Create Polygon PLY File

Use the POLYDEF GX to create a new polygon file or add polygons to an existing polygon file. Polygon files are used in a number of dialogs for purposes such as masking and area selections.

The option is available win the following menus:

  • Database Tools > Window Data > Create Polygon PLY File

  • Map Tools > CAD Tools > Create Polygon PLY File

  • Airborne Quality Control > Generate Flight Path Plan > Create Boundary File > Create Polygon PLY File

  • Geochem Analysis > Classify by Region > Create Polygon Mask

Create Polygon PLY File dialog options

Polygon file name (.ply)

Specify the name of the polygon file to create or append to.

Inclusive or Exclusive?

Exclusive polygons define areas to be excluded from the mask, which can be useful for defining holes in the area. Exclusive polygons are not supported on their own; you must always put them inside a larger inclusive polygon to obtain consistent results.

[New File]

Click this button to create a new polygon file.

[Append]

Click this button to append a new polygon to the existing polygon file.

Application Notes

You will be able to define a polygon using the mouse in the currently active map window.

Use Exclusive polygons to define holes in the data.

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:

 /
				
 / Sample single polygon file
 /----------------------------
 4325.2 8421.8
 6800 8421.8
 6850 4000
 4300 4000
 
Following is an example of a three polygon file:
 /
 / Sample three polygon file with an exclusive polygon
 /---------------------------
 poly
 4325.2 8421.8
 6800 8421.8
 6850 4000
 4300 4000
 poly
 7000 8421.8
 8000 8421.8
 8000 4000
 7000 4000
 poly
 exclusive
 7400 7000
 7800 7000
 7800 5000
 7400 5000