Minimum Altitude Over a Built-Up Area
You are pilot-in-command of a commercial aerial photography flight in a Cessna 172. The client wants photographs of a town at 800 ft AGL. The town's tallest obstacle is a 1,200-ft AGL radio tower. Your planned track passes 1,500 ft horizontally from the tower. The airport elevation is 500 ft MSL. The flight is not in the takeoff or landing phase. Later, the client asks you to fly over a nearby lake at 300 ft AGL to photograph boats; the lake is outside the town and has no obstacles. You have a passenger on board and the aircraft is within weight and balance.
1. Determine the minimum legal altitude over the town and whether 800 ft AGL is legal.
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Over a built-up area, CAR 602.14 requires flight at least 1,000 ft above the highest obstacle within a 2,000 ft horizontal radius. The 1,200-ft tower is only 1,500 ft from track, so it is inside that radius. Minimum altitude = 1,200 + 1,000 = 2,200 ft AGL.
At 800 ft AGL the flight is not legal, even though the tower is not directly under the track. The pilot must climb to at least 2,200 ft AGL or remain outside the 2,000 ft radius and still meet the applicable minimum. The airport elevation (500 ft MSL) does not change the AGL calculation.
2. Is 300 ft AGL over the lake legal? What should the pilot do?
Read the worked answer
Over the lake, outside the built-up area, the general minimum is 500 ft AGL, except for takeoff and landing. At 300 ft AGL the flight is not legal. The absence of obstacles does not create an exception; the 500 ft minimum still applies.
The pilot should decline the 300 ft request, or conduct the photography at or above 500 ft AGL with the client briefed accordingly. If the lake is within a control zone or other restricted area, additional airspace requirements may also apply.