FAA Private Pilot Helicopter (PRH)Navigation and AirspaceMedium
On a sectional chart, an obstruction symbol is labeled '1,825' above the symbol and '(352)' beneath it in parentheses. What does the number in parentheses represent?
- AThe obstruction's height above ground level
- BThe obstruction's lighting classification code
- CThe obstruction's charted length in feet
- DThe obstruction's height above mean sea level
Show answer & explanationAnswer & explanation
Correct answer: A. The obstruction's height above ground level
Sectional chart obstruction symbols show the top elevation in MSL feet as the larger unbracketed number, and the height of the obstruction above ground level (AGL) in parentheses below it. Here, 1,825 is MSL and 352 is the AGL height.
Why the other options are wrong
- B. Lighting is shown by symbol shape/flash marks, not by the parenthetical number.
- C. Chart obstruction symbols do not depict physical length.
- D. MSL height is the top number (1,825), not the one in parentheses.
Sectional Obstruction Symbol
Obstructions on sectional charts are labeled with two numbers: the top number is elevation MSL, and the number in parentheses is the height AGL.
- Top number = MSL elevation
- Parenthetical number = AGL height
- Symbol shape indicates lighted vs unlighted
- Group obstructions use a different symbol
Memory trick: Parentheses 'hug the ground' — that's your AGL number.