FAA Flight Instructor Airplane (FIA)Navigation and AirspaceMedium
A pilot notices an obstruction symbol on a sectional chart labeled '1200' with '(300)' printed beneath it in parentheses. What do these two numbers represent?
- A1200 is the obstruction's height MSL; 300 is the terrain elevation MSL
- B1200 is the obstruction's height MSL; 300 is its height AGL
- C1200 is the terrain elevation; 300 is the obstruction's total height MSL
- D1200 is the obstruction's height AGL; 300 is its height MSL
Show answer & explanationAnswer & explanation
Correct answer: B. 1200 is the obstruction's height MSL; 300 is its height AGL
On sectional charts, the larger, unparenthesized number next to an obstruction symbol represents the obstruction's height above mean sea level (MSL), while the smaller number in parentheses beneath it represents the obstruction's height above ground level (AGL).
Why the other options are wrong
- A. The parenthetical number represents AGL height, not terrain elevation MSL.
- C. The parenthetical number is AGL height of the obstruction, not the terrain elevation.
- D. This reverses the standard MSL/AGL convention used on sectional charts.
Sectional Obstruction Symbol
Obstruction symbols on sectional charts display height above mean sea level (MSL) as the larger number and height above ground level (AGL) in parentheses beneath it.
- MSL height listed first, without parentheses
- AGL height listed second, in parentheses
- Symbol shape/size indicates obstruction type and height category
Memory trick: 'Big number up top is MSL sky-high; small parenthesis is Above Ground Level.'