GSD & flight altitude calculator
Ground sampling distance (GSD) is how much ground one pixel covers. Enter your altitude and camera details, or pick a preset, to get GSD, image footprint and the altitude for a target GSD.
The formula
GSD (cm/px) = sensor width (mm) × altitude (m) × 100 ÷ (focal length (mm) × image width (px)). Use the real focal length, not the 35 mm-equivalent figure, and get the sensor width and image width from your camera’s spec sheet. The 4/3 preset is an approximation for a 20 MP 4/3-type sensor like the one in the Mavic 3 Enterprise.[2] Check your exact values before planning paid work.
Sanity check
Wingtra quotes 2.7 cm/px from 120 m for its 61 MP MAP61 camera.[6] Bigger sensors and more pixels get finer GSD from the same altitude.
In the U.S., Part 107 limits most flights to 400 ft (about 122 m) above ground level.