Working with Point Clouds in QGIS: A Step-by-Step Guide

Point clouds are sets of data points in a coordinate system, often representing the external surfaces of objects. In the context of geospatial analysis, point clouds are typically generated using LiDAR technology. QGIS, a popular open-source Geographic Information System (GIS) software, provides tools to visualize and analyze point cloud data. In this guide, we’ll walk you through the steps to work with point clouds in QGIS, incorporating the latest advancements in QGIS 3.32.

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1. Setting Up:

Ensure you have the latest version of QGIS installed. Some features might not be available in older versions.

2. Importing Point Cloud Data:

• Launch QGIS and create a new project.
• Navigate to Layer > Add Layer > Add Point Cloud Layer.
• Browse to your point cloud data file (commonly with .las or .laz extensions) and click Open.

3. Visualizing Point Clouds in 2D:

Once imported, the point cloud layer will appear in the Layers Panel. By default, QGIS will display the point cloud in a 2D view.

4. Switching to 3D View:

• Navigate to View > New 3D Map View.
• A new window will pop up displaying the point cloud in 3D. You can navigate using your mouse: left-click to pan, right-click to tilt and rotate, and scroll to zoom.

5. Adjusting Display Settings:

In the 3D view, you can adjust various settings to enhance the visualization:

• Point Size: Adjust the size of individual points for better clarity.
• Color Rendering: Change the color scheme based on attributes like elevation or intensity.
• Point Budget: Determine the number of points displayed. A higher budget will show more detail but may affect performance.

6. Advanced Point Cloud Processing in QGIS 3.32:

With the release of QGIS 3.32, users can now access powerful point cloud algorithms directly within the QGIS Processing framework. Here are some of the new features:

• Convert Formats: Convert point cloud data between LAS and LAZ formats.
• Export to Raster: Export point cloud data to a regularly gridded raster data using inverse distance weighting.
• Export to Vector: Export point cloud data to other vector formats like CSV, Shapefile, and DXF.
• Assign Projection: Assign a projection to a point cloud layer.
• Clip: Clip a point cloud layer by a vector polygon layer.
• Merge: Join multiple point cloud layers into a single file.
• Reproject: Reproject the input file to a different coordinate reference system.
• Thin: Reduce the number of points either by sampling radius or by skipping nearby points.
• Tile: Generate a set of tiles based on the input point cloud layer and tile size.
• Boundary: Generate a (multi)polygon from your point cloud data.
• Density: Output a raster file based on the number of points within each raster cell.
• Filter: Create a new file based on a set filter expression.

7. Behind the Scenes:

All the heavy lifting of point cloud processing in QGIS is done by PDAL, an open-source library for processing point clouds. The new standalone command line tool, pdal_wrench, built on top of PDAL, simplifies the process, and offers parallel execution for faster processing.

8. Conclusion:

Working with point clouds in QGIS opens up a world of possibilities for geospatial analysis and visualization. With the advancements in QGIS 3.32, users can now access a broader range of tools and algorithms, making the process more efficient and comprehensive.

Happy mapping!

(FAQs) About working with point clouds in QGIS:

What is a point cloud?

• A point cloud is a collection of data points defined in a three-dimensional coordinate system.

Which file formats does QGIS support for point clouds?

• QGIS commonly supports .las , .laz and .copc formats for point clouds.

How is LiDAR data different from a regular point cloud?

• LiDAR data is a type of point cloud generated using light pulses from a laser. It often includes additional attributes like intensity and return number.

Why is my point cloud not displaying correctly in QGIS?

• This could be due to various reasons, including large file size, incorrect coordinate reference system, or software compatibility issues.

Can I edit point cloud data directly in QGIS?

• QGIS is primarily used for visualization and analysis. Direct editing of point cloud data might require specialized software.

How can I improve the performance of QGIS when working with large point cloud datasets?

• You can adjust the point budget, filter out unnecessary data, or use a more powerful computer.

What is the difference between a Digital Elevation Model (DEM) and a Digital Surface Model (DSM)?

• A DEM represents the bare ground surface without any objects, while a DSM includes the tops of buildings, trees, and other objects.

How do I filter points based on their classification?

• You can use the filter option on the point cloud layer and apply SQL-like queries based on classification attributes.

Can I integrate point cloud data with other GIS layers in QGIS?

• Yes, you can overlay point cloud data with other GIS layers like vector data, raster images, and more.

Is there a way to automate point cloud processing tasks in QGIS?

• Yes, QGIS offers a processing toolbox that allows for batch processing and automation of certain tasks.

How do I change the color scheme of my point cloud visualization?

• You can adjust the color rendering settings based on various attributes of the point cloud data.