• Distance from a point
• Latitude/longitude rectangle
• An arbitrary polygon
• The names of objects in the file

This document describes using the filter by polygon program. The polygon could be any closed boundary defined in a BNA file, such as a county, a coverage contour, or a polygon drawn on the TAP Map Window with your mouse and then exported to a BNA file.

Filter by Polygon

1. Suppose you want all of the county boundaries within your 70 dBu coverage contour. From the TAP Boundary menu, select "Filter by Polygon".
   
1. This will display the Polygon Filter form. Click the "Select" button to choose the input files you want to read and filter:
   
1. You can select the boundary file(s) to use. To select multiple files, hold down the Ctrl key and click on each file you want. (In this example, the Arizona file is selected to illustrate the multi-select option.)
   
1. Click "OK" to use the files you have selected.
   
1. The selected files will be displayed in the "Input Files" list:
   
2. For the filter, we need a .BNA boundary file containing the polygon(s) to be used. Objects in the input files will be evaluated to determine if they are in the filter polygon(s) from this file.
1. Enter the file name, or click the "Browse" button to select the file. For this tutorial, we will use a sample file named MYCOV70.BNA.
   
2. The check boxes marked "Containing" and "Intersecting" allow you additional control over the results of the program that are written to the output file.
1. If you want objects (county lines, roads, etc.) in the input boundary files that are completely (i.e., all points) inside the specified polygon, check the "Containing" box. If you want to include objects that are partly within the polygon check the "Intersecting" box.
   
2. For example, if you want only those counties that are completely within 50 miles, you could check the "Containing" box and uncheck the "Intersecting" box.
1. Enter the name of an output .BNA file where you want to write the results. (You can also use the "Browse" button to find an existing path and/or file.)
   
1. Click the "Start" button to begin the filter process:
   
1. If the path you entered does not exist you will be prompted with a question about creating the path:
   
1. If the file already exists, you have the option of overwriting the file or appending to the existing file:
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1. The polygon filter process uses several of the graphic functions in the map window, and a map will be drawing automatically during this process. You should not attempt to edit or modify this automated operation.
1. When the filter process is completed the word "Done" will appear near the "Close" button. Click the "Close" button to continue.
   
1. To view the file you just created, select "New Map" from the TAP File menu:
   
1. On the Coverage Plot form, click the "Boundaries" button:
   
1. Find the path and file you just created, as well as the filter polygon file, then click the "OK" button:
   
1. The files will be displayed in the boundary file list:
   
1. Double-click the coverage contour file:
   
1. On the Layer Properties form, set the line width to 3 pixels and click the "Close" button:
   
1. On the Map Window Boundary Files form, click the "Continue" button:
   
1. On the Coverage Plot form click the "Plot" button:
   
1. The filtered boundary file and the coverage contour polygon will be displayed, showing only those counties contained in or intersected by the specified contour.