|Starting in CatchmentSIM 3, a grid layer can now be used to define impervious proportions for each pixel instead of using vector impervious polygons. This has the advantage of being much faster than the polygon approach and handling more detailed datasets.|
The easiest way to take advantage of this functionality is to add a vector or raster layer to your project. Convert to a decimal grid layer via right clicking on the layer and then selecting this layer in the Raster Impervious Areas tab of the Impervious Areas form. Ensure you select the correct Scale option depending on if the grid layer values are between 0 and 1 or 0 and 100%. A background impervious area value can also be specified for areas of the grid layer that are Non-Defined.