Aerial Ground Sample Distance Calculator
Ground sample distance (GSD) is the ground size of a single image pixel, the headline resolution figure for drone and aerial mapping. Using the pinhole camera model, GSD equals the sensor pixel pitch times the flying height divided by the focal length. This calculator takes the sensor width, image width in pixels, focal length and flying height, then returns the GSD in centimeters per pixel and the ground footprint width of one image. Flying lower or using a longer lens reduces GSD and sharpens detail.
GSD formula
Pixel pitch (mm) = sensor width / image width
GSD (m/pixel) = pixel pitch (m) * altitude / focal length (m)
GSD (cm) = GSD (m) * 100
Footprint width (m) = GSD (m) * image width
This is the pinhole camera similar-triangles relation. Pixel pitch is reported in microns (millionths of a meter), the usual sensor spec unit.
GSD context
- GSD is directly proportional to flying height: fly lower for finer detail.
- A longer focal length lowers GSD but narrows the image footprint.
- Pixel pitch is the sensor width divided by the pixel count across that width.
- Survey accuracy is often specified as a multiple of the GSD.
- Keep sensor, focal length and altitude in consistent units before converting.
Ground sample distance: frequently asked questions
What is ground sample distance?
Ground sample distance (GSD) is the real-world size on the ground represented by one pixel in an aerial or satellite image, usually given in centimeters per pixel. A smaller GSD means finer detail. It is the key resolution metric for mapping and survey flights.
How is GSD calculated?
GSD per pixel equals the sensor's physical pixel size times the flying height, divided by the focal length. Equivalently, GSD equals (sensor width times altitude) divided by (focal length times image width in pixels). Keep all lengths in the same units, then convert to centimeters.
What inputs do I need?
You need the sensor width in millimeters, the image width in pixels, the lens focal length in millimeters, and the flying height above the ground in meters. From these the calculator derives the pixel pitch and the GSD, plus the ground footprint width of a single image.
Why does flying lower improve resolution?
GSD is directly proportional to altitude, so halving the flying height halves the GSD and doubles the detail. A longer focal length also reduces GSD at a given altitude, at the cost of a narrower ground footprint and more images to cover the same area.
How does GSD relate to map accuracy?
GSD sets the smallest feature that can be resolved, and survey accuracy standards are often expressed as a multiple of the GSD. Photogrammetric positional accuracy typically lands within one to three times the GSD under good conditions and adequate ground control.
Official sources
- U.S. Geological Survey: U.S. Geological Survey.
- NIST: Fundamental physical constants and units.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.