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Flight Altitude from GSD Calculator

The greatest camera-to-ground height that keeps both image axes at or finer than your target pixel size, with terrain and height-limit checks.

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How to use this calculator

Inputs

The greatest camera-to-ground height that keeps both image axes at or finer than your target pixel size.

Target

Both axes is the default when the camera has both; x-only is used automatically (and labelled) when the y geometry is missing.

Camera

The lens's real focal length, not its 35 mm-equivalent figure.

More options
Height limit and terrain

A limit YOU supply with its source (project, permit, regulator). This tool does not determine any legal height.

Lens comparison

Enter the values and press Calculate.

Or load an example to see a worked result.

Maximum height for the target pixel size
Not to scale
Maximum height for the target pixel sizeCamera above the ground with its field-of-view cone; the binding height is measured to the lowest ground.Camera heightHmax
The camera may fly no higher than the height at which one pixel covers the target size; over varying terrain the lowest ground is the binding case.
Calculate first: a stale result cannot be exported.

Batch from CSV

One row per calculation, with a header row. Values use the units currently selected in the form above. Up to 10,000 rows; nothing is uploaded.

Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.

How to use this calculator

  1. Enter the target pixel size (mm, cm or m per pixel).
  2. Enter the physical sensor size, focal length and image pixels; both axes are constrained when both are given.
  3. Optionally add your own height limit and the lowest/highest ground elevations on one vertical datum.
  4. Press Calculate for the maximum camera-to-ground height and the limiting axis.

How it works

Hₓ = g × f × Nₓ ÷ sensor width and Hᵧ = g × f × Nᵧ ÷ sensor height. The answer is min(Hₓ, Hᵧ), so neither axis is coarser than the target; the binding axis is named.

Over varying terrain at one flight elevation the binding case is the lowest ground: F ≤ Z_min + H_max. If the relief exceeds H_max the geometry is infeasible — no negative height is given.

A height limit you enter is compared with the result; the target is never changed for you. This is geometry, not a legal or safe flight height.

Worked example

2 cm/px with the illustrative 36 × 24 mm, 36 mm, 6000 × 4000 camera. Hₓ = 0.02 × 36 × 6000 ÷ 36 = 120 m and Hᵧ = 0.02 × 36 × 4000 ÷ 24 = 120 m, so 120 m on both axes. With ground from 50 to 80 m the highest constant flight elevation is 170 m, giving 120 m above the lowest ground and 90 m above the highest. At a 100 m limit the pixel is 1.666667 cm.

Frequently asked questions

Is this the height I am allowed to fly?

No — it is the geometric height for your pixel size. Legal limits, obstacles and airspace are separate, and come from your regulator and site.

Why does a longer lens allow more height?

GSD scales with H ÷ f, so doubling the physical focal length doubles the height for the same pixel size — but the footprint at any fixed height gets narrower.

Related tools

Explore more in Surveying, Coordinates, GIS & CAD.

Cite this tool

Zerdly. (2026). Flight Altitude from GSD Calculator. Retrieved from https://www.zerdly.com/tools/flight-altitude-from-gsd-calculator/

Tip: Enter any known values to calculate the remaining results.

Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.