Using QGIS to make indices

PIX4Dmapper PIX4Dmapper Questions/Troubleshooting
1

Good day,

Which ones of the output files does Pix4D Mapper use to produce NDVI from a Sequoia source? More to my point: which Mapper outputs should be used in GIS software (QGIS) if we want to produce other indices? I know Mapper has an index calculator, but I prefer using QGIS.

Thank you,

FJ

2

Hi FJ, You will need to use the reflectance maps for producing vegetation indices. The “noalpha_reflectance” gives a black color value to the no value data pixels. It will result in a .tiff file with black color where there is no information.
The “transparent_reflectance” does not display color information (it applies a transparent band) to the no value data pixels. It will result in a .tiff file where areas with no are not displayed as black color.

3

Thank you Momtanu -

I want to make sure I understand you correctly : I should use the “transparent_reflectance” since it does not ‘fill in the blanks’ with a black colour value? Are there uses for which I should use the “noalpha_reflectance” instead of the “transparent_reflectance”?

Thanks again,

FJ

4

Yes, you are right. But transparent_reflectance creates an extra band, the alpha band. If for some reason you don’t want an extra band, you can use no alpha. But I myself have used transparent_reflectance for generating indices in Matlab and doing further analysis, as you don’t want the black border. I have also seen users use the transparent_reflectance band.