Overlap, trigger interval, and line spacing

Photo spacing, trigger interval, and flight-line spacing for your front and side overlap, with a check that the camera can keep up.

Planning and education aid. Not for primary navigation. Full disclaimer

A published result changed on 2026-09-23: The forest overlap preset (version 1.1.0) is now 85% front and 85% side. It used 85% front and 70% side, but Pix4D's page recommends at least 85% frontal and side overlap for forest and dense vegetation; 85/70 is its advice for snow and sand. With the preset, flight lines are now closer together: 22.5 m instead of 45 m for a 1-inch camera at 100 m. The superseded vector pinned the old line spacing. Changelog

Computing your own values needs JavaScript and WebAssembly. The worked example below was computed when this page was built, and the documentation under "How we got this" applies.

2.5s

Take a photo every 2.5 s (25 m) and space flight lines 52.5 m apart.

Trigger distance
Line spacing
Footprint along track
Footprint across track

Provenance

Computed by: drone.photogrammetry.trigger 1.1.0, core 0.1.0
Model: Trigger distance = along-track footprint × (1 − front overlap); line spacing = across-track footprint × (1 − side overlap)
Accuracy: Exact over flat ground at the given height; terrain changes the effective overlap
Notes: None
Cites: Wolf, P. R., Dewitt, B. A., and Wilkinson, B. E., McGraw-Hill, Elements of Photogrammetry with Applications in GIS; Pix4D support documentation, Selecting the image acquisition plan type (overlap guidance)

Something look off?

Your values

Showing an example. Change anything.

Height above ground Like 100 m AGL · plain numbers mean m Sensor width Physical width, like 13.2 mm for a 1-inch sensor · plain numbers mean mm Focal length Physical focal length, like 8.8 mm · plain numbers mean mm Image width Pixels across the long side, like 5472 Sensor height Physical height, like 8.8 mm · plain numbers mean mm Groundspeed Like 10 m/s · plain numbers mean m/s

More options 8

Front overlapoptional Percent, like 75 Side overlapoptional Percent, like 65 Overlap presetoptional general (75/60) or forest (85/85), Pix4D guidance Camera orientationoptional landscape (long side across track, default) or portrait Camera minimum intervaloptional Fastest the camera can shoot, like 2 s · plain numbers mean s Image heightoptional Pixels on the short side, like 3648 Focal length typeoptional physical (default) or equivalent-35mm Crop factoroptional Needed with a 35 mm-equivalent focal length, like 2.7

Run many at once from a CSV

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How we got thisFormula, worked example, sources, and proof

Model: Trigger distance = along-track footprint × (1 − front overlap); line spacing = across-track footprint × (1 − side overlap)

Show your work

Footprint along the flight line
what one photo covers in the direction of travel
at 100 m above the ground = 100 m
Distance between photos
spacing = footprint × (1 − front overlap)
100 m × (1 − 75%) = 25 m
Trigger interval
$interval = spacing / groundspeed$
25 m / 10 m/s = 2.5 s

The same steps an agent gets from the MCP server with explain: true.

Accuracy: Exact over flat ground at the given height; terrain changes the effective overlap

When to use this: Use this when you set up a mapping flight and need the numbers the flight app asks for: how far apart to take photos, how often to trigger at your groundspeed, and how far apart to fly the lines for the front and side overlap you want. It also tells you whether the camera can shoot fast enough.

Limitations: It assumes a nadir camera over flat ground at the height you give. Ground that rises toward the drone shrinks each photo, so the real overlap there is lower; check it with the terrain overlap tool. Wind, gimbal tilt, and a camera that cannot hold a steady interval also cut overlap in flight. It does not plan the lines over your area.

Worked example: 75/65 overlap at 100 m and 10 m/s with a 1-inch camera. Source: add-drone-suite scenario: 25.0 m, 2.5 s, 52.5 m. It is golden test vector v001, and every build checks the tool still gives its answer within its tolerance.

You enter

Focal length: 8.8 mm
Front overlap: 75
Groundspeed: 10 m/s
Height above ground: 100 m
Image width: 5472
Sensor height: 8.8 mm
Sensor width: 13.2 mm
Side overlap: 65

You get

Trigger interval: 2.5 s
Trigger distance: 25 m
Line spacing: 52.5 m
Footprint along track: 100 m
Footprint across track: 150 m

Review: Not yet independently reviewed by a Part 107 remote pilot.

Last verified: 2026-09-18, when a maintainer last confirmed this tool's sources at the issuer. See the sources ledger.

Status: version 1.1.0, core 0.1.0. See this tool in the verification report.

Changes

2026-09-23, result change: The forest overlap preset (version 1.1.0) is now 85% front and 85% side. It used 85% front and 70% side, but Pix4D's page recommends at least 85% frontal and side overlap for forest and dense vegetation; 85/70 is its advice for snow and sand. With the preset, flight lines are now closer together: 22.5 m instead of 45 m for a 1-inch camera at 100 m. The superseded vector pinned the old line spacing. Changelog

Checked against: 22 golden test vectors (download the test vectors, each with its source and tolerance). See how results are checked and every source.

Sources

Elements of Photogrammetry with Applications in GIS, Wolf, P. R., Dewitt, B. A., and Wilkinson, B. E., McGraw-Hill, 4th edition. Chapter 6 (vertical photographs: scale and ground coverage). Read free.
Selecting the image acquisition plan type (overlap guidance), Pix4D support documentation, Vendor guidance, not a standard. General case: at least 75% front, 60% side; forest and dense vegetation: at least 85% front and side.

Learn the concept: Photo overlap and flight lines explained, What is ground sample distance (GSD)?