Lat/Long, Scale & Elevation
~11 min read · Locate coordinates, measure distance and read terrain and obstacle elevations.
The exam hands you a sectional and asks: where exactly is this point, how far apart are these towers, and how tall is that obstacle? Latitude-longitude, chart scale, and elevation figures are pure mechanics — free points if you drill them.
Latitude and longitude
Latitude lines run parallel to the equator (0°) and increase northward to 90°; longitude lines run pole to pole from the Prime Meridian (0°) and increase westward in the US. Coordinates read degrees-minutes: each degree = 60 minutes, tick marks on the chart grid mark single minutes. A position like 38°27'N 94°02'W is found by counting minutes from the printed degree lines. Remember: 1 minute of latitude ≈ 1 nautical mile — a built-in ruler on every chart's vertical edge.
- US coordinates: N latitude, W longitude
- 60 minutes per degree; chart ticks every minute
- 1' of LATITUDE ≈ 1 NM (longitude minutes shrink toward the poles)
Scale and distance
Sectional charts are 1:500,000 — about 6.86 NM per inch; VFR terminal area charts (around Class B) are 1:250,000. Measure distance with the graphic scale bar or the latitude ticks. For flight planning at drone ranges, minutes of latitude are the quickest honest ruler.
Elevation and obstacles
Terrain elevation shows through contour lines and color tint, with the Maximum Elevation Figure (MEF) printed per quadrangle: a large number like 3² meaning 3,200 ft MSL — the height that clears the tallest terrain or obstacle in that box. Obstacles print two numbers: the top number is height MSL, the parenthesized number is height AGL. A tower marked 1549 (400) tops out at 1,549 MSL, 400 ft above the ground beneath it. Towers over 1,000 ft AGL use a taller symbol; 'UC' means under construction.
- MEF: quadrangle's highest obstacle/terrain, in hundreds of feet MSL
- Obstacle: MSL on top, (AGL) in parentheses
- Lighted obstacles show lightning-bolt tips
Worked example
Your client's tower is charted as 2105 (455) in a quadrangle with MEF 2⁴. Terrain at your launch point reads about 1,650 MSL. May you legally reach the tower top, and what altitude does that put you at MSL?
The tower is 455 ft AGL — above your 400-ft default ceiling. But the structure exception allows flight within a 400-ft radius of the tower up to 400 ft above its top: legality is not the problem, reaching the top certainly isn't (455 < 400+455). To hover at the tower top: 2,105 ft MSL, which is 2,105 − 1,650 = 455 ft above your launch terrain — consistent. Cross-check with the MEF of 2,400 MSL: the quadrangle's tallest feature is higher than this tower, so scan the chart for the other obstacle before transiting at altitude.
Common exam pitfalls
Swapping the obstacle's MSL and AGL numbers.
Top number = MSL; the number in parentheses = AGL. The parenthesized number is the one your 400-ft rule cares about.
Using longitude minutes as miles.
Only LATITUDE minutes equal 1 NM. Longitude minutes compress as you move north.
Reading the MEF as a restriction.
The MEF is information — the highest elevation in the quadrangle — not an operating limit for drones.
MSL on top, (AGL) in the pocket; a minute of latitude is a mile in your ruler.
Recap
- Coordinates: degrees + minutes; 60 minutes per degree; ticks every minute
- 1 minute of latitude ≈ 1 NM — the chart's built-in ruler
- Sectional scale 1:500,000; TAC 1:250,000
- Obstacles: MSL over (AGL); AGL drives the 400-ft analysis
- MEF = highest terrain/obstacle per quadrangle, hundreds of feet MSL
- Towers 1,000+ ft AGL get the tall symbol; UC = under construction
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