How To: Mask a grid using a polygon mask

Symptom/Problem:
How can I create a mask of a grid using a polygon that I create myself?

Environment:
This resolution applies to all versions of Oasis montaj and Target.

Resolution:
In order to mask a Grid to a polygon you'll need a Geosoft Polygon File (*.PLY). PLY files can be created using numerous methods. For the steps to create a polygon file see FAQ http://www.geosoft.com/support/faq/2008/03/how-to-create-geosoft-polygon.asp

1. Create a polygon (this will be your .ply file) of the area on your grid that you wish to mask.
2. Note that once you create the polygon, it will not be placed on the map. If you would like to verify that the polygon is suitable, go to Map Tools | Draw from PLY File to display the polygon on your map. If you do not wish to view the polygon on your map, skip to step 3.
3. Go to Grid and Image | Utilities | Window a Grid Using Polygon File and select the options most appropriate for what you are trying to show. Click [OK].