What is the NDVI?
The Normalised Difference Vegetation Index (NDVI) is commonly used to simplify multispectral visualisation by combining the NIR and red reflectance into a single layer that can indicate vegetation health.
NDVI is calculated using the following equation:
(NIR - Red) / (NIR + Red)
When creating an NDVI layer, we apply this equation to every pixel in the multispectral image to return an output of between -1 and +1.
To learn more about how the NDVI is calculated and how to understand the output, check out this video.
Deriving NDVI
It's very simple to derive the NDVI (and other indices) on GeoNadir - learn more here.
However, if you would like to do this in QGIS, we cover the steps below. It might look complicated but I promise you it's not too bad and you can do it!
In brief, the video addresses:
Upload your multispectral data to GeoNadir for processing
When complete, download the multispectral orthomosaic
Drag and drop the orthomosaic into QGIS
Change the contrast and band display of the orthomosaic
Use the raster calculator to apply the NDVI equation to your orthomosaic
For best results, change the contrast of the resulting NDVI
Use the identify features tool in QGIS to inspect individual NDVI pixel values