Multispectral capture checklist

A short reminder for multispectral flights. The practices that apply to supported sensors are here:

https://support.pix4d.com/hc/multispectral-basic-capture-practices

Nadir, 75/75 overlap, and clear-sky or overcast weather are already described in Multispectral and Ag RGB.

Time of day

  • Fly the mission on a single day, within about ±3 hours of local solar noon.

  • Clear sky, or a uniform overcast only. Scattered cloud cover puts sun and shade in the same frame, for which the sun sensor cannot compensate.

  • Plan the flight track across the sun light direction (if sun is on south, fly west-east-west directions), so a high sun does not sit as a hotspot in every frame.

Flight plan

  • Use mission-planning software with flight planning that offers overlap modes. Let the software trigger the capture by the camera position.

  • Fly nadir, one altitude, at or above approximately 40 meters from the canopy or terrain. Ensure that the grid extends beyond the site boundaries. Orient the frame landscape in the direction of the flight.

  • Keep the mission grid frame captures and the panel frame captures. Discard takeoff, landing, and the path between them.

  • Use auto exposure, the full sensor, the native aspect ratio, and de-warping disabled for every frame. Leave elevation optimization off, as it tips the camera off nadir at the end of the mission.

Overlap

  • Plan 80/80. 75/75 is the floor in the starter settings.

On site

  • Capture the reflectance panel at least three times before the grid and three times after, in the same light as the field is. Keep the panel flat and unshaded, step back, and stay about 1–2 m above it so the QR code is easy to read.

  • Give the sun sensor a clear view of the sky, clear of the props, the frame, and any wires.

  • Note whether the sky was clear or overcast. The weather condition is used in processing.

  • Execute the capture missions continuously and within the same day.