Graueradler
Pattern Altitude
I haven't been flying for several years. Just noticed that the VFR chart accessed through Airnav.com shows a small blue square, similar to the landmark symbol, in the center of nearly every airport symbol. It isn't on any with runway layout depictions that I checked, just the hard surface synbols. I checked the FAA VFR Chart Guide and didn't find any enlightenment. What is it?