I have done “Since only one-panel image set is supported in Pix4D, if you are procesing together as one project, the best set of panel images are recommended to be used (mostly one after the first flight and before the second flight will correspond to the weather conditions the most)”
Because separetely, it was completely different…
And finally, I have found NDVI=0.03 for my area with all the multispectrale images (over than 800) + the target2 images.
I still do not understand why the difference because the target images are supposed to balance the values, take into account the atmospheric conditions so the same area overflown twice at 8h30 and 9h15, should have the same NDVI. Here, we have 0.03 with the target images 2 (take before the second flight) and 0.12 for the target images 1 (take before the first flight).
But at least I find 0.03 for all combinations with target 2.