Hello
i use Parrot Sequoia and Pix4D AG to calculate index maps for fertilizer prescriptions. Removing the tramlines in the picture (e.g. filling the cells with the average value of the neighbour cells) would highly increase the quality of the data. As we use GPS for driving in the field the tramlines have a defined spacing.
Regards
Hi Hubertus,
I think drawing regions would help you with this.
If not I could see that most of the tramlines have a high NDVI value. You could identify this value and if is at the extremity of the range you could set the maximum value of the interval lower and deselect Clamped. That way all the pixels outside the min-max will be displayed with transparency and not included in the prescription map.
However, if other pixels than the one from the tramlines have the same value (>max) those pixels will be also excluded.
Let me know how it goes 
Have a good day,
Ina