LAS dataset to create DTM and DSM rasters

From the LAS dataset, you can create full-resolution raster files on disk in TIFF format for both the DTM and the DSM. This is the workflow recommended by Esri to ensure the most efficient use of disk space and the greatest scalability for organizations that may have large or numerous lidar collections.

Additionally, some organizations prefer to have pre-built raster datasets that can be copied or downloaded, ensuring that all users access a single, authoritative version of the elevation data.

Workflow for DTM and DSM derived from points

This workflow begins with the LAS dataset used to perform QC on the lidar files.

Create output rasters—DTM

This workflow is based on creating rasters in multiple tiles to accommodate very large data collections. For large data collections, it is recommended to use the LAS Dataset To Tiled Rasters geoprocessing tool, which can be downloaded from 3D Samples. Note that if your LAS data comprises approximately 20 GB or less, you may choose to use the LAS Dataset to Raster geoprocessing tool within ArcGIS and create a single output raster. In this case, use the same settings noted below, ignoring the steps related to defining output tiles.

1. Load your LAS dataset into ArcGIS Pro.
2. Configure the LAS dataset for bare earth by using the ground filter on the LAS Dataset toolbar (or by opening the layer properties in the Contents pane and selecting last returns only, and then setting class codes to GROUND & MODEL KEY).

   Note:

   If implementing this in ModelBuilder, use the Make LAS Dataset Layertool to create a layer, and then apply these filters to that layer, used as input to the next tool.

3. Run the LAS Dataset To Tiled Rasters tool and enter the following data.
   1. For Input LAS Dataset, drag the LAS dataset layer from the table of contents into the GP tool. (Do not reference the LAS dataset from the Catalog pane or the filter for ground points will not be applied.)
   2. Under LAS Values to Export, choose Elevation.
   3. Under Output Destination, enter the folder to store the DTM tiles.
   4. Under Output Base Name, you can enter a common base name for all tiles, such as ProjectName_DTM_. Unique tile numbers will be appended to the base name for each DTM tile, stored in TIFF format.
   5. For Cell Size, enter the resolution for the DTM tiles as determined in the QC step.
   6. Under Z Factor, you should typically enter 1. Any other value will rescale the z-values of your output DTM. If your lidar data is recorded in feet, a value of 0.3048 will rescale the values to meters, but it is generally recommended to build all raster surfaces in the coordinates of the source data to facilitate QC, and then their height values can be rescaled in the later Elevation workflow.
4. Set the following for the tool options.
   1. Under Interpolation Options/Interpolation Type, use the setting determined above that is best suited to your data.
   2. Under Interpolation Options/Void Fill Method, use the setting determined above. The recommended selection is Natural Neighbor, assuming you have a polygon to define the usable data extents (see above).
   3. Under Tiling Options/Tile Overlap in Pixels, it is recommended to use the default value of 64. This ensures tiles will overlap (at full resolution, and also for several levels of pyramids); overlap can be important if your data is ever reprojected into a different coordinate system.
   4. For Tiling Options/Tile Definition, choose Columns & Rows if you want the tool to generate tiles automatically, or choose Features if you have an existing feature class to define the boundaries and names of the output DTM tiles.

      Note:

      If you would like to create a polygon feature class to define the output raster tiles, use the Create Fishnet geoprocessing tool. Alternatively, if you prefer to create DTM and DSM tiles that match the extents of your input LAS or zLAS tiles, you can use the LAS File Extent as Polygon geoprocessing tool available from LAS Custom GP Tools for ArcGIS.

   5. Tiling Options/Columns and Rows in Pixels may be left blank if you are inputting polygons to define output tiles. Otherwise, for automatic tiles, the default values of 5000x5000 pixels are recommended.
   6. Use Tiling Options/Tile Features to enter the path and name to your predefined tile polygon feature class. If this feature class has a text field included with a unique name for each tile, you can use the Name Field to direct the tool to the appropriate field.
   7. Finally, it is recommended to use the Raster Storage environments setting to build pyramids for these DTM tiles. Choose bilinear resampling and LZ77 compression.

   When this tool runs, it will create a set of DTM tiles that may be processed as a new elevation data collection, as described in Elevation best practices.

Create output rasters—DSM

You can now build the first-return DSM.

1. Load your LAS dataset into ArcGIS Pro.
2. Configure the LAS dataset (or LAS dataset layer) for the first-return DSM either by using the all returns filter on the LAS Dataset toolbar or by opening the layer properties in the Contents pane and selecting first returns only, and set class code to ANY.
3. Run the LAS Dataset To Tiled Rasters tool, which can be downloaded from 3D Samples, and enter the following data:
   1. For Input LAS Dataset, drag the LAS dataset layer from the table of contents into the GP tool. (Do not reference the LAS dataset from the Catalog pane or the filter for ground points will not be applied.)
   2. Under LAS Values to Export, choose Elevation.
   3. Under Output Destination, enter the folder to store the DSM tiles.
   4. Under Base Name, enter a similar name as above but include DSM, for example, ProjectName_DSM_.
   5. For Cell Size, enter the resolution for the DSM tiles as determined above.
4. For the tool options, under Interpolation Options/Interpolation Type, the typical selection is Bin with Maximum Value for the DSM.

At this point, the basic workflow is complete for one lidar project. You can repeat it for other lidar projects, and then continue to Elevation best practices. You may also want to consider adding the steps in Share 3D point files for user download for serving the lidar files for download.

Optional addition of constraints for DTM

Some users require the bare-earth DTM to be constrained by additional data to more accurately model the terrain, for example, to ensure peak height values are represented, water bodies appear flat, and streams show monotonically decreasing elevation values. This is most applicable where additional datasets such as breaklines, river vectors, and water bodies are collected, or already exist, in addition to the lidar. This modification to the first workflow applies preexisting 3D features to constrain the bare-earth DTM in key areas, such as breaklines and hydrology.

Note:

This is not applicable to the DSM, since 3D constraint features are typically only applied to the ground. This discussion will list only the steps that are different.

Create a LAS dataset

1. Create a LAS dataset as described in Manage lidar collections with LAS datasets, but be sure to add the 3D constraint features available for your project area. Refer to Types of data supported in LAS datasets in the ArcGIS help for details on using line and polygon features as terrain constraints.
2. Complete your QC process before creating the output DTM.

Create an output raster—feature-constrained DTM

As in the workflow above, use the LAS Dataset To Tiled Rasters geoprocessing tool to create output DTM tiles. Follow the settings you determined at the end of the QC stage, but note that when using features to constrain the DTM, the interpolation method must be one of the triangulate methods. After exporting the DTM tiles, follow the steps described in Elevation best practices. This workflow is complete, unless you intend to share the lidar files for download.