Ground Sample Distance (GSD) Calculator
Compute GSD for spaceborne imaging payloads. GSD = (h · p) / f, where h is altitude, p is pixel pitch, and f is focal length. Nadir and off-nadir variants.
Inputs
Geometry
Optics
Detector
Imaging performance
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Sign up →Frequently asked questions
What does GSD actually mean?
Ground Sample Distance is the projection of one detector pixel onto the Earth's surface. A 1m GSD means each pixel covers a 1m × 1m footprint at nadir. It sets the finest feature your system can distinguish (per Nyquist, about 2× GSD).
Why is off-nadir GSD worse?
Two reasons: slant range grows as h / cos(θ), and the footprint is elongated along the line of sight. This tool shows the cos(θ)-scaled ground projection; full modeling includes the skew-asymmetric footprint ellipse.
What is the diffraction limit and why does it matter?
Rayleigh diffraction sets the smallest spatial feature your optics can resolve: 1.22·λ/D radians. If your pixel IFOV is smaller than diffraction, you're oversampled. If larger, pixel size limits you, not optics.
Are there US export restrictions on high-resolution imaging?
Yes. Under NOAA remote-sensing licensing (51 USC 60101), commercial US operators are subject to data-distribution and resolution caps that vary by category. Sub-meter panchromatic imagery may require specific licensing.
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- Revisit time analysis against constellation geometry
- Link to downlink budget and onboard storage