I have a P4 Multispectral drone and I plan to fly over dense woodland and use the point cloud produced in Pix4D Mapper to map the canopies of individual tree crowns. I am reading about how to plan the ideal flight for this purpose and a recurring piece of advice is to fly as high as possible and have as high overlap as possible. I can understand the purpose of having very high overlap but I do not understand why I should fly as high as possible. If anything, it seems counterintuitive- surely the point cloud will be more accurate if the drone is closer to the vegetation and can ‘see’ the trees more closely? Can anyone explain to me why it’s better to fly higher when mapping dense vegetation?
Hi Scarlet,
if it’s the same reason of RTC 360 Laser-Scanner, it’s a matter of over-precision: if you are flying too low (or scanning too close), you’ll be able to see each branch and leaf; however, Pix4DMapper will be unable to match the photos, because it’s almost impossible to have each leaf in the exact previous coordinates, due to the light winds, or birds posing on the branches.
When you choose to fly higher, one pixel will count for a broader group of leaves and branches, so it will be possible to calculate a mean value that will suffer less from winds or movements.
Regards,
Giancarlo