In LP360 for ArcGIS, while trying to Draw a Profile Line, LP360 errors stating, “Completing the construction of the profile line failed. (17020)”. Expanding the error message dialog for more information reveals, “QI to ISpatialReference failed (21422)”.
The most probable cause is the lack of a Spatial Reference System (SRS) specified on the LAS Layer (LAS Layer properties -> Source -> Data Source -> Current Coordinate System). The Current Coordinate System shows as blank. This can occur when an LAS file lacks the required SRS information in the header, or contains a user defined value for LAS v1.3 or earlier file formats. Manually assign an SRS (LAS Layer properties -> Source -> Data Source -> Current Coordinate System) to the LAS Layer to resolve the issue. Even if the coordinate system is unknown, assign and then clear the Current Coordinate System so that it shows “Unknown” will resolve the issue.