The charts are published "in accordance with Interagency Air Cartographic Committee specifications and agreements, approved by the Department of Defense and the Federal Aviation Administration".
The legend of an aeronautical chart lists many of the symbols, colors and codes used to convey information to the map reader.
The legend divides these into several types of information, namely: airports, radio aids, traffic and airspace services, obstructions, topographic, and miscellaneous.
The location of each airport and presence of control towers is indicated with a circle, or with an outline of the hard-surfaced runways (if over 8,069 feet long).
Based upon standard mapping symbols, these markings usually designate man-made structures that may be identifiable from the air, including: Where relevant, a mountain pass and its elevation may be shown with curved lines.