Introduction
Ground extraction is a new feature introduced in iTwin Capture Modeler 2023 as a tech preview.
It allows to extract ground/non ground point cloud segmentations from various inputs (see image below – left: the original textured 3MX mesh – right: extracted ground points in purple and non-ground points in light blue).

Here is a video tutorial describing the operation
 

The supported inputs data are:

• Production meshes in 3MX or 3SM formats.
• Production point clouds in the following formats: LAS, LAZ, POD or OPC.
• ContextScene (advanced) that describe the input entries

The output generated is a segmented point cloud with 2 classes: Ground and non-ground that will be displayed in the result 3d view (result tab) and exported in various point cloud formats.
This output could be easily transformed to a DTM or TIN mesh by importing the segmented result in Microstation and generate a Terrain mesh passing to the ground points.

General workflow
To create a ground extraction job, here are the main steps in iTwin Capture Modeler:
1) Open the Ground Extraction dialog to define your source input and settings for the extraction
2) Optionally create a clip polygon to restrict the extraction in a smaller area. This can be done in the 3d view directly over the input data (Settings tab)
3) Submit the extraction processing and choose the final output formats (needs the iTwin Capture Modeler Engine to be launched)
4) Check the result in the 3D view (Result Tab) – Possible to overlay output and input data.


Ground extraction process
We describe here the steps to create a ground labeled point cloud in more details.
Start a Ground Extraction
There are several ways to create a ground extraction from iTwin Capture Modeler Interface. It will open a dialog in which you will be able to set the inputs and settings of the ground processing.
1) The more general way is to open the main Menu and select “New Analysis” then “Extract Ground…”.

2) Select the project in the in the project tree, then select the “New Analysis” green button and choose the “Extract Ground…” entry.

3) In project tree press the “+” button and select the correct entry

4) Another convenient way of opening this dialog is to select the source capture item directly - for example a mesh production that you already made in this project. By selecting it in the Project tree you will see
the green button “Extract Ground…” in the workflow tool bar. Right clicking on the production item will also show the same entry in the contextual menu.

This latest method has the advantage to already select this production as the source input for the Ground extraction dialog (see Input and settings).