Mesh Input File

The mesh input file can be either a .2dm or a .gr3 file in order to work with schimpy’s prepare_schism utility. The mesh input file contains the horizontal grid information, including the node coordinates and the connectivity of the elements.

The mesh input file is typically generated using a preprocessor tool, such as AquaVeo’s SMS. This section will not discuss how to generate the mesh input file, but rather how to use it in the context of the BayDeltaSCHISM model setup. For information on generating the mesh input file, see the Advanced topics: Gridding the Horizontal Mesh section.

2dms

The 2dm format is a proprietary format used by AquaVeo’s SMS software. We use SMS and 2dm formats for mesh generation and editing, and provide the most up-to-date mesh input files in the <PUT LINK TO 2dm FOLDER>.

The 2dm is strictly a horizontal mesh format with no additional information about boundaries or any other model input. It only contains nodes, edges, and elements as well as the connectivity between them.

The 2dm becomes useful to SCHISM when it is converted to an hgrid.gr3 file using schimpy’s prepare_schism utility. During preprocessing with prepare_schism, bathymetric data are added to the mesh as well as boundary edges and their indices. The hgrid.gr3 file is the format that SCHISM uses for the horizontal grid.

hgrid.gr3

The hgrid.gr3 file is the horizontal grid file that SCHISM uses for its simulations. It contains information about the nodes, edges, elements, bathymetry, and boundaries of the mesh. Review SCHISM’s documentation on the Horizontal grid here.

All other spatial inputs (e.g. manning.gr3, sav_N.gr3, diffmin.gr3, etc.) are generated based on the hgrid.gr3 file during preprocessing. Therefore, one can’t change the horizontal grid without regenerating all of the other spatial inputs. This is why we recommend using the preprocessor to implement changes to the mesh, as it will automatically regenerate all of the necessary files based on the new hgrid.gr3 or 2dm input file.