See the effects of shadows...

When compared to C3 products, it is easy to see how the shadow issues that effect NDVI images detract from the agronomist's ability make accurate interpretations of canopy size and health.

 

shadows1-1.png

 The individual trees are NOT clearly visible in this black & white NDVI image of a mature orchard (with large landscape trees in the southern part of the image). The reason for this is that in NDVI images shadows and shaded parts of the trees tend to have the same NDVI values as the dense vegetation. When zoomed in to see that the NDVI values it is startling just how suspect the values are within the shadows and shaded parts of the trees (appear as lush vegetation on the shadowed, notheast, side of the trees).

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 Note that each tree and row of trees is much more identifiable in the black & white C3 Vegetation Index. This is because C3 products are not effected by the same issues with shadows that effect NDVI maps. In the close-up image you can see that the C3 Vegetation Index map accurately represents the canopy detail.