Photogrammetry Overlap Calculator
Drone mapping needs each part of the ground to appear in many overlapping photos so software can reconstruct it in 3D. From the camera ground footprint and your desired forward and side overlap percentages, you can work out how far apart to trigger photos along a flight line and how far apart to space the lines. This calculator returns the shot (trigger) spacing, the flight-line spacing, and the effective non-overlapping ground advance per photo, so you can plan a mission that hits your overlap targets.
Overlap and spacing formula
shot spacing = footprint height * (1 - forward overlap / 100)
line spacing = footprint width * (1 - side overlap / 100)
new ground per photo = shot spacing * line spacing
photos per sq km = 1,000,000 / (new ground per photo)
Overlap percentages are entered 0 to 100. Shot spacing controls trigger interval along a line; line spacing controls how far apart parallel lines fly. Photo density estimates total images needed per square kilometre.
Photogrammetry overlap context
- Typical mapping overlap is 70 to 80 percent forward and 60 to 70 percent side.
- Higher overlap improves 3D reconstruction but increases photo count and processing time.
- Featureless surfaces (water, sand, snow) need more overlap to match reliably.
- Shot spacing and aircraft speed together set the required camera trigger rate.
- Line spacing determines how many parallel passes cover the survey area.
Photogrammetry overlap: frequently asked questions
What is forward and side overlap?
Forward (front) overlap is how much consecutive photos along a flight line share; side (lateral) overlap is how much adjacent flight lines share. Photogrammetry needs high overlap (commonly 70 to 80 percent forward and 60 to 70 percent side) so every ground point appears in several images for accurate 3D reconstruction.
How is shot spacing calculated?
Shot (trigger) spacing along a line equals the footprint height times (1 minus forward overlap). For example, an 88 m footprint height at 75 percent forward overlap triggers a photo every 22 m. Higher overlap means shorter spacing and more photos.
How is flight-line spacing calculated?
Line spacing equals the footprint width times (1 minus side overlap). At 60 percent side overlap with a 132 m footprint width, lines are 52.8 m apart. Lower line spacing means more flight lines to cover the same area.
Why does more overlap improve a 3D model?
Structure-from-motion photogrammetry matches features across images. The more images a ground point appears in, the more rays intersect at it, reducing error. High overlap also handles featureless or repetitive surfaces and reduces gaps from occlusion.
What is the trade-off of high overlap?
More overlap means more photos, longer flights, larger datasets and more processing time. Mapping missions balance overlap against battery life and storage. This calculator shows how shot and line spacing change so you can plan that trade-off.
Official sources
- U.S. Geological Survey: aerial photography and photogrammetry.
- U.S. Federal Aviation Administration: drone (UAS) operations.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.