For 2020, TerrAvion will be providing services with new and improved product specifications and operational improvements designed to increase our reliability while delivering more images. While we are focused on exceeding the expectations of our customers with our current product offering for 2020, our R&D department always has an eye on the future. Our team is experimenting and exploring the possibilities of adding new remote sensing technologies to our product offering all the time. The following is some information on a new product that we currently are testing, red edge imagery.
Limitations of NDVINormalized Difference Red Edge (NDRE), or “Red Edge” is an index product (image constructed from a combination of two distinct frequencies of light) much like the more familiar Normalized Difference Vegetation Index (NDVI). While NDVI is one of the most widely used and trusted indexes in agriculture, in certain situations, NDRE imagery is a better-suited tool for analyzing crop health.
While NDVI imagery has so many great benefits as a crop health index, it does have one limitation that is evident when certain crops reach their peak canopy level. The visible red light that is used for NDVI imagery is mostly absorbed by the top of the plant canopy. This means that when a crop reaches its full canopy, the visible red light may get more strongly absorbed by the canopy, leaving lower levels of the canopy under-represented in an NDVI measurement. This effect generally impacts plants with more layers of leaves, like tree canopies, but in some cases can affect commodity crops like later-stage corn as well.
What is Red Edge, and how can it help?
While NDVI is built from a combination of visible red light and near-infrared (NIR) light, NDRE uses a combination of NIR light and a frequency band found between visible red and NIR light, or the “red edge.” The red edge refers explicitly to the wavelengths between approx. 0.7 and 0.8 µm, the region between the red light, where reflectance from green vegetation is very low, and the NIR light where the reflectance is very high. The substitution of NDVI’s red band with NDRE’s red edge band provides a measurement that is not as strongly absorbed by just the topmost layers of a plant. Studies have shown that the transition between the red absorbance and the NIR reflection (the Red Edge) can indicate variations in both the chlorophyll content and the leaf density.
In short, NDRE imagery is sometimes capable of indicating very subtle signs of crop health variability in a mature crop faster than NDVI imagery.
Can TerrAvion deliver NDRE imagery?
TerrAvion is already well into the development of our own NDRE product. We are currently testing this product in parts of South America. Specifically, our red edge is taken at 710 nm +/- 10 nm. While our NDVI product is already one of the best value crop monitoring solutions on the market, we are always looking to develop and improve our products.
For more information on our current product specs, including our new Synthetic Color and Pansharpened Thermal imagery, visit our product info page or complete the form below.