GSD: what one pixel covers on the ground
What GSD is, how it is calculated, and why it decides flight height.
GSD — Ground Sample Distance — is the real-world size one pixel covers. A GSD of 2 cm means one pixel represents a 2 cm square on the ground.
It is the figure that turns a capture into a level of detail.
How it is calculated
Three things set it: flight height, the lens focal length and the sensor size. The higher you fly, the more ground each pixel covers — so GSD rises and detail falls.
Hence the constant trade-off:
| Low GSD | High GSD | |
|---|---|---|
| Flight height | low | high |
| Detail | fine | coarse |
| Area covered | small | large |
| Flight duration | long | short |
Why it is the figure to ask for
Because it determines what you will be able to see — and therefore whether the mission answers your need.
A 3 mm crack does not show at 3 cm per pixel: it occupies a tenth of a pixel. A persistent rule of thumb holds that an object needs several pixels across to be identified with confidence — not one.
That is why a serious inspection quote states a GSD, not merely "high-resolution photos". Sensor resolution says nothing until you know the flight height.
⚠️ GSD is not accuracy. GSD says what you can distinguish; accuracy says how right a measurement is. That also depends on overlap and ground control points — see photogrammetry.
What Waypoint360 does
We do not compute your photogrammetric flight plans. What we hold is everything around the mission: zones, compliance, logbook, documents.
And the directory lets you find an operator who declares survey and mapping among their activities — the one to ask about GSD.
Going further
- Photogrammetry — what decides accuracy.
- Orthophoto — the deliverable whose fineness GSD sets.