This checkbox affects the operation of the Show Grid command. If it is is unchecked, then
the program will calculate for you the positions of the grid circles and lines.
If it is checked, then a new window appears which allows
you to set these values yourself.
The "Set Intervals" button brings back the window that was opened by the Fix Grid Interval box, so that you can once again set the values of the grid overlay. Note that these values will have no effect unless the Fix Grid Intervals box is checked. |