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
- Sunlight sensor on P4M / M3M — keep it unobstructed; DroneField computes reflectance from it, no calibration panel needed
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 4–20 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 used by DroneField for
agricultural processing (the
M3 Elevationoptimisation oblique photos — tilt over 15° — are imported but skipped during processing)
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, and DJI Pilot 2 may prompt you to photograph it. DroneField does not use panel shots: reflectance is computed from the drone’s sunlight sensor (irradiance) data, together with vignetting and sensor-gain (SensorGainAdjustment) correction. Keep the sunlight sensor on top of the drone clean and unobstructed.
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 the MRK, if present), 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)
You can put these in the project’s description field — they will appear in the report too.