Free tool · drone photogrammetry

GSD and photogrammetry flight calculator

Work out the GSD from the height (or the height for the GSD you need), the footprint of each photo, the distance between photos and lines, the number of photos, the flight time and the maximum speed so photos are not blurred.

Example camera footprint, overlaps and GSD

What it calculates

GSD and height

The size of each pixel on the ground from the camera and the height, or the height you need for a target GSD. It warns you above 120 m.

Footprint and overlaps

The area covered by each photo and, with the front and side overlaps, the distance between photos (CAM1_TRIGG_DIST in ArduPilot) and between lines.

Speed and blur

The maximum speed so the motion during exposure stays within the allowed blur and the camera has time to trigger.

Photos and time

For a rectangular area: lines, photos per line, total photos, path length and approximate flight time.

Guide: how to plan a photogrammetry flight

How to plan a photogrammetry flight

Decide the GSD you need for the deliverable: detailed topographic surveys usually work at 1–2 cm/px, while construction progress or crop maps accept larger GSDs.
Work out the height for that GSD with your camera and check you stay below 120 m above ground if you fly in the open category.
Choose the overlaps for the terrain: more overlap over vegetation, water or uniform surfaces, where the software finds fewer common points.
Set the speed to the lower of the two maximums: the one that avoids blur and the one that gives the camera time to trigger.
Plan the grid in Mission Planner or QGroundControl with those values and check the mission with the mission validator.

GSD, height and focal length

GSD grows in proportion to height and falls with focal length: with the same camera, at 120 m the GSD is 20 % larger than at 100 m. Always use the lens’s real focal length (not the 35 mm equivalent) and the sensor width in millimetres. On uneven terrain the GSD varies across the area: terrain following keeps a constant height above ground.

Front and side overlap

Front overlap is the area shared by two consecutive photos on the same line; side overlap, the area shared by two neighbouring lines. They give the distance between photos and between lines. Too little overlap leaves gaps or poorly reconstructed areas; too much lengthens the flight and processing without improving the result.

Motion blur

While the shutter is open the aircraft moves forward. If that movement approaches the ground pixel size, the photo loses sharpness. With small GSDs you must fly slower or use shorter exposures, which needs more light or higher ISO.

Photo distance in ArduPilot

In ArduPilot, the camera triggers by distance with the CAM1_TRIGG_DIST parameter or the DO_SET_CAM_TRIGG_DIST mission command, which Mission Planner’s grid tool adds automatically. Before flying in the field, you can rehearse the mission in the photogrammetry and remote sensing simulator.

Other free tools

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Questions

What is GSD?

Ground Sample Distance: how much ground one pixel of the photo represents. A GSD of 2 cm/px means each pixel covers 2 × 2 cm.

How is it calculated?

GSD (cm/px) = sensor width (mm) × height (m) × 100 / (real focal length (mm) × image width (px)). So at twice the height, twice the GSD.

Which overlaps should I use?

For orthomosaics and surface models, at least 75 % front and 60 % side overlap is common. Over dense vegetation, water or low-texture areas it is better to go up to 85 % and 70 %.

Why are my photos blurred?

Because during the exposure the aircraft moves further than the GSD allows. At 10 m/s with 1/1000 s it moves 1 cm: with a 1 cm/px GSD that is already one pixel of blur. Slow down or shorten the exposure.

Is the height above take-off good enough?

GSD depends on the height above the terrain being photographed. On uneven terrain, use your planner’s terrain following or calculate with the height over the highest and lowest parts.

What height do I need for 2 cm/px?

It depends on the camera. With a 13.2 mm wide sensor, 5472 pixels and an 8.8 mm focal length it is just under 73 m; choose your camera in the calculator and select “I want a GSD”.

Does it work for any drone?

Yes, for any camera whose sensor width, resolution and real focal length you know. Some DJI models are preloaded with the manufacturer’s data.