Sectional Chart Symbology Decoder
Sectional symbology and the vertical math behind it are the two topics that sink the most Part 107 and private pilot candidates. Tap a boundary to see the airspace it marks, its floor, and whether that floor is MSL or AGL.
The fuzzy magenta band, faded on the side facing the airport. Below 700 AGL inside it is Class G. This floor is always AGL, never MSL.
- Airspace numbers on the chart are MSL unless the number is followed by AGL. The Class E 700 and 1,200 vignettes are the AGL exceptions, by definition.
- A drone flies AGL. Under Part 107 you may not fly higher than 400 feet AGL, unless within 400 feet of a structure. To compare against a charted MSL floor, add the ground elevation: drone MSL = terrain MSL + height AGL.
Boundary colors and floors follow the FAA Aeronautical Chart Users' Guide. Colors here approximate the printed sectional; always read floors and ceilings from the current chart for the area you are flying.
Color tells you the class, the line style tells you the shape
On a sectional, blue and magenta do most of the work. Blue draws Class B and Class D and the transition where Class E steps up from 1,200 feet AGL. Magenta draws Class C, Class E that reaches the surface, and the transition where Class E starts at 700 feet AGL. Once you know the color pair, the line style separates the classes: solid versus dashed versus the soft faded vignette.
The classic trap is reading solid magenta as Class E when it is Class C, or missing that a dashed magenta ring means controlled airspace all the way to the ground. Work through each boundary above until the color and style pair is automatic.
The number is MSL unless it says AGL
Airspace floors and ceilings are charted in MSL, in hundreds of feet. The two exceptions are built into the chart itself: the 700 and 1,200 foot Class E floors shown by the magenta and blue vignettes are AGL. For drone work this matters twice over, because a drone's own altitude is measured AGL. To check a drone against a charted MSL floor, add the ground elevation to the drone's height.