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Visualise the supplied land_sea_mask.grib icon using the grid_shade icon. This Contouring icon is set up to shade the grid points exactly as they are in the data with no interpolation. To help illustrate what's going on, we've chosen low-resolution fields - this one is 4x4 degrees. The values are 0 over the sea, 1 over the land and somewhere between 0 and 1 on points which are close to both sea and land. Before we can use this field as a mask, we must do something with those "in-between" points and decide whether they count as land or sea! Let's say that a value of 0.5 or more is land. The plots above show the 'raw' land-sea field and then the 'cleaned' one.
Create a new Macro icon and rename it land_points. Type the following code:
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