Polygon Outlines (Interpolation Masks)

Irregular shapes can be interpolated or excluded from interpolation by defining inclusive or exclusive polygons prior to interpolating. In this window you can define these polygons by entering coordinates of polygon vertices, i.e. x-y points that outline the polygon.

Polygons must be closed, thus they must have at least 3 vertices (3 vertices describe a triangle). You may specify as many vertices per polygon as you like (up to several million), and polygons may be nested within one another as in the example below. However, the vertices for each polygon must define a single, closed polygon, i.e. no segments of the polygon may cross another segment. Also the first and last vertex specified must connect to one another. You can check the shape of the polygon while it is being defined with the Map command.

There are two types of polygons, defined by the keyword “Include” and “Exclude” in the worksheet as noted in the example below:

•      In inclusive polygons, the area within the polygon is interpolated.

•      In exclusive polygons, the area within the polygon is not interpolated.


The example below defines two polygons: the first is a 6-sided area that is excluded from interpolation, the second defines an inclusive 4-sided area (rectangle) inside the 6-sided area. You can use the Map command to produce a picture of these polygons. The "Polygon" statement on the top line is optional. The word "Exclude" or "Include" is not optional; each set of polygon vertices must be preceded by either “Exclude” or “Include”.



Clear the worksheet.


The Import command brings into the worksheet a text file containing vertex locations. The text file can be formatted in a variety of ways with fields separated by either commas or spaces. The default file name extension for polygon interpolation outline files is .int.


Produces an outline map of each polygon within the larger interpolation grid area. Exclusive polygons appear in red, inclusive in blue. Drawing a map is a useful way to test your polygon coordinates.

Other Actions

You may Print, Copy, or Export the contents of the worksheet using the menu commands of the main GS+ window, or via a right-click menu. You may also change the Decimal Places reported by highlighting a column and pressing the Increase or Decrease Decimals icon (or use the Data | Change Decimals menu command). Clicking on the top of a column will Sort the worksheet based on the column selected in alternating ascending or descending order. You may also change Column Widths by placing the cursor over the line between two columns and dragging to a new location.