Reprojecting the vertical coordinate system of point cloud data in an LAS dataset

Description

Currently, the Extract LAS (3D Analyst) geoprocessing tool supports reprojecting the spatial reference of point cloud data in an LAS dataset to a different horizontal coordinate system, but not to a different vertical coordinate system.

Cause

A vertical datum transformation is not currently supported, per the Extract LAS (3D Analyst) tool reference.

Solution or Workaround

To reproject the vertical coordinate system of point cloud data in an LAS dataset, we can convert the LAS file to a point cloud scene layer and reproject it using tools in the Projections and Transformations toolset. The workflow is outlined below. The example below transforms the vertical coordinate system of an LAS dataset from NAD 1983 (2011)/WKID 115755 to NAVD88 height (ftUS)/WKID 6360, with a NAD_1983_2011_Height_To_NAVD88_Height_USFT_CONUS_GEOID18 geographic transformation applied.

1. Ensure that the LAS dataset has a defined vertical coordinate system in ArcGIS. If it does not, use the Define Projection (Data Management) tool to specify the correct coordinate system. For example, if the LAS dataset comes in with a vertical coordinate system of GRS80, which is undefined in ArcGIS, we can use the Define Projection tool to specify a vertical coordinate system of NAD 1983 (2011)/WKID 115755, which is functionally equivalent, since NAD83 uses GRS80 for ellipsoidal heights.
2. Run the Create Point Cloud Scene Layer Content (Data Management) tool using the original LAS file as the input dataset. Set the horizontal and vertical output coordinate systems to the horizontal and vertical coordinate systems of the LAS dataset. The output will be a point cloud scene layer package (.slpk) with the same spatial reference as the LAS dataset.
3. Reproject the point cloud scene layer package (.slpk) data using the Project (Data Management) tool. Set the horizontal output coordinate system to, for example, NAD 1983 (2011) StatePlane North Carolina FIPS 3200 (US Feet)/WKID 6543, and the vertical output coordinate system to NAVD88 height (ftUS)/WKID 6360, check the box to apply a vertical transformation, and make sure NAD_1983_2011_Height_To_NAVD88_Height_USFT_CONUS_GEOID18 is specified as the geographic transformation.
4. Once the point cloud scene layer is reprojected, use it as an input point cloud in the Extract LAS (3D Analyst) tool to obtain a new LAS file.
5. If a .prj file associated with the new LAS file is needed, which contains a well-known text (WKT) representation of the LAS file's coordinate system, we can run the Create LAS Dataset (Data Management) tool, with the new LAS file as input and the Create PRJ For LAS parameter enabled, to generate it.