Visual Imaging

Visual imagery is captured by the drone as we see the world with the naked eye.  Examples of uses of visual imagery are plant health analysis, plant stand counts and many other agricultural applications. Visual images have value in that a high resolution color photo can show up problems with plant stands, drainage, or other environmental issues. However, vegetative analysis performed on visual images can not be compared absolutely season long because sunlight affects the visual images differently depending on conditions. Analyses can only be compared absolutely if they are taken the same day under the same conditions. Common analyses performed on the visual imagery include:
  • Green Leaf Index (GLI): Shows the greenness and yellowness of the crop.
  • Visible Atmospherically Resistant Index (VARI): Includes a correction for the atmosphere in analyzing the vegetation fraction from the visible range of light.
  • Visual Normalized Difference Vegetation Index (NDVI): Also called the Normalized Green Red Difference Index (NGRDI), it is an indicator of surface greenness in the canopy.
The images below show the types of data you can expect from Visual Imaging.
Examples of Visual Imagery and Analysis

Orthomosaic of tobacco flown at 300 feet.

Green Leaf Index (GLI) analysis of tobacco from the visual image.

Detail view of the GLI on the tobacco. The individual leaves can be seen as well as the missing plants from disease.

Soybean field following herbicide application. Drowned areas clearly show up as well as spray overlap in the turn rows and field.

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Detail view showing plant burn due to herbicide injury where the sprayer overlapped:

  1. Turnrows at the end of a pass.

  2. In the row due to improper spacing.

  3. On the angled turnrow.

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