Ground sampling distance calculator for drone mapping flights
Enter your camera and flight altitude to get the ground sampling distance and the ground footprint of each photo. The calculator runs in your browser, in metric or US units, and the formula is written out below so you can check every number.
Calculator
Ground sample distance calculator
Ground sampling distance (cm/px)
Ground sampling distance (in/px)
- Footprint width per image
- Footprint height per image
The basics
What ground sampling distance means
Ground sampling distance (GSD) is the distance on the ground between the centers of two neighboring pixels in a photo. A GSD of 2 cm/px means each pixel covers a square about 2 cm across. The smaller the GSD, the finer the detail in the orthomosaic and the denser the surface model.
GSD is set by the camera and the altitude. A larger sensor or a longer lens lowers it, and so does flying lower. Flying higher raises it and lets each photo cover more ground, so one battery maps more area at a coarser resolution.
The formula
How the calculator computes GSD and footprint
GSD (cm/px) = (sensor width x altitude x 100) / (focal length x image width)
Sensor width and focal length are in millimeters, altitude in meters and image width in pixels. The factor 100 converts meters to centimeters.
Footprint width (m) = GSD x image width / 100
Footprint height (m) = GSD x image height / 100
For US units the calculator converts altitude from feet to meters first and shows GSD in inches per pixel (cm/px divided by 2.54) and the footprint in feet.
A worked example
Take a camera with a 13.2 mm sensor width, an 8.8 mm focal length and images 5472 by 3648 px, flown at 100 m. GSD = (13.2 x 100 x 100) / (8.8 x 5472) = about 2.74 cm/px. The footprint is about 150 m wide and 100 m tall per photo.
Fly the same camera at 60 m and the GSD drops to about 1.64 cm/px, with a footprint of about 90 m by 60 m. The detail improves, and the flight needs more lines and more photos to cover the same site.
Choosing a GSD
Which ground sampling distance fits the job
There is no single right value. Pick the coarsest GSD that still shows what the job needs, because a finer GSD costs flight time, battery swaps and processed images. The ranges below are general guidance widely used in the industry, not a guarantee of accuracy.
| Job | Typical GSD guidance |
|---|---|
| Topographic survey with GCPs | About 1 to 2.5 cm/px, finer for tight tolerances |
| Stockpile volumes | About 2 to 4 cm/px |
| Construction progress | About 2 to 5 cm/px |
| Field mapping and crop health | About 3 to 10 cm/px, coarser for large fields |
| Roof and facade inspection | Often under 1 cm/px, set by the smallest defect to see |
A common rule of thumb is that achievable horizontal accuracy is a small multiple of the GSD when the flight has good overlap and ground control, and that vertical accuracy is looser than horizontal. Read drone mapping accuracy for the full picture and drone mapping overlap for spacing your flight lines.
Common mistakes
Things that change the real GSD
- Terrain: on a slope or a tall stockpile the camera is closer to the top, so the GSD there is finer than over the base.
- Altitude reference: many flight apps set altitude above the takeoff point. If you took off from a pit or a roof, the height above the ground differs.
- Equivalent focal length: the 35 mm equivalent printed in specs gives a wrong answer in this formula. Use the physical focal length.
- Motion blur: a slow shutter smears pixels, so the usable detail is worse than the GSD suggests.
From your own photos
Read GSD straight from your flight
The demo reads the metadata of your drone JPEGs in the browser and estimates the GSD, the footprint per image and the overlap of the actual flight, with nothing uploaded. Try it on the drone image processing software page.
Pricing
Turn the flight into a map
Process the photos into an orthomosaic, surface and terrain models and measurements on Starter at $99 per month or $990 per year, with 3,000 processed images a month. Team at $249 per month adds GCPs, the accuracy report and contours.
Questions
Ground sampling distance FAQ
No. A smaller GSD gives finer detail but needs more photos, more flight time and more processing. Choose the GSD the deliverable needs.
No. GSD is resolution. Accuracy also depends on overlap, image quality and ground control. With GCPs and checkpoints, an accuracy report on Team and above shows the measured residuals of your own flight.
In the camera specifications from the manufacturer. For many drone cameras it is also stored in the photo metadata, which the demo reads for you.
The distance from the camera to the ground changes with the terrain. High ground is closer to the camera and has a finer GSD, low ground a coarser one. Terrain following in the flight app keeps it more even.
No. The calculation runs in your browser.
Related pages
Plan the flight, then process it
Fly at the right GSD, then process the flight
Upload your photos and get an orthomosaic and elevation models at the resolution you chose.