Final answer:
The circle with weird triangle lines represents an airport with a control tower.
Step-by-step explanation:
The circle with weird triangle lines on sectional charts represents an airport with a control tower. The control tower is a tall structure located at an airport that provides air traffic control services to guide and direct aircraft in the airspace around the airport. It plays a crucial role in ensuring safe and efficient operations at the airport.
A control tower enables air traffic controllers to communicate with pilots, provide them with necessary instructions, and monitor the movement of aircraft on the airport's runways, taxiways, and airspace. The circle with weird triangle lines is a visual representation of an airport's control tower on a sectional chart, helping pilots easily identify airports with control towers.