Visible NDVI (vNDVI)

[edblanch]

I have been researching a new vegetation index visible NDVI proposed by Lucas Costa from the University of Florida.

I noticed it has been incorporated in the Plant Health indices in WebODM. When I tried to use it today it does not seem to work. Any ideas why?
When I used the same equation in the Raster Calculator of QGIS it worked fine returning values from 0.3 to 0.6.

[Saijin_Naib]

Have any example data, error messages, or anything else?

What exactly didn’t work?

[edblanch]

Here is a screen image of the result of trying to use the vNDVI index. There is no histogram or image.

[Saijin_Naib]

Do you know if you’re using the absolute current/latest WebODM release? Have you issued a ./webodm.sh update recently and tried again?

Also, have you checked your process/task manager in Linux Minut to see if it might not just be processing the index in the background still?

[edblanch]

Yes, I updated it after I tried to use the index the first time.

I don’t think the issue is with Linux Mint as it runs all the other indices.

Have you been able to get to run?

[Saijin_Naib]

Looks like this index might be tricky since it isn’t being normalized or is otherwise going out of range.

Try changing the min/max values to 0 for min and 2 for max and see if it draws more sensibly.

[edblanch]

Thanks,

When I put the range of 0.3 to 0.5 the image appeared and it looked very similar to the Raster Calculator image in QGIS

The range should be the same as NDVI eg 0 to 1.

[edblanch]

Just tried it again and it worked like a charm provided all the numbers are between 0 and 1.

[Saijin_Naib]

Yes, ideally, it should be a normalized index, but according to the paper we used for the index, it is not normalized:

Add vNDVI to formulas.py