Flight planning (overlap, GSD)
The quality of the result is 80% the quality of the flight. Even the best processor cannot save a poorly planned mission. This page gathers the key planning parameters.
Four basic rules
Section titled “Four basic rules”- High overlap — at least 75% along-track, 70% cross-track
- Constant AGL altitude — avoid manual altitude changes
- Overcast or thin clouds — direct sun shadows add noise
- Calibration panel on P4M / M3M — before and after the flight
Video: DJI M3M mission planning — how to fly a good survey with the Mavic 3 Multispectral, and the settings that matter:
Overlap
Section titled “Overlap”Overlap is the area of the field that two adjacent images share.
- Along-track overlap (along the direction of flight): aim for 80%
- Cross-track / side overlap: aim for 75%
Lower overlap means:
- Weaker feature detection
- Holes in the orthomosaic in some areas
- The BA optimisation sees fewer tie points
In DJI Pilot 2’s 2D Mapping mission, overlap is configurable. Defaults are 75% / 70%; for agricultural surveying, raise to 80% / 75%.
Flight altitude (AGL — above ground level)
Section titled “Flight altitude (AGL — above ground level)”Altitude directly determines the GSD. DroneField’s supported GSD range is 3–20 cm/px, default 5 cm/px.
| AGL altitude | GSD (M3M) | GSD (P4M) | Images / ha (~75% overlap) |
|---|---|---|---|
| 80 m | ~3 cm/px | ~4 cm/px | ~20 |
| 100 m | ~4 cm/px | ~5 cm/px | ~12 |
| 120 m | ~5 cm/px | ~6 cm/px | ~9 |
| 150 m | ~6 cm/px | ~8 cm/px | ~6 |
| 200 m | ~8 cm/px | ~10 cm/px | ~4 |
Recommended altitudes by purpose:
- NDVI / detailed analysis (3–5 cm/px): 80–120 m AGL
- Drone-applied application map (5–7 cm/px): 120–150 m AGL
- Ground (tractor) application (10 cm/px): ~200 m AGL
- Quick overview (15–20 cm/px): 250+ m AGL (check airspace restrictions)
On hilly terrain it’s worth setting the planned altitude to the average elevation of the field — survey drones at typical mapping heights do not actively follow the terrain; they fly at constant absolute altitude.
Coverage — fly over what you want to see
Section titled “Coverage — fly over what you want to see”At the edges of an aerial image, parallax tilts tall objects (trees, terrain features, poles) — the further from image centre, the more they distort. Therefore:
Whatever you want to see in detail in the result, fly over it. Don’t just observe an obstacle from the side of the field — fly above it.
If you need NDVI on a tree at the field edge, or to clearly see a corner wire obstacle, the drone should fly over the tree / wire — not only up and down the field’s centre.
- 5–8 m/s — optimal; minimal motion blur
- 10 m/s — upper boundary, slight blur
- >10 m/s — avoid; image alignment degrades
Weather
Section titled “Weather”| Weather | Suitable? |
|---|---|
| Overcast | ✓ Ideal — no stochastic shadows |
| Thin clouds (1–2 octa) | ✓ Suitable |
| Clear sky, midday | △ Strong shadows — avoid near trees |
| Dawn / dusk, low sun | △ Colours skewed, NDVI uncertain |
| Rain, fog | ✗ Don’t fly |
| Strong wind (>10 m/s) | ✗ Drone can’t hold altitude |
For multispectral indices (NDVI, NDRE), it’s especially important that all bands experience the same illumination — hence overcast is ideal.
Pattern
Section titled “Pattern”The lawnmower (back-and-forth parallel strips) pattern is standard. Avoid grid patterns (perpendicular passes) — they take longer and DroneField’s BA is tuned for lawnmower.
Gimbal
Section titled “Gimbal”- Nadir (straight down, −90°) — standard surveying pose
- Oblique (45° forward) — not handled by DroneField for
agricultural processing (the
M3 Elevation45° photos are filtered out at import)
The gimbal must remain fixed — manual intervention or gimbal oscillation injects noise.
Calibration panel (multispectral)
Section titled “Calibration panel (multispectral)”P4M and M3M drones ship with a white / grey calibration panel in the box. Photograph it before take-off and after landing. DJI Pilot 2 prompts for this automatically.
DroneField detects calibration shots automatically and excludes them from the processing pool (but uses them for reflectance scaling).
Flight time of day
Section titled “Flight time of day”Optimal is 2 hours before sunset — 1 PM. Too early or too late amplifies long-shadow noise.
For multispectral, 10:00–14:00 is ideal (in Europe).
Common problems
Section titled “Common problems””Banded NDVI”
Section titled “”Banded NDVI””NDVI shows parallel bands that line up with the flight strips:
- Weather changed mid-flight (a cloud reached half the field)
- The drone’s automatic exposure (M3M) operated under different parameters on the two halves
Fix: re-fly under stable weather, or exclude the bad strips from processing.
Holes in the imagery
Section titled “Holes in the imagery”“Holes” in the orthomosaic (blank patches):
- Overlap was insufficient in that region
- The drone went around an obstacle
- Firewall or wind issues led to bad GPS
Fix: fly a smaller pass over the affected region and add the new imagery to the existing project.
Excessive file size
Section titled “Excessive file size”If your imagery is >50 GB in a project:
- Unnecessarily high resolution — perhaps you didn’t need to fly at 60 m over a 200-hectare field (10–15 cm/px would have been fine)
- Excessive overlap (90%+) — 80% is usually enough
Flight log
Section titled “Flight log”DroneField reads everything from the XMP and MRK, but it’s worth recording on paper:
- Date, start and end time
- Weather (overcast / sunny / cloud cover)
- Drone and pilot name
- AGL altitude, overlap percentages
- Notes (on-site problems, calibration panel success)
You can put these in the project’s description field — they will appear in the report too.