How does drone altitude affect vertical accuracy for photogrammetry mapping projects
Short answer: Often yes — flying lower can improve vertical accuracy — but only up to an optimal altitude for your camera, overlap, and terrain. Below that point, accuracy can plateau or even degrade if coverage/geometry suffer.
GSD and why altitude matters
When you fly higher, your ground sampling distance (GSD) increases. Each pixel represents a larger ground area, reducing detail. Lower altitude → smaller GSD → finer detail, which typically improves photogrammetric point matching and surface modeling.
Why it isn’t strictly “lower is always better”
- Coverage & overlap: Too low can shrink footprint and cause gaps unless you increase flight lines and image count.
- Geometry: Good vertical accuracy depends on varied viewing geometry. Nadir-only, very low flights may not add helpful parallax. Add obliques or increase sidelap/endlap.
- Camera limits: Lens quality, shutter speed, and rolling‑shutter effects can cap gains from flying lower.
- Terrain & obstacles: Trees/structures can force altitude changes; safety and regulations come first.
Practical approach
- Choose altitude to hit your target GSD for the deliverable (e.g., 1–2 cm/pixel for design topo).
- Use 70–80% frontlap and 70–85% sidelap; add an oblique pass for complex terrain or tall features.
- Lock exposure and fly with adequate shutter speed to reduce motion blur.
- Include GCPs and independent checkpoints for QA — RTK/PPK helps but doesn’t replace checkpoints.
Bottom line
Lower altitude generally improves vertical accuracy via smaller GSD, but optimal results come from balancing altitude, overlap, camera settings, and ground control to suit the site and required tolerance.