Difference in index raster values between PIX4D and QGIS


I have noticed in my processed datasets a difference in values between what is shown in PIX4D index calculator and the same raster when inserted in QGIS.

Why is that so and which is the correct?

The same applies for reflectance values as shown in the screenshot.

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I assume you are looking at the min/max. This is most likely because the two software treat outliers differently to give the mean/max. Often, a few pixels have values really outside the rest of the pixels and should be treated as noise. Depending on how these outliers are treated, you will get different values for the min/max. The actual values in the map should be exactly the same. 

Ok, this is a possible explanation, however I will try to perform a check once I find time, unless someone else beats me (which I sincerely hope)… Thank you for the answer Marc.

Hey Agro, 

It is exactly how Marc described it. QGIS removes the %2 outliers by using the Cumulative Count option whereas  Pix4D uses the min/max option. If you change the load min/max values settings in QGIS to Min/Max, you would get the same results as Pix4D. I have tried that few times before. I hope that helps.