Visualizing Point Clouds in ArcGIS Pro
This tutorial will describe some basic visualizations of point cloud data that can be performed in ArcGIS Pro.
Point clouds are geospatial information stored as a collection of points in three-dimensional space (latitude, longitude and elevation). Point clouds are commonly captured using a aerial laser scanning technique called Lidar. Unlike vector and raster data that is analogous to a flat two-dimensional map, point clouds can be used to more-faithfully represent structures and topography, albeit at the cost of greater storage and processing demands.
The traditional digital elevation model is considered a two-point-five dimension surface. At each longitude and latitude, there is exactly one elevation or z value.
If there are layers of features at a location, say a tree planted in the ground, the 2.5 D surface can only represent the top of the tree or the ground underneath the tree. If there is a building, a 2.5D surface can only represent the top of the building or the ground, not each individual floor in the building.
In contrast, a point cloud is a model where there can be multiple points at multiple elevations for each latitude and longitude. A point cloud is true 3-D.
Point clouds generated by airborne laser scanners (Lidar) can be used to create digital elevation models. However, each pulse of light can be six inches in diameter or wider (Lohani 2010). This means that part of a pulse may reflect off of a high object like a tree leaf or building edge, but other parts of the pulse may continue all the way to the ground before being reflected back to the sensor. Accordingly a single pulse sent down by the laser may return to the sensor multiple times. These multiple returns allow Lidar to see through gaps in tree canopies and see features on the ground hidden by vegetation, such as the remains of ancient city earthworks. This has made Lidar very useful for archaeological work.
Acquire the Data
Lidar data and digital elevation models for much of the United States are made available to the general public by the US Geological Survey (USGS) via the National Map web data portal.
- Search for a location. For this example we will use the Spokane Falls, a dramatic landscape where the Spokane River passes just north of downtown Spokane, WA.
- Zoom in to the area and select Current Extent so you see the different available options.
- To get point clouds, select Elevation Source Data (3DEP) - Lidar, lfSAR.
- Find Products at that location.
- If the search returns no products, there may be no coverage in that area. Try another area.
- Show the Thumbnail on the listed products to find the one covering an area you want to explore.
- Download the .zip archive of the
- LAS file. is a standard file type developed in 2003 by the American Society for Photogrammetry and Remote Sensing. LAZ files
- LAZ files are in a newer compressed format that reduces the file size of Lidar data, but they have to be converted using the Convert LAS tool, so you should download LAS files whenever they are available.
- Extract all... the contents of the .zip archive. You should see the .las file in the extracted directory.
Symbolize the Data
Create a Scene
Although you can place point cloud data on a two-dimensional map, the data is much more useful when viewed in three-dimensions. ArcGIS Pro has a type of map called a Scene that allows the user to navigate around three-dimensional data to give different perspectives as if you were flying around the data.
- Under the Insert tab, in the New Map dropdown, select New Local Scene.
- Add Data to the map with the .las file.
- If you get a message about an unknown coordinate system, the
LAS file may be old and have no coordinate system information and you
will have to set it so everything lines up.
- If there is a .xml file in the folder with the LAS file, open it with Notepad, and see if there is any coordinate system information. In this case, the coordinate system is the Washington North (feet) State Plane Coordinate System.
- View the Catalog Pane.
- Under Folders, add a Folder Connection to the folder containing the LAS file.
- Right click on the LAS file, go to Properties and Coordinate System, and Set Coordinate System.
- Remove and Add Data the LAS file again and it should be in the right place.
- The data may take some time to load and you may need to zoom in to get it to come into view.
- You can adjust the view by Show Full Control icon at the bottom left of the scene, and then dragging on the different elements to change the different angles of view.
- If you get lost in navigation, right click on the point cloud layer in the drawing order pane and select Zoom to Layer.
Viewing Different Levels of Returns
One of the strengths of Lidar is that the laser can occasionally penetrate the tree canopy or pass in gaps between structures to reveal multiple layers of objects at a single location. This causes the laser signal to return multiple times from a single location. When the Lidar data is processes, these returns can be classified to find the different levels of objects in a landscape.
If you right click on a point cloud layer, the LAS Filters option allows you to choose different layers of returns:
- All Points shows everything at all levels.
- Ground shows only the returns that represent the bare ground underneath vegetaion or any other objects above the surface.
- Non-Ground is everything above the ground.
- 1st Return is the top level of objects including the tops of vegetation and structures.
Digital Elevation Model
One common use for Lidar point clouds is to create digital elevation model (DEM) surfaces. This can be done using the LAS Dataset to Raster tool.
- Right click on the point cloud and under LAS Filters select Ground points. This will limit the DEM to bare earth.
- In the Analysis tab, select Tools and search for the LAS Dataset to Raster tool.
- For Input LAS Dataset, choose the point cloud layer you want to use.
- For Output Raster, choose a name for the output file.
- In the Imagery tab, under Raster Functions and Surface are a variety of viewing functions that may be appropriate to the topography and/or the use of the map.
You can get accurate statistics about the point cloud using the LAS Dataset Statistics tool.
- In the Analysis tab, select Tools and search for the LAS Dataset Statistics tool.
- The Input LAS Dataset should be your point cloud.
- The Output Statistics Report Text File is the name of the .csv file. Be sure to put a .csv at the end of the file.
- This creates a CSV file that you can open in Excel.
From this we see that the First Returns or the top level of points constitutes the majority of the points (95%).
Because this is an area of both dense structures (downtown) and significant vegetation (Riverside Park), the percentage of Ground points representing bare earth or pavement is fairly small (21.7%).
Present Your Scene
Scenes should be exported directly from the scene rather than through a layout because a bug in layout of scenes causes point clouds to render at low resolution.
- Turn off the elevation and topographic base maps so the service layer credit text doesn't obscure your image.
- Share and Export.
- Export to a PNG file. A portable network graphics (PNG) file is a lossless image format that generally looks good in documents without being too large or causing problems when printing.
- Select the output file Name.
- Select Preview so you can see how the output will be framed.
- Hide the Contents pane so you have the full screen width.
- Adjust the Width and Height to the size of the figure. At 300 DPI, a 6 x 4" figure should be 1800 x 1200 pixels.
- Export a PNG and insert that image file into your document.
Save Your Project
Upload to ArcGIS Online
You should save your project as a project package to ArcGIS Online so you can open the project on another machine, and so you have a backup.
- You may want to rename your maps and layouts to keep them organized. You can do this from View and Catalog Pane.
- Go to the Share tab and select Project.
- Provide a name to save the project under. The default is the name of the current project.
- Copy the name into the Tags and Summary fields.
- Click the Share outside of organization box so your project database containing your layers is included in your project package.
- Unclick the Include Toolboxes and Include History Items check boxes so that history or toolbox errors to not cause your upload to fail.
- Analyze the project to find any problems.
- Package the project to upload it to ArcGIS Online. With large point clouds, this can take several minutes.
Reopen Your Project
You can reopen your project from the ArcGIS Pro home screen by going to Open another project, navigating to My Content and selecting the project package you uploaded.
When you reopen your project, the LAS layer may have an exclamation mark beside it indicating that the layer cannot be found.
- Presuming that you saved the project with Share outside of organization checked, the LAS data will be downloaded, but ArcGIS Pro may not know where to find it.
- Right click on the layer and select Properties, Source, and Set Data Source.
- Navigate through the Folders to commondata and you should find the LAS file somewhere in there.
General Failure Workaround
Projects containing point clouds and DEMs are large, which appears to cause ArcGIS Pro to die with a cryptic General Function Failure message.
A workaround is to use the Project Project tool and Save package to file, then upload that package to ArcGIS Online.