Drone GSD Calculator

Ground Sample Distance (GSD) is the distance between the centers of two adjacent pixels measured on the ground. It tells you the spatial resolution of your drone imagery. A GSD of 2.5 cm/px means each pixel in the image represents a 2.5 cm x 2.5 cm square on the ground surface.

GSD is the single most important metric in drone mapping and photogrammetry. It determines what features you can identify in the final orthomosaic or 3D model. A 1 cm/px GSD lets you detect hairline cracks in concrete. A 5 cm/px GSD is enough to map property boundaries and terrain contours.

The GSD formula uses four camera parameters and your flight altitude. The sensor width and focal length define the physical optics. The image width determines how many pixels span that field of view. Altitude scales everything linearly: double the altitude, double the GSD.

Worked Example: DJI Air 3S at 120m

The DJI Air 3S has a 1-inch sensor (13.2mm wide), 6.72mm focal length, and captures 5280 x 3956 pixel images. At 120 meters altitude:

GSD = (13.2 x 120 x 100) / (6.72 x 5280) = 158,400 / 35,481.6 = 4.46 cm/px

That produces a single-image footprint of approximately 235m x 176m, covering about 4.14 hectares per photo. This resolution works well for agricultural monitoring, large-area mapping, and terrain modeling.

Different applications require different ground resolutions. The table below shows typical GSD requirements by industry. These are general guidelines. Always check your project specifications for exact requirements.

The relationship between altitude and GSD is linear. If you double your flight altitude, you double your GSD. This means you get half the detail but cover four times the area per image (since both footprint dimensions double).

This trade-off is fundamental to mission planning. Lower altitude gives better detail but requires more flight lines, more images, and longer processing times. Higher altitude gives faster coverage but less detail. Finding the right balance depends on your project requirements.

For projects requiring sub-centimeter GSD, you will need to fly at 30 meters or below. At these low altitudes, be especially careful about obstacle clearance and plan flight paths that account for terrain elevation changes.