Thermal capture checklist

The practices that apply to every sensor are here:

https://support.pix4d.com/hc/processing-thermal-images-in-pix4dmatic

Nadir, the 80/80-90/90 overlap, a minimum resolution of 640x512, radiometric files, and the temperature parameters are already described in Photogrammetric Processing Algorithms and Thermal IR.

Time of day

  • For a temperature value, fly while the sky and the surface stay steady for the whole grid. Uniform overcast is the reliable case. Clear noon is a weak hour, because the sun keeps changing the surface through a long flight.

  • For something warmer or colder than the ground (stones, animals, nests), late evening or night is the suitable time.

Flight plan

  • Use mission-planning software: a distance trigger, a single grid, one height AGL, and coverage beyond the boundaries of the site.

  • Capture at a nadir angle. Oblique photos can succeed for some missions, but they are not yet officially supported.

  • A camera outside the supported list can also succeed on some missions. Only the cameras on the camera support list are supported.

Overlap

  • Plan 90/90.

On site

  • Let the camera warm up before the first flight, and leave the flat-field shutter enabled.

  • Disable dewarping.

  • Ensure every thermal frame has a GPS position. RTK or PPK is preferable, especially when only thermal captures are taken.

  • Maintain a maximum of 25 meters above ground level.

  • Record the air temperature and humidity.

  • Keep vehicles, people, livestock (anything warm moving) out of the grid.

  • Prefer night or overcast cloud cover, avoid direct sunlight and rapidly changing weather conditions.