Grid Tools and Utilities

Owned by Kester Scandrett
Last updated: 08 Mar, 2017 by Duy Pham
3 min read


The Grid Tools function on the toolbar contains a range of different functions and utilities that have been needed. Figure 1 shows a screen capture of the current functions available under the Grid Tools button.


Figure 1  Grid Tools functions.


Orthogonality Deviation Statistics:

This utility provides summary statistics on the orthogonality of the grid. A perfectly orthogonal grid will have a zero deviation angle at every grid intersection. The goal during the gridding process is to produce a representative and computationally efficient grid of the model domain with as low as practical deviation angles (e.g. < 3 degrees). The user can view a map of the deviation angles using the ViewPlan function.

Generate a CORNERS.INP File:

This utility allows the user to generate a CORNERS.INP file. This is which is in the DRIFTER module, and determines the centroid of a cell from the coordinates of the four cell corners. This file is generated automatically by EE when a new model is built, but this tool allows the user to force EE to recompute the cell corners, if needed

Export Outline of Model Domain:

Use this function to output a bounding polygon in the coordinate system used by the model. The output file format is P2D. This file can be used as an overlay in ViewPlan or imported into GIS systems.

Export Grid Cells:

Use this function to export the cells by cell polygons in the coordinate system used by the model. The output file format is P2D. This file can be used as an overlay in ViewPlan or imported into GIS systems.

Export Model Grid for Delft's RGFGrid:

Use this function to export the currently loaded EFDC model grid out to a Delft RGFGrid formatted GRD file. This file can then be directly loaded into RGFGrid for editing. RGFGrid edited grids can be imported into EFDC_Explorer by selecting "Generate New Model | Import Grid | Delft RGFGrid".

Export Bottom Elevations:

Use this function to export an XYZ data file at the cell center coordinates of the bottom elevations.

I-J Map: Transpose I-J's:

These I-J Map functions are used during the grid generation- importing process to correct any model I-J orientation issues. This function switches I to J and J to I. If boundary conditions are already assigned, the IJ mapping is remapped to the new IJ space.

I-J Map: Reverse Order: These I-J Map functions are used during the grid generation-importing process to correct any model I-J orientation issues. This function flips the numbering direction for either the I or the J index. If boundary conditions are already assigned, the IJ mapping is remapped to the new IJ space.

Fix DX/DY/Angle Problems:

This routine attempts to correct DX, DY and Cell Angle problems before computing cell metrics. EE picks a South cell face for cell L=2 then assigns DX/DY/Angles. The user may enter a face shift of n, where n=0 (the default) means no shift but correct the angles (if needed), and n can vary from -2 to +2. Entering a -1 EE reorients the IJ map and corresponding DX/DY -90 degrees.

Rotate Cell Angles:

This function applies a rotation to the cell rotation angles. It does not rotate the actual cell. If using the CORNERS.INP file it just applies a user specified rotation to the cell rotation matrix. In EFDC the cell's rotation matrix is used for velocity plots and interaction with the wind field.