I am new to aerial mapping. I am an eucalyptus farmer and plan to perform forest inventory by getting tree heights and also count then per unit of area. The measurements will be performed over trees from 15 to 30 m (45 to 100 ft aprox). Which WebODM parameters should I use, as well as flight height above ground?
I have already done a few flights, but unhappy with quality, the canopy height is not good or the orthophoto distorced. I used default parameters and overlap of 80% to get orthophoto, dsm and dtm.
I’m assuming that the tree heights are 15-30m (45-100ft).
One thing to keep in mind is your 80% overlap at ground level drops quite a bit at canopy height.
For example, if you fly at 100m altitude at 80% overlap … your overlap at the top of 30m trees drops to 70 to 71%. If you fly lower, the overlap decrease is even greater. At 75m altitude, overlap drops to 65% at canopy height.
I’ve had issues with tall pine forests and had to make additional flights to get more detail.
In my opinion, 90% overlap is too much and a waste of battery.
Not only is overlap important, but the quality of the images captured. Flight speed and camera settings can affect the quality of your images.
Was all of the area distorted or poor quality? If it was only smaller areas that need to be re-done, thats good! Fly those areas at a slower speed and double-check the camera settings (ISO, shutter speed, EV). You might consider flying those areas at 120m instead of 100m altitude. You lose a bit of bit of detail at ground level, but not as much at canopy height.
The additional images will merge with your originals.
At 100m altitude, the overlap will decrease like this: (These calculations are for my Mavic 2 Pro)
What program did you use to set up your flights and what drone are you flying?
