Window X ,Y to Polygon Mask

Use the Database Tools > Window Data > Window X ,Y to Polygon Mask menu option (WINXY GX) to mask the X and Y channels to the area defined by a polygonal mask file. This restricts all subsequent map-based processing to data within the defined region.

Window X ,Y to Polygon Mask dialog options

Mask polygon file	Specify the ASCII file defining polygon masks. Script Parameter: WINXY.MASK
Dummy inside or outside	Indicate whether you want to dummy inside or outside of the polygon mask area. Script Parameter: WINXY.DUMMY

Application Notes

This GX is used to limit the X and Y coordinates to the part of the area to be plotted. All MAP based processes will use the X and Y channels as the plotting coordinates. By dummying those parts of the area outside the area of interest, all plotting will be restricted to the defined area.

A copy of the original X and Y channels is saved to __X and __Y (if these channels do not already exist). Future windowing operations will use these channels as the source channels. (If running interactively, a warning message is displayed asking whether you wish to overwrite the backup channels).

Polygon Mask Files

• Polygon files are ASCII text files with the default .ply extension.

• Each file contains a list of X,Y coordinates defining one or more polygons.

• Files can include any number of polygons, each with any number of vertices.

• The first and last points of each polygon are assumed to be connected.

File Structure Guidelines:

• Each polygon begins with a line starting with poly # (with p or P in column 1).

• Comment lines begin with / in column 1.

Creating Polygons Interactively

You can also create clip polygon files interactively using the digitising tools available in the Map Tools menu.

Example of a single polygon file: