Site Area Mask

The model works within a square or rectangular grid, but that's not very realistic is it? So, you can define the exact shape of your site using a mask to include cells (cell mask value=1) or exclude cells (cell mask value=0). This deals with any inconsistancies from having partial data for cells outside the site area, and also makes the model run faster as it omits the excluded cells from the simulation process. Any combinations of cells are valid, i.e., it doesn't need to be a solid shape, instead of which you could have a discontinuous shape with 'islands'. The mask application level dictates which processes are regulated by the mask.

Your Site Area Mask is a GIS layer that you can use to define the extent of your site if less than the entent of the entire model grid.

Consider your mask layer as a grid pattern of opaque (outside your site) and transparent (inside your site) cells that, when superimposed on top of your other spatial data, excludes off-site values and only includes data within the confines of your site area. It's as simple as that, yet the benefits are huge. Off-site data can often be dubious, and the modelling software performance is greatly enhanced if it is not having to process irrelevant model grid cells.

You can set your Site Area Mask using this Site Area Mask window or in the GIS Control.

This Site Area Mask window comprises the mask viewing grid in its upper section below which are a few controls and an information panel. The information panel informs you whether you have activated your GIS inputs in your Preferences which you need to do to ensure that your GIS will work, in addition to identifying the location of your GIS input files in the GIS Control.

If you have activated your GIS inputs then the panel will look like this
Alternatively, without the correct activation the panel will look like this
You can still work with your Site Area Mask (and you other GIS data) even if it is not activated, but it will not be included in your simulations.

The Clear button deletes your current entry for your Site Area Mask and resets the associated settings in the GIS Control. This is probably a useful precursor to identifying a new file for your Site Area Mask but you will prompted to continue with a message box

To identify a new file for your Site Area Mask using this window, click on the Load GIS data... button and use the standard dialog box to find your file

You can set the mask to operate at different levels of application. Firstly, set your mask active using the apply my mask tick box then set the level that you want it to operate at using the radio buttons
This is useful when investigating the impact of including either your Site Area Mask itself or the spatial data that it modifies.

You can choose from

If in doubt, then you should select the default level 3 to activate the mask for all of the modules in your model.

To help orientate your Site Area Mask use the Show Co-ordinates option which displays the grid co-ordinates of each cell, and the OK button closes the window when you have finished.
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