Learn how to calculate earthwork volumes from Plex-Earth terrain models in AutoCAD, Civil 3D, or BricsCAD. This tutorial explains how to generate cut and fill calculations by comparing a terrain surface with a reference plane elevation or with another terrain surface, configure parameters, review results using the Volume Object and Volume Editor, and optionally insert Volume Bars as drawing objects.
Introduction
In many engineering and construction projects, calculating earthwork volumes is essential for planning grading operations and estimating project costs. Plex-Earth allows you to quickly calculate cut and fill volumes using terrain data imported into your drawing.
You can generate volume calculations in two ways:
Both methods allow you to evaluate how much material must be removed (cut) or added (fill) to achieve the desired ground conditions.
Method 1: Calculate Volumes between Surface and Plane
This method is used when you have an existing terrain model and want to compare it with a target elevation plane. It is commonly used for grading operations, where the ground must be leveled to a specific height.
Step 1: Import a Terrain Model
After georeferencing your drawing, import a terrain model that will be the initial/original surface. To create a terrain, go to the Plex-Earth ribbon → Create Terrain → specify the cover area → choose the Create Terrain Model option when selecting the surface type.
See the full guide here: Create Terrain
Alternatively, you can use other sources such as GeoTIFF files, survey data (TXT/CSV), existing objects, etc. to create a dynamic terrain model.
Step 2: Use the Calculate Volumes between Surface and Plane Command
Go to the Plex-Earth ribbon → Create Terrain dropdown button → Volume Between Surface and Plane. Alternatively, type in the following command: PXV_TERRAIN_VOLUME_PLANE
To run this command, at least one terrain model must exist in the Terrain Manager.
Step 3. Define the Volume Calculation Parameters
A Plane Volume Dialog box appears where you define the parameters of the analysis.
Existing Ground
Select the terrain model representing the current ground conditions.
Final Ground
Define the elevation of the plane that represents the desired final ground level. Negative and positive values can be inputted.
The dialog also displays the minimum and maximum elevation of the terrain to help you select an appropriate plane height.
The grounds can also be interchanged by using the double-direction arrow between them.
Advanced Options
You can also configure:
Cut and Fill colors to visualize excavation and fill areas
Grid Cell Size, which controls the size of the cells used to calculate the volume
Cut refers to the amount of ground that should be removed to achieve the final ground we set. Fill, on the other hand, refers to the amount of ground that should be put in to reach the level of the final ground.
Plex-Earth automatically selects an optimal grid cell size, and it is generally recommended to keep the default value.
After setting the parameters, click Calculate.
Here is an example:
After executing the command, a Volume Object appears in our drawing as shown below.
Method 2: Calculate Volume between Surfaces
This method is the best option when we have terrain data on how we want to form our project area, and we want to compare it with the current site conditions to calculate our earthworks.
Step 1: Import the Existing Terrain
After georeferencing your drawing, import a terrain model that will be the initial/original surface. To create a terrain, go to the Plex-Earth ribbon → Create Terrain → specify the cover area → choose the Create Terrain Model option when selecting the surface type.
See the full guide here: Create Terrain
Step 2: Create or Import the Proposed Terrain
Next, create or import the terrain surface representing the final design or proposed grading plan. You can use other sources such as GeoTIFF files, survey data (TXT/CSV), existing objects, etc. to create a dynamic terrain model.
Step 3: Use the Calculate Volume between Surfaces Command
Go to the Plex-Earth ribbon → Create Terrain dropdown button → Volume Between Surfaces. Alternatively, type in the following command: PXV_TERRAIN_VOLUME_SURFACES
Step 4: Define the Volume Calculation Parameters
Both terrain models that will be considered in the volume calculation should appear in the Terrain Manager. In the Grid Volume Dialog box, select:
The existing terrain as the Existing Ground
The proposed terrain as the Final Ground
After confirming the parameters, Plex-Earth calculates the cut and fill volumes and generates a new Volume Object.
Edit and Adjust the Volume Object Results
After the calculation is completed, Plex-Earth creates a Volume Object in the drawing. This object appears in the Collection Manager (Terrain tab) and can be managed similarly to other Plex-Earth objects.
You can adjust it as any other terrain manager object.
Hide/Show - This button hides/shows the Volume Object
Zoom to Area - This will allow AutoCAD to zoom to the extents of the respective terrain.
Rename - Rename the volume object
Toggle Auto-restore - Lock to automatically restore the item on drawing open, unlock to disable auto-restore.
Edit - This will show the Volume object editor.
You can also see the Name of the Terrain object and the plane elevation, as well as the cut and fill volumes.
Selecting Edit opens the Volume Editor.
Rename: Rename the Volume Object
Delete: Delete the Volume Object
Hide/Show - This button hides/shows the Volume Object
Zoom to Area - This will allow CAD to zoom to the extents of the respective terrain.
Send to Back/Bring to Front: Send Volume object to back or bring it to the front
Edit: Opens the Volume Object's Volume Calculation Dialog Box, presented in Step 3 and Step 4 of each method, respectively
Cut and Fill Labels: Inserts the labels of the Cut and Fill volume bars as drawing objects
Volume Bars: Insert the Volume Bars as drawing objects (check Step 5 for more info)
In the Results tab, the total Cut and fill amounts can be found. Volume colors can be changed using the respective buttons:
In the Labels tab, you can select to show/hide and adjust the text height of volume labels.
Insert Volume Bars Drawing Objects
The generated volume object initially exists as a dynamic Plex-Earth object stored in the drawing.
If you need to share the results with collaborators who may not be using Plex-Earth, you can convert the volume analysis into standard CAD drawing objects.
To do this, open the Volume Editor → Insert button → Volume Bars into the drawing. These bars visually represent the calculated cut and fill quantities and remain visible even when Plex-Earth is not active.
This allows the volume results to be included in drawings, reports, and project documentation.
FAQs
Which method should I use — Surface and Plane, or Surface and Surface?
Use Method 1 (Surface and Plane) when you want to level the ground to a specific target elevation, such as grading a site to a flat height. You only need one terrain model and define the desired final elevation as a number. Use Method 2 (Surface and Surface) when you have two terrain models to compare, for example an existing site survey and a proposed grading design. This method is more accurate for complex projects where the final ground is not a flat plane.
The volume calculation command is not available or not working — why?
Both methods require a dynamic Plex-Earth terrain model — they do not work with terrain imported as static CAD objects such as contour polylines, a TIN mesh, or points. For Method 2, both the existing and proposed terrain must be dynamic models present in the Terrain Manager before running the command. If you only have static objects, re-import the terrain and select Create Terrain Model as the surface type.
Should I change the Grid Cell Size, or leave it at the default?
In most cases, leave it at the default. Plex-Earth automatically selects an optimal grid cell size based on your terrain. A smaller cell size increases calculation precision but also increases processing time and drawing complexity. Only adjust it if you have a specific accuracy requirement for your project and understand the tradeoff.
How do I share the volume results with someone who does not have Plex-Earth?
The volume calculation initially exists as a dynamic Plex-Earth object, which requires Plex-Earth to be active to display. To make it shareable, open the Volume Editor → Insert → Volume Bars. This converts the results into standard CAD drawing objects that remain visible in the drawing regardless of whether Plex-Earth is installed. You can also insert cut and fill labels as drawing objects from the same editor.
Related Questions
This article explains how to calculate cut and fill earthwork volumes from Plex-Earth terrain models in AutoCAD, Civil 3D, or BricsCAD. You may have searched for:
- How to calculate cut and fill volumes in AutoCAD using satellite terrain data
- How to calculate earthwork quantities from a terrain model in Civil 3D
- How to compare existing and proposed terrain surfaces for grading in CAD
- How to calculate excavation or fill volume for a site in AutoCAD
- How to export earthwork volume results to a drawing or report