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How to subset a database based on a PLY polygon file

Joe McPherson

Objective:

I have a polygon PLY file and would like to remove all of the data points from a database that lie outside of that PLY file.

Resolution:

The database needs to masked based on the PLY file first, and then subset using a mask channel.

To window the X, Y channels in the GDB:

  1. Open the database > Database Tools menu > Window Data > Window X,Y, to polygon mask.
  2. Select the PLY file and specify whether you want to dummy the database values inside of it or outside of the mask > OK.
    This will dummy the X and Y coordinates according to your selection.  Your original X and Y channels are backed up in new channels called __X and __Y.
    You can restore the original channels through Database Tools > Window Data > Restore Full X, Y.

To subset the database:

  1. Database Tools menu > Window Data > Subset database.
  2. Enter a name for the output Subset database.
  3. For the Remove mask dummys parameter, select All dummies.
  4. Select your X or Y channel as the mask channel and specify the desired parameters for subsetting > OK.

To restore the full X, Y coordinates in the original database:

  1. Make the original database the active window.
  2. Database Tools menu > Window Data > Restore Full X, Y.

Related Documents: How to window a grid using a polygon file.