I am processing drone imagery with OpenDroneMap using a native Ubuntu installation of OpenDroneMap. I see the the LAS generated returns points in UTM for X and Y coordinates as stated in the documentation. The Z values are about 18 meters below the actual surface. I cannot explain this shift based on differences in vertical datums for my area of interest. What is the vertical datum values produced by OpenDroneMap when no ground control point file is incorporated?
The reconstruction will use the Z values from the image EXIF header as derived from the on-board GNSS unit. The resulting surface will be in WGS EGM96 as returned by the satellites.