[Xastir] What is very large rectangle with X in center on station?

[Bill Bird]

Hi,

In the St. Louis, MO area I see from time to time on my Xastir map (rf 
only) a very large rectangle (more than 50 miles in North/South 
direction) with an X on the station AC0MW-7.  The X goes from corner to 
corner of the rectangle.  The X and the rectangle are made of dashes.  I 
have been using APRS since APRSdos and continue to enjoy it.  The 
current Xastir map is shown on my website, www.billbird.com.  I've tried 
to discover the answer on my own but have not been able to.

Thanks and 73,

Bill Bird
KG0YJ