We will demonstrate the Gen-Vx-Mask "shape" masking type using freely available shapefiles from Natural Earth. While multiple resolutions are provided, we'll use the coarsest version for this example since it's the smallest in size.
Download the Natural Earth administrative shapefiles for countries boundaries.
mkdir ne_shapefiles; cd ne_shapefiles
wget https://www.naturalearthdata.com/http//www.naturalearthdata.com/download/110m/cultural/ne_110m_admin_0_countries.zip
unzip ne_110m_admin_0_countries.zip
Run gen_vx_mask to define the mask for the USA (index 4).
Re-run to compute the union with Canada (index 3).
Re-run to add Mexico (index 27).
The result is good but not perfect. There are a few missing grid points along the boundary. But this demonstrates how the tool works. Consider re-running all three commands again, but this time use the "-value" command line option to define the mask value to be written. Just make "-value" match the "-shapeno" option (.e.g. -value 4 for USA, -value 3 for Canada, and -value 27, for Mexico). What impact does that have on the result?
Next, we'll take a look at the functionality that Grid-Stat offers.
