What’s the difference between multispectral and hyperspectral?
Imagine we could safely view the world through the eyes of different creatures, enabling us to view infrared radiation, ultraviolet light and reflected electromagnetic energy*. Well, we can, with the use of multispectral and hyperspectral sensors.
Each technology is able to sense (“see”) outside the range of normal human vision. The difference is the number of bands and the narrowness of the bands.
Multispectral imagery generally refers to 3-10 wide bands, using a remote sensing radiometer.
Hyperspectral imagery consists of many more bands (hundreds or thousands) that are much narrower (10-20nm), using an imaging spectrometer.
It’s a question of detail.
The more detailed the spectral information recorded by a sensor, the more information that can be extracted from the spectral signatures.
Hyperspectral sensors have much more detailed signatures than multispectral sensors and thus provide the ability to detect more subtle differences in aquatic and terrestrial features.
Consider this example about a US project to inspect orange groves, looking for citrus blight disease, which used a Headwall Photonics’ Hyperspec® VNIR hyperspectral solution with an OEM camera mounted on a UAV.
Citrus blight destroys the vitality of trees and can spread throughout the grove. One of the early signs of this disease is a byproduct secreted on the surface of the leaves. Inspection for this used to require a person climbing a ladder to inspect the top of each tree. More often, growers might not know of a problem until trees started dying. With hyperspectral imaging, this can be seen 300-400 meters above the crops covering a large area quickly (mounted on UAVs), allowing quick action to eliminate the spread and minimise the destruction.
For precision ag, the more detail, the better.
Imagine flying over a property and looking down at fields of different colours and appearance. You might decide you know what is planted in each paddock, with accuracy dependent on how low you are flying.
With multispectral detection, you would certainly be able to see differences between various elements, such as a tree plantation versus another crop.
With hyperspectral capabilities, you will see individual trees and plants, and even the subtle differences in the EMR emitted by disease and soil moisture levels etc.
In its 2017-2019 Strategic Plan, the NSW Department of Primary Industries’ first goal is Innovation in primary industries to improve resilience and boost productivity.
There is no doubt that hyperspectral imagery is the most advanced precision ag solution to transform our analysis and optimisation of production, risk management, use of resources and reducing disease.
Talk to PAS about the possibilities for the use of hyperspectral solutions in your agricultural context.