If you have two boundary files, each containing a single polygon, and you want to merge those into a single shape to use in assigning NoData to your grid file:
- Click Home | New Map | Base.
- Select your first boundary file and click Open.
- Select the Base layer in the Contents window.
- Click Home | Insert | Graphic.
- Select the second boundary file and click Open.
- Click Home | Selection | Select All.
- Click Features | New Features | Union of Polygons.
- In the Union Polygons dialog, uncheck Keep original objects and click OK. The original boundary files will not be changed, so you can reload these later if desired.
- Click Grids | Edit | Assign NoData.
- In the Assign NoData to Grid dialog,
- In the Input Grid section, click the Browse button.
- Select your grid file and click Open.
- In the NoData Polygon Boundary section, select your base layer from the dropdown list.
- At the bottom of the NoData Polygon Boundary section, toggle NoData Outside to assign NoData values to grid nodes outside of this boundary.
- Give your Output Grid file a name, such as grid_nodata.grd.
- If you wish to add this map to the boundary map, check Add grid as layer to, select Map from the list, and set the New layer type to the type of map you want to create from the grid with NoData values.
- Click OK to create the grid with NoData values, and add the map layer selected in step 11f.
Updated November 12, 2021