To read Part 107 sectional charts, first locate the exact point in the question, then identify the airspace boundary around it and read that airspace's floor and ceiling. Convert the aircraft's height to the same reference before comparing numbers. A point inside an airport's outer ring can still lie below its controlled-airspace shelf. If you are organizing your exam preparation, place this airspace lesson within the Part 107 study sequence.
The useful habit is to separate three questions: Where am I? What does the chart show at this altitude? What does that mean for the proposed flight? The worked examples below show how to keep those answers straight.
On This Page
- Find the exact point before decoding symbols
- Read boundaries as three-dimensional airspace
- Put altitude numbers on the same reference
- Decode airports, obstacles and nearby activity
- Work through five practice problems
- Practice with FAA figures, then check current flight information
Find the exact point before decoding symbols
A sectional is a visual navigation chart showing airports, airspace, terrain, obstacles and other aviation information. Read the figure number and any named area in the question before searching for an airport. A nearby label can belong to a navigation aid, town or different airport.
For coordinates, latitude measures north or south; longitude measures east or west. Latitude lines run across the chart, while longitude lines run between the poles. In the contiguous United States, north-latitude values increase toward the north and west-longitude values increase toward the west. The FAA's Remote Pilot Study Guide, Chapter 11, explains this coordinate system.
For example, suppose an exercise asks you to locate 35°30′ N, 97°15′ W. Find the 35° and 36° latitude lines: 30 minutes is halfway between them. Then find the 97° and 98° west-longitude lines: 15 minutes is one-quarter of the way from 97° toward 98°. Their intersection is the target. Do not interpret 35°30′ as 35.30 decimal degrees; 30 minutes is half a degree, so it is 35.5°.
Use the chart's labeled ticks and scale when an exercise gives distance. Sectionals have a published scale of 1:500,000, but a resized screenshot does not preserve the original inches-to-distance relationship. Keep nautical miles and statute miles distinct. A map measurement in nautical miles cannot be substituted directly for a question asking statute miles.
Only after locating the point should you trace the enclosing boundaries. Follow each line far enough to find its own altitude label. The closest printed number may describe an adjacent sector.
Read boundaries as three-dimensional airspace
Airspace has both a footprint and vertical limits. The following table summarizes U.S. sectional conventions from the FAA's Aeronautical Chart Users' Guide, effective July 9, 2026, pages 16–17 and 26–27. Read line style, labels and notes together; color alone is insufficient.
| Chart marking | What it identifies | What to read next |
|---|---|---|
| Solid blue boundary | Class B sectors | Each sector's blue floor and ceiling figures |
| Solid magenta boundary around labeled Class C sectors | Class C airspace | Magenta floor and ceiling figures, including any surface sector |
| Dashed blue boundary | Class D airspace | Boxed ceiling in hundreds of feet MSL and operating-time notes |
| Dashed magenta boundary | Class E beginning at the surface, including airport areas and extensions | Area designation, exclusions and effective-time notes |
| Faded magenta band, or vignette | A 700-foot-AGL Class E floor on the indicated side | Any overlapping surface airspace and adjoining floor |
| Blue vignette | Class E boundary adjoining Class G; commonly a 1,200-foot-AGL floor | The legend and any specifically annotated floor |
The shaded side of a vignette matters: the magenta band fades toward the area with the 700-foot-AGL floor. Do not assume every area beyond that band has identical airspace. The guide describes Class E beginning at 1,200 feet AGL unless designated otherwise; special floors, surface areas and overlapping sectors still control the point you are studying.
Read ceiling over floor
For Class B and C, stacked figures express ceiling over floor in hundreds of feet MSL. MSL means mean sea level. In the FAA Class C example in the cited chart guide, 48 over 30 means a ceiling of 4,800 feet MSL and a floor of 3,000 feet MSL. It is not a fraction to divide, and it does not mean 30 feet above the ground.
SFC means the surface. A sector marked 48 over SFC begins at ground level. A Class C
ceiling marked T ends just below the overlying Class B floor. In a Class D ceiling
box, a minus sign before 27 means the airspace extends from the surface to below 2,700
feet MSL, excluding that top altitude. A plus sign before a Class B floor means the
sector starts above the stated altitude. Small marks can change a boundary answer.
Separate the airspace answer from the authorization answer
Part 107 requires prior air traffic control (ATC) authorization for operations in Class B, C or D airspace and within the lateral boundaries of Class E surface airspace designated for an airport. The FAA's Part 107 authorization procedures specify that the relevant Class E category is the airport surface area, Class E2.
A dashed magenta extension to a surface area is not automatically the same authorization case. Likewise, a magenta vignette showing a 700-foot-AGL Class E floor does not mean Class E reaches the ground. Determine the actual area and altitude before applying an authorization rule. For flight planning, check the current designation instead of deciding from the dashed line alone.
Put altitude numbers on the same reference
AGL means above ground level. It measures height above the local surface. MSL measures elevation or altitude against a common sea-level reference. Comparing 300 feet AGL with a 3,000-foot-MSL shelf without accounting for ground elevation mixes two different starting points.
For a chart exercise with a known ground elevation:
Aircraft altitude MSL = local ground elevation MSL + aircraft height AGL.
Height of an airspace floor above local ground = floor altitude MSL − local ground elevation MSL.
Suppose the exercise gives ground elevation as 2,750 feet MSL and an ordinary Class C shelf floor of 3,000 feet MSL. The shelf begins 250 feet above that ground. An aircraft 200 feet AGL is at 2,950 feet MSL, below the shelf. At 300 feet AGL it is at 3,050 feet MSL, inside the shelf, assuming it remains within that sector's lateral limits and below its ceiling.
This is why a statement such as “the drone is below 400 feet” does not settle the airspace question. Nor does being below a shelf identify the lower airspace by itself: another Class D or E area may occupy that space.
Use the elevation at the point specified. The airport elevation describes the highest point of its usable landing areas, not every field, hill or valley nearby. For an actual flight over changing terrain, a height display referenced to takeoff cannot be assumed to equal height above the ground beneath the aircraft.
The FAA chart guide distinguishes the main number systems as follows:
| Number and context | Interpretation | Common wrong reading |
|---|---|---|
| 48 over 30 in a Class C sector | 4,800-foot ceiling and 3,000-foot floor, both MSL | Ground clearance or an authorization ceiling |
1,854 above (424) beside an obstacle | Top at 1,854 feet MSL; structure 424 feet AGL | Treating 1,854 as the structure's height |
| Large 2 followed by a smaller 8, a maximum elevation figure | 2,800 feet MSL for that quadrangle | A local ground elevation or flight altitude limit |
| 700-foot Class E vignette | Floor 700 feet above the surface | Floor at 700 feet MSL |
The obstacle numbers in the table are an illustrative pair. Subtracting them gives 1,430 feet MSL at the obstacle's base, not the elevation of the entire area. A maximum elevation figure, or MEF, summarizes the highest relevant terrain or obstacle within its chart quadrangle with allowances and rounding. It is not a promise of clearance at every location. The chart guide also warns that obstacle information can be incomplete. These distinctions matter when an answer choice contains a plausible number with the wrong meaning.
Decode airports, obstacles and nearby activity
Airport information groups several kinds of data into little space. In the chart guide's airport legend, blue airport symbols and associated data indicate towered airports; magenta indicates other airports. That airport color does not identify every airspace layer around it.
Read the labels attached to a frequency. CT identifies a control-tower frequency;
ATIS identifies a recorded terminal-information broadcast. A circled C identifies
the common traffic advisory frequency, or CTAF. The number printed in hundreds for the
longest runway is runway length, while the airport elevation is given in feet MSL. RP
followed by runway numbers identifies right traffic patterns. A star can indicate
part-time operation or a limitation depending on the symbol it accompanies, so consult
the legend for that specific use.
A radio frequency is not a Part 107 airspace authorization. Also, a tower closing does not universally turn its surface area into Class G. The Aeronautical Information Manual's controlled-airspace section explains that the Chart Supplement identifies the applicable Class E or Class G status outside tower hours.
Other markings deserve a separate pass:
- Mode C veil: The magenta ring labeled for Mode C and ADS-B Out around a Class B primary airport is not itself a Class C boundary. Read the label, not just the ring's color.
- Obstacles: Parentheses distinguish AGL height from MSL top elevation. A group symbol may represent multiple obstacles; the chart is not a complete catalog of wires, trees or new construction.
- Military training routes:
IRandVRidentify route types. Four-digit numbers indicate routes with no segment above 1,500 feet AGL. Three or fewer digits indicate at least one segment above 1,500 feet AGL, not that every segment stays above it. - Special-use areas: Read the identifier, altitude limits, times and controlling
agency.
P-identifies a prohibited area andR-a restricted area. A named military operations area (MOA) identifies military training airspace; it is not a blanket prohibition on other traffic, but active operations can present serious hazards. The FAA's special-use airspace guidance explains the distinctions and how to obtain activity status.
If a question asks what hazard is nearby, the relevant answer may be a training route or obstacle rather than the airspace class. Answer the requested question before making broader conclusions about the flight.
Work through five practice problems
These are original study scenarios using FAA chart conventions, not questions from a live exam. Unless stated otherwise, assume the identified airspace is active, the point is unambiguously inside its lateral boundary, and there are no overlapping areas.
1. Does the shelf reach the drone?
A Class C sector is labeled 48 over 30. Ground elevation is 2,650 feet MSL. The proposed aircraft height is 300 feet AGL. Is the aircraft in that Class C shelf?
Answer: No. Add 2,650 + 300 = 2,950 feet MSL. The floor is 3,000 feet MSL, so the aircraft is 50 feet below it. The arithmetic answers this shelf question; it does not establish that the entire operation is authorized. The trap is treating the sector's footprint as Class C all the way to the ground.
2. Which Class E marking changes the surface answer?
One site is inside only a magenta vignette marking a 700-foot-AGL Class E floor. Another is inside an active Class E2 airport surface area. Both aircraft would be 200 feet AGL. Are the airspace and authorization answers identical?
Answer: No. Under the stated assumptions, the first aircraft is in Class G below Class E. The second is in the airport's Class E surface area, where prior Part 107 ATC authorization is required. The trap is remembering “magenta means Class E” without reading the floor or area type.
3. What does the obstacle height mean?
An obstacle is labeled 1,854 with (424) beneath it. How tall is it above the ground,
and what is its top elevation?
Answer: 424 feet AGL and 1,854 feet MSL. If asked for the base elevation, subtract: 1,854 − 424 = 1,430 feet MSL. Do not add the two chart values; the top elevation already includes the ground elevation.
4. Is the Class D ceiling included?
A dashed blue area has a boxed ceiling of minus 27. Does its Class D airspace include exactly 2,700 feet MSL?
Answer: No. The minus sign excludes that altitude. To identify the airspace at exactly 2,700 feet, read the overlying area. Without the minus sign, the depicted ceiling has a different inclusion meaning. Do not read the sign as a negative physical elevation.
5. Does a grid number permit flight?
A UAS Facility Map grid shows 100. May a Part 107 pilot launch in the associated controlled airspace at 80 feet AGL solely because the planned flight is lower than that number?
Answer: No. The FAA's UAS Facility Maps guidance says grid values inform authorization requests and do not authorize operations. A grid number is also not the MSL shelf floor shown on a sectional.
Practice with FAA figures, then check current flight information
Use the FAA's Computer Testing Supplements page to obtain FAA-CT-8080-2H, the listed supplement covering remote pilots. Practice locating the requested figure and area, tracing boundaries, reading the legend and showing the altitude calculation. Use the question's supplied figure for that exercise, even when it depicts older geographic information.
For each missed practice problem, record the mistake in plain terms: wrong point, wrong boundary, wrong floor, wrong units or wrong rule. Then solve a different example with the same type of distinction. Explaining why the tempting answer is wrong is more useful than memorizing the correct letter.
For an actual flight, move from training figures to current charts, the Chart Supplement and current NOTAMs, including applicable temporary flight restrictions. The current chart guide expressly identifies its own graphics as educational and unsuitable for flight navigation. Airport hours, temporary restrictions and permissions cannot all be resolved from one sectional excerpt.
Finish every chart problem with a sentence that names the point, airspace and altitude reference: “At this location, 300 feet AGL equals 2,950 feet MSL, below the 3,000-foot Class C floor.” That sentence exposes the assumptions and makes it easier to spot the wrong answer before choosing it.
If you are new to drone aviation, use our guide to becoming a drone pilot to place this lesson in the broader training and certification process.
Sources
- FAA Aeronautical Chart Users' Guide, July 9, 2026: primary charting reference for boundaries, altitude notation, airport data, obstacles, MEFs and military training routes; page 27 contains the cited educational figure.
- FAA Remote Pilot Study Guide, August 2016, Chapter 11: introductory coordinate and sectional-scale explanations. Its older operational and chart-update statements are not used as current rules.
- FAA Part 107 authorization procedures, Section 19-6: ATC authorization requirements and the Class E2 distinction.
- FAA Aeronautical Information Manual, Section 3-2: controlled-airspace structure and part-time surface-area status.
- FAA Aeronautical Information Manual, Section 3-4: special-use airspace categories and activity-status information.
- FAA UAS Facility Maps: what grid altitudes establish and why an authorization is still necessary.
- FAA Computer Testing Supplements: official listing for the remote-pilot testing supplement, FAA-CT-8080-2H.
Last checked: September 6, 2026.