Create Geographic PLY File

Use the option Create Geographic PLY File (POLYGEO GX) from the Database Tools > Window Data menu or the Map Tools > CAD Tools menu, to create a map polygon mask file based on latitude, longitude map limits. The defined polygon will be converted to projected map coordinates, and the longitude, latitude outline will be sampled at a specified number of points. This file can then be used to clip data or grid files, or it can be applied to a view to clip graphics in a map.

Create Geographic PLY File dialog options

Polygon file name (.ply)

The name of polygon file (*.ply) to create or append to.

Script Parameter: POLYGEO.PLYFILE

New file or append

If appending, the polygon will be added to an existing polygon file. This allows you to make a polygon mask from multiple regions on a map. 1 to append to an existing polygon file.

Script Parameter: POLYGEO.APPEND

Minimum longitude

Minimum Longitude.

Script Parameter: POLYGEO.LONMIN

Maximum longitude

Maximum Longitude.

Script Parameter: POLYGEO.LONMAX

Minimum latitude

Minimum Latitude.

Script Parameter: POLYGEO.LATMIN

Maximum latitude

Maximum Latitude.

Script Parameter: POLYGEO.LATMAX

Divisions per side

Division per side.

Script Parameter: POLYGEO.DIVSIDE

Inclusive or Exclusive?

Inclusive or Exclusive. Inclusive polygons define areas to be included in the mask. Exclusive polygons define areas to be excluded from the mask, which can be useful for defining holes in the area.

Script Parameter: POLYGEO.INEXCL

Next>

This will display the projected coordinate system for you to either verify or modify. By default, the projected coordinate system is assumed to be the same as the data view in the current map, or, if there is no map, from the "X" coordinate of the current database.

Application Notes

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.

Use Exclusive polygons to define holes in the data.

  • The input Long/Lat coordinates must be in the same datum as the output coordinates. Long/Lat coordinates can be entered as either DD.dddd or as DD.MM.SS.ss (same format as displayed in the database).

    • See Also: