You can use LAS datasets to manage your lidar collections.
Create a LAS dataset and perform quality control
After preparing your data, you'll create a LAS dataset to reference all .las or .zlas files in the project. See Create a LAS dataset for additional information.
When using a LAS dataset for lidar collections, the following should be considered:
- Define the proper coordinate system in the properties of the LAS dataset.
- Add the .las or .zlas files to the LAS dataset, and calculate full statistics on all files.
- Review the statistical data in the LAS dataset for quality control (QC) purposes as follows:
- Ensure that the point classifications meet the project requirements.
- Verify that the zMin and zMax values (excluding points classified as noise) are reasonable (for example, no below-ground points or high points are included).
- Load the LAS dataset into a 2D map or 3D scene in ArcGIS Pro, and perform a visual review of the data to ensure that noise has been properly classified, or use the editing tools to reclassify erroneous points.
- Create a raster representation of the outgoing pulse density using the LAS Point Statistics as Raster tool (set the Method parameter to Pulse Count) to ensure that the data meets project specifications in all important areas. This raster can be summarized at relatively low resolution (for example, 5 to 20 times the digital terrain model [DTM] resolution), but you must normalize the values according to cell size. For example, if you summarize pulse density at 20-meter resolution, divide all values by 20², equaling 400, so the raster values represent pulses per square meter.
- A similar raster representation of the density of ground points is also recommended to be used to determine the appropriate resolution for the DTM. This can be created as follows:
- Load a LAS dataset covering the full project into ArcGIS Pro, and filter for ground points only.
- Open the LAS Point Statistics as Raster tool, load the LAS dataset layer from the Contents pane into the tool (to ensure that the filter for ground points only is honored) and set the Method to Point Count.
- Create this raster at the same spatial resolution as the outgoing pulse density raster, and normalize so each cell represents point density per square meter as described above.
- Add any requirements from your organization to complete the QC process on the lidar data before proceeding.
Determine project extents
It is recommended that you add a polygon to the LAS dataset that outlines the usable extent of the lidar data (the Soft Clip option on the Surface Constraints tab of the LAS Dataset Properties dialog box). This polygon will prevent problems with attempts to interpolate and fill voids outside the project boundary. The usable extent of the lidar data is distinguished from all data to emphasize that lidar points at the extreme edges of the dataset should generally not be used, and attempting to include all data at the very edges may create a much more complicated outer boundary.
When determining project extents, consider the following;
- Lidar data is typically acquired based on a desired project area, so a polygon defining the desired project extent may exist.
- If a project extent polygon does not already exist, you can create one by doing either of the following:
- Manually create a polygon to approximate the project extents.
- Synthesize a data boundary as described in Data area delineation from lidar points in the ArcGIS Desktop help (the workflow applies in ArcGIS Pro as well).
A complicated polygon can diminish performance. Use a generalized polygon (with a minimal number of vertices) that is conservatively within the extreme edges of the lidar points.
Overlay the project polygon with the pulse density raster to ensure that the project coverage is complete, or identify any areas that may have been omitted.