Ground Sampling Distance
The distance between the centers of adjacent pixels in a satellite image, measured on the ground — the fundamental metric for spatial resolution.
Explanation
Ground Sampling Distance (GSD) is the spatial resolution of a satellite image. A 30 cm GSD means each pixel represents a 30 cm × 30 cm area on the ground. Lower GSD numbers mean finer detail. GSD is determined by the sensor's focal length, detector pixel pitch, and orbital altitude. Tradeoffs are pervasive: finer GSD requires larger optics, lower orbits (which decay faster), or smaller swath widths. Satellite imagery is commonly categorized by GSD: very high resolution (VHR, under 1 m), high resolution (1-5 m), medium resolution (5-30 m), and low resolution (over 30 m). Commercial licensing and national regulations often restrict the finest GSD that private companies can sell. GSD is only one dimension of image quality — signal-to-noise ratio, spectral resolution, and temporal resolution all matter — but it remains the most intuitive specification for comparing Earth observation systems.
Why It Matters
GSD determines what features can be resolved in satellite imagery. It separates defense-grade surveillance from environmental monitoring. Higher resolution commands premium pricing and often requires government licensing.
Concept Map
How Ground Sampling Distance connects to other glossary terms:
Frequently Asked Questions
What is the best GSD available commercially?
As of 2026, the finest commercially available GSD is around 30 cm, offered by Maxar's WorldView-3. Defense systems may achieve finer resolution.
Does lower orbit always mean better GSD?
Yes, all else being equal. A satellite at 300 km altitude can achieve finer GSD than one at 600 km with the same sensor. However, lower orbits mean more drag and shorter mission life.
Sources
Last updated: July 1, 2026