Hydro Enforced DTMThe hydro-flattened bare earth DEM was generated using the 2018 DC lidar bare earth points and 3D hydro breaklines to a resolution of 1 m. The bare earth points that fell within 1NPS along the hydro breaklines were excluded from the DEM generation process and put into class 20 ignored ground. This is analogous to the removal of mass points for the same reason in a traditional photogrammetrically compiled DTM. This process was done in batch using proprietary software. The technicians then used proprietary software for the production of the lidar-derived hydro-flattened bare earth DEM surface in initial grid format at 1 m GSD. Water bodies (inland ponds and lakes), inland streams and rivers, and island holes were hydro-flattened within the DEM. Once the initial, hydro-flattened bare earth DEM was generated, the tiles were checked to ensure that the grid spacing met specifications. The surface was also checked to ensure proper hydro-flattening.
