Existing ground models - Part 2

Part 2 - My ground surface process

As I said in Part 1, a poor setup of the existing ground model has knock on impacts not only on the ground model opening times but also on every other model that interacts with it, whether that's displaying it or some other interaction like interfacing earthworks.  So starting off with a clean and well performing ground model is fundamental to your project.

The diagram below shows the high level process I use for developing those master ground model(s).  The main problem I see at the minute the majority of users jump straight to master ground model creation, skipping the first two very important steps.

So, lets talk about the "Pre-process" step.  

What do I mean by "Pre-process"?  Well, fundamentally that's getting the data in to a format and size that will allow it to be imported in to the modelling software to create a surface so it can be post processed and validated.

This pre-process phase predominantly applies to large datasets most commonly associated with lidar, drone, laser scan and mobile mapping datasets.  They often

• have millions of points so the surface would be excessively large
• lack feature strings e.g. kerblines that give a more accurate representation of the existing ground
• contain "noise" such as vehicles or above surface features such as trees that wouldn't give a true representative ground surface

Luckily there are tools that can help us with this pre-processing.  We aren't going to talk about the specialist tools that come with capture devices but we will talk about tools that are in the Civil Engineer's normal tech stack

Autodesk Recap has some great features we can use to help in this process, including some new features that came along in 2023.1.  

• Cutting down the point cloud to size so you only import what you need
• Manual removal of specific point or group of points to remove an feature that's not required
• New in 2023.1, the ability to classify the point cloud.  This will quickly removal of non-ground points.  Check out the video here  

We can also use Autodesk Infraworks for

• Creating a surface from point data.  Infraworks does a good job of creating quite lightweight ground surfaces from the point cloud
• Linear feature extraction can be used to extract 3D feature strings of kerb lines, centrelines etc. This tool can also be used to extract additional feature springs that could be perpendicular, or any  angle, to other features (kind of like a cross section), to augment the surface in key areas.  Check out this video

Once I gather some suitable data I'll produce some videos to accompany this post

Next in the Series

Part 3 - Ground surface validation models and processing

Part 4 - Master ground model creation