Updated: Sep 12, 2018
Now that you have pre-processed the LiDAR raw data and served up the LAS data, you’re faced with another series of operations to move the data into a format usable by engineering and mapping solutions. The exact approach may vary, depending on your applications and intended uses. In general, the process is known as data extraction and it typically follows these steps:
1. Using ground survey control, you’ll further adjust the raw LAS data to match the ground control. This is a quality control process allowing you to determine the true accuracy of the LiDAR data set.
2. If you gathered imagery during the LiDAR collection process, you can mix it in with the raw point data in real world coordinates. Use this imagery for backdrop information or combine it with the raw LiDAR points to update the red/green/blue (RGB) values of the points so that they reflect the imagery. This allows further point and feature classification during your data extraction process.
3. Using the various attributes contained within your LAS data file, you can automatically change the point classification from undefined to whatever the points actu-ally represent. Points may be bare earth, vegetation, buildings, or countless other things. This will help your engineering and mapping applications to build surfaces and closed shapes from the classified point types, dis-playing such things as a bare earth surface.
4. After classifying the point types, you can create linear features from the data. These might be the edge of pavement, striping, curb lines, and any other type of linear feature that you can deduce from point-to-point relationships. Put simply, you’re connecting the dots. You can also create linear features by digitizing onto the classified points, using the triangulated model to obtain the elevation value for the linear features, all the while using your backdrop imagery.
NOTE: Once you’re through this process, you’ll output the data into various formats, including fully classified LAS files, contour drawings, GIS features, and 3D image files.
Autodesk has data extraction solutions available today that will accommodate LAS data sets in the billions of points. The data extraction software is designed to provide the required engineering and mapping information that can be directly used by Autodesk’s engineering and mapping solutions.
Young, James. LiDAR for Dummies. Hoboken: Wiley Publishing, Inc., 2011.