cut/fill map by selecting a boundary, setting the proper reference and clicking the Volume Difference button. The cut/fill map is displayed in the viewport and the volume difference calculation appears in the lower left corner. You typically want to set a minimum value to show as colors. This allows you to hide the noise that will always be present between the drone surveys.
2) Cut versus Fill
By default, the cut/fill map is shown as continuous colors. You can also set it to discrete colors. Red means cut and blue means fill. Cut is the material that will be cut away from the current state to the reference state. Fill is the volume that is going to be deposited in the current state like a ramp that is built for improved accessibility.
3) Reference states
You can change the reference terrain state of your cut/fill map at any time. The colors will update automatically. The volume difference might not be available yet for this set reference state. You can initiate that calculation by clicking the circling arrow. The net, cut and fill volume appear in the lower left corner.
4) Work areas
It is a good practice to create one cut/fill map per work area. This has the advantage that when you pin the cut/fill map, it will also appear in all the other states. This will help you to monitor changes over time. Also, it allows to switch quickly between your current terrain state and the reference state. Cut becomes fill and fill becomes cut. This helps you understand really well what’s going on in your area. For the human brain it is easier to think something existing away then to imagine something that isn’t there yet.
5) Clean Terrain
Machines like excavators come with every earthworks project. You don’t want to include them in your volume difference calculations. They can be removed easy with the Clean Terrain tool from the Home tab. You simply trace around the machine and right click to remove it. The cut/fill map updates immediately. Also, unexpected colors indicate there might be machines in the reference state. You need to remove those as well in order to get an accurate volume difference measurement. When you remove an object, you can recalculate the volume difference by clicking the circling arrow.
6) Replacement surfaces
For machines that hang over breaks in the terrain you need to create a replacement surface. Trace around the machine and densify the boundary. Remove the vertices that are on the machine by pressing delete. Then add some breaklines to model the breaks in the terrain. Triangulate within the boundary and modify the terrain to the resulting replacement surface.
7) Terrain States
You can create a terrain state by clicking in the dropdown menu above the project view. Enter a name and click Enter. Typically, enter a date or the name of the design scenario as the name for the terrain state. When you select the state, it will become active and you can start adding your orthophoto and DSM. You can also Cut (Ctrl+X) and Paste (Ctrl+V) orthophotos and DSMs from one state to another. Terrain states are described in detail in a dedicated movie.
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