WMS:Active/Inactive Cells

Each of the cells in a cell-centered grid can be active or inactive. An inactive cell is a cell which is not part of the computational domain. For example when doing a surface runoff analysis using GSSHA cells inside the watershed boundary should be active while cells outside the boundary should be inactive.

An inactive cell is ignored when contours are displayed on the grid. A set of selected cells can be made inactive by selecting the Inactivate Selected command in the Grids menu. A set of inactive cells can be made active again by turning on the display of inactive cells using the Display Options dialog, selecting the cells, and selecting the Activate Selected command in the Grids menu (inactive cells can only be selected if they are being displayed).

Activate Polygon Region In many cases it is useful to delineate the active/inactive regions in a grid using a polygon. A region can be activated by selecting the Activate Polygon Region from the Grids menu. A dialog appears prompting you to select either Read polygon from file or Select polygon interactively. If the Read polygon from file option is selected, WMS brings up the File Browser dialog, and prompts the user to specify a polygon file. If the Select polygon interactively option is selected, WMS prompts the user to define the polygon by selecting at least three points and double-clicking when done.

Once a polygon is entered, each cell is compared to the polygon. If the cell center is on the interior of the polygon, it is made active. Otherwise, the cell is made inactive.

Related Topics

• Creating Grids
• 2D Grid Display Options