Autonomous Drone Software

Ground sample distance calculator

Work out ground sample distance, photo footprint, line spacing, photo count and flight time for a drone mapping job from camera specs and altitude.

Official source: Pix4D documentation, flight height and GSD (equation 4). Checked

1 min reading time — Next check planned by 2026-11-24

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The formula

Ground sample distance (GSD) is the size of one image pixel on the ground. Pix4D's documentation gives the flight height for a target GSD as H = imW × GSD × Fr / (Sw × 100). Turned around:

GSD [cm/pixel] = Sw [mm] × H [m] × 100 / (Fr [mm] × imW [px])

where Sw is the real sensor width, Fr the real focal length (not the 35 mm equivalent), H the height above ground and imW the image width in pixels (Pix4D). Pix4D's own example: a 6.17 mm sensor, a 5 mm lens and 4,000-pixel images give 5 cm per pixel at about 162 m.

From GSD to a flight plan

  1. Footprint: GSD × image width and GSD × image height give the ground covered by one photo.
  2. Spacing: with 75% front overlap, the drone moves a quarter of the footprint height between photos; with 65% side overlap, flight lines are 35% of the footprint width apart.
  3. Lines and photos: the planner divides a square area by these spacings.
  4. Time: total path length divided by speed, before take-off, turns and battery swaps.

Typical choices

  • 1–2 cm/px: detailed inspection and small sites.
  • 2–5 cm/px: construction progress, volumes, most survey work.
  • 5–10 cm/px: large areas, agriculture overviews.

Watch the limits

The planner warns you when the altitude goes above 120 m, the EU open-category limit and close to the usual US limit of 400 ft, and when photos would come less than two seconds apart. Then fly lower or slower, or check your camera's interval.