There is not a way to fill outside a polygon, but there are other methods to consider:
- To mask (or assign NoData values to) contours or any grid-based map outside a boundary, save the boundary (as a polygon) to a vector file (BLN, SHP, DXF, etc.), then use the Grids | Edit | Assign NoData command to assign null values to grid nodes that are outside the polygon. Set the header flag in the BLN file to 0 to assign NoData values outside. Create a new map with the new GRD file.
- Alternatively, you can create a complex polygon that covers the area outside the boundary polygon. To do this:
- Load the boundary polygon as a base layer (if it is saved in a base map file format, like DXF, SHP or BLN), or add an empty base map layer and draw the boundary polygon over the map.
- Right click over the Base(vector) layer in the Contents window, and click Start Editing.
- Click Home | Insert | Polygon and draw another larger polygon outside the outer edge of all four corners of the map (so it is a rectangle that is larger than the map).
- Select both the large polygon you just drew and the smaller polygon defining the boundary and click Features | Islands/Lakes | Combine. This combines the two polygons into one complex polygon.
- Right click over the Base layer in the Contents window, and click Stop Editing.
- You can now fill the complex polygon with whatever fill pattern you wish. The fill will be between the boundary polygon and the larger polygon you drew.
Example of a complex polygon.
Updated October 20, 2017