This is the Florida Middle Grounds which is a very large area of sea mounds about 90 miles west of Tarpon Springs. The area is know for its great fishing and scuba diving. Each X represents the center of an area that is 1.4 by 1.4 miles. Out charts are so detailed and the files so large that we needed to break up the area into these square areas. Our charts are so much more detailed than any other company out there. We have contour lines and depth markings unlike the other guys. Also just pay a few bucks for what you need and select from any of the many formats we provide. Don't pay hundreds of $ for a chip.
We are working to populate this area. Email me if you have an immediate need.