What Ground Sample Distance Is
Ground Sample Distance (GSD) is the real-world size represented by a single pixel in an aerial or drone photo. A smaller GSD means higher resolution imagery — important for mapping, surveying, and photogrammetry work where measurement accuracy matters.
The Formula
GSD (cm/pixel) = (Altitude × 100 × Sensor Width) ÷ (Focal Length × Image Width in pixels). All physical measurements should be in the same units (this calculator uses meters for altitude and millimeters for the camera’s sensor and focal length).
- Flying higher increases GSD (lower resolution); a longer focal length (more zoom) decreases GSD (higher resolution) at the same altitude.
- Camera manufacturers publish sensor width and focal length specs — check your specific drone or camera model for exact values.
- This is a planning estimate; actual GSD can be affected by lens distortion and terrain elevation changes.
Last reviewed August 2026