Ground sampling distance, in centimetres per pixel.

Ground Sampling Distance (GSD) is the size on the ground that one pixel of your image represents. It’s the single most important number in any drone mapping mission — it determines what you can see, what you can measure, and whether the deliverable is worth the flight.

§ 01Try it

Drag any of the four inputs. Watch the GSD readout update — and the “suitable for” tier rebadge as you cross thresholds.

§ 02The formula

It’s a single equation with four variables:

GSD (cm/px) = (altitude_m × sensor_width_mm × 100) / (focal_length_mm × image_width_px)

Three of those numbers come from your drone’s camera spec sheet (sensor width, focal length, image width). The only one you control mission-to-mission is altitude — which is why altitude is the first knob on every flight planner.

§ 03The geometry

The pinhole camera model — three centuries old, still used by every modern photogrammetry engine — explains why the formula looks the way it does:

Light from a point on the ground passes through the lens and projects an inverted image on the sensor. The ratio of focal length to altitude tells you the scale, and the sensor width plus pixel count tells you how that scale gets divided into pixels.

§ 04Sensor anatomy

Spec sheets quote “sensor size” in inches (a leftover from vacuum tube nomenclature) but for GSD math you need w, the physical sensor width in millimeters:

§ 05What each tier is good for

The tier indicator on the calculator is grounded in industry conventions. Roughly:

§ 06Common GSDs at typical altitudes

For a Mavic 3 Enterprise with a 24mm equivalent lens (the common case):

§ NEXTRelated field-guide pages