VARI Index Histogram

Greetings! I’m starting to get some flights of corn fields under my belt with DroneDeploy and a standard camera on my DJI3.

Using the VARI index (RGB), I see the analysis just fine, but I would like to generate some discussion on the meanings of the reds, yellows, and greens from the analysis. I understand green means more green in the field, but I’m wondering what the shape of the histogram could tell us. In a perfect field, what shape would we like to see in the histogram? Should it be peaked more to the right, the left, or the middle? Finally, what do the values on the X axis represent?

The way I’ve approached this so far has been to pull the left slider in until it meets the left foothill of the mountain, and I drag the right slider in until it meets the right foothill of the mountain. This has worked well to a degree to not give a “poor” looking scan, but I’m very interested in hearing other workflows and usage.

Thanks or your time!


Hi Brian,

It would help if you can share a screenshot of your histogram and map display as well as the type of crop. The values on the X axis represent the range of VARI values for your data while the Y axis is the frequency of those values.

The histogram shape will strongly depend on how much soil is visible, whether any cultural features are in the image scene, whether any adjacent fields with plants are visible in the image, and the crop development stage. Early growth will have much more mass on the left end of the histogram (low VARI values) than later on when the crop canopy fills in.

The map and histogram below show VARI for a vineyard (not DD interface, it’s QGIS). If the ranch manager wanted more vigorous vine growth and irrigated/fertilized accordingly then you would see the center of the histogram decrease on the Y axis (between around 0.2-0.4) and the right tail of the histogram increase on the Y axis (between around 0.4-0.6).

There is no ideal shape if you are looking at the histogram distribution of every pixel in an image unless the image is very neatly cropped to include only the crop of interest. You can see from this histogram that most of the VARI pixels correspond to soil and the cover crop. The vine shoots are only in the far right tail of the distribution.